EPA-R3-73-019
FEBRUARY 1973 Ecological Research Series
DEVELOPMENT OF
DISSOLVED OXYGEN CRITERIA
FOR FRESHWATER FISH
2 fm \
UJ
Office of Research and Monitoring
US. Environmental Protection Agency
Washington, D.C. 20460
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL
RESEARCH series. This series describes research
on the effects of pollution on humans, plant and
animal species, and materials. Problems are
assessed for their long* and short-term
influences. Investigations include formation,
transport, and pathway studies to determine the
fate of pollutants and their effects. This work
provides the technical basis for setting standards
to minimize undesirable changes in living
organisms in the aquatic, terrestrial and
atmospheric environments.
-------
EPA-R3-73-019
February 1973
DEVELOPMENT OF DISSOLVED OXYGEN CRITERIA
FOR FRESHWATER FISH
By
Charles E. Warren
Peter Doudoroff
Dean L. Shumway
Oregon State University, Corvallis, OR
Project 18050 DJZ
Project Officer
Dr. Gerald R. Bouck
Western Fish Toxicology Laboratory
200 South 35th Street
Corvallis, Oregon 97330
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
For sale by tho Superintendent of Documents, U.S. GovernmeaJ; Printing Office, Washington, D.C. 20402
Price $2JlQ.4ciMSUc,afl6taiaid or $l.f§P!GPO Bookstore
-------
EPA Review Notice
This report has been reviewed by the Environmental Protection
Agency .and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies of
the Environmental Protection Agency, nor does mention of trade
names or commercial products constitute endorsement or recommen-
dation for use.
ii
-------
ABSTRACT
This terminal report nominally covers laboratory research on the dis-
solved oxygen requirements of salmonid and centrarchid fishes conducted
from September 1, 1968 through August 31, 1971. But because our inter-
pretation of the results of this research, our conclusions, and our
recommendations are to a considerable extent based on the results of
research we conducted from September 1, 1955 through August 31, 1968, we
have included a summary of this earlier work.
The research here reported has involved laboratory studies on the survival,
development, bioenergetics and growth, swimming performance, and avoidance
behavior of chinook and coho salmon, steelhead trout, and largemouth bass.
Some of the studies have been conducted under very simple laboratory con-
ditions, as in aquaria or other apparatus, but some of the studies on
bioenergetics and growth have also been conducted under rather natural
conditions in laboratory streams and ponds. In some important cases, we
have found close correspondence between the effects of reduced oxygen
concentration in aquarium studies of growth at maximum rations and its
effects under more natural conditions in laboratory streams and ponds.
Some of the biological responses of the fish studies were affected by
any appreciable reduction in dissolved oxygen below the air saturation
levels, whereas others were affected only at levels below about 50 per-
cent the air saturation levels.
This report was submitted in fulfillment of Grant No. 18050 DJZ between
the Environmental Protection Agency and Oregon State University.
Key Words: Oxygen standards, oxygen requirements of fish, Pacific
salmon, steelhead trout, largemouth bass.
111
-------
CONTENTS
CONCLUSIONS xiii
SUMMARY OF RECOMMENDATIONS xvii
GENERAL INTRODUCTION 1
METHODS, RESULTS, AND INTERPRETATION OF RESEARCH CONDUCTED 3
FROM SEPTEMBER 1, 1968 THROUGH AUGUST 31, 1971
Introduction 3
Aquarium Studies of Bioenergetics and Growth 3
of Salmon and Largemouth Bass
Respiration Chamber and Other Studies of 14
Bioenergetics and Growth of Coho Salmon
Experimental Pond Studies of the Bioenergetics 24
and Growth of Largemouth Bass
Laboratory Stream Studies of the Growth of Chinook Salmon 34
SUMMARY OF RESULTS OF RESEARCH CONDUCTED FROM 43
SEPTEMBER 1, 1955 THROUGH AUGUST 31, 1968
Introduction 43
Survival 43
Avoidance Reactions 46
Swimming Performance 47
Development 49
Bioenergetics and Growth 52
GENERAL DISCUSSION 59
SUGGESTIONS CONCERNING WATER QUALITY CRITERIA 63
FOR PROTECTION OF FISHERIES
RECOMMENDATIONS FOR FUTURE RESEARCH ON THE DISSOLVED 71
OXYGEN REQUIREMENTS OF FISHES
Lethal Levels 71
Effects on Reproduction 71
Effects on Growth of Juvenile Fishes 72
Effects on Swimming Performance and Activity 72
Avoidance Reactions 72
Respiratory and Oxygen Consumption Rates 73
Fish Populations in Natural Habitats 73
Research Priorities 73
APPENDIX I PUBLICATIONS AND THESES RESULTING FROM THIS RESEARCH 75
APPENDIX II A TENTATIVE LOGICAL SCHEME FOR IDENTIFYING RESEARCH 79
NEEDED FOR THE DEVELOPMENT OF DISSOLVED OXYGEN CRITERIA AND
STANDARDS
-------
CONTENTS
(Continued) Page.
APPENDIX III ONE POSSIBLE SYSTEM FOR DEVELOPING STANDARDS 91
APPENDIX IV TABLES FOR RESEARCH CONDUCTED FROM SEPTEMBER 1, 1°7
1968 THROUGH AUGUST 31, 1971
VI
-------
FIGURES
PAGE
Photograph showing one of the two sets of vessels used for 5
growth in this study.
Relationships between mean dissolved oxygen concentration and 9
growth rate of juvenile largemouth bass fed to repletion on
small, live fish for 14 to 30 days at temperatures from 10
to 29C. Growth rates are based on dry weights.
Relationships between dissolved oxygen concentration and 11
growth rate of juvenile chinook salmon fed unrestricted
rations of tubificid worms at temperatures from 8.4 to
21.7C. Growth rates of salmon are based on dry weights.
Influence of dissolved oxygen concentration on the food 12
consumption and growth rate of juvenile chinook salmon
held in aquaria at 12C and fed two fluctuating levels of
ration of tubificid worms (see text for details of pro-
cedure). Growth rates of salmon are based on dry weights.
Relationships between mean dissolved oxygen concentration 13
and food consumption and growth rates of juvenile chinook
salmon held in aquaria at 12 and 17C and fed two fluctu-
ating levels of ration of tubificid worms (see text for
details of procedure). Growth rates are based on dry
weights.
Relationships between dissolved oxygen concentration and 15
growth rate of juvenile coho salmon fed unrestricted
rations of tubificid worms at temperatures from 8.6 to
21.8C. Growth rates of salmon are based on dry weights.
Schematic diagram of one of six respirometers used to 16
determine oxygen consumption rates of coho salmon. The
left side of the styrofoam water bath has been removed
to show respirometer detail. Not shown is the variable
speed device used to change pump speed.
Photograph of some of the laboratory apparatus used in 17
bioenergetic studies. The styrofoam boxes (water baths)
at the left contained the respirometers. The styrofoam
boxes shown at the right were used in the growth
experiments.
Relationships between food consumption rate, energy and 20
material uses and losses, and dissolved oxygen concentration
for juvenile coho salmon held at 15C during summer.
VII
-------
FIGURES
(Continued) PAGE
10 Relationships between food consumption rate, energy and 21
material uses and losses, and dissolved oxygen con-
centration for juvenile coho salmon held at 15C during
fall.
11 Relationships between food consumption rate, energy and 22
material uses and losses, and dissolved oxygen concen-
tration for juvenile coho salmon held at 15C during
spring.
12 Schematic drawing of one of two experimental ponds used in 25
this study. Each pond was equipped with an observation
chamber, temperature control equipment, and an adjustable
standpipe to maintain the desired water level in the pond.
13 The experimental ponds shown with and without the plastic . 2^
cover. The degasser and other associated equipment were
housed in the small building.
14 Relationships between water temperature and growth rate of 31
individual largemouth bass reared in the experimental ponds
at near air-saturation and reduced (4 to 6 mg/1
below air-saturation) dissolved oxygen levels. The ponds
were stocked with an initial mosquitofish biomass of 170
g/pond.
15 The relationship between mean growth rate and rate of food 33
consumption of largemouth bass reared under various con-
ditions of dissolved oxygen, food density, and temperature,
in the experimental ponds.
16 Photographs of some of the nine laboratory streams used in 35
this investigation. The translucent plastic and metal
paddlewheel covers are in place in the lower photograph.
Shading material is shown draped over the streams.
17 The relationship between dissolved oxygen concentration aiid 38
growth rate of juvenile chinook salmon held for 10 days
in the experimental streams in experiments 3 and 4. The
open plot denotes test in which one fish was caught in
export trap for up to 48 hours and may not have fully
recovered.
18 Relationships between dissolved oxygen concentration and 39
growth rates of juvenile chinook salmon reared in the
experimental streams for 10 and 20 days in experiments
2 and 8.
Vlll
-------
FIGURES
(Continued) PAGE
19 The relationship between food density and growth rate of 41
juvenile chinook salmon held for 10 and 20 days in
laboratory stream experiments 2 and 7, when food density
was low and limiting food consumption and growth of the
salmon.
20 Relationships between dissolved oxygen concentration and 68
the normalized growth rate of juvenile largemouth bass
reared in aquaria and fed to repletion on live food at
temperatures ranging from 10 to 29C. Growth rates were
normalized on the basis that maximum growth occurred at
air saturation levels of oxygen.
21 Relationships between dissolved oxygen concentration and the 70
normalized growth rate of juvenile coho salmon reared in
aquaria and fed unrestricted rations of live food at
temperatures ranging from 9 to 22C. Growth rates were
normalized on the basis of determined or estimated growth
rates at air saturation levels of oxygen. The 18-20C
curve is based on many more experiments than the other
curves and is considered to be more reliable.
IX
-------
TABLES
No. Page
Text Tables
I The responses of various species of fish held under labora- 65
tory conditions to reductions of dissolved oxygen concen-
tration. The letters H (saturation or above), I (>4.0
mg/1, but much less than saturation} and L (<4.0 mg/1)
indicate the highest level of dissolved oxygen at which
the indicated response changed. The temperatures at which
the various experiments were conducted are close, but not
identical to those shown in the table headings.
Appendix Tables
I Initial and final weights, growth and food consumption 107
rates, and gross food conversion efficiencies of
juvenile largemouth bass held in 12-gal bottles at
different dissolved oxygen concentrations and tempera-
tures. The bass were fed to repletion on small fish.
II Initial and final weights, weight gained, food consumption 108
and growth rates, and gross food conversion efficiencies
of juvenile largemouth bass held for 10 days at 20C in
12-gal bottles. One, five, and ten fish were held in
separate bottles and fed to repletion on small fish.
All values are based on wet weights.
Ill Initial and final weights, growth and food consumption 109
rates and gross food conversion efficiencies of juvenile
chinook salmon held in 12-gal bottles at different
temperatures and dissolved oxygen concentrations.
The salmon received unrestricted rations of live tubificid
worms.
IV Experimental conditions, weights, food consumption rates, 110
growth rates, and gross food conversion efficiencies
for juvenile chinook salmon during cyclic ration feeding
studies. Ten fish were held in each test chamber.
V Initial and final weights, food consumption and growth 112
rates, and food conversion efficiencies of juvenile
coho salmon held in 12-gal bottles at various dissolved
oxygen concentrations and temperatures. The salmon
received an unrestricted supply of live tubificid worms.
XI
-------
Appendix Tables
(Continued)
No.
VI Food consumption, growth rates, and food conversion 113
efficiencies for juvenile coho salmon held individually
in 1.5 liter plexiglas containers and fed various
rations (percent of the wet body weight of the individual
fish) of housefly larvae for 14 days. During the three
seasons of the study, the temperatures was maintained at
15C and the dissolved oxygen concentration was kept at
3, 5, or 8 mg/liter.
VII Mean and range of temperature and dissolved oxygen concentra-
tion, prey density, and lengths, weights and growth rates
of largemouth bass for the pond experiments.
VIII Initial and final densities, and sample weights and caloric
values of mosquitofish used in the pond experiments and
estimated food consumption rates of bass.
IX Statistical comparison between the growth rate values of 117
bass reared at high and low dissolved oxygen levels in
the experimental ponds. All values are based on wet
weights.
X Initial and final weights, growth rates and biomass of 118
juvenile chinook salmon held in laboratory streams and
confronted with different food densities at different
oxygen concentrations and temperatures.
XI Statistical evaluation of the growth rates of coho salmon 121
held at high, intermediate, and low dissolved oxygen levels
in laboratory streams. Only experiments in which growth
rates appeared dependent on dissolved oxygen concentration
were compared. All values are based on dry weights.
XII
-------
CONCLUSIONS
1. Under laboratory conditions, the juvenile centrarchids and salmonids
tested were usually capable of surviving for indefinite, prolonged
periods of time at dissolved oxygen concentrations as low as 2 mg/1 and
less, except at relatively high temperatures.
2. Under certain laboratory conditions, juvenile centrarchids and
salmonids were capable of avoiding low oxygen concentrations well above
lethal levels, but these fish did not avoid some higher concentrations
that have been shown to have adverse sublethal effects.
3. Any considerable reduction of dissolved oxygen concentration from
the air-saturation level resulted in some reduction of the maximum
sustained swimming speeds of juvenile coho and chinook salmon at
temperatures between 10 and 20C; juvenile largemouth bass were so
affected only by reductions of dissolved oxygen to levels below 5
or 6 mg/1 at 25C.
4. Any reduction from the air-saturation level of the dissolved oxygen
concentration to which embryos of coho and chinook salmon and steelhead
trout were exposed throughout their development resulted in some
reduction in size of the hatching fry and some delay of hatching, but
the percentage of embryos hatching at normal temperatures was demon-
strably impaired under the experimental conditions in the laboratory
only at levels below 3 mg/1; the size of the hatching fry was a function
also of water velocity and increased with increase of water velocity.
5. The maximum sizes attained by salmonid fry of different species at
the time of complete absorption of the yolk sacs were often reduced, in
varying degrees, by reduction of the oxygen concentration to which the
alevins were exposed, but this effect was never nearly as pronounced as
was the reduction in initial size of fry hatching from eggs exposed
continuously to the same low oxygen concentration.
6. Increase of carbon dioxide concentration to levels likely to occur
in waters whose oxygen content is moderately reduced by decomposition
of organic matter had little or no effect on the resistance to low
oxygen concentrations, on the swimming ability, and on the embryonic
development of fish species tested; furthermore, effects of higher
carbon dioxide concentrations on the maximum sustained swimming speeds
of juvenile coho salmon were much less pronounced at very low oxygen
concentrations than at high oxygen concentrations; acclimation to high
levels of free carbon dioxide was found to be rapid.
7. Except at relatively low temperatures, any considerable reduction of
dissolved oxygen from air-saturation levels usually resulted in some
reduction of the food consumption and growth rates of juvenile coho and
chinook salmon and largemouth bass provided with unrestricted food
Xlll
-------
rations in laboratory aquaria; when rations were uniformly, restricted
and small, the growth of coho salmon was not so affected, except
perhaps at very low levels of dissolved oxygen.
8. When food rations were unrestricted, wide fluctuations of dissolved
oxygen between very low and high levels had an adverse effect on the
growth of both coho salmon and largemouth bass, the impairment of
growth being as great as that caused by continuous exposure of the
fish to low oxygen concentrations not far above the low levels to which
the fish subjected to the fluctuating concentrations had been exposed.
9. The dependence of the food consumption and growth of largemouth bass
in laboratory aquaria on dissolved oxygen concentrations above very
low levels disappeared abruptly with reduction of temperature from
20 to 15C; coho and chinook salmon showed a less pronounced temperature
effect, or a more gradual decline of the critical level of dissolved
oxygen with reduction of temperature.
10. In art-ificial ponds at moderately high temperatures, the growth
rates of juvenile largemouth bass feeding more or less naturally on
mosquitofish were dependent on the availability of the food, yet were
reduced by reduction of the oxygen concentration about as much as were
the growth rates of bass in aquarium tests in which rations were un-
restricted and growth was much more rapid than it was in the ponds. The
noted agreement between the results of the pond and aquarium tests, as
well as other related data and bioenergetic (energy-balance) compu-
tations, indicate that the metabolic rates of the bass in the ponds
are high and virtually independent of food-organism density, their
activity increasing as food availability, food intake, and the specific
dynamic action of the food decrease.
11. As in aquarium experiments, the growth of juvenile chinook salmon
held in laboratory streams at 9-13C and feeding on organisms produced
in these streams was reduced by reductions of oxygen concentration
from the air-saturation level, when food availability and growth rates
were relatively high; they were virtually independent of oxygen con-
centration when food availability and growth rates were low- In view
of the apparent dependence of the critical dissolved oxygen levels
upon food availability and intake in the laboratory streams, close
correspondence of the effects of dissolved oxygen reduction on the
growth of salmon in the streams and in laboratory aquaria with unlimited
food cannot be assumed, particularly when temperatures are high.
12. Although adverse effects of reduced oxygen concentrations on
embryonic survival and growth sometimes may result in serious reduction
of fish production, only the effects on growth rates, determined
experimentally, can now be reasonably relied upon in arriving at
estimates of maximum reductions of oxygen concentration that would
result in impairment (percent reduction) of fish production in nature
not exceeding some particular degree of impairment that may be deemed
xiv
-------
acceptable. Such estimates may be useful in arriving at water quality-
standards intended for the protection of the natural production of
particular species of fish.
xv
-------
SUMMARY OF RECOMMENDATIONS
1. If dissolved oxygen criteria are to be adopted for wide (e.g.,
Nationwide or worldwide) application in the protection of freshwater
fisheries in general, the adoption of criteria proposed by Doudoroff and
Shumway (1970) is recommended. These criteria (see Appendix III for full
details) are based on the pertinent world literature. They are in the
form of curves relating "acceptable" dissolved oxygen minima deemed
compatible with each of several different levels of protection of fisher-
ies to the estimated natural seasonal minima for the waters to which the
criteria apply, in a given season of the year.
2. If, on the other hand, the criteria adopted are to be designed for
the protection of the production of particular species of fish and
based on the assumption that the degree of impairment of this production
at reduced oxygen concentrations is adequately indicated by the reduction
of growth rates of the fish under experimental conditions when rations
are unrestricted, the following criteria (acceptable dissolved oxygen
minima) pertaining to largemouth bass and coho salmon (the species
emphasized in our studies) are recommended:
A. If no reduction of production rates from the rates possible at high
(near-saturation) levels of dissolved oxygen is to be accepted as
permissible at any time:
(1) For largemouth bass, no reduction of dissolved oxygen concen-
tration from the high levels at temperatures above 15C, and a minimum
concentration of 4.2 mg/1 at temperatures near and below 15C.
(2) For coho salmon, no reduction of dissolved oxygen concentration
from the high levels at any temperature.
B. If only a 10 percent reduction of production rates from the rates
possible at high oxygen concentrations is to be deemed the maximum
acceptable reduction at any time:
(1) For largemouth bass, minimum dissolved oxygen concentrations
of 3 mg/1 at temperatures near and below 15C, and 5 mg/1 at
temperatures near and above 20C.
(2) For coho salmon, 5 mg/1, except at unusually high temperatures,
near 22C, at which a minimum requirement of 5.5 or 6 mg/1 is
indicated.
C. If a 20 percent reduction of production rates from the rates
possible at high (near-saturation) levels of dissolved oxygen is to
be deemed the maximum acceptable reduction at any time:
xvi i
-------
(1) For largemouth bass, minimum dissolved oxygen concen-
trations of 2.5 mg/1 at temperatures near and below 15C and 4
mg/1 at temperatures near and above 20C.
(2) For coho salmon, about 4 mg/1, except at unusually high
temperatures, near 22C, at which a minimum requirement of 5 mg/1
is indicated.
The rationale of these proposed criteria is fully explained and assumptions
on which they are based are critically examined in the section of this
report entitled "Suggestions Concerning Water Quality Criteria for Pro-
tection of Fisheries." It is pointed out there that, although dissolved
oxygen minima in streams where coho salmon spawn are not likely to occur
when coho salmon embryos or larvae are present, effects of reduced oxygen
concentrations in these streams on coho salmon reproduction may often be
more important or critical'than the effects on juvenile growth, because,
among other reasons, oxygeiji concentrations in water percolating through
streambed gravels where coho salmon eggs are deposited are often much
lower than those in water flowing over the gravels.
xvi 11
-------
GENERAL INTRODUCTION
There will continue to be a very real need for information on the
dissolved oxygen requirements of fish, so long as there is concern for
the protection of fisheries by means of water quality standards.
And in any period of time, regardless of the information available,
there is and will be the problem of just how this laboratory and other
information is to be interpreted in order to determine reliable dis-
solved oxygen standards that are adequate to protect fishery resources
in natural waters. And still further, there is always the problem of
identifying the most important research remaining to be pursued, for
theie are limitations of time, talent, and money that we must face in
pursuit of our pollution control objectives. This report presents a
rather substantial amount of information on the dissolved oxygen
requirements of several species of freshwater fish, as determined under
laboratory conditions. But it goes beyond the ordinary limits of such
research reports to include various materials—as will be explained—
that seem to us to be necessary in maximizing the value of existing
information and future research for water pollution control.
This terminal report nominally covers the methods, results, and inter-
pretation of research we have conducted from September 1, 1968 through
August 31, 1971, on the dissolved oxygen requirements of freshwater
fishes. But the interpretation of these results and recommendations as
to dissolved oxygen standards and research yet needed derive to a con-
siderable extent from the results of research we conducted during the
period from September 1, 1955 through August 31, 1968, with support
from predecessor agencies of the Environmental Protection Agency.
Thus, we have included in this report a general summary of the
results and interpretation of this earlier research. Whereas the
results of the more recent research are presented in considerable
detail in text figures and appendix tables (Appendix IV), no figures
or tables are included for the earlier work, which has been already
reported in detail in the publications and theses listed in Appendix
I. Nearly all literature citations in the body of this report can be
found in Appendix I. All others are given in footnotes.
After major sections on recent research and earlier research, there
follows a discussion of the possible significance of our laboratory
results as these may relate to the oxygen requirements of fish in
their natural environments. Next in sequence are major sections in
which we make suggestions concerning water quality criteria for
the protection of fisheries and recommendations for future research
on the dissolved oxygen requirements of fishes.
Knowledgeable biologists often disagree strongly as to the kinds of
research most needed. This is in part because of their different
backgrounds and the different importances they assign to various
environmental factors and responses of the animals. But much of such
-------
disagreement derives from failure to identify alternative assumptions
or propositions crucial to consideration of the problem. Once this
has been done, one can logically deduce, for any set of assumptions,
the research most necessary to resolve the problem. We have attempted
in Appendix II to develop a logical scheme for identifying, given
different assumptions, the kinds of research most needed. This sort
of approach should prove of value not only in planning research but
also in setting standards, as it will identify the assumptions
involved in either case. It should prove of value in considering not
only oxygen problems but also other kinds of pollution problems.
The matter of setting standards poses several dilemmas. As indicated
above, we have included in the body of this report some suggestions
on this problem. In addition, in Appendix III, we have reprinted—
with permission of FAO--a scheme Doudoroff and Shumway (1970) proposed
for setting oxygen standards. We are not recommending this scheme,
which like any scheme has difficulties. But we do believe that those
concerned with water quality regulation should give it careful atten-
tion, because it represents one of the few viable alternatives for
setting oxygen standards for the protection of fisheries.
-------
METHODS, RESULTS, AND INTERPRETATION OF RESEARCH CONDUCTED FROM
SEPTEMBER 1, 1968 THROUGH AUGUST 31, 1971, ON THE BIOENERGETICS AND GROWTH
OF SALMON AND LARGEMOUTH BASS IN AQUARIA, RESPIRATION' CHAMBERS, EXPERIMENTAL
PONDS, AND LABORATORY STREAMS
INTRODUCTION
The presentation in this major part of this report covers the methods,
results, and interpretation of research we have conducted during the past
three years, September 1, 1968 through August 31, 1971, the period nomin-
ally covered by this terminal report. As indicated in the general intro-
duction to the overall report, however, we will, in the major part follow-
ing this one, include a general summary of our research on the oxygen
requirements of fish for the period September 1, 1955 through August 31,
1968. But consideration of research conducted during the past three years
will be in greater detail than consideration of the earlier research. We
are doing this because this report is nominally for the past three years
of research, the earlier research has been previously reported in detailed
progress reports and publications, and because the procedures of the past
three years have led to results that are in some ways more easily
interpreted with regard to the oxygen requirements of freshwater fish in
nature.
This present major part of this report will be presented in four sections:
Aquarium Studies of Bioenergetics and Growth of Salmon and Largemouth Bass
as Influenced by Dissolved Oxygen Concentration; Respiration Chambers and
other Studies of Bioenergetics and Growth of Coho Salmon as Influenced by
Dissolved Oxygen Concentration; Experimental Pond Studies of the Bioenergetics
and Growth of Largemouth Bass as Influenced by Dissolved Oxygen Concentration;
and Laboratory Stream Studies of the Growth of Chinook Salmon as Influenced
by Food Density and Dissolved Oxygen Concentration. Because the methods
employed by research presented in each of these four sections are in some
ways peculiar to that research, a methods subsection will be included in
each of these four sections.
AQUARIUM STUDIES OF BIOENERGETICS AND
GROWTH OF SALMON AND LARGEMOUTH BASS
AS INFLUENCED BY DISSOLVED OXYGEN CONCENTRATION
Experimental Apparatus, Materials, and Procedures
Experimental Apparatus
The purpose of the apparatus used in this investigation was to provide
measured flows of water of controlled temperature and dissolved oxygen
concentration to a series of sealed chambers containing test fish. The
two identically constructed and independently operated sets of experimental
gear, each containing six test chambers, were located in a constant-temperature
-------
room, provided with filtered water from a small springfed stream, and
illuminated 16 hours daily by timer-controlled fluorescent lights.
Pyrex glass bottles, each having a capacity of 45 liters, were used as
test chambers. This apparatus was similar to apparatus used by Herrmann,
et al. (1962), Fisher (1963), and Stewart et al. (1967). One set of
six test chambers and associated control equipment is shown in Figure 1.
Water from the main supply was distributed from two const ant-level head-
boxes to the two sets of experimental chambers. In the headboxes,
incoming water was vigorously aerated with compressed air and heated to
the desired temperature by a thermostatically controlled stainless-steel
immersion heater. From each headbox, warmed water passed through tygon
plastic tubing into six columns constructed of 50 mm ID glass pipe.
Water entered each column through a glass tube inserted through the
stoppered base and extending to its upper one-third. Water of the
desired oxygen concentration left each column near the base and passed
through a flow-adjustment stopcock, a ball-displacement flowmeter, and a
250 ml BOD bottle used for water sample collection, and into the test
chamber at a rate of near 300 ml/min, through a glass tube inserted
through the stopper and extending to near the bottom of the test chamber.
After flowing out through a glass tube extending into the neck of the
test vessel, the water passed through a second 250 ml BOD bottle and was
discharged from the system via the floor drain.
Compressed oxygen and nitrogen gases were used to obtain the desired '
dissolved oxygen concentrations in the water leaving the glass columns.
Two-stage pressure regulators were used to control the discharge of gases
from the compressed gas cylinders into a gas manifold constructed of
threaded and capped steel pipe tapped with brass gas valves. Two such
manifolds were used, one for oxygen and one for nitrogen. Gas from the
manifold flowed through one of twelve ball-displacement gas flowmeters
and entered each glass column, where it was dispersed into bubbles by an
aquarium airstone placed near the base. The gas bubbles streamed upward
to form a counterflow to the downward flow of water and effectively brought
oxygen concentrations to the desired levels.
Experimental Materials
The fish tested in these experiments were juvenile largemouth bass seined
from ponds in the Willamette Valley, juvenile coho salmon seined from
the upper Yaquina River near Nashville, and juvenile chinook salmon
seined from the Sixes River located on the southern Oregon coast.
f
Once obtained, the stocks of fish used in experiments were held in a
continuously illuminated, 189-liter aquarium at near the test temperature
and'fed a diet of live food organisms. Largemouth bass were fed large
quantities of salmonid fry and tubificid worms; coho and chinook salmon
were provided tubificid worms only. The test fish were held under these
conditions for a minimum of one week prior to their removal and use in
experiments.
-------
I
Figure 1. Photograph showing one of the two sets of vessels used for growth in this study.
-------
Salmonid fry used as food for largemouth bass were either chinook
salmon or coho salmon obtained as fry, or were steelhead trout obtained
as eggs, which were then incubated, hatched, and reared to the desired
size. The salmonid fry and eggs were obtained from various hatcheries
operated by the Oregon State Game Commission or the Fish Commission of
Oregon. The fry were held in outdoor tanks and fed Oregon Moist Pellet.
Tubificid worms used as food were obtained from the Roaring River Trout
Hatchery of the Oregon State Game Commission. These worms were held in
outdoor troughs prior to use as food organisms.
Experimental Procedures
Four days prior to the start of each experiment, about one-half the
available stock of fish was removed from the 189-liter aquarium and sorted
into seven groups of an appropriate number of fish of nearly equal size.
In most experiments, the fish in each group were lightly anesthetized with
tricane methanesulphonate (MS 222), individually marked by the cold
branding technique described by Ellis (1968)*, weighed, and measured. In
other experiments, the fish were not individually marked. All weights
taken during the study were recorded to the nearest 0.01 g and lenths to
the nearest 1.0 mm, unless otherwise stated.
Prior to the start of an experiment, six of the seven groups of test fish
were introduced into the experimental apparatus and held for four days
at dissolved oxygen concentrations near to those at which they were to be
tested. The seventh group of fish was placed in a small aquarium and held
for the same period of time at near the air-saturation level of oxygen.
All seven groups of fish were held at the selected test temperature during
the four-day adjustment period. Test fish were fed daily a near-maintenance
ration of food; all seven groups of fish received the same amount of food
each day. With the exception of one group in each experiment with large-
mouth bass, salmonid fry were used as food organisms in the test with
largemouth bass, and tubificid worms were used as food for the salmonids.
The excepted group of largemouth bass were fed tubificid worms. Test
fish were not fed for 24 hours prior to the start of each experiment.
This allowed for the elimination of most of the food and fecal material
from their digestive tract before they were reweighed.
At the start of each experiment, the groups of fish acclimated for four
days were removed from the test vessels and aquarium and lightly
anesthetized with MS 222. They were then individually weighed and measured.
The extra group of fish from the aquarium was dried to a constant weight
in an oven at 70C for determination of the ration of dry weight to wet
* Ellis, R. H. 1968; Effects of kraft pulp mill effluent on the
production and food relations of juvenile chinook salmon in
laboratory streams. M.S. Thesis. Oregon State University,
Corvallis. 55p.
-------
weight. This ratio was used in computing the initial dry weight of all
fish used in that experiment.
The test fish were fed shortly after being returned to the test vessels.
With the exception of three experiments with chinook salmon, the rations
provided exceeded by a small margin the maximal amount of food that could
be consumed by the fish during a 24-hr period and are termed unrestricted
rations, according to the definition of Doudoroff and Shumway (1970).
In the excepted tests, restricted rations were provided the chinook salmon
five out of seven days; on the other two days of each week, unrestricted
rations were provided. The test fish were normally fed each day in the
morning.
In order to maintain the desired experimental conditions, it was neces-
sary to check the apparatus twice each day between 7:00 and 9:00 am, and
between 4:00 and 6:00 pm, in order to make any needed adjustments. During
these checks, the gas and waterflows, temperature, and oxygen concentra-
tions were recorded. Oxygen concentrations near and below the air-
saturation level were determined by the azide modification of the iodometric
method (American Public Health Association, et al., 1965)*. Those above
the air-saturation level were determined by the Pomeroy-Kirschman-
Alsterberg modification.
Oxygen consumption rates of test fish were determined two days prior to
the termination of some experiments with largemouth bass and coho salmon.
Water samples for dissolved oxygen analyses were collected every two hours
during the 24-hour oxygen consumption test period. Oxygen consumption
rates of the fish were computed from differences of oxygen concentration in
the inflow and outflow water sample bottles of each test vessel and
expressed as milligrams oxygen consumed per gram dry weight of fish per
hour (mg 02/g-hr).
Results and Interpretation
Food consumption and growth rates were determined for juvenile large-
mouth bass, chinook salmon, and coho salmon held at various constant
dissolved oxygen concentrations and temperatures and fed unrestricted
rations of live food organisms. Appendix Tables 1, 3, and 5 list the
total initial and final wet and dry weights, food consumption and growth
rates and gross food conversion efficiencies for largemouth bass, chinook
salmon, and coho salmon, respectively, and the dissolved oxygen
* American Public Health Association, American Water Works Association,
and Federation of Sewage and Industrial Wastes Association.
1965. Standard methods for the examination of water, sewage, and
industrial wastes. 12th ed. New York, 769p.
-------
concentrations and temperatures at which the fish were held. Appendix
Tables 1, 3, and 5 also present the number of fish held in eaoh test
ahanibev, the date the experiment was initiated, and its length in days.
The influence of dissolved concentration on the food consumption and growth
of juvenile chinook salmon fed at low and moderately low levels on a
cyclic basis (ration size being changed daily) was determined at 12 and
17C. The total initial and final wet and dry weights, food consumption
and growth rates, and gross food conversion efficiencies for these salmon
are presented in Appendix Table 4, along with the temperature, ration
level, and dissolved oxygen concentration tested in each experiment. In
the experiments reported herein, unless otherwise stated, growth rates are
expressed in milligrams gained per gram mean weight of fish per day (rag/
g/day) and food consumption rates are expressed in milligrams food con-
sumed per gram mean weight of fish per day (mg/g/day).
i
Largemouth Bass
Figure 2 presents the results of experiments conducted on the influence
of reduced dissolved oxygen concentration on the growth rate of large-
mouth bass, held 17 to 30 days and fed to repletion on small live fish,
at temperatures of about 10, 15, 20, 24, and 29C. At the temperatures of
29, 24, and 20C, dependence of growth rate of the largemouth bass on
dissolved oxygen concentration at all oxygen levels below the air-saturation
level was demonstrated. Similar relationships may be seen between food
consumption rate and dissolved oxygen concentration at these moderate to
high temperatures (Appendix Table 1J. At 15C, dependence of growth rates
on dissolved oxygen concentration was apparent only at levels below about
3.5 mg/1. Even less oxygen dependence was noted between growth rate of
largemouth bass and dissolved oxygen concentration at IOC, the lowest
temperature tested. Thus, a critical temperature above which growth rates
of largemouth bass become markedly susceptible to depression by moderate
reduction of the dissolved oxygen concentration appears to be between 15
and 20C. ,
An experiment was conducted on the influence of the number of fish held in
a test chamber on the food consumption and growth rates of largemouth bass.
One, five, and ten bass were placed in each of two test chambers and fed
unrestricted rations of small live fish for 10 days at 20C. The initial
and final weights, food consumption and growth rates, and gross food
conversion efficiencies for these largemouth bass are presented in
Appendix Table 2. The roean growth rates of one, five, and ten bass held in
the 12-gal bottles and fed to excess were 29.9, 23.7, and 25.9 mg/g/day,
respectively. Thus, largemouth bass held individually In aquaria appear
to grow somewhat better than those held at densities of Tive or ten fish
per aquarium.
Chinook Salmon
The results of experiments on the influence of dissolved oxygen concentra-
tion on the growth of juvenile chinook salmon held for 20 days and fed
-------
70
^ 60
>
<
Q
N»
K5 50
X
O
Id
I-
CD
40
30
20
10
29-3 C (SEPT)
24-1 C (SEPT)
20-0 C (JUL-AUG)
15-0 C (APR-MAY)
15-0 C (JUL-AUG)
10-0 C (APR-MAY)
I I
2 3 456789 1011
DISSOLVED OXYGEN (M6/L)
Figure 2. Relationships between mean dissolved oxygen concentration
and growth rate of juvenile largemouth bass fed to repletion on
small, live fish for 14 to 30 days at temperatures from 10 to 29C.
Growth rates are based on dry weights.
-------
unrestricted rations of tubificid worms at constant temperatures
ranging from 8.4 to 21.7C are shown in Figure 3. In experiments con-
ducted at temperatures of 21.7, 18.6, and 17.8C, the growth rate of
Chinook salmon appeared dependent on dissolved oxygen concentration at
all levels below air saturation. Experiments conducted at 13.2, 13.0,
and 8.4C showed little or no dependence of growth rate on dissolved
oxygen concentration, until the concentration was depressed to levels
below about 5 to 6 mg/1. The greatest independence of dissolved oxygen
concentration occurred at 8.4C, the lowest tmperature tested. Chinook
salmon reared at near air-saturation levels of dissolved oxygen grew more
rapidly at 17.8C than did salmon reared at higher and lower temperatures.
It is interesting to note that chinook salmon reared at 18.6C in July
grew quite poorly in comparison to those reared at 17.8C a month earlier
in June. A similar reduction in growth rate between experiments conducted
in June and July was observed in studies with coho salmon, the results of
which will be reported in the following section. ,
The influence of dissolved oxygen concentration onithe food consumption and
growth rates of juvenile chinook salmon fed tubificid worms on a weekly
cycle of different daily rations varying from near starvation to excessive
food was determined at 12 and 17C. The results of these experiments are
presented in Figures 4 and 5 and in Appendix Table 4. As may be seen in
these figures, the food consumption rate of chinook salmon fed low and
moderately low cyclic rations tended to decrease with reductions in
dissolved oxygen concentration at both temperatures tested. The growth
rate of the salmon showed little or no decline with reduction in dissolved
oxygen concentration below the air-saturation level. In fact, chinook
salmon reared at the low cyclic rations at both temperatures in experiment
2 (Fig. 5) showed slight increases in their growth rates with decreasing
dissolved oxygen concentration. This may in part be due to the fact that
the salmon reared at the reduced dissolved oxygen levels were less active
than those reared at air saturation, thus directing into growth energy
and materials that would have been lost through activity.
In the experiments with cyclic rations (Appendix Table 4), the chinook
salmon received food in excess on two consecutive days each week. On
those days, food consumption was found to be dependent on dissolved oxygen
concentration, with the greatest reduction occurring during the second
day. Depression of the food consumption rate on the first day at reduced
oxygen concentration was probably due to a 'direct effect on appetite.
The somewhat greater depression of food consumption rate observed on the
second day appeared to be due to an indirect effect on appetite through a
direct reduction of the rate of food digestion.
Coho Salmon
Results of experiments conducted on the effect of reduced dissolved
oxygen concentration of the food consumption and growth of juvenile
coho salmon held for 13 to 20 days and fed unrestricted rations of tubificid
worms at temperatures ranging from 8.6 to 21.6C are presented in
10
-------
17-8 C (JUNE)
13-2 C (JUNE)
O
13-0 C (MAR-APR)
18-6
(JULY)
8-4 C (MAR-APR)
2I-7C (JULY)
7 8 9 10 II 12
DISSOLVED OXYGEN (MG/L)
Figure 3. Relationships between dissolved oxygen concentration and
growth rate of juvenile chinook salmon fed unrestricted rations of
tubificid worms at temperatures from 8.4 to 21.7C. Growth rates of
salmon are based on dry weights.
11
-------
z
o
3 CD
S5
O
o w
Q <
O o
O
90
80
70
60
50
40
LOW RATION
HIGH RATION
l I I
UJ
o —
cr
40
30
20
10
4
L__l
8 9 10 II
DISSOLVED OXYGEN (MG/L)
Figure 4. Influence of dissolved oxygen concentration on the food con-
sumption and growth rate of juvenile chinook salmon held in aquaria at
12C and fed two fluctuating levels of ration of tubificid worms (see text
for details of procedure). Growth rates of salmon are based on dry weights.
12
-------
UJ
H
oc
z
o
a.
(O
z
o
o
Q
O
O
100
90
80
60
50
12 C I7C
O D LOW RATION
• • HIGH RATION
12 C
j i i
UJ
h-
23
f- o
£ z
o ~
a:
o
30
20
10
3 . 4
DISSOLVED
5 6
OXYGEN
12 C
17 C
789
(MG/L)
10 II
Figure 5. Relationships between mean dissolved oxygen concentration
and food consumption and growth rates of juvenile chinook salmon held
in aquaria at 12 and 17C and fed two fluctuating levels of ration of
tubificid worms (see text for details of procedure). Growth rates are
based on dry weights.
13
-------
Figure 6 and Appendix Table 5. In general, the growth rate of coho
salmon proved dependent on dissolved oxygen concentration at or only
moderately below air-saturation levels at all temperatures tested. The
growth rates of the salmon reared in May at 8.6C and in July at 18C,
however, exhibited only minor depressions at dissolved oxygen concentra-
tions as low as 5 to 6 mg/1. Chinook salmon reared at air-saturation
levels of oxygen grew more rapidly in experiments conducted at temperatures
near 18C than at other temperatures (Fig. 3); thus, higher and lower
temperatures appeared to depress the growth rate of chinook salmon
reared at air-saturation levels of dissolved oxygen.
As was noted above for chinook salmon, season of the year appears to
play an important role in controlling the food consumption and growth
rates of coho salmon. Coho salmon reared in June at 18.3C exhibited
growth rates ranging from 52 to 65 mg/g/day, coho salmon reared in July
at 18C grew at rates near 23 to 34 mg/g/day, and those reared in October
at 18C grew at rates ranging from 10 to 37 mg/g/day (Fig. 6). The same
general relationship can be observed by comparing the growth rates of
coho salmon reared at 12.9C in May with that of those reared at 13C in
October. Similar differences in growth rates of coho salmon can be
seen between those reared at near 21C in June and those reared at the
same temperature in July.
RESPIRATION CHAMBER AND OTHER STUDIES
OF BIOENERGETICS AND GROWTH OF COHO
SALMON AS INFLUENCED BY DISSOLVED
OXYGEN CONCENTRATION
Experimental Apparatus, Materials, and Procedures
Experimental Apparatus
Several types of test chambers were used in these experiments. A set
of six respiration chambers, each with a cylindrical test compartment,
was used in experiments on oxygen uptake rates, in which the fish were
forced to swim continuously at nearly constant water velocities. The
water velocity in each chamber could be varied from 0.3 to 0.7 feet per
second by means of a small centrifugal pump. Figure 7 is a schematic
drawing of one respiration chamber.
Six square aquaria made of styrofoam, each containing 12 liters of water,
were used for these growth experiments. Each aquarium was subdivided
with perforated plexiglas partitions into eight compartments. Each
compartment contained about 1.5 liters of water. The water in each
aquarium was renewed continuously, at a rate of about 200 ml/min. A
manifold and plastic tubes distributed the water to the compartments of
each aquarium. The styrofoam aquaria may be seen in the photograph
presented in Figure 8.
14
-------
70 r
0 60
to
i 5°
%.<
H 40
*
O
30
20
10
18-3 C (JUNE)
-21-8 C (JUNE
" 12-9 C (MAY
m 8-6 C (MAY)
18-0 C (JUL)
L 13-0 C (OCT
18-0 C (OCT
21-6 C (JUL)
6
7 8 9 10 II 12
DISSOLVED OXYGEN (M6/L)
Figure 6. Relationships between dissolved oxygen concentration and
growth rate of juvenile coho salmon fed unrestricted rations of
tubificid worms at temperatures from 8.6 to 21.8C. Growth rates of
salmon are based on dry weights.
15
-------
STYROFOAM
WATER BATH
FLUSHIN8
INLET
COUNTER-CURRENT
HEAT EXCHAN8ER
Figure 7. Schematic diagram of one of six respirometers used to determine oxygen consumption
rates of coho salmon. The left side of the styrofoam water bath has been removed to show
respirometer detail. Not shown is the variable speed device used to change pump speed.
-------
Figure 8. Photograph of some of the laboratory apparatus used in bioenergetic studies. The
styrofoam boxes (water baths) at the left contained the respirometers. The styrofoam boxes shown
at the right were used in the growth experiments.
-------
Six, plexiglas chambers, each with two 1-liter compartments, were used
for food assimilation efficiency studies. The water in these chambers
was not circulated or renewed.
Dissolved oxygen concentrations of 8, 5, and 3 mg/1 were maintained in
each experiment. Two chambers or aquaria--each having eight compartments-
were maintained at each concentration in the growth studies. In the
oxygen uptake and growth experiments, the desired oxygen levels were
maintained by passing the incoming water through glass columns having a
counterflow of nitrogen. In the food assimilation efficiency tests, the
dissolved oxygen concentration was controlled by continuously bubbling
an air-nitrogen mixture through the water in each test chamber.
Experimental Material
The test fish used in these experiments were juvenile coho salmon col-
lected periodically throughout the year from the Yaquina River near
Nashville, Oregon. The size of salmon used in each experiment ranged
from fry, recently emerged from the gravel, to fingerlings about one
year old but not yet showing evidence of smolting. Once collected, the
test fish were transported to the laboratory and placed in an aquarium
and held at 15C for at least two weeks. During the two-week tempera-
ture adjustment period and during experiments, the salmon were fed live
housefly larvae.
Experimental Procedures
After the two-week temperature adjustment period, the fish were held
for at least nine days in the compartmented styrofoam aquaria (one fish
per compartment). During this period, they were sparingly fed housefly
larvae and were exposed daily for twelve hours to artificial illumination
alternating with twelve hours of darkness. From the ninth to the four-
teenth day of a 17-day period for acclimation to test conditions, the
fish to be used in growth experiments were fed daily at the same rate
they would receive during the growth tests. These salmon were then
starved for two days, weighed and measured, and returned to the test
chambers for an additional 24 hours before the tests proper were begun.
In preparation for the food assimilation tests, salmon were held individu-
ally in the compartmented styrofoam aquaria under test conditions and
fed sparingly for a total of 14 days, and then they were deprived of
food for two days, prior to initial weighing and transfer to the plexiglas
test chambers.
Fish to be used in determination of standard metabolic rates and specific
dynamic action of consumed food were transferred from the compartmented
styrofoam aquaria to the respirometers after nine days of acclimation
to the test conditions. In the respiration chambers, they were fed
Sparingly for five days and then deprived of food for two days before
weighing and for one more day thereafter before the beginning of the
experiments proper.
18
-------
Four types of tests were performed with individual fish in the various
types of experimental chambers. These included measurements of growth,
food assimilation, standard metabolism and specific dynamic action of
consumed food.
Growth. Each growth experiment consisted of 14 days of feeding in
the compartmented styrofoam aquaria plus three days during which the
fish were deprived of food before their reweighing at the end of the
experiment. Daily records were kept of weights of food consumed by each
fish and the experimental conditions of temperature and dissolved oxygen.
Caloric values of samples of fish similar to those to be used in an
experiment were initially determined. At the conclusion of an experiment,
caloric determinations were made on all test fish. Caloric values of
samples of the food fed were also determined.
Food assimilation efficiency. In these experiments, the fish were
placed in the test chambers immediately after their initial weighing and
were fed 24 hours later. After this they were held in the chambers for
four days without food and their waste materials were allowed to accumu-
late. Each liter of water was then analyzed for ammonia nitrogen and
chemical oxygen demand, and this data was converted to caloric value
equivalents.
Standard metabolism. During these tests, the fish in the respir-
ation chambers were deprived of food and were forced to swim for one-
hour periods at each of several velocities between 0.3 and 0.7 ft/sec.
Their oxygen consumption rates were measured during these periods, and
after sufficient tests, the data were plotted on semilog graph paper,
with swimming velocity and oxygen consumption rate as the coordinates.
The oxygen consumption at zero velocity was then determined by extrapo-
lation and taken to be the standard metabolic rate.
Specific dynamic action. These tests were performed in the
respiration chambers used for the determination of standard metabolism.
The baseline oxygen consumption rate of the fish was determined by
making measurements every other hour during the two days of starvation
that followed their five-day retention in the respirometer on restricted
rations. They were then weighed and measured and returned to the
respirometers for 24 hours. After this, the salmon were fed, and their
oxygen consumption rate determined hourly until it returned to the base
line. The total oxygen consumed over and above baseline consumption was
attributed to specific dynamic action of the food (SDA).
Results and Interpretation
The data obtained from aquarium and respiration chamber experiments on
the food consumption, growth, and bioenergetics of juvenile coho salmon
are presented in Figures 9, 10, and 11, and in Appendix Table 6. The
energy budgets shown in the figures were developed from all the data
(after converting it to caloric values) obtained from the measurements of
19
-------
0 20 40 60 80 100
0 20 40 60 80
N
-I
=> 60
40
Iti
z
Ul
20 40 60
AC* FOOD CONSUMPTION
Aw- WASTE
AG» GROWTH
Ap+AA- S. D. A. + ACTIVITY
Ag» STANDARD METABOLISM
FOOD ENERGY CONSUMPTION (CAL/KCAL/DAY)
Figure 9. Relationships between food consumption rate, energy and
material uses and losses, and dissolved oxygen concentration for
juvenile coho salmon held at 15C during summer.
20
-------
o
100
80
60
40
20
AD4AA
lOOr
0 20 40 60 80 100
20 40 60 80 100
Ac- FOOD CONSUMPTION
AW= WASTE
A6= GROWTH
AD+AA= S. D. A- + ACTIVITY
AS* STANDARD METABOLISM
0 20 40 60 80 100
FOOD ENERGY CONSUMPTION (CAL/KCAL/DAY)
Figure 10. Relationships between food consumption rate, energy and
material uses and losses, and dissolved oxygen concentration for juvenile
coho salmon held at 15C during fall.
21
-------
20 40 60 80 100
20 40 60 80 100 120
Ac* FOOD CONSUMPTION
AW= WASTE
A6= GROWTH
AD+AA= S. D. A. + ACTIVITY
As= STANDARD METABOLISM
0 20 40 60 80 100
FOOD ENERGY CONSUMPTION (CAL/KCAL/DAY)
Figure 11. Relationships between food consumption rate, energy and
material uses and losses, and dissolved oxygen concentration for juvenile
coho salmon held at ISC during spring.
22
-------
coho salmon food consumption rate, food assimilation efficiency,
nitrogenous wastes, standard metabolic rate, and growth rate. Growth
was measured at eight food consumption levels to obtain the growth
information used in the budgets. Food assimilation efficiency and
nitrogenous excretion were measured at three food consumption levels and
standard metabolism was measured in recently starved fish in order to
obtain data on waste products and standard metabolic rates for the
budgets. The categories of muscular activity (Aa) and SDA (Aa) shown in
the figures, were combined because of the difficulty of relating SDA
determinations on swimming fish to actual levels in less active fish.
This latter combined category was derived by subtracting the sum of total
waste products, standard metabolism, and growth from the energy value of
food consumed. Energy use illustrated in the budgets at zero food con-
sumption came from utilization of previously formed tissues (i.e. loss
in calories of body materials).
As is shown in the budgets for three seasons (Figs. 9, 10, and 11), the
principal effect of reduced dissolved oxygen concentration was to restrict
food consumption at 3 mg/1, the lowest test level. The fish at this low
oxygen concentration in all cases exhibited much lower maximum food
consumption rates than at 5 or 8 mg/1. Thus, the maximum possible growth
rates of the coho salmon at 3 mg/1 were much less than they were at the
two higher levels of dissolved oxygen tested.
In the summer and spring seasons, the growth rates (indicated by the
vertical heights of the shaded segment, A , at each food consumption rate)
at 5 mg/1 were greater than at the other oxygen concentrations over
the entire food consumption range. In the fall, growth rates at 5 mg/1 were
higher than at the other concentrations at food consumption rates up to
approximately 85 cal/kcal/day. Only in the fall at the highest feeding
levels did the cohos at 8 mg/1 show higher growth rates than those at
5 mg/1. At given consumption rates, the fish at 5 mg/1 generally
expended less energy for SDA and activity than those at 8 or 3 mg/1.
This appears to be the principal reason for the generally better growth
at 5 mg/1.
Another interesting observation concerning the expenditures for
activity at zero food consumption is shown in Figures 9, 10, and 11.
In all three seasons, unfed cohos tested at the oxygen concentration of
8 mg/1 were much more active than those tested at 5 or 3 mg/1. Much
of this excess activity was apparently due to "searching" for food.
The starved fish at 8 mg/1 often exhibited a frenzy of swimming for
20-30 minutes during the time nearby fish were being fed. Fish at other
rations or dissolved oxygen concentrations often became quite active
at feeding time, but this increased activity did not persist for more
than four or five minutes.
Energy losses through wastes (A^) and energy uses through standard
metabolism (As) appeared to be largely independent of the dissolved
oxygen concentration. Energy losses through fecal and nitrogenous waste
products generally accounted for 20 to 30 percent of the energy value
of the food consumed.
23
-------
EXPERIMENTAL POND STUDIES OF THE
BIOENERGETICS AND GROWTH OF LARGEMOUTH
BASS AS INFLUENCED BY DISSOLVED
OXYGEN CONCENTRATION
Experimental Apparatus, Materials, and Procedures
Experimental Apparatus
Two oval, concrete-lined, experimental ponds—approximately 6 meters in
diameter and with a capacity of about 19,000 liters—were used in these
experiments. A drawing of one of these ponds is shown in Figure 12.
From a shallow peripheral area, the bottom of each pond slopes sharply
to a central area', where the depth is about 1 meter. A rectangular
observation chamber, with seven underwater glass ports, projects to
near th'eVcenter of each pond. Cylinders constructed of chickenwire and
painted with non-toxic paint were placed end to end around the shallow
periphery of the ponds to provide escape cover for the mosquitofish.
These ponds are described in detail by Lee (1969).
Each pond was fitted with a transparent polyethelene cover sealed to the
edge of the pond by a water seal and supported by a frame made of
aluminum conduit (Fig. 13). These covers prevented the entry of
unwanted food organisms and made it possible to maintain low-oxygen
atmospheres above the ponds, this slowing reoxygenation of the pond water.
Small wooden doors on both sides of the observation chambers slightly
above the water level provided access to the ponds beneath the plastic
covers.
Each pond was equipped with air lines supplying five dispersion stones,
which were distributed evenly around the bottom of the pond and through
which nitrogen or air could be forced. Introduction of oxygen or nitrogen
through the stones promoted mixing of the water and helped to maintain the
desired dissolved oxygen level.
The temperature of each pond was maintained by two 2000-watt, stainless-
steel, immersion heaters controlled by thermoregulators. The water
temperature was monitored with a continuously recording thermograph.
The well water in each pond was renewed continuously through a flowmeter
at a rate of 4 to 10 liters/min. The flow rate was adjusted as necessary
for maintaining the desired dissolved oxygen level and water temperature.
The water delivered to one of the ponds passed through a degasser, an
apparatus designed by Mount (1964)* to remove dissolved gases from water.
Mount, D. I. 1964. Additional information on a system for controlling
the dissolved oxygen content of water. Trans. Amer. Fish. Soc.
93:100-103.
24
-------
Figure 12. Schematic drawing of one of two experimental ponds used in
this study. Each pond was equipped with an observation chamber, tempera-
ture control equipment, and an adjustable standpipe to maintain the
desired water level in the pond.
25
-------
•
Figure 13. The experimental ponds shown with and without the plastic
cover. The degasser and other associated equipment were housed in the
small building.
-------
Once in the degasser, water is circulated by a pump through a vacuum
chamber where the gases come out of solution and are removed continuously
with a vacuum pump. A mixture of renewal and recycled pond water
passed through the degasser at a rate of 15 to 25 1/min. The water flow
through the degasser and the vacuum were adjusted to produce the desired
dissolved oxygen concentration in the experimental pond.
Experimental Materials
The largemouth bass used in these experiments were seined from a pond
near Jefferson, Oregon. The fish were graded according to size and only
those up to 120 mm in length were selected. The bass were transported to
the Oak Creek Laboratory and were placed in 190-liter glass aquaria held
near 18C. During this holding period, the bass were fed live mosquito-
fish.
The mosquitofish used as food for the bass were collected from several
small log ponds in the local area. It was necessary to collect mosquito-
fish from more than one source because of limited abundance and because
the fish in some areas became diseased as the water fell to a low level
in the late summer. After transportation to the laboratory, the
mosquitofish were held outdoors in a wooden tank equipped with a 2000
watt stainless-steel immersion heater and were fed Oregon Moist Pellet.
Experimental Procedures
These experiments were 14-day tests during which bass were maintained in
both experimental ponds simultaneously on equal densities of mosquito-
fish. During each experiment, the dissolved oxygen concentration of
the water in one pond was maintained at the air-saturation level, while
that Of the other was reduced to a desired level. An attempt was made
to avoid any other differences in test conditions, such as temperature,
water level, exchange rate, during an experiment. Several days before
the start of an experiment, the ponds were filled with water and regulated
to the desired test conditions.
Once the test conditions had been established in each pond, an appro-
priate number of mosquitofish of fairly uniform size was selected from
the available stock. The largest and smallest individuals and those
that appeared unhealthy or were in late stages of pregnancy were not
used. After an adequate quantity of mosquitofish had been selected, one
of two techniques was used to select samples of the mosquitofish before
each experiment. In experiments 1, 2, 3, and 7, samples of about 5
grams of mosquitofish were sacrificed, dried to a constant weight in
an oven at 70C, and then reweighed to obtain dry weights. In the
remainder of the experiments, samples consisting of 50 mosquitofish
were selected at random and handled in the manner described above.
27
-------
The desired weight of mosquitofish was stocked in the ponds two days
before the beginning of each experiment to allow these prey animals to
become oriented before the bass were introduced. Normally, 170 g of
mosquitofish were placed in each pond, but in experiments 6 and 7 the
initial prey densities were 100 and 240 g per pond, respectively. The
quantity of mosquitofish in the ponds decreased as they were consumed
by the bass. No attempt was made to replace the prey fish eaten during
the test period, because it was observed that mosquitofish recently
placed in the pond were initially disoriented and easily captured by the
bass, thus upsetting the more natural prey-predator relationship
previously established. The prey density was thus permitted to decrease
during the experiment, sometimes to about one-half of the initial level.
Since the experimental ponds contained little or no food for the mosquito-
fish, a small quantity of a dry commercial guppy food was fed at a
rate estimated to be a maintenance ration—the ration that would allow
neither weight gain nor loss during the experimental period.
Several days before the start of each experiment, 10 bass of similar
size were selected from the available stock, individually marked with
'the cold-brand technique described by Ellis (1968),* and then returned
to a 190-liter aquarium and held at the temperature to be maintained in
the ponds in the ensuing experiment. At the start of the experiment, the
marked bass were individually weighed and measured, and four bass were
placed into each experimental pond. The bass were selected to provide
about the same total weight in each pond. The two remaining bass were
sacrificed and dried to a constant weight in an oven at about 70C.
During the experiments, experimental conditions were checked twice daily;
and, when necessary, adjustments were made in the temperature, dissolved
oxygen concentration, and water level in the ponds. The dissolved oxygen
concentration in each pond was determined at least twice daily using the
azide modification of the iodometric method (American Public Health
Association, et al., (1965)**. Adjustments of the dissolved oxygen
concentration in the pond were made by changing the amount of nitrogen
being dispersed through the water, by adjusting the amount of vacuum in
the degasser, or by changing the amount of water circulating through the
degasser.
When each experiment was terminated, the bass and remaining mosquito-
fish were removed from the ponds. The bass were identified according
to their marks, individually weighed, measured, sacrificed, and dried
to a constant weight. The mosquitofish were weighed in aggregate and
samples were taken and processed in the manner described above.
* Previously cited.
** Previously cited.
28
-------
In every experiment both planktonic and filamentous algae grew much
faster in the pond held at the reduced oxygen level than in the pond
held at the air-saturation level. Although the exact cause of the
difference in the growth rates of algae in the two ponds is not known,
it may have been due to the difference in oxygen concentrations.
Gibbs (1970)* reported that in many kinds of plants, including algae,
the production of usable photosynthate is measurably reduced in the
presence of normal oxygen concentrations. Growth reportedly increased
as the level of oxygen in the plant's environment decreased.
The oxygen produced by the algae during photosynthesis caused large
diurnal fluctuations in the dissolved oxygen concentration of the
water in the pond which made it difficult to maintain a reduced oxygen
level. The algae may also have influenced food availability by reducing
the visibility more in the pond with the heaviest algal growth. To
control the algal growth, both ponds were treated with an 80 percent
preparation of simizine (2-chloro-4, 6, bis [ethylamino]-s-triazine)
at a concentration of 3 mg/1. The ponds were treated with simizine during
each of the experiments, except experiment 1. Normally, the excessive
algae growth was effectively controlled by one treatment near the begin-
ning of each experiment, but two treatments were required for experiments
conducted during the late summer months.
Results and Interpretation
Results of this investigation show that the food consumption and growth
rates of juvenile largemouth bass reared in experimental ponds, at
moderate densities of prey fish, increased with temperature and decreased
with moderate reductions of dissolved oxygen concentration below the air-
saturation level, except at low temperatures. Appendix Table 7 lists
the individual initial and final weights and lengths and the growth rates
of largemouth bass held for two weeks in the experimental ponds. The
mean temperatures and dissolved oxygen concentration and initial prey
densities for each experiment are also given in Appendix Table 7. The
initial and final prey densities, food consumption rates of the bass,
and the wet and dry weights and caloric content of the initial and final
samples of mosquitofish used in each experiment are presented in
Appendix Table 8. The growth of bass during the experiments was
determined by direct measurement; food consumption was estimated from
the change in mosquitofish biomass during the experiment.
The weight gained by bass held in the experimental ponds was determined
by calculating the difference in the initial and final weights of each
bass. The growth values were converted to rate terms to provide a
Gibbs, M. 1970. The inhibition of photosynthesis by oxygen.
Amer. Sci. 58:634-640.
29
-------
basis for comparison between experiments. Growth rates are expressed in
terms of milligrams of weight gained per gram of mean weight of bass per
day (mg/g/day). These were calculated by dividing the amount of wet
weight gained during the test period by the mean weight (i.e., the
average of the initial and final wet weights) of the individual bass.
The gain in weight per mean gram of bass was then divided by the length
of the experiment in days. The growth rates of the individual bass
were averaged to provide mean growth rates for each experiment. The
food consumption rates are also expressed in milligrams per mean gram
of bass per day (mg/g/day). These were calculated by dividing the total
wet weight of mosquitofish consumed by the average total weight of bass
in the pond during the test period, and finally by the number of days
in the test period.
Figure 14 shows the relationships between the growth rates of largemouth
bass held at high and moderately reduced oxygen concentrations at an
initial prey density of 170 g/pond and at temperatures ranging from 13.3
to 27.6C. The upper curve was fitted to the growth rates of individual
bass held in the experimental ponds at oxygen concentrations near the
air-saturation level. The lower curve was fitted to the growth rates of
individual bass held at oxygen levels 4 to 6 mg/1 below air-saturation
levels, with the exception of the high values plotted at 26.5C. The
high values at 26.5C were not used in fitting the curve, because the
dissolved oxygen concentration of the pond during this test was only
about 2.5 mg/1 below the air-saturation level. Both curves were visually
fitted.
As can be seen from the upper curve in Figure 14, the mean growth rates
of the bass reared near air-saturation oxygen levels increased from 11.4
mg/g/day at 13C to 38 mg/g/day at 27C. At the reduced oxygen levels,
a similar increase in temperature resulted in an increase in mean growth
rates from 11.4 mg/g/day at 13C to 27 mg/g/day at 27C. The distance
.between the two curves illustrates the amount growth was depressed at
each test temperature by a 4 to 6 mg/1 reduction in dissolved oxygen
concentration. The greatest reductions in growth rate caused by reduced
oxygen concentration occurred at the higher temperatures, at which the
fish grew more rapidly. The vertical distance between the points plotted
at each test temperature shows that the variation between growth rates
of individual bass was also greater at temperatures at which the bass
grew more rapidly.
In experiments 5, 6, and 7, largemouth bass were provided initial prey
densities of 170, 100, and 240 g per pond, respectively. During the
experiments the ponds were maintained at about 18C, and dissolved oxygen
concentrations near air saturation in one pond and 4.7 mg/1 in the other
(Appendix Table 7). Bass in the experiments having the higher initial
mosquitofish density of 240 g per pond grew substantially more than
those in experiments having either of the lower prey densities. The
food consumption and growth rates of bass held at reduced dissolved
oxygen levels were restricted at all three prey densities tested, but
the percent reduction in growth rate was greater at higher prey densities.
30
-------
50
<
o
40
H-
<
cr
O
a:
30
20
10
A AIR-SATURATION LEVEL
o REDUCED OXYGEN LEVEL
J L
J L
' ' ' ' ' 1 1 1 1 L
12 14 16 18 20 22 24 26 28 30
TEMPERATURE (C)
Figure 14. Relationships between water temperature and growth rate of individual largemouth
bass reared in the experimental ponds at near air-saturation and reduced (4 to 6 mg/1 below
air-saturation) dissolved oxygen levels. The ponds were stocked with an initial mosquitofish
biomass of 170 g/pond.
-------
As the mosquitofish were preyed upon by the bass during the experiments,
the total weight (density) of the mosquitofish in each pond was gradually
reduced (Appendix Table 8). Since prey fish were not added during the
course of the experiments, the prey densities normally fell to about 40
to 60 percent of the initial level by the end of an experiment. At the
low prey density of 100 g per pond, however, the bass in experiment 6
consumed 74 percent of the mosquitofish initially added. Because of the
lower food consumption rates of bass held at the reduced dissolved
oxygen level in each experiment, the greatest variation in prey fish
density occurred in the pond held at air-saturation level, except at low
temperatures. This probably reduced the apparent effect of reduced
dissolved oxygen concentration on growth, since food was relatively more
abundant in the low-oxygen ponds toward the end of experiments even
though the prey biomass was the same in both ponds at the beginning of
each experiment.
The wet and dry weights and caloric values of the mosquitofish samples
collected before and after each experiment are presented in Appendix
Table 8. An estimate of change in the condition of the mosquitofish
can be made by comparing the ratio of dry to wet weights or the caloric
values of the initial samples to those of the final samples. The data
in Appendix Table 8 show that there was little or no change in the
condition of the mosquitofish during the experiments, except in experiment
2. In this experiment, the mosquitofish appear to have utilized bodily
energy reserves, probably because they were fed insufficient food during
the course of the experiment.
The results of statistical tests of differences in the mean growth rates
of the bass reared at high and reduced dissolved oxygen levels in each
experiment are presented in Appendix Table 9. At the 95 percent confi-
dence level, the "t-test" values computed for differences in the mean
growth rates show a significant difference for all experiments except
1, 2, and 10. Experiments 1 and 2 were conducted at a relatively low
temperature (near 13C) and the difference in the dissolved oxygen
concentrations tested had essentially no effect on the growth or food
consumption of the bass. Experiment 10 was maintained at 26C, a.
relatively high temperature, resulting in a large variation in individual
growth rate values, but the small reduction in dissolved oxygen concen-
tration (8.3 mg/1 to 5.8 mg/1) caused only a small difference in growth
rates between the two ponds. The variance within all the samples increased
with temperature and was usually greater at the higher oxygen level in
each experiment.
Figure 15 illustrates the relationship between the mean growth rates
and food consumption rates of largemouth bass held in the ponds for
two-week test periods. The growth and food consumption rates plotted
in Figure 15 are also given in Appendix Tables 8 and 9. Values are not
included for experiment 2, because the individual mosquitofish appear to
have lost substantial weight during that test period. Although several
different variables are involved (oxygen concentration,.temperature,
prey density, season), the coefficient of linear correlation between
the mean growth and food consumption rates of bass reared in the ponds
32
-------
LK)
40 r
o
^
10
o
yj
30
cr
o
cr
20
10
A AIR-SATURATION LEVEL
O REDUCED OXYGEN LEVEL
O
30
40
50
60
70
80
90
100
FOOD CONSUMPTION RATE (MG/5/DAY)
Figure 15. The relationship between mean growth rate and rate of food consumption of largemouth
bass reared under various conditions of dissolved oxygen, food density, and temperature, in the
experimental ponds.
-------
was 0.96. This strong relationship suggests that regardless of the
factors controlling food consumption, the proportion of the consumed
food materials required for metabolic processes remained the same with
increasing consumption rates.
LABORATORY STREAM STUDIES OF
THE GROWTH OF CHINOOK SALMON
AS INFLUENCED BY FOOD DENSITY
AND DISSOLVED OXYGEN CONCENTRATION
Experimental Apparatus, Materials, and Procedures
Experimental Apparatus
Nine laboratory streams were used in this investigation (Fig. 16). Each
stream consisted of two wooden troughs (each 12" by 12" by 120"} placed
side by side with openings in the adjacent sides near both ends of the
troughs permitting circulation of water, down one trough and back the
other. Stainless steel paddle wheels were used to maintain this circu-
lation providing a stream current velocity of about 0.5 ft/sec. In
order to seal each stream from the atmosphere, a metal cover was placed
over the paddle wheel and a transparent plastic cover was fitted over
the remainder of the stream. The photographs presented in Figure 16 show
one laboratory stream with its cover removed and other streams with covers
in place. The bottoms of the streams were covered with near-equal amounts
and assortments of natural stream rubble and gravel. This material was
arranged in each stream in a manner to form four riffles and six pools.
The water in each stream was exchanged with sand-filtered stream water at
a rate of 1.5 liters/min.
The laboratory streams were housed in a building with a translucent
plastic roof allowing sunlight to enter. During the summer months
of June, July, and August, temperatures and light levels in the building
were controlled to a limited degree. To reduce the light level, a green-
house compound was applied to the plastic roof of the building, and burlap
strips were placed directly on the plastic, stream covers. The green-
house compound also served to reduce the air temperature in the building.
Further control of the air temperature was provided by drawing large
quantities of air into the building through large fiber mats that were
kept wet. No direct attempt was made to control water temperature in
the streams.
Experimental Material
Juvenile chinook salmon were periodically obtained by seining from the
Sixes River and its tributaries on the southern coast of'Oregon. Once
collected and transported to the laboratory, the young salmon were held
in laboratory streams similar in construction to those described above.
During the time the stock of fish was maintained in these streams, they
were fed daily a near-maintenance ration of live tubificid worms and
34
-------
Figure 16. Photographs of some of the nine laboratory streams used in this
investigation. The translucent plastic and metal paddlewheel covers are in
place in the lower photograph. Shading material is shown draped over the
streams.
35
-------
Oregon Moist Pellet. During experiments, however, the fish in the
laboratory streams subsisted on food organisms, mainly insect larvae,
produced in the streams.
Experimental Pvooeduves
Prior to the start of an experiment, the streams were colonized rather
uniformly with algae and insects collected from two small streams in the
local area. After the colonization, time was allowed for the organisms
to become well established. Once the-streams were colonized, a bottom
(benthic) sample consisting of 0.5 ft of pool bottom and 0.5 ft of
riffle bottom was removed from each stream and analyzed for fish-food
organisms.
At the start of an experiment, juvenile chinook salmon were selected from
the available stock of fish. The salmon were individually weighed and
measured and were marked by the cold-brand technique. The marked fish
were allowed a few days to .recover from this handling before they were
introduced into the laboratory streams. Equal numbers and nearly equal
total weights fbiomasses) of salmon were placed in each stream. The
number of salmon placed in each stream varied from 2 to 4 in different
experiments, according to the size of the fish and food level in the
streams. At the time the salmon were placed in the streams, an initial
sample of salmon, similar in size and condition to those introduced, was
removed from the stock stream and the ratio of wet weight to dry weight
determined.
Immediately after the salmon were introduced, the stream covers were put
in place and sealed. Flows of nitrogen gas and air were then introduced
under the covers of the streams, in order to adjust the dissolved oxygen
content of the water to the desired levels. About 12 hours were required
to reduce the dissolved oxygen concentration to near 3 mg/1, the lowest
level tested. During the 20 and 27-day experiments, drifting food
organisms were collected continuously by passing the water discharged
from the streams through a fine-mesh plankton net. In the 10-day
experiments, drift samples were collected continuously for eight of the
ten days. During the course of an experiment, dissolved oxygen concentra-
tions and gas and water flow rates were determined daily and adjusted as
necessary. Temperatures were continuously recorded.
At the termination of each experiment, the chinook salmon were removed
from the streams and placed in 5-gallon containers, where they were
kept for 24-hours, to allow for the digestion of stomach contents. The
salmon were then sacrificed, and wet and dry weights were determined.
Once the salmon were removed from the streams) bottom samples like
those described above were taken from each stream and analyzed for fish-
food organisms.
36
-------
Results and Interpretation
The influence of reduced dissolved oxygen concentration on the growth of
juvenile Chinook salmon held in laboratory streams was studied in nine
experiments, which varied in length from 10 to 27 days. Appendix Table
10 gives the initial and final wet and dry weights and the growth rates
of the Chinook salmon, the mean dissolved oxygen concentrations, and
average stream temperatures. Also presented in Appendix Table 10 are the
number and biomass of salmon placed in each stream, the starting date
and duration of each experiment, and the densities of food organisms
present in the benthos and drifting in the current.
In experiments 1, 3, 4, and 8, conducted at average temperatures of 9.0,
11.6, 13.5, and 14.3C, respectively, the growth rates of the chinook
salmon were found to be dependent on the dissolved oxygen concentration.
In these experiments, the average biomasses of salmon introduced into the
streams were relatively low, ranging from 1.1 to 2.2 g/m2. This tended
to make the relative abundance of food per unit of fish biomass rather
high. Figure 17 presents the results of experiments 3 and 4, which
show dependence of growth rate on dissolved oxygen concentration. In
general, the data presented in Figure 17 and Appendix Table 10 suggest
that the higher temperatures tested, when coupled with high food avail-
ability, led to greater dependence of growth rate of the salmon on
dissolved oxygen concentrations. As can be seen in Figure 17, the growth
rates of salmon held at 13.5C showed a fairly strong dependence on dis-
solved oxygen concentration at all levels tested, while the growth rates
of salmon held at 11.6C showed dependence only at oxygen concentrations
of about 5 mg/1 and below.
In experiments 2, 5, 6, 7, and 9, growth rates of the chinook salmon
were found to be independent of dissolved oxygen concentration. The
results of two such experiments (experiments 2 and 8) are presented in
Figure 18. The salmon biomasses in the experiments showing oxygen ;
independence ranged from 2.2 to 4.9 g/m2—consistently higher than the
salmon biomasses in experiments showing oxygen dependence (1.1 to 2.2
g/m2). Thus food was relatively less available to the salmon in:the
experiments showing independence of growth rate on oxygen concentration
(Appendix Table 10). Lower food availability appears, then, to have
led to lower food consumption and the substantially lower growth rates of
salmon in experiments showing no dependence as compared with the growth
rates of salmon in experiments showing dependence on dissolved oxygen
concentration (Appendix Table 10). At near air-saturation levels of
dissolved oxygen, coho salmon in experiments 3 and 4 (Fig. 17) grew at
rates from about 35 to 60 mg/g/day, while the growth rates of salmon at
similar dissolved oxygen levels in experiments 2 and 7 (Fig. 18) ranged
from about 4 to 15 mg/g/day.
It appears, then, that food availability and not dissolved oxygen con-
centration limited the growth rates of the salmon in experiments where
food availability was low. The rather strict dependence of growth rate
37
-------
60
50
40
io
"x
o
LU
30
20
< 10
or
50
K-
O 40
OC
O
30
3-5 C
j i
j i
20
10
11-6 C
2 3 4 56789 10 II
DISSOLVED OXYGEN (MG/L)
Figure 17. The relationship between dissolved oxygen concentration
and growth rate of juvenile chinook salmon held for 10 days in the
experimental streams in experiments 3 and 4. The open plot denotes
test in which one fish was caught in export trap for up to 48 hours
and may not have fully recovered.
38
-------
30.
20
Q
>»
KD
*v
CD
UJ
I-
-10
-20
9-3 C
i i i i i i
o
oc
(9
20
10
-10
-20
11-0 C
i i i
8 9 1011
DISSOLVED OXYGEN (M6/L)
Figure 18. Relationships between dissolved oxygen concentration and
growth rates of juvenile chinook salmon reared in the experimental
streams for 10 and 20 days in experiments 2 and 8.
39
-------
on food availability, at oxygen concentrations of 3 mg/1 and above, when
food is limiting is well illustrated in Figure 19, for experiments 2
and 7, which had low food levels.
But, our evidence indicates that when food availability is not limiting
the growth of juvenile salmonids, their growth rate is dependent on
dissolved oxygen concentration, so long as temperatures are favorable
for growth. Under some conditions of food availability and temperature,
any appreciable reduction of dissolved oxygen concentration below the
air-saturation level is likely to reduce salmonid growth rates.
40
-------
dV
UJ 10
o: S
x 10 o
H CD
^ S
o —
K -io
CD
f*r\
•A
a
_ ._ — =
A IT
O D. 0. 3 5 |0 (MG/L)
EXP 2 A • •
A ° EXP 7 A O D
1 1 1 1 1 ! J
01 234567
INSECT DRIFT (MG/M3)
Figure 19. The relationship between food density and growth rate of juvenile chinook salmon held for
10 and 20 days in laboratory stream experiments 2 and 7, when food density was low and limiting food
consumption and growth of the salmon.
-------
SUMMARY OF RESULTS OF RESEARCH CONDUCTED FROM
SEPTEMBER 1, 1955 THROUGH AUGUST 31, 1968 WITH SUPPORT FROM
PREDECESSOR AGENCIES OF THE ENVIRONMENTAL PROTECTION AGENCY
INTRODUCTION
This terminal progress report nominally covers the methods, results,
and interpretation of research we have conducted from September 1, 1968
through August 31, 1971, on the dissolved oxygen requirements of fresh-
water fishes. But the interpretation of these results and the recom-
mendations as to dissolved oxygen criteria and needed research derive
to a considerable extent from the results of research we conducted
during the period from September 1, 1955 through August 31, 1968, with
support from predecessor agencies of the Environmental Protection
Agency. Although the results of this earlier work are reported in
numerous publications and theses and have been reviewed by Doudoroff
and Shumway (1970), we are here briefly summarizing this work for the
convenience of those who must evaluate our recommendations. It may
also be helpful to others to have in one place an overview of the
results of our 16 years of research on the oxygen requirements of fish.
Very generally, this research has been concerned with the effects of
decreases in dissolved oxygen concentration on the survival, avoidance
reactions, swimming performance, embryonic development, and bioenergetics
and growth of freshwater fish. During the last three years of this
research, our entire effort on the project has been devoted to bio-
energetics and growth. Thus, the work on the other problems was done
prior to the period nominally covered by this progress report and will
be included only in this section of this report, except as these results
must be considered in discussing the more recent work, in making criteria
and research recommendations, and in our general summary.
SURVIVAL
Studies on the survival of fish conducted during this investigation
have been directed primarily toward determination of the influence of
carbon dioxide concentration and pH on the oxygen requirements of
juvenile coho salmon(0ncorhynehus kisutch'). These studies were con-
ducted largely in 1955 and in 1956 and have been reported in detail
by McNeil (1956).
Evidence has been accumulated which indicates that temperature
acclimatization, necessary activity, feeding status of the fish, and
seasonal changes in the fish all influence the oxygen requirements of
fish for survival. The influence of temperature on the minimal oxygen
concentrations tolerated by coho salmon for periods of one to five days
was studied prior to 1955. Davison et al. (1959) found that the 24-hour
median tolerance limits (TL^) for underyearling coho salmon 4-11 cm
43
-------
long exposed to constant 02 concentrations in autumn did not increase
at all with rise of temperature from 12 to 16C, the TI^rfl remaining
near 1.2 mg/1. These increased by only about 10 to 15 percent with
increase of temperature to 20C. At higher temperatures, however,
especially above 22C, the TL« value rose steeply, being about 2.0 mg/1
at 23.5C. McNeil (1956) observed 0 to 90 percent mortalities of
juvenile coho salmon after 24 hours at nearly constant 02 concentra-
tions averaging 1.7 to 2.0 mg/1, temperatures of 20 to 22C, and free
C02 concentrations of 3 to 20 mg/1, in summer. These data indicate
perhaps an unusual susceptibility to 02 deficiency of these fish that
is considerably greater than that shown by the data of Davison et al.
(1959). Data of Katz, Pritchard, and Warren (1959) show the 24-hour
TI^ for juvenile chinook salmon at 20C to have been about 1.7 to
1.8 mg/1 in summer and spring; and McNeil (1956) observed 50 to 70
percent mortality of juvenile steelhead trout at 02 concentrations
averaging 1.6 to 1.7 mg/1, temperatures of 16 to 20C, and free C02 levels
of 3 to 8 mg/1, in late spring and early summer.
In experiments with coho salmon, Davison et al. (1959) observed few
deaths of the animals after their exposure for more than 24 hours to 02
concentrations that proved lethal to some of the fish in less than one
day. Their tests were usually continued for five days, after gradual
reduction of 02 to constant levels in six to eight hours. They con-
cluded that estimates of five-day tolerance limits would not have
differed markedly from their estimates of 24-hour tolerance limits. In
five-day tests with reticulate sculpins (Cottus perplexus*), however, a
number of deaths occurred after more than one day of exposure. Inasmuch
as mortalities were recorded daily for exposure periods ranging from
one to five days only, the relationship of survival time to 02 concen-
tration was not fully explored, and the true threshold of tolerance
could not be established. It was suggested that the sculpin may have
relatively limited acclimation capacity, as compared with coho salmon.
The five-day TI^ for sculpins 4-7 cm in length at 18-19C was found to
be near 1.5 mg/1, the recorded mortalities having been 40 percent at
that oxygen concentration, 80 percent at 1.4 mg/1, and 0 percent at 1.6
mg/1 dissolved oxygen, after five days of exposure. The 24-hour TL
was about 1.3 mg/1, and the 48-hour TLm about 1.4 mg/1.
In the studies of the influence of carbon dioxide and pH on the oxygen
requirements of fish, the fish were held either in flowing-water
apparatus or in sealed bottles. Oxygen concentration was controlled
in the flowing water experiments by continuously replacing the water
in the experimental chambers with water passed through columns having
counter-current flows of nitrogen bubbles. The apparatus for the
carbon dioxide and pH experiments was provided with means for continuously
introducing carbon dioxide gas and sodium bicarbonate solution at the
desired rates into the exchange flow of water. In the experiments with
flowing water, the fish were gradually acclimatized to the desired
experimental conditions, which were reached in the test chambers only
after several hours; thereafter, constant conditions were maintained.
44
-------
In the sealed bottle experiments, the fish were exposed to tested
carbon dioxide and pH levels suddenly, but the periods of acclimatiza-
tion to accompanying low oxygen levels were varied by varying the
initial levels. There was a progressive decline of dissolved oxygen
until all of the fish died, but the higher the initial level the
longer was the acclimatization period. These experiments were con-
ducted at a temperature of about 20C.
Preliminary flowing-water experiments with juvenile steelhead trout
(Salmo gaivdnevi} and coho salmon indicated thai carbon dioxide
concentrations of 55 mg/1 or less cause little increase of the minimum
dissolved oxygen requirements of these species. Definitive experiments
with coho salmon showed that in water having less than 5 mg/1 of free
carbon dioxide mean concentrations of dissolved oxygen varying from
1.7 to 2.0 mg/1 are fatal to some but not all of the fish in 24 hours.
Experiments in which the carbon dioxide concentration of the water was
increased, but in which no bicarbonate solution was added and consequently
the pH dropped to values ranging from 5.55 to 6.70, showed that a
marked increase in the minimum dissolved oxygen concentration tolerated
by coho salmon began at about 50 mg/1 of carbon dioxide. Experiments
in which the carbon dioxide concentration was increased and in which
bicarbonate solution was added, so that pH values ranged from 6.35 to
7.25, showed a marked increase in the minimum dissolved oxygen con-
centration tolerated by coho salmon at concentrations of carbon
dioxide above 80 mg/1. Though the coho salmon are able to tolerate
lower levels of dissolved oxygen in the presence of high concentrations
of carbon dioxide when the pH and total alkalinity are also high, it
will be difficult to determine which of the latter two factors is the
primary cause of this.
In sealed-bottle experiments in which coho salmon had little time to
acclimatize to oxygen deficiency, a marked increase in the minimum
dissolved oxygen concentration tolerated occurred at carbon dioxide
concentrations less than 40 mg/1. On the other hand, when the initial
oxygen concentration was high, so that a lethal level was not reached
for a long time, such a large increase of the oxygen requirement
occurred only at much higher carbon dioxide concentrations. Carbon
dioxide appears to have much less effect on the tolerance of coho
salmon to low levels of oxygen when the fish have been acclimatized to
the high carbon dioxide levels for moderate periods before critical
oxygen concentrations are reached.
In some sealed-bottle experiments, reductions in pH were made through
the addition of sulfuric acid to the test water, and carbon dioxide
liberated from the bicarbonates was removed by aeration. These experi-
ments indicated that the levels of dissolved oxygen lethal for coho
salmon do not vary materially within the pH range of 4.45 to 6.70,
and that the levels lethal for bluegill sunfish (lepomis macroohirus}
do not vary significantly when the pH is between 4.0 and 7.5.
45
-------
AVOIDANCE REACTIONS
Possible influences that low concentrations of dissolved oxygen and
elevated concentrations of carbon dioxide might have on the movements
of salmonid and centrarchid fishes were studied in the laboratory.
Studies of avoidance reactions exhibited by fish confronted with waters
of sharply different oxygen concentrations but nearly equal carbon
dioxide concentrations were conducted during 1956 and 1957 and have
been presented in detail by Whitmore (1957) and Whitmore et aL (1960).
Studies in which carbon dioxide concentrations were purposely varied,
were conducted during 1957 and 1958 and have not been published as yet.
The experimental results indicate rapid recognition and avoidance by
some fish, notably salmonids, of water with reduced oxygen concen-
trations well above those known to be lethal for these fish. The
observed avoidance of these oxygen concentrations by fish under the
experimental conditions cannot be ascribed entirely to mere stimulation
or increased activity caused by oxygen deficiency. It may not be
assumed, however, that the same oxygen concentrations are usually
avoided in the same way under more natural conditions.
The apparatus used for the avoidance reaction studies was a large tank
into which opened four channels each measuring 6 inches wide and 36
inches long. Two of the channels received a continuous flow of water
having reduced concentrations of dissolved oxygen and two received
water having air saturation levels of dissolved oxygen. Special drains
assured a sharp boundary condition at the channel entries. Avoidance
indices were computed on the basis of the number of entries into
channels, and on the basis of the number of times fish crossed a trans-
verse line located well inside each channel, as well as on the basis
of the numbers of fish observed in the channels at 60-second intervals.
Based on one of the three different kinds of observations mentioned
above, each avoidance index was computed by the formula:
Avoidance index = 100(M-A)/M
where M is the sum of the observations for all channels (experimental and
control) divided by two, and A is the sum of the observations for the
experimental channels only.
Studies were conducted on the avoidance reactions of juvenile chinook
salmon (Onoovhynohus tshawytsaha'), coho salmon, largemouth bass
(Mioroptevus salmoides}, and bluegill (Lepomis maaroehirus') to four
concentrations of dissolved oxygen ranging from about 1.5 to 6 mg/1.
All the species tested avoided some of the low oxygen concentrations,
the degree of avoidance generally decreasing with increasing oxygen
concentration. The chinook salmon avoided oxygen concentrations near
1.5, 3.0, and 4.5 mg/1, but they did not avoid concentrations near
6 mg/1, and they showed little avoidance of concentrations near 4.5
mg/1 in the fall, when water temperatures were relatively low (near 12C).
The avoidance of low concentrations generally was more pronounced in
June and July, when water temperatures were high, than in the fall. The
seasonal difference of the avoidance reactions was apparently primarily
46
-------
because of temperature differences.
Coho salmon in July avoided all tested oxygen concentrations at
temperatures averaging 18.4 to 19C, but their reactions were more
erratic than those of chinook salmon. Their avoidance of low oxygen
concentrations was less than that of chinook salmon at corresponding
temperatures, but the coho salmon showed some avoidance of concentra-
tions near 6 mg/1, which were not avoided by the chinook salmon.
Largemouth bass markedly avoided 1.5 mg/1 dissolved oxygen and showed
slight avoidance of concentrations near 3 and 4.5 mg/1. Bluegill
avoided oxygen concentrations near 1.5 mg/1 rather markedly, and they
apparently spent less time in channels with concentrations near 3
mg/1 than in control channels. Channels with oxygen concentrations
near and above 3 mg/1 were entered almost as readily as control
channels.
When the oxygen concentration was near the saturation level, juvenile
coho salmon responded to differences in carbon dioxide concentration
as low as 1 mg/1 at temperatures around 20C, but at temperatures around
8C, they did not respond to differences as high as 30 mg/1. Some
studies were directed toward evaluating the relative importances of
elevated carbon dioxide and reduced dissolved oxygen in influencing the
movements of juvenile chinook salmon in waters in which these conditions
occur together. When tested separately at temperatures of about 18C,
concentrations of about 2.5 mg/1 of dissolved oxygen were avoided by
some juveniles much more than were concentrations of about 15 mg/1 of
carbon dioxide. At about the same temperatures, older juvenile chinook
salmon avoided carbon dioxide concentrations of approximately 35 mg/1
about as much as they avoided concentrations of dissolved oxygen of
approximately 2.6 mg/1. Juvenile chinook salmon showed much greater
avoidance of water with carbon dioxide high (20 mg/1) and dissolved
oxygen low (2.5 mg/1) than of water with both carbon dioxide and oxygen
high or with both carbon dioxide and oxygen low.
SWIMMING PERFORMANCE
Studies of the swimming performance of fish were primarily directed
toward determining the influence of dissolved oxygen and carbon dioxide
on maximum sustained swimming speeds. Initial studies conducted
during 1955, 1956, and 1957 were concerned with the ability of fish
at low oxygen concentrations to swim at relatively low velocities for
extended periods of time, and these studies have been reported in
detail by Katz et al. (1959). The influence of dissolved oxygen on
the maximum sustained swimming speed of coho and chinook salmon at
different temperatures was studied during 1958 and 1959, and these
studies have been reported in detail by Davis (1960) and Davis et al.
(1963). During 1962, the influence of dissolved oxygen and carbon
dioxide on the swimming speed of coho salmon and largemouth bass was
investigated, these studies being reported by Dahlberg (1963) and
47
-------
Dahlberg et al. (1968). Later studies conducted by E. M. Smith on
the effects of reduced oxygen concentration on the length of time
juvenile coho salmon can swim at very high velocities have been sum-
marized by Doudoroff and Shumway (1967).
Juvenile coho salmon 95 to 124 mm in total length and chinook salmon
54 to 121 mm long, teste4 at 20C were able with few exceptions to
swim for 24 hours against a current of 24.4 cm/sec at 02 concentrations
of 3.0 mg/1 or more. Largemouth bass 63 to 93 mm long, tested at 25C in
September, were able to resist this current speed for 24 hours at 02
concentrations near 2.0 mg/1. In December at temperatures of 15.5 to
17C, the bass were unable to resist this current when the 02 concentration
was reduced to 5.0 mg/1, although they were able to do so at concentra-
tions near the air-saturation levels. The velocity of 24.4 cm/sec may,
however, have been very near the maximum velocity that could be resisted
in the well-oxygenated water at the relatively low experimental tempera-
tures in December. In the other experiments with bass and salmon, the
tested current velocity of 24.4 cm/sec doubtless was much below the
maximum swimming speed that could be maintained for 24 hours by the
fish in well-oxygenated water. The ability of the fish to swim at this
speed at 02 concentrations little higher than the lowest concentrations
at which the fish can live under conditions necessitating no sustained
activity is not evidence that there was little impairment of swimming
capability.
The maximum swimming speeds sustained for ten-minute time intervals at
different 02 concentrations by coho and chinook salmon that were
forced to swim at various temperatures against a gradually increased
current usually declined with any considerable reduction of the 02
concentration from the air-saturation level. The test temperatures in
different experiments were from 10 to 20C. Increasing the 02 concen-
tration beyond the air-saturation levels had little or no favorable
effect on the swimming performance of coho salmon. Largemouth bass
tested at 25C showed impairment of the sustained swimming performance
only when 02 was reduced to levels below 5 or 6 mg/1. At the concentra-
tion of 3 mg/1, the final swimming speed of the bass was lower than the
speed at the air-saturation level of 02 by only about 10 percent.
That of coho salmon tested at various temperatures was reduced by about
30 percent at this concentration (3 mg/1) and by about 10 percent at
concentrations of 5 to 6 mg/1. Reduction of the swimming speed of the
bass by 30 and 50 percent, from the speed at the air-saturation level
of 02, was found to occur at concentrations near 1.5 and 1.0 mg/1,
respectively.
Doudoroff and Shumway (1967) mention some additional observations on
the swimming performance of juvenile coho salmon at different 02
concentrations made by E. M. Smith (unpublished data, Oregon State
University). Smith observed a marked influence of 02 on the length of
time that the salmon swam against a suddenly accelerated current
(previously of low velocity), which could be resisted by the fish for
48
-------
only half a minute to six minutes. Doudoroff and Shumway concluded that
Smith's data suggest the possibility of less effect of dissolved oxygen
on the duration of very rapid swimming than on the duration of less
strenuous swimming.
In studies reported above, 02 was removed from the water by means of
nitrogen, so that free C02 concentrations did not increase as 02
concentrations decreased, as they usually do under natural conditions.
The maximum sustained swimming speeds of bass at 25C were not adversely
affected at any 02 level even by C02 concentrations averaging 48 mg/1
(the highest concentrations tested) after overnight acclimation of the
fish to the elevated C02 levels. The performance of coho salmon tested
at 20C and high 02 levels apparently was impaired somewhat by C02
concentrations averaging 18 mg/1, after overnight acclimation of the
fish. The effect was greater when little time was allowed for adapta-
tion of the fish to the elevated C02 level. Even after overnight
acclimation, higher concentrations of C02 averaging 61 mg/1 had a pro-
nounced depressing effect on the final swimming speeds of the salmon at
high 02 levels. This effect decreased, however, as the 02 concentra-
tion was reduced, and no effect was demonstrable at the 2 mg/1 level.
After overnight acclimation, 18 mg/1 of C02 apparently had very little,
if any, effect at 02 concentrations near and below 6 mg/1, and none at
levels below 3.5 mg/1. Free C02 concentrations much above 18 mg/1 dp
not usually occur in waters that are not seriously deficient in 02. One
can conclude that the free C02 level is not generally an important
consideration in deciding how much reduction of 02 is likely to result
in material impairment of the sustained swimming performance of coho
salmon and largemouth bass in waters receiving organic wastes.
DEVELOPMENT
Salmonid embryos that are buried in streambed gravel depend on the
movement of water through the gravel to supply them with the oxygen
necessary for survival and growth and to remove metabolic wastes.
Changes in the composition of the stream bottom can drastically reduce
the rate at which this water is moving in the gravel and can lead to
reduction of the concentration of dissolved oxygen and increase in
the concentration of metabolic wastes. Such reductions of water
velocity and oxygen content of the water can result in conditions within
the gravel that are not conducive to survival, normal development, and
good growth of salmonid embryos and fry. Even under conditions that
are not lethal for embryos, delay of hatching and reduction in size
of fry may result in poor emergence and survival. The above consider-
ations have pointed to a need for detailed studies of the natural
environments of salmonid embryos and experimental studies of the effects
of specific environmental changes on their survival and growth.
Laboratory studies on the influence of dissolved oxygen concentration,
metabolic wastes, and water velocity on the survival, growth, yolk
49
-------
utilization, and normal development of salmonid embryos and sac fry
were conducted during this investigation. Early studies on the growth
and survival of chinook salmon, coho salmon, and steelhead trout
embryos were conducted from 1957 through 1959 and are reported in
detail by Silver (1960), Shumway (I960), and Silver et al. (1963).
Studies undertaken to define more completely the influence of water
velocity and oxygen concentration on the growth, incubation time to
hatching, and yolk utilization of coho salmon and steelhead trout
embryos are reported in detail by Shumway et al. (1964) and Chapman
(1969). The influence of metabolic wastes on development and growth of
salmonid embryos and larvae are reported in detail by Putnam (1967),
and further studies of the influence of oxygen concentration and water
velocity on the growth of alevins and the time of complete yolk sac
absorption are summarized by Doudoroff and Shumway (1967).
The apparatus used for these studies was designed to provide developing
salmonid embryos and sac fry with a constant rectilinear flow of water
having independently controlled velocities and oxygen concentrations
and uniform temperature. With this apparatus, which was located in a
constant-temperature room, it was possible to test four different
water velocities at each of six different oxygen concentrations during
a single experiment. Several hours after fertilization, 60 to 140 eggs
from a single female were placed into each of the test cylinders within
the apparatus, the number of eggs being the same in all cylinders during
any single experiment. The water velocities and oxygen concentrations
to be tested were then established and maintained until the termination
of the experiment. Removal of dead material, or sampling of live
material, was possible. Wet and dry weights were usually determined,
rather than volumes, as it was found by comparison that either the wet
or the dry weights, and especially the dry weights, could be far more
precisely determined than the volumes. Both volumes and wet weights
were determined after the yolk and excess water had been removed, and
the embryos with yolk removed were dried to constant weight for the
dry weight determination.
Under laboratory conditions, good survival of embryos of steelhead
trout and coho and chinook salmon has been repeatedly observed when
eggs were exposed—continuously from the time of their fertilization
until hatching—to mean 62 concentrations as low as 2.5 to 3.0 mg/1 at
temperatures of 9 to 11C. Embryo mortalities were often greater and
deformities tended to occur more frequently at these low 03 concentra-
tions than at higher concentrations, but hatching proved impossible
only at tested concentrations below 2.0 mg/1. Survival of chinook
salmon and steelhead trout embryos at concentrations averaging 2.6 and
2.5 mg/1 was equal to that of controls, and 100 percent success in
hatching chinook salmon eggs (at 11C) was observed at concentrations
averaging 3.9 mg/1.
50
-------
Any considerable reduction from air-saturation levels (i.e., even to
levels as high as 8 or 9 mg/1) of the Q2 content of water in which the
embryos were reared at various vater velocities resulted, however, in
some reduction in size of the newly hatched larvae (alevins). Mean
weights--determined after removal of the yolk—of coho salmon, chinook
salmon, and steelhead trout alevins at the time of hatching at 02
levels of 2.5 to 3.0 mg/1 were about one-fourth to one-half of those of
controls reared at levels near air-saturation. The dry weights of coho
salmon alevins (with yolk sac removed) hatching at 02 concentrations
that averaged 2.8, 3.8, 4.9, 6.5 and 8.6 mg/1 in an experiment at IOC
were less than those of the controls (at 11.2 mg/1) by about 70 percent,
59 percent, 40 percent, 20 percent and 5 percent, respectively. These
percentages are means of values obtained at four different water
velocities. Mean dry weights of steelhead trout alevins hatching at
02 concentrations that averaged 2.9, 4.1, 5.7, and 8.0 mg/1 were less
than those of controls (at 11.4 mg/1) by about 56 percent, 36 percent,
21 percent, and 7 percent, respectively, on the average, in two like
experiments at IOC and 300 cm/hr water velocity.
Studies on the three species of salmonids have shown that reductions in
velocity of water passing the embryos can result in reduction in size
of the embryos at the time of hatching. Water velocities tested in
different experiments were from 3 to 1400 cm/hr. The favorable effect
of increased water velocity on the size of hatching larvae apparently
is ascribable for the most part, if not entirely, to improved delivery
of 02 to chorion surfaces. Increases of water velocity that had this
effect did not, however, always result in appreciable shortening of
incubation periods required for hatching, especially at high and only
moderately reduced 02 concentrations. In addition to delivery of 02,
removal of some metabolic products, which likewise can influence
development, also may be involved. The influence of water velocity is
not nearly as pronounced as is the influence of oxygen concentration; the
influence of water velocity is, however, nearly as great at high oxygen
concentrations as it is at low concentrations.
Reduction in oxygen concentration resulted in a delay in hatching of
the salmonid embryos. In a typical experiment with coho salmon
embryos, the delay of hatching is taken to be the difference in days
between the median hatching time for fry reared under the various test
conditions and 44 days, which was the median hatching time recorded
under the most favorable experimental conditions tested in the
experiment. Any reduction of oxygen concentration resulted in delayed
hatching of fry at all water velocities, the greatest delay occurring
at the lowest oxygen level tested (2.8 mg/1), where the delay was 11
days. However, a reduction of water velocity from 800 to 3 cm/hr did
not cause any delay of hatching at the highest oxygen concentration
(11.2 mg/1). Also, there was not much delay attributable to reduction
in water velocity at oxygen concentrations of 8.6 and 6.5 mg/1. At
lower oxygen concentrations, a more pronounced effect of water velocity
on hatching time was observed.
51
-------
Metabolites produced by a large mass of developing embryos slightly
inhibited growth of steelhead trout embryos but did not inhibit growth
of sac fry. An ammonia concentration of 5 mg/1 and carbon dioxide
concentrations above 28 mg/1 were also found to inhibit embryonic growth.
But the water passed through the mass of developing embryos before
being introduced into the chamber holding the experimental embryos
contained only 0.1 mg/1 or less of ammonia and 3 to 6 mg/1 of carbon
dioxide. Thus, such growth inhibition as occurred must haf e been
primarily owing to other metabolites. These and other results lead us
to conclude that oxygen concentration rather than metabolites are most
important in affecting embryonic development and that water velocities
sufficient for oxygen delivery are more than sufficient for metabolite
removal.
The maximum dry weights attained by unfed salmonid alevins at reduced
02 concentrations were reduced only moderately (by about 25 percent
or less) or were nearly equal to those of controls, by the time yolk
sac absorption was complete. These maximum sizes were attained at the
reduced concentrations usually with some delay, up to maxima of about
18 days (25 percent) for steelhead trout and 30 days (35 percent) for
coho salmon. The stated results were obtained at mean 02 concentra-
tions even as low as 2.9 to 3 mg/1, in experiments in which the alevins
were reared at temperatures near IOC and a relatively high water velocity
(300 cm/hr). When both the 02 concentration and the velocity of water
movement around the alevins were very low (02 about 3 mg/1; velocity
about 10 cm/hr), the growth of the alevins was much impaired. Mortalities
of the alevins then were relatively high, and nearly complete absorption
of yolk had not yet been attained by the surviving ones when the
experiments were discontinued. It was evident, however, that had the
experiments been prolonged, the maximum size attained by the unfed,
surviving alevins would have been much less than that of controls
reared at the low water velocity but at a high 02 level. Chinook salmon
alevins appeared to be affected by these adverse conditions more than
were the other species tested. Reduction of dissolved 02 to about 5.6
mg/1 had, however, very little effect on their growth and on that of
the other species even at the low water velocity of 10 cm/hr. Exposure
of developing embryos to a very low 02 level until hatching had no
appreciable adverse effect upon the rate of subsequent growth of alevins
returned to a high level of 02-
BIOENERGETICS AND GROWTH
Although our studies on the influence of dissolved oxygen on the growth
of juvenile coho salmon began in 1955 and those on the growth of large-
mouth bass began in 1961, the more bioenergetic aspects of our growth
studies were not undertaken until 1964. From 1964 through 1968, bio-
energetic studies of coho salmon and bass and studies of bass in
experimental ponds--where conditions were more natural than in the
more typical laboratory studies—were undertaken. The earlier studies
52
-------
on growth were mainly concerned with the influences of dissolved oxygen
when food availability was, largely unrestricted, but two experiments
were performed in which, coho salmon were fed low restricted rations.
Nearly all the above mentioned studies are reported in detail in the
following series of theses and publications: Herrmann (1958), Herrmann
et al. (1962), Fisher (1963), Stewart (1962), Stewart et al. (1967), and
Lee (1969).
Decreases in the growth rates of juvenile coho salmon and largemouth
bass with decreases in oxygen concentration from the air-saturation
level to 3 or 4 mg/1 can be attributed mainly to decreases in appetite
and food consumption, when largely unrestricted rations were fed. When
restricted rations were fed, there was little or no difference in the
growth of the salmon at oxygen concentrations ranging from 3 or 4 mg/1
to the air-saturation level.
In laboratory experiments at temperatures of 18 and 20C, the growth
rates of underyearling coho salmon—fed largely unrestricted rations of
amphipods or tubificid worms — tended to decline with any reduction of
02 from the air-saturation levels, which are near 9 mg/1. The results
of those experiments that were deemed fairly reliable indicate decreases
of growth rates (based on wet weights) averaging about 8 percent, 17
percent, and 42 percent (30 percent in the three experiments at 18C) at
02 levels of 5, 4, and 3 mg/1, respectively. These percentages are
means of estimates that we derived by calculation of the growth rates
and graphical interpolation.
A rather abrupt change in slope, at about 4.5 mg/1 02, of the curve
relating percent gains in weight to the 02 concentrations was indicated
by the results of one group of experiments, in which the fish were fed
amphipods twice daily. We have found, however, that when growth rates
of the fish are plotted against logarithms of 02 concentrations a
smoother curve fits the data well. In similar subsequent experiments
performed at 18C, live tubificid worms were used mainly as food, and
the live food was available to the fish continuously. The growth at high
02 levels in these experiments with unrestricted rations was faster
than it was in the earlier tests, and smooth curves relating the growth
rates to the logarithms of 02 concentration were easily fitted to
plotted data. The slope of these curves decreased, but not abruptly, as
the 02 concentration increased to and beyond the air-saturation level.
At 02 levels of 30-35 mg/1, very far above the air-saturation level,
growth rates were less than maximal, but were depressed by only about
4 percent on the average, as compared with growth at the air-saturation
level. The optimum for growth when rations are unrestricted appears
to be about 12 to 15 mg/1. However, in one additional experiment,
virtually equal growth rates were observed at 02 concentrations near
6 and 12 mg/1. This result indicated an optimum near the air-
saturation level.
Food consumption rates of underyearling coho salmon declined, as did
their growth rates, with reduction of 02 from levels near saturation
53
-------
levels in the experiments at 18 and 20C. The gross efficiency of food
conversion tended to be considerably reduced only when food consumption
was very low because of much reduced 02 concentrations (i.e., somewhat
below 4 mg/1 in all experiments whose results were deemed reliable).
In several tests at mean 02 levels of 2.0 to 2.3 mg/1, consumption of
intermittently available food was extremely reduced and the fish lost
weight. In two experiments performed in May and June at 18C, however,
underyearlings that were fed unrestricted rations of tubificid worms
consumed enough food to grow moderately well at mean 02 levels of 2.4
and 2.5 mg/1. Their growth rates were reduced, as compared with those
of controls, by about 45 percent; this value can be compared with a
reduction by about 30 percent at the 3.0 mg/1 level of 02 observed in
the same and in entirely similar experiments at 18C. The coho salmon in
these experiments obviously would have gained some weight at concen-
trations well below 2.4 mg/1, if not below 2.0 mg/1. Thus, the results
of all the pertinent tests considered together indicate that average 02
concentration at which underyearling coho salmon can just maintain their
weight without growing when they are offered abundant food rations at
temperatures of 18 to 20C is not much above 2.0 mg/1.
An experiment in which groups of juvenile coho salmon of nearly equal
initial weight were fed equal rations of tubificid worms at 18C and at
six different, constant 02 concentrations ranging from 3 to 18 mg/1 was
conducted. Each group of fish received only as much food as could be
readily consumed by the fish held at the lowest 02 level. Reduction of
02 to 4 mg/1 had no evident effect on the growth of these fish. At the
3 mg/1 level, the fish grew a little less than did the fish at the higher
concentrations. Gains in wet and dry weights and in crude fat all
proved nearly independent of the 02 concentration. In a similar later
experiment, in which the lowest 02 level was 2.3 mg/1 and rations were
correspondingly reduced, no impairment of growth was observed even at
this very low concentration. It is evident that coho salmon consuming
equal amounts of food utilized this food for growth about as efficiently
at the much reduced 02 concentrations (certainly at concentrations as
low as 4.0 mg/1) as they did at higher concentrations.
Six experiments in which groups of juvenile largemouth bass were fed
earthworms at temperatures near 26C and at different, nearly constant
02 concentrations (1.6 to 24 mg/1) were conducted. The worms were
available to the fish at all times. Food consumption and growth rates
of the bass clearly tended to be reduced by any considerable reduction
of 02 from levels near the air-saturation level, which is about 8 mg/1.
The optimal concentration appeared to be very near the air-saturation
level; at levels much above saturation both food consumption and growth
rates tended to be depressed. The indicated decreases of the growth
rates of the bass (from the rates of growth at the air-saturation level
of 02) at reduced 02 concentrations of 5, 4, 3, and 2 mg/1 averaged
about 8.5 percent, 16.5 percent, 30 percent, and 52 percent, respectively.
These values are means of estimates that we derived by graphical inter-
polation from the results of five of the six experiments, disregarding
one experiment, the results of which were deemed too erratic. The gross
efficiency of food conversion by the bass usually was considerably
54
-------
impaired at 02 levels below 3 or 4 mg/1, and nearly independent of 02 at
higher levels. The bass invariably gained weight or were evidently
capable of growing at an GU concentration of about 2 mg/1; concentra-
tions considerably lower than this (but not as low as 1.0 mg/1) apparently
would not usually have prevented growth entirely. The average depression
of growth rates at excessive 02 concentrations averaging 20 mg/1 in
three experiments was about 11 percent.
The growth of juvenile coho salmon and largemouth bass kept on unrestricted
rations at widely fluctuating 02 concentrations was markedly less than
their estimated growth at constant concentrations equal to the means
(arithmetic and geometric) of the fluctuating concentrations. The fish
were subjected daily to high and low concentrations, usually for equal
periods following periods of gradual transition; low concentrations
occurred at night and early in the morning. Mean limits of the 02
fluctuations in the experiments with coho salmon were 2.3 and 9.6, 3.0
and 9.5, 3.0 and 18, 4.9 and 35.5 mg/1. In the experiments with large-
mouth bass, the mean lower limits were usually about 2 mg/1 and the
upper limits were usually about 6, 8, or 17 mg/1. Weight gains that would
have occurred at intermediate constant concentrations were derived for
comparative purposes by interpolation from results of simultaneous
tests at several constant concentrations, including concentrations near
the limits of the tested fluctuations. The growth of the fish subjected
to diurnally fluctuating concentrations often proved equivalent to that
which would have occurred at constant levels only a little above the
lower limit of the wide fluctuations. Their food consumption rates
were correspondingly depressed.
As we have noted, when food is not limiting, any reduction in the
concentration of dissolved oxygen below the air-saturation level can be
expected to reduce the rate of food consumption of fish, unless low
temperatures are leading to low consumption rates. The rate of food
consumption of juvenile coho salmon, forced to swim at constant low
velocity was found to increase with increasing oxygen concentration.
Growth rate increased slightly with increasing availability of oxygen,
but not so much as food consumption rate, because respiration increased,
primarily as a result of increased specific dynamic action. It was the
ability of the fish to increase their rate of respiration with increase
in oxygen availability that permitted consumption rate and, in conse-
quence, growth rate to increase. Oxygen, here, was acting as a
limiting factor.
Not only very high levels of food consumption but also very high levels
of activity can lead to oxygen acting as a limiting factor, even at
air-saturation levels of oxygen. Juvenile coho salmon were found to
reduce their food consumption rate to make oxygen available for
swimming at the increased velocities. Reduction in the energy cost of
food handling thus permitted increased energy utilization for activity,
even though respiration rate remained constant.
55
-------
Oxygen consumption rates of juvenile coho salmon and largemouth bass
tended to decline with, any reduction of dissolved 02 below the air-
saturation levels. We have reported already that the food consumption
and growth rates of the fish, likewise were dependent on the 02 concen-
tration at all levels below the saturation level. Some pertinent
observations incidental to already reported experiments on the growth
of coho salmon that were fed uniform, restricted rations at 18C at
various 02 concentrations have been examined. These data indicate no
dependence of 02 uptake rates on 02 concentration over the wide range
of concentrations that had no demonstrable influence on the growth
rates of the fish, from the air-saturation level to 4 mg/1 or less. No
dependence was to be expected in this case, because ration size was
equally restricted at all 02 levels tested.
Results of the preliminary experiments in the experimental ponds
indicate that, over a wide range of prey densities, the metabolic rate
of largemouth bass preying on mosquitofish, Gambusia affin-is, which were
usually provided suitable escape cover, did not vary much with changes
in prey density. The food consumption and growth rates of the bass
increased with increasing prey density over the entire range of densities
tested. Yet, at the moderate test temperatures, averaging about 21C, the
average metabolic rate—determined by the energy-balance method--
apparently remained nearly constant at about 26 calories per kilocalorie
of bass tissue per day. The apparent constancy of the metabolic rate
of the bass indicates that, as the availability of food and the rate of
food consumption increased, so that more energy was required for the
cost of food handling, the activity of the bass decreased. In other
words, a decrease of the expenditure of energy for activity apparently
compensated for the increase of the so-called "specific dynamic action"
of the food that was consumed in increasing amounts as the density of
prey increased. This conclusion was in accord with visual observations.
When the prey density was high, or when the escape cover for the mosquito-
fish was removed, the bass often were able to capture their prey with
relatively little effort. When food was less abundant, they evidently
expended more energy in seeking the prey and pursuing it, usually fail-
ing to capture it.
There are reasons for believing that the dissolved 02 concentration,
which was near the air-saturation level in these experiments with bass,
may have determined the metabolic rate of the bass, thus limiting their
activity and food consumption. It was found that, at 20C and 02 levels
near air-saturation, the metabolic rate of more rapidly growing largemouth
bass kept in aquaria on unrestricted rations of unprotected and easily
captured mosquitofish was not materially different from that of the
bass in the ponds. This observation suggests that the average metabolic
rates of these fish at the same temperature in nature are not much lower
or higher, and that critical levels of 02 may be about the same in nature
as they are for fish fed unrestricted rations in the laboratory at the
same temperature. We have already reported that the food consumption,
growth, and 02 uptake rates of largemouth bass that were kept on unrestricted
56
-------
rations in laboratory aquaria at about 20 and 26C tended to decrease with
any considerable decrease of dissolved C>2 from the air-saturation level.
This finding definitely indicates restriction of the metabolic rate of
the abundantly fed bass at 2Q-26C by the availability of 02 even in
nearly air-saturated water. One can conclude that the apparently not
very different metabolic rates of bass in the ponds also may well be
oxygen dependent at 02 levels near the saturation level.
57
-------
GENERAL DISCUSSION
We shall here consider mainly possible relations between our laboratory
findings and effects of reduced dissolved oxygen concentrations
on the well-being and production rates of populations of fish in
nature.
Our data on avoidance reactions of fish to low oxygen concentrations
under the highly artificial test conditions are of some physiological
interest and suggest—as does also the distribution of fish in nature--
that fish in their natural environment will not avoid all reduced
oxygen concentrations that are likely to impair their performance or
physiological functions. No conclusion can, however, be reached as to
the concentrations that are avoided in natural situations where trans-
ition from high to low oxygen concentrations is not nearly as abrupt as
that in our experimental tank.
The demonstrated reduction of maximum sustained swimming speeds of sal-
monid fishes by only slight reduction of dissolved oxygen concentration
from air-saturation levels may be important in some natural situations.
But very rapid swimming for short intervals of time is probably more
often required in nature than is prolonged swimming at maximum speeds
sustainable. The influence of dissolved oxygen on "burst" speeds that
are maintainable only for fractions of a minute and on the frequency
with which such burst swimming can be repeated has not been investigated.
There are physiological reasons for doubting that reduced oxygen
concentrations have as much influence on burst speeds as on maximum
sustainable speeds.
The observed reduction in size of salmonid alevins hatching from eggs
exposed continuously to low oxygen concentrations at moderate to high
water'velocities and the delay of their hatching may or may not
materially influence their ability to survive in stream-bed gravels
and after emergence from these gravels. By the time of complete
absorption of the yolk sacs of fry reared at high and low oxygen concen-
trations at which the eggs were incubated and hatched, the size dif-
ferences are not nearly so pronounced. But substantial differences in
maximum sizes attained by fry, reduced rates of growth, and much
higher mortality rates were observed at moderately reduced oxygen con-
centrations when salmonid embryos and fry were held at low water
velocities, such as are common in streambed gravels. Failure of
salmonid embryos and alevins to survive at favorable temperatures in
heavily silted stream-bed gravels where oxygen concentrations are only
moderately reduced cannot always be attributed only to oxygen deficiency
in the water moving through the gravels, because silt may impair
oxygen movement across the chorions of the eggs, and in other ways
influence the alevins. In laboratory experiments, only low oxygen
concentrations when water velocities were low proved fatal or prevented
attainment of nearly normal size of alevins. Nevertheless, even under
59
-------
entirely natural conditions, oxygen concentrations in riffle-bottom
gravels are not everywhere sufficient for successful development of
salmonid fishes, and any reduction of oxygen concentrations in water
flowing over and through the gravels must result in some reduction of
stream-bottom areas suitable for salmonid spawning.
We can now turn to discussion of the results of our experiments on the
influence of dissolved oxygen on the growth of juvenile fishes under
various conditions, the main subject of our investigations of the
last three years of the overall study.
There is no indication that the effects of reductions of oxygen con-
centration on the growth of largemouth bass feeding more or less
naturally on mosquitofish in our artificial ponds are very different
from the effects on the growth of these fish in laboratory aquaria when
they are fed unrestricted rations. At temperatures near 19C (18-20C),
agreement between the percentages by which growth rates of bass feeding
on mosquitofish were reduced upon reduction of the oxygen concentration
to the same mean level (4.3-4.4 mg/1) in the ponds and in aquarium
tests was excellent (about 20 percent reduction in each case). In both
the pond and aquarium tests at temperatures around 13C (13-14C in ponds,
10-15C in aquaria), similar reductions of oxygen concentration had
very little or no effect on the growth rates of the largemouth bass.
There are reasons for supposing that the observed impairment of growth
in the ponds by reductions of oxygen concentration at temperatures of
16-17C were greater than those that would have occurred in the aquarium
tests, but no aquarium tests at these temperatures were performed.
Also, at temperatures between 23 and 28C, the impairment of growth in
the ponds at reduced oxygen concentrations appeared to be somewhat
greater than that found to occur in the aquarium tests at the same
oxygen concentrations. But the difference of these results could well
have resulted from experimental error.
The influence of food availability, or food-organism density, on the
degree of depression of growth rates of bass in the ponds at reduced
oxygen concentrations has not been adequately evaluated. In three
experiments at about 18-19C in which the food-organism density was
varied, the greatest depression of growth rate at reduced oxygen con-
centrations was observed when the food density was highest. The differ-
ence between the results obtained at the two lower food-organism den-
sities was negligible. The noted good agreement between the results
(percent depressions of growth rates) obtained in the pond tests and
the aquarium tests in which food consumption and growth rates of the
bass were much greater than they were in the pond experiments indi-
cates that food availability may have had little or no influence on
these results. This conclusion is indirectly supported by the avail-
able bioenergetic data, which indicate that the metabolic rate of the
bass in the ponds was independent of food-organism density. If
metabolic rates remain constant, the dissolved oxygen requirement for
unimpaired growth of the fish also should be constant, and the degree
of impairment of growth by a given, large reduction of dissolved oxygen
60
-------
presumably also should not vary greatly. On the basis of the above
considerations, it now appears that the effects of dissolved oxygen
reduction on the growth of largemouth bass in their natural environ-
ments can be fairly reliably predicted from the results of simple
aquarium tests in which food rations are unrestricted.
The degree of impairment of the growth of juvenile chinook salmon in the
laboratory streams upon reduction of the oxygen concentration to a
given low level varies widely with the availability of food. Therefore,
close correspondence between the results of laboratory stream tests,
in which different relatively low levels of food availability are
maintained, and those of aquarium tests in which food rations are
unrestricted cannot be expected at all temperatures. But at the rela-
tively low temperatures of our laboratory stream experiments, the critical
dissolved oxygen levels below which growth was oxygen-dependent in
the streams having higher levels of food availability were not markedly
different from the critical levels determined in aquarium experiments
with unrestricted food rations at similar low temperatures. No labora-
tory stream experiments were performed at relatively high temperatures
at which the growth rates of juvenile chinook salmon in aquarium tests,
as well as those of coho salmon, proved dependent on oxygen concentra-
tion at all concentrations below the air-saturation level. It appears
that, at the higher temperatures at least, the effects of dissolved
oxygen reductions on growth in the laboratory streams with low to
medium levels of food availability should be less pronounced than the
effects observed in laboratory aquarium tests with unrestricted food
rations.
The dependence of the critical level of dissolved oxygen on food
availability that has been observed in the experiments with laboratory
streams, however, does not necessarily exist in nature. In the
laboratory streams, the salmon feeding on drifting organisms probably
could gain little when food availability was low by exerting themselves
more than they did when food was relatively abundant. We cannot safely
assume that the same is true in nature, where, when food is scarce,
it may be advantageous for young salmon to expend more energy in
exploiting stream resources. A competitive advantage perhaps could be
gained by maintaining a nearly maximum metabolic rate, whatever the
level of food availability. Then, any reduction of oxygen concentra-
tion would result in reduction of food consumption and growth rates,
and the impairment of growth could be similar to that observed at the
same oxygen concentration and temperature in aquaria with an unlimited
and readily available food supply. Only further research can reveal
to what extent the depression of growth rates of salmon by reduction
of dissolved oxygen in laboratory aquaria is indicative of the
depression that would occur in the laboratory streams and in nature at
the same temperature.
61
-------
SUGGESTIONS CONCERNING WATER QUALITY CRITERIA FOR PROTECTION OF FISHERIES
Water quality criteria and standards can be designed for the protection
of particular species, or even of particular populations, of fish deemed
of sufficient economic or recreational importance, when adequate infor-
mation is available on the environmental requirements of those species
or populations. Such specific criteria and standards have obvious
advantages over those pertaining to fish in general. Unfortuantely,
however, reasonably complete information on the dissolved oxygen
requirements of only a few important fish species is now available.
And convincing evidence that these requirements are adequately represen-
tative of those of major taxonomic groups or ecological types to which
the particular species belong is also lacking. An alternative approach
to the development of water quality criteria involves consideration and
synthesis of all available information on the relations of fishes in
general to particular environmental factors, with careful attention to
general biological principles.
Faced with the task of devising dissolved oxygen criteria to be
recommended for worldwide application, Doudoroff and Shumway (1970) had
no choice but to adopt the latter approach. Their recommendations, based
on a comprehensive survey of the pertinent world literature, as well
as on all the data available in our laboratory at the time of prepara-
tion of their publication, are reprinted in Appendix III of this report.
But here we shall discuss in some detail only the possibilities per-
taining to the first-mentioned approach, inasmuch as most of our data
have to do with only a few fish species whose dissolved oxygen
requirements we have intensively investigated. The reader must decide
for himself whether or not, or to what extent, conclusions or criteria
based on the research into the requirements of certain populations of
these species are to be regarded as applicable to other species, or
to other populations of the same species, whose requirements have been
investigated little or not at all. We need not take any position here
with regard to the advisability of such general application of specific
information, in our present state of knowledge.
As noted by Doudoroff and Shumway (1967, 1970), water quality criteria
can be designed for total protection of valuable fish populations,
admitting virtually no impairment or risk of impairment of fish pro-
duction, or they can be designed for various lower levels of protection
of fisheries that would merely limit the impairment of production.
Realizing that different levels of protection of fisheries may be
appropriate under different circumstances, Doudoroff and Shumway (1970)
proposed different dissolved oxygen criteria that they deemed appropri-
ate to several different levels of protection described by them (see
Appendix III). These criteria pertain to freshwater fish populations
in general, but criteria designed for the protection of particular
species likewise can provide for more than one level of protection.
We are now ready to consider criteria that may be appropriate for
63
-------
different levels of protection of those particular fishes that we
have instensively studied.
Table 1 shows the lowest level of dissolved oxygen at which each of a
variety of responses of fish to reduction of oxygen concentration does
not appear to us to have proved demonstrable under the specified
experimental conditions. It can be seen from this summary of our
findings that, while some presumably undesirable effects of dissolved
oxygen reduction were apparent only at relatively low oxygen concen-
trations, other effects or responses were demonstrable upon any con-
siderable reduction of dissolved oxygen from the air-saturation values,
at least at moderately elevated temperatures. Specifically, some of
the latter responses are: reduction in hatching size of salmonid
embryos, delay of hatching of salmonids, reduction of maximum sustained
swimming speeds of salmonids (but not of largemouth bass), and reduction
in growth rates of coho salmon fed unrestricted rations in aquaria and
of largemouth bass fed unrestricted rations in aquaria as well as .
feeding more naturally in artificial ponds. These findings lead
inevitably to the conclusion that any considerable reduction of dis-
solved oxygen below saturation levels is likely to have some adverse
effect on the functions or performance of the fish species studied and,
therefore, on their production rates under natural conditions, except
perhaps at low temperatures unfavorable for growth.
But let us now grant that some limited impairment of fish production
rates, say a reduction by no more than 20 percent, often must be and
will be accepted in establishing dissolved oxygen criteria or standards
for moderate protection of fish populations. Can the lowest dissolved
oxygen level at which the impairment of production would not exceed
this maximum acceptable impairment be estimated? If so, on what kinds
of data should such estimates be based?
We can offer no justification whatsoever for the assumption that a 20
percent reduction of the maximum sustained swimming speed of a fish,
or a 20 percent reduction of the size of its embryos at the time of hatch-
ing, or a 20 percent delay of hatching, would usually result in a
reduction of the production rate of that fish in nature by about 20
percent, or by any other particular (more or less predictable) percentage.
On the contrary, there are good reasons for believing that such moderate
effects of dissolved oxygen reduction would not, by themselves, usually
result in any appreciable impairment of production. Prolonged swimming
at nearly maximum sustainable speeds is not often required of fish in
nature. Moderate reduction of hatching size has not been found to
result in a corresponding reduction of the size attained by salmonid
larvae by the time of complete absorption of the yolk sac. Even some
reduction in size of the emerging fry should not result in increased
competitive disadvantage for any of them if the reduction is uniform.
Spawning seasons of fish usually are fairly extended, and hatching
time can vary more widely with natural variations of temperature than
with moderate variations of oxygen concentration. Generally, many
more young fish are produced than can survive and grow to maturity,
64
-------
Cn
Table 1. The responses of various species of fish held under laboratory conditions to reductions of dissolved oxygen concentration. The letters H
(saturation or above), I (>4.0 mg/1, but much less than saturation), and L (<4.0 mg/1) indicate the highest level of dissolved oxygen at
which the indicated response changed. The temperatures at which the various experiments were conducted are close, but not identical to
those shown in the table headings.
Response
Juvenile sustained
swimming speed
Development—
(size at hatch)
Larval— growth
(max. size attained)
Hatching success
Survival- through
yolk absorption
Delay in hatching
Avoidance
Juvenile growth
(aquaria)
Juvenile growth
(ponds )
Juvenile growth
(streams)
Coho salmon Largemouth bass Chinook salmon Steelhead trout Bluegill Sculpin
Temp, degrees C Temp, degrees C Temp, degrees C Temp, degrees C Temp, degrees C Temp. degrees C
10 15 20 >21 10 15 20 25 30 10 15 > 20 10 15 20 20 18-19
I-H H H I H H
H H H H
H L-I I-H
L L L
L H
H H H I-H
I-1 L LI I
I-H I-H H I-H L L H H H L-I I H
L I-1 H
— At moderate to high water velocities.
2f Small effect observed at >4.0 rag/liter, but no higher level tested below the air-saturation level.
— Depending on food availability.
-------
available space and food supplies being limited, and competition for
food among excessive numbers of young can even result in depression of
production rates. Presumably for these reasons, stocking .of natural
waters with fry of prolific warmwater fishes has been found usually to
have no beneficial effect on fisheries. All these considerations lead
to the conclusion that the extent to which non-lethal dissolved oxygen
reduction will impair fish production cannot be predicted, or even
approximately estimated, on the basis of known effects on sustained
swimming speeds or on hatching time and size, or even hatching success,
except when reproduction is quite considerably reduced.
Effects of dissolved oxygen reduction on growth rates of fish in the
laboratory, especially under simulated natural conditions such as those
in our laboratory streams and artificial ponds, seem to offer more
promise as a basis for estimates of effects on production rates. The
rate of production is directly proportional to growth rate, since it is
the mathematical product of biomass and growth rate. And, unexpectedly,
we have observed rather close correspondence between effects of reductions
of dissolved oxygen on the growth rates of largemouth bass kept on
unrestricted rations in laboratory aquaria and their effects on the
growth rates of these fish under the much more nearly natural condi-
tions in our artificial ponds, where the rates of growth were far less
than the maximal rates attainable in the aquaria. This observation
suggests that growth rates under entirely natural conditions may be
similarly affected by decreases in oxygen concentration, if the avail-
ability of food is not decreased.
We cannot, of course, assert that organic pollution or enrichment of
waters will have no effect on the supplies of fish foods; it may
brinp about either an increase or a decrease in the abundance of
suitable food organisms. We also cannot assert that the reproduction
of fish will never be seriously impaired by organic pollution and
cnnsenuent dissolved oxvgen reduction that has only a moderate effect
on the prowth rates of juveniles. But Dudley C1969)* concluded from
the results of his experiments that the production of normal larvae of
largemouth bass equal to that which occurs at the 90 percent satura-
tion level of dissolved oxygen apnarently is possible at levels above
2.0, 2.5 and 3.5 mg/1 when incubation temperatures are 15, 20, and 25C,
respectively. Thus, the assumption that the reproduction of large-
mouth bass will not usually be materially impaired bv reduction of
dissolved oxygen to levels above 3.5 mp/1 at normal temperatures appears
to be not without justification. Yet reductions of juvenile growth
rates of this species in excess of 20 percent from rates observed at
Dudley, R. G. 1969. Survival of largemouth bass embryos at low
dissolved oxygen concentrations. M.S. Thesis. Cornell Univ., Ithaca
New York. 61p.
*
66
-------
concentrations near the air-saturation levels were demonstrable at
such reduced concentrations, except in some experiments at low
temperatures (Fig, 20).
If, then, we accept the several necessary assumptions specified above,
and take a 20 percent reduction of production rates to be the maximum
acceptable degree of impairment (as compared with the production
possible at the saturation levels of dissolved oxygen), from the
curves in Figure 20 we can arrive at the following provisional esti-
mates of oxygen concentrations above which production of largemouth
bass should not be excessively impaired, especially if these minimum
concentrations do not persist for very long periods: 2.5, 2.6, 3.7,
3.8, and 4.2 mg/1, at temperatures of 10, 15, 24 and 26, 29, and 20C,
respectively. If only 10 percent reduction of production rates from
the rates possible at high oxygen concentrations is to be regarded
as acceptable, the corresponding estimated dissoive(j oxygen levels
compatible with this degree of impairment of production, according
to Figure 20, become: 3.0, 5.5, 5.0, 4.7, 5.1 mg/1 at temperatures of
10 and IS, 20, 24, 26, and 29C, respectively.
Coho salmon, whose eggs are buried in gravel, present a more complex
problem. Our experiments with this species and other salmonids have
shown oxygen concentrations above 3 mg/1 to be adequate for success-
ful hatching of alevins and eventual attainment by them of nearly
normal size, at high water velocities in the laboratory. Oxygen con-
centrations in water percolating through streambed gravels, often,
however, are far below those to be found in the water flowing over the
gravels. Water velocities in these gravels are also usually very low.
Thus, reduction of dissolved oxygen in above-gravel stream waters to
levels well above demonstrably lethal levels can result in total or
almost total destruction of embryos and fry in the gravels. Fish pro-
duction is not possible, of course, in the absence of successful repro-
duction.
We may perhaps assume, however, that the most serious reduction of
dissolved oxygen concentration in streams inhabited by coho salmon
will occur during periods,of low stream flow and high temperatures, when
coho salmon embryos are not in the gravel, and 'not during the late fall
and winter spawning season. Then, production again can be regarded
as being impaired by reduced oxygen concentrations predominantly
through their effects on juvenile growth rates. It must be recognized
that, since most of the growth of coho salmon occurs during their
residence in salt watex, success of their reproduction may be a more
important factor affecting the yield to fisheries than is the growth rate
of the young in the streams, when reproduction is not sufficient to
populate the streams to the extent of their holding capacity. Further-
more, since the oxygen concentrations in streambed gravels of some
portions of riffle bottoms are very low naturally, any reduction of the
oxygen concentration in water flowing over the gravels must result in
some restriction of areas suitable for spawning. Thus, the possible
effects on reproduction of even moderate reductions of dissolved oxygen
67
-------
1001—
00
LU
!5
o:
I
UJ
o:
o
90
80
70
60
50
40
30
1
II i I I i
8
10 II
DISSOLVED OXYGEN (MG/L)
Figure 20. Relationships between dissolved oxygen concentration and the normalized growth rate
of juvenile largemouth bass reared in aquaria and fed to repletion on live food at temperatures
ranging from 10 to 29C. Growth rates were normalized on the basis that maximum growth occurred
at air saturation levels of oxygen.
-------
in streams where coho salmon embryos or larvae are present cannot be
disregarded. Still, it seems not unreasonable to suppose, for present
purposes, that the dissolved oxygen conditions most critical for coho
salmon production in streams will generally occur during periods of
low 'stream flow and high temperature. Then we can estimate, by refer-
ence to the curves in Figure 21, as we have done in the case of largemouth
bass, that if production is not to be reduced at any time by more than 20
percent from that possible at the air-saturation level of dissolved oxygen,
then oxygen concentrations above 4 mg/1 must be maintained when tempera-
tures are not much above 20C. If no more than a 10 percent reduction of
production rate is to be acceptable at any time, the corresponding lower
limit of dissolved oxygen will be near 5 mg/1. These values are based
predominantly on the 18-20C curve in Figure 21, which curve represents
the combined (averaged) data from a large number of experiments per-
formed at different times by three investigators, whereas the curves
for other temperatures represent results of only one or two experiments.
The 22C curve (based on two experiments) indicates that, at unusually
high temperatures near 22C, the minimum dissolved oxygen requirements
for coho salmon production equal to 80 and 90 percent of that possible at
high oxygen concentrations may be about 5 mg/1 and 5.5 or 6 mg/1,
respectively.
In arriving at these estimates, it has been necessary for us to ignore
the seemingly aberrant and still unexplained results of some of our
experiments, performed in summer or early fall, in which reductions of
oxygen concentration to about 4 and 5 mg/1 caused reduction of growth
rates of coho salmon far exceeding 20 percent and even caused high
mortalities of the test animals. Considerations such as this, among
many others, led Doudoroff and Shumway (1970) to recommend criteria for
a moderate level of protection of freshwater fisheries in general in
waters naturally rich in dissolved oxygen that are considerably more
conservative than the above criteria based on most of our growth rate
data. It should be noted, on the other hand, that the latter criteria
are based on the stated limits of depression of growth or production
rates from rates observed under nearly ideal conditions at air-
saturation levels of dissolved oxygen. Average natural dissolved
oxygen levels, especially in habitats of the largemouth bass, are
often well below saturation levels. When such is the case, reduction
of dissolved oxygen in the natural habitat to the specified minima
should not reduce growth and production rate's from the natural levels
by as much as the percentages indicated'by us. Unlike the criteria
presented here, which are simple minimum concentration limits, those of
Doudoroff and Shumway prescribe acceptable reductions below estimated
natural levels (seasonal minima) of dissolved oxygen (See Appendix III).
69
-------
o
L&J
100
90
"- 80
I
O 70
cr
o
S 60
N
_
< 50
O
40
30
I8-2O C
8
10 II
3 4 567
DISSOLVED OXYGEN (MG/L)
Figure 21. Relationships between dissolved oxygen concentration and the normalized growth rate of
juvenile coho salmon reared in aquaria and fed unrestricted rations of live food at temperatures
ranging from 9 to 22C. Growth rates were normalized on the basis of determined or estimated growth
rates at air saturation levels of oxygen. The 18-20C curve is based on many more experiments than
the other curves and is considered to be more reliable.
-------
RECOMMENDATIONS FOR FUTURE RESEARCH ON THE DISSOLVED OXYGEN REQUIREMENTS
OF FISHES
LETHAL LEVELS
Mere determination, or redetermination by improved techniques, of lethal
thresholds, or lower incipient lethal levels, of dissolved oxygen con-
centration for adults and juveniles of various fish species no longer
appears to be worthwhile, because water quality standards apparently
cannot be reasonably based on these lower limits of tolerance. Deter-
minations of tolerance limits could, however, be profitably undertaken for
comparative purposes in connection with further studies of intraspeaifia
variation of dissolved oxygen requirements, such work heretofore having
been reported in the USSR literature only. The extent to which populations
of fishes of the same species vary in their dissolved oxygen requirements
with variations of dissolved oxygen and other environmental conditions
in their native habitats is a matter that appears to be highly perti-
nent to the establishment of water quality criteria intended for
nation-wide application. A question of biological interest and practical
importance, apparently not touched upon in the Soviet literature, is
the extent to which the intraspecific differences in question are genetic
and not due to reversible or irreversible physiological acclimation or
adaptation of individual organisms to their environment. Seasonal
variations of dissolved oxygen requirements, not yet well understood,
also can be profitably investigated through comparative evaluation of
lethal levels.
EFFECTS ON REPRODUCTION
The effects of dissolved oxygen on the embryonic development, hatching,
and larval growth of the salmonid fishes have been rather extensively
studied in the laboratory. Nevertheless, further studies are needed
of the relation between size (or stage of development) of salmonid
embryos at the time of hatching (as determined by dissolved oxygen
conditions during embryonic development) and their subsequent survival
until and after successful emergence from gravels under natural or
simulated natural conditions. Detailed studies of the direct effects
of fine sediments on the survival of embryos and larvae in gravels sub-
ject to siltation are also needed. There is considerable evidence
that reduction of dissolved oxygen in water percolating through the
gravels is not the only cause of observed impairment of survival in
silted gravels (Doudoroff and Shumway, 1970).
Much more pressing than the need for more information on the influence
of dissolved oxygen on the development of the salmonid fishes is the
need for similar information pertaining to various warmwater fishes.
There is now a notable dearth of such information. Data in the USSR
literature indicating very high dissolved oxygen requirements for suc-
cessful development and survival of embryos of some warmwater fishes,
71
-------
especially those that normally develop in standing water, need veri-
fication. If these requirements are indeed as high as they have been
reported to be, water quality standards designed for the protection of
important American fishes must be based in very large degree on per-
tinent information of this kind, which is almost totally lacking in
published American literature. Studies of the influence of dissolved
oxygen on the fecundity of mature fishes can be profitably undertaken,
as can studies of influences on reproductive behavior.
EFFECTS ON GROWTH OF JUVENILE FISHES
Further studies of the influence of dissolved oxygen on food consumption
and growth almost certainly are needed. But until close correspondence
has been conclusively demonstrated between the effects of dissolved
oxygen reductions on growth under nearly natural conditions and their
effects on growth under the highly unnatural conditions in laboratory
aquaria in which consumption of restricted or unrestricted rations
requires virtually
-------
neither proved nor disproved by published results of laboratory experi-
ments. Experimental studies of the movements of fishes in oxygen
concentration gradients in which the transition from high to low con-
centrations is very gradual (i.e., occurs over relatively long dis-
tances) could be more instructive that the reaction studies reported in
the past, and the results would be more applicable to practical problems
than the information now available. Additional studies in the field on
interference with spawning, migrations of fishes, especially salmonids,
by reduced oxygen concentrations certainly are needed.
RESPIRATORY AND OXYGEN CONSUMPTION RATES
It is unlikely that much of practical value in connection with the
establishment of water quality criteria is to be learned through fur-
ther studies of the influence of dissolved oxygen on respiratory and
oxygen consumption rates of fish confined in the respirometers. This
applies also to determination of critical levels of dissolved oxygen
for respiratory metabolism, except perhaps under nearly natural conditions
(by means of energy-balance methods for estimation of metabolic rates).
FISH POPULATIONS IN NATURAL HABITATS
More field studies of the variety, abundance, and growth rates of fishes
in waters subject to organic pollution, in relation to dissolved oxygen ,
concentrations (seasonal minima and averages) that occur in these
environments can provide much information of value, even though observed
responses of the fish populations may not be responses to reduced oxygen
concentrations alone. With modern, continuous-recording, dissolved
oxygen meters, much more reliable information of this nature can be
obtained than that on which early conclusions and water quality criteria
have been based.
RESEARCH PRIORITIES
. t • ' •• \
Assignment of priorities for investigations such as those suggested
above involves necessarily a choice of assumptions to be made that bear
on the practical significance or relative value of different kinds of
information. An appropriate procedure, or logical scheme for research
planning, is presented and explained in Appendix II, where the most
important alternative assumptions that may be accepted or rejected are
presented in a systematic manner. In arriving at the above recommenda-
tions for future research, we have tentatively accepted some of these
assumptions or propositions, thus rejecting the alternative (antithetical)
ones, or we have indicated a preference; but we chose to take no definite
position at this time with respect to many others.
73
-------
APPENDIX I
PUBLICATIONS AND THESES RESULTING FROM THIS PROJECT
PUBLICATIONS
Dahlberg, M., D. L. Shumway, and P. Doudoroff. 1968. Influence of
dissolved oxygen and carbon dioxide on the swimming performance
of largemouth bass and coho salmon. J. Fisheries Res. Bd.
Canada 25(1):49-70.
Davis, G. E., J. Foster, C. E. Warren, and P. Doudoroff. 1963. The
influence of oxygen concentration on the swimming performance of
juvenile Pacific salmon at various temperatures. Trans. Amer.
Fish. Soc. 92:111-124.
Doudoroff, P. 1960. How should we determine dissolved oxygen criteria
for fresh water fishes? Pages 248-250. In Biological Problems in
Water Pollution (Transactions of 1959 Seminar). Tech. Rept. W60-3,
R. A. Taft Sanit. Eng. Center, U.S. Public Health Service,
Cincinnati.
, and C. E. Warren. 1965. Dissolved oxygen requirements of
fishes. Pages 145-155. In C. M. Tarzwell (Editor), Biological
Problems in Water Pollution, Third Seminar, 1962. R. A. Taft
Sanitary Eng. Center, U.S. Public Health Service, Cincinnati.
, and D. L. Shumway. 1967. Dissolved oxygen criteria for
the protection of fish. In Water Quality Criteria to Protect
Aquatic Life. Special Publication No. 4, Amer. Fish. Soc. 96(2):
13-19.
, and D. L. Shumway. 1970. Dissolved oxygen requirements of
freshwater fishes. Food and Agricultural Organization of the
United Nations. FAO Fisheries Tech. Paper #86. 291pp.
Herrmann, R. 6., C. E. Warren, and P. Doudoroff. 1962. Influence of
oxygen concentration on the growth of juvenile coho salmon.
Trans. Amer. Fish. Soc. 91:153-167.
Katz, M., A. Pritchard, and C. E. Warren. 1959. The ability of some
salmonids and a centrarchid to swim in water of reduced oxygen
content. Trans. Amer. Fish. Soc. 88:88-95.
Shumway, D. L. 1969. At least there is someone thinking of the poor
fish. Northwest Magazine, The Oregonian, Portland, Oregon, p. 13.
75
-------
Shumway, D. L., C. E. Warren, and P. Doudoroff. 1964. Influence of
oxygen concentration and water movement on the growth of steelhead
trout and coho salmon embryos. Trans. Amer. Fish. Soc. 93(4):
342-356.
Silver, S. J., C. E. Warren, and P. Doudoroff. 1963. Dissolved oxygen
requirements of developing steelhead trout and chinook salmon
embryos at different water velocities. Trans. Amer. Fish. Soc.
92:327-343.
Stewart, N. E., D. L. Shumway, and P. Doudoroff. 1967. Influence of
oxygen concentration on the growth of juvenile largemouth bass.
J. Fish. Res. Bd. Canada 24(3):475-494.
Whitmore, C. M., C. E. Warren, and P. Doudoroff. 1960. Avoidance
reactions of salmonid and centrarchid fishes to low oxygen con-
centrations. Trans. Amer. Fish. Soc. 89:17-26.
THESES
Brake, L. A. 1972. Influence of dissolved oxygen and temperature on
the growth of juvenile largemouth bass held in artificial ponds.
M.S. Thesis. Oregon State University, Corvallis.
Carline, R. F. 1968. Laboratory studies on the food consumption,
growth, and activity of juvenile coho salmon. M.S. Thesis. Oregon
State University, Corvallis.
Dahlberg, M. L. 1963. Influence of dissolved oxygen and carbon dioxide
on the sustained swimming speed of juvenile largemouth bass and
coho salmon. M.S. Thesis. Oregon State University, Corvallis.
Davis, G. E. 1960. The influence of dissolved oxygen concentration on
the swimming performance of juvenile coho salmon at different
temperatures. M.S. Thesis. Oregon State University, Corvallis.
Eddy, R. M. 1972. The influence of dissolved oxygen concentration and
temperature on the survival and growth of chinook salmon embryos and
fry. M.S. Thesis. Oregon State University, Corvallis.
Fisher, R. J. 1963. Influence of oxygen concentration and of its diurnal
fluctuations on the growth of juvenile coho salmon. M.S. Thesis.
Oregon State University, Corvallis.
Herrmann, Robert B. 1958. Growth of juvenile coho salmon at various
concentrations of dissolved oxygen. M.S. Thesis. Oregon State
University, Corvallis.
Lee, R. A. 1969. Bioenergetics of feeding and growth of largemouth bass
in aquaria and ponds. M.S. Thesis. Oregon State University, Corvallis,
76
-------
McNeil, W. J. 1956. The influence of carbon dioxide and pH on the
dissolved oxygen requirements of some fresh-water fish. M.S.
Thesis. Oregon State University, Corvallis.
Putnam, G. B. 1967. The influence of metabolites on the growth and
development of salmonid embryos and sac fry. M.S. Thesis. Oregon
State University, Corvallis.
Shumway, D. L. 1960. The influence of water velocity on the develop-
ment of salmonid embryos at low oxygen levels. M.S. Thesis.
Oregon State University, Corvallis.
Silver, S. J. 1960. The influence of water velocity and dissolved
oxygen on the development of salmonid embryos. M.S. Thesis. Ore-
gon State University, Corvallis.
Stewart, N. E. 1962. The influence of oxygen concentration on the
growth of juvenile largemouth bass. M.S. Thesis. Oregon State
University, Corvallis.
Whitmore, C. M. 1957. Avoidance reactions of some salmonid and
centrarchid fishes to low concentrations of dissolved oxygen.
M.S. Thesis. Oregon State University, Corvallis.
PUBLICATIONS AND THESES IN PREPARATION
Hutchins, F. E. 1972. Influence of dissolved oxygen and swimming velocity
on the food consumption and growth of juvenile coho salmon. M.S.
thesis in preparation. Oregon State University, Corvallis.
Lee, R. A., and D. L. Shumway. 1972. Bioenergetics of feeding and
growth of largemouth bass in aquaria and ponds. Manuscript in
preparation.
Thatcher, T. 0. 1972. Some effects of the dissolved oxygen concentra-
tion on the feeding, growth, and bioenergetics of juvenile coho
salmon Oneorhynehus kisutoh (Walbaum). Ph.D. thesis in prepara-
tion. Oregon State University, Corvallis.
Trent, T. W. 1972. The influence of temperature and oxygen concen-
tration on the food consumption and growth of largemouth bass and
coho salmon. M.S. thesis in preparation. Oregon State University,
Corvallis.
77
-------
APPENDIX II
78
-------
A TENTATIVE LOGICAL SCHEME FOR IDENTIFYING RESEARCH NEEDED FOR THE
DEVELOPMENT OF DISSOLVED OXYGEN CRITERIA AND STANDARDS
EXPLANATORY INTRODUCTION
There continues to be a serious need to identify those kinds of
research on the dissolved oxygen requirements of fish that will most
directly lead to information adequate for setting reliable water quality
standards. And, because the information is likely to continue to be
more or less inadequate, there is a need to identify the real weaknesses
in the information, so that as we necessarily set standards we are well
aware of just how they are likely to be unreliable.
Biologists knowledgeable about the water quality requirements of fish
have often been hesitant to advance firm recommendations as to water
quality standards for the protection of these fish. Considering the
complexity of factors and responses involved in determining the oxygen
needs of fish, and the inadequacy of knowledge, such hesitancy is
understandable. But the social need to make use of such knowledge as
we may have, the complexity of natural systems, and the inadequacy of
existing knowledge are not peculiar to biology as a science or to
present times. Any use of or advance in knowledge is based on a
system of assumptions, known and unknown, stated and unstated. The
physical sciences have advanced more rapidly than the biological sciences,
and advances have been more expediently applied, in very large part
because of formal recognition of the assumptions underlying any system
of thought or application. Given certain assumptions or propositions,
we can deductively arrive at valid conclusions. If the assumptions do
not correctly represent reality, our conclusions, even if logically
valid, may not be true.
But such a deductive system in which conclusions are clearly tied to
specified assumptions permits the scientist to make scientific judg-
ments and the administrator to make social judgments, according to how
they want to weight the risks involved in the assumptions. If the
risks are too great, more research is necessary, and the nature of that
research is identified.
Much of the disagreement over the research necessary to set water quality
standards and over just how the research should be interpretated in
setting standards has been trivial or semantic, even when very knowledge-
able people have been involved, because of failure to specify the
assumptions on which any line of reasoning or argument is based. We
have here attempted to develop a logical scheme for identifying research
necessary for setting dissolved oxygen standards for fish. Development
of such a scheme is not an easy thing to do. Nor is reading with
understanding such a scheme. But both are preferable to years of
poorly conceived research, failure of biologists to make_clear recommen-
dation based on identified assumptions, or poor application of
79
-------
knowledge in the setting of standards. We believe that general develop-
ment of such schemes in water pollution research and control would be
a very great step ahead.
The scheme that we have developed is based on the assumption that it
is a product of interest to be protected, not that the biological com-
munity is to be protected against any change whatsoever. Furthermore,
this scheme is based on the assumption that it is the production of
the product of. interest—its total tissue elaboration (relative growth
rate x biomass)—that is most important and is to be protected.
Reproduction, behavior, and other biological responses, then, become
important only insofar as they influence production. The scheme as
developed is only sufficiently complex to suggest the research necessary
to determine water quality standards that would be adequate to prevent
any considerable level of impairment of fish production. If other levels
of protection are to be considered, then not only the logical scheme but
also the research necessary must become more complex.
In general, two kinds of assumption or propositions, regulatory and
biological, have been used in developing this logical scheme. The neces-
sary assumptions may have to do with the nature or manner of application
of the criteria, with the importance of various other environmental
factors that may influence the oxygen requirements, with the relative
sensitivity of different life-history stages or of different ecologically
important physiological functions of fish to oxygen deficiency (i.e., their
relative susceptibility to injury), and so forth. The present scheme
represents an attempt to identify the more important assumptions that
sometimes have been or may possibly be made, and to present them in a
systematic fashion, together with conclusions to which they are
believed to lead concerning the nature of needed investigations.
The logical scheme here presented consists of a series of pairs of
antithetical propositions or assumptions. These are designated by
arabic numerals or combinations of these and the letter A. The letter
A at the end of a numerical designation signifies that the proposition
or assumption so designated is the antithesis of the preceding proposi-
tion or assumption. For example, Proposition 1A is the antithesis of
Prop. 1; Prop. 8.1A is the antithesis of Prop. 8.1; and Prop. 10A.1A is
the antithesis of Prop. 10A.1. One or the other or neither of the
two propositions or assumptions of each pair may be rejected. If
only one proposition of each pair is accepted and the other is rejected,
use of this scheme will lead (with only one exception) to but a single
final conclusion concerning the nature of needed investigations.
Whenever, because of inadequacy of available information and consequent
uncertainty, neither proposition of a pair is rejected, more than
one final conclusion usually will be reached, this result indicating that
more than one kind of study is needed. The different conclusions are
designated by roman numerals. Some of the conclusions so designated
(Conclusions I, II, III, IV, and V) are not final conclusions. They
are "modifying conclusions" indicating that the conclusion or conclusions
80
-------
finally reached by proceeding with the use of the scheme (i.e., going
to the next appropriate pair of antithetical propositions according to
directions given) must be modified in the specified manner. Each
modifying conclusion and each proposition that does not immediately
lead to a conclusion is followed by a notation directing the reader to
the next appropriate proposition to be considered.
Some of the stated propositions are deemed certainly untenable, but all
are presented impartially, no preference for acceptance or rejection of
any proposition being indicated. It should be understood, however, that
innumerable assumptions other than those listed had to be made in
devising this scheme. We must and can safely assume, for example, that
the condition of the stock market or the national economy has no influ-
ence on the oxygen requirements of fishes. The validity of some other
assumptions that have been made is not as incontestable as the validity
of the foregoing assumptions. For example, on the basis of available
information, we have assumed that hydrostatic pressure has no important
influence on the dissolved oxygen requirements of fish, or no significant
bearing on dissolved oxygen criteria designed for their protection.
This assumption and its antithesis could have been included in the
listed series of assumptions, but the inclusion of all such assumptions
would have rendered the list too long and the scheme too involved.
For the sake of simplicity, many pertinent considerations, such as
possible or known influences on the dissolved oxygen requirements of
size and age of fish, of season of the year, of the velocity of water
around developing fish embryos, etc., have been largely or entirely
disregarded. Also not specifically considered is the bearing on the
design of water quality criteria of the sometimes wide diurnal fluctu-
ations in dissolved oxygen in fish habitats, and of the large differences
between dissolved oxygen levels to which fish embryos are exposed that
are buried deep in streambed gravels (e.g., salmonid embryos) and the
dissolved oxygen concentrations in the waters flowing over the gravels.
It is assumed, instead, that all of these matters will be given proper
consideration in the design of the experimental or other investigations
recommended in the "conclusions," to the extent that they appear to
be pertinent. Further elaboration of the proposed logical scheme doubt-
less would have made possible the inclusion and full consideration of
all these matters, but the present scheme is tentative and is deemed
sufficiently involved. Present knowledge of the dissolved oxygen (DO)
requirements of fishes and of factors influencing these requirements
being still very limited, it is clearly impossible to delimit the
scope of needed further investigations very precisely or narrowly.
81
-------
THE TENTATIVE LOGICAL SCHEME
1. Concentrations of toxic pollutants are to be limited to levels_
not harmful at approved DO levels: Concentrations of toxic
substances in waters receiving wastes are to be regulated so as
to have no seriously adverse effect on fish production as long as
acceptable DO levels are maintained (i.e., levels not below
prescribed minima based on requirements of fishes in the absence
of these substances). See Prop. 2.
1A. Concentrations of toxicants are not to be so limited, and thus
DO criteria must vary with the kind and degree of toxic pollution.
See. Conclusion I.
/Conclusion I. DO requirements of fishes must be
determined in the presence of every possible combina-
tion of toxic pollutants and at widely varying levels
of pollution with each of these toxicants and combina-
tions of toxicants (or at least at the highestlevel
that may occur3 if such maxima can be predicted or are
to be prescribed). The following additional alter-
natives can then be used to determine the kinds of
studies required for evaluating a minimum DO level
that is harmless or acceptable under each of these
possible conditions. See Prop. 2.
2. Ordinary variations of water quality, except temperature, need
not be considered in establishing DO criteria: Variations of the
dissolved mineral and gas content, other than DO content, of
water receiving oxygen-demanding organic wastes — including
variations of free carbon dioxide content and pH within the limits
of usual variation--do not materially influence the DO requirements
of fishes. See Prop. 5.
2A 'Ordinary variations of water quality cannot be neglected. See
Conclusion II.
Conclusion IT. The dissolved oxygen requirements of
fish must be determined under widely varying conditions
of dissolved mineral and gas content of their medium,
ors if the same criteria are to be applied to all
waters3 under 'the most adverse conditions likely to
be encountered. The following additional alterna-
tives can then be used for determining what studies
are needed to arrive at the minimum DO levels that
are harmless under the different conditions or under
the most adverse conditions. See Prop. 3.
82
-------
3' Prescribed DO concentrations are not to vary with water tempera-
ture | D0 concentrations are to be maintained at levels harmless
to fish and their embryos at the maximum temperatures to which
they or their embryos may be subjected. See Prop. 4.
3A. DO criteria are to vary with the water temperature.
Conclusion III. The DO requirements of fishes must
be determined at different temperatures varying over
the entire range of temperatures likely to oeaur in
the natural habitats of the fish. The following
additional alternatives can then be used for deter-
mining what studies are needed to arrive at the
minimum DO level that is harmless at each of a series
of selected temperatures3 rather than at the maximum
temperature. See Prop. 4.
4. DO criteria are to be prescribed for large classes of fish
habitats or fish faunas, and not for individual fish species:
Acceptable DO levels can and are to be based on requirements
for essentially unimpaired production of one or a few selected,
important fish species believed to be relatively sensitive to
DO deficiency and adequately representative of species to be
protected in all fish habitats of a given kind or class (e.g., all
cold waters in which salmonid fishes are of outstanding importance).
See Prop. 5.
4A. DO criteria are to be prescribed for particular species of fish
to be protected. See. Prop. 4A.1.
4A.1. Possible genetic adaptation and racial differences can be
neglected. The possibility of considerable genetic adaptation (i.e.,
adaptive alteration of genotypes through natural selection) and
consequent intraspecific differences of fish populations can
be disregarded in evaluating the DO requirement of a fish species.
See Conclusion IV.
Conclusion IV: DO requirements must be determined for
a representative population of each fish species of
interest. The following additional alternatives can
then be used for determining what studies are needed
to arrive at the minimum DO level that is harmless or
suitable for a given species. See Prop. 5.
83
-------
4A.1A. The possibility of genetic adaptation can not be disregarded.
See Conclusion V:
Conclusion V:DO requirements must be evaluated
for a population of each species of interest that
has been adapted through several generations to
ossygen-defioient water that is tolerable but
clearly unfavorable for a nonadapted population.
The following additional alternatives oan then be
used for determining what studies are needed to arrive
at minimum DO levels that are harmless or suitable
for the adapted populations of the species of
interest. See Prop. 5.
5. Non- lethal DO levels harmful to fish production will not persist
where rapidly lethal levels are prevented: In waters receiving
organic wastes, DO levels near or below levels that are lethal
for juvenile and adult fish will persist for short periods only,
such as (a) 6 hours, (b) 24 hours, or (3) 4 days; and if
the depression of DO to lethal levels is prevented at all times,
adequate DO levels generally will prevail, so that fish pro-
duction will not be materially impaired. See Conclusion VI.
Conclusion VI: Only the more or less rapidly lethal
levels need to be determined for the selected,
representative fish species^ at the maximum tempera-
tures likely to occur in their natural habitats when
DO levels are low.2/
— Or all species of interest if Prop. 4 is rejected.
Suitably genetically adapted stocks of these fish
must be used if Prop. 4A. I also is rejected.
Or at a series of widely different temperatures,
if Prop. 3 is rejected.
5A. Prevention of lethal levels is insufficient to ensure unimpaired
fish production. See Prop. 6.
6. Fish are not found in jrnture at unfavorable DO levels that can
be avoided: By reacting appropriately to low DO or associated
increased C02 levels, fish almost invariably avoid in nature
DO levels detrimental to their production unless they are
trapped in waters having such low DO content. See Conclusion VII.
Conclusion VII: Only field studies of fish distribution
or movements in relation to DO need to be undertaken,
determining minimum DO levels at which selected,
representative species of fishz/ occur naturally,
and which they apparently could have avoided, at
maximum habitat temperatures .%/
84
-------
6 A. Fish will not always avoid in nature DO levels inimical to
their production. See Prop. 7.
7' Avoidance of unfavorable DO levels, and of those levels only,
in laboratory tests will occur: Under appropriate laboratory
conditions, fish will always markedly avoid DO levels that
are inimical for their production under natural conditions,
even though they may be unable to do so in nature (where
gradients are not as .steep or regular), but they will not avoid
harmless concentrations. See Conclusion VIII.
Conclusion VIII. Only DO levels that are avoided by
selected representative fish —' in appropriate
laboratory tests at maximum habitat temperatures-'
need, to be determined.
1 .A. Avoidance reactions in laboratory tests may not indicate limits
of favorable DO concentration. See Prop. 8.
8. Effects of reduced DO on the swimming performance and behavior
of fish are of primary importance: The swimming ability of fish
or their behavior is affected materially, so that production under
natural conditions is reduced (because of increased suscepti-
bility of the fish to predation, etc.) at DO levels above those
at which harmful effects on reproduction or growth are clearly
demonstrable. See Conclusion IX.
Conclusion IX: Laboratory studies of the influence
of DO on the swimming ability (both "sustained" and
"burst" swimming performance)- or the behavior of
selected., representative fish speoies^/, at nearly
the highest temperatures occurring in their environ-
ments^/'f are needed.
8.A. Effects of reduced DO on swimming ability and behavior of fish
at DO levels favorable for their reproduction and growth are
immaterial. See Prop. 9.
9. Effects of reduced DO on reproduction are important: At DO
levels that have any depressing effect (direct or indirect)
on growth, the impairment of reproduction is pronounced and
sufficient to have a significant depressing effect on production.
See Prop. 9.1.
9 .A. Reduced DO levels at which reproduction is materially impaired
are below those at which growth begins to be affected. See
Prop. 10.
9.1. Lowest DO levels in the waters under consideration are likely
to occur where spawning normally takes place and during the
reproductive season. See Prop. 9.2.
85
-------
9.1 .A. DO minima occurring during the reproductive season and where
spawning normally takes place are well above levels that
occur at other times or elsewhere in the normal habitats of
the fish. See Conclusion X.
Conclusion X: Studies of the influence of DO on
both growth and reproduction (fecundity or early
development) are needed. The following additional
alternatives can be used for determining the nature
of needed studies of both kinds. See both Prop. 9.2
and Prop. 10.
9.2. Unimpaired fecundity in the laboratory indicates DO levels
sufficient for adequate reproduction in nature: Reduced DO
levels at which the fecundity of fish is not materially reduced
in the laboratory are adequate also for adequate reproduction
under natural conditions (i.e., reproduction sufficient for
unimpaired production). See Conclusion XI.
Conclusion XI: Laboratory studies are needed of the
influence of DO on the fecundity and spawning of
selected^ representative fish species^/ at maximum
temperatures likely to occur in their environment
during the reproductive season. =/
9.2.A. Lowest DO levels at which fecundity is not reduced materially
in laboratory tests are less than those necessary for virtually
unimpaired reproduction in nature. See Prop. 9.5.
9.3. Unimpaired laboratory hatching success and survival of young
indicate DO levels suitable for adequate reproduction in
nature: Reduced DO levels at which the percentage of success-
ful hatching of fish eggs and survival of young fry in the
laboratory under appropriate test conditions are not materially
reduced are adequate for adequate reproduction under natural
conditions (i.e., reproduction sufficient for unimpaired
production). See Conclusion XII.
Conclusion XII. Laboratory determination is
needed of DO levels at which the hatching: success
of selectedt representative fish specieslx begins
to be materially impaired under the most unfavor-
able water velocity and temperature conditions to
which their embryos and larvae are likely to be
frequently exposed in nature (i.e.3 at relatively
low water velocities and at temperatures relatively
high for the reproductive season). %/
9.3.A. Lowest DO levels at which hatching success and survival of
young fry are not materially reduced in simple laboratory tests
are less than those necessary for adequate natural reproduction.
See Prop ^9.4.
86
-------
9-4- Hatching size and time in laboratory tests indicate DO levels
required for adequate reproduction in nature: Reduced DO
levels at which the size and degree of development of hatching
larvae are appreciably reduced or hatching is measurably
delayed under appropriate test conditions in an unnatural
laboratory will result in materially impaired reproduction
(i.e., production of young and their survival to the juvenile
stage) under natural conditions, whereas higher DO levels will
not, there being no material impairment of fecundity, repro-
ductive behavior, or viability of the larvae at the higher
levels. See Conclusion XIII.
Conclusion XIII. Laboratory studies of the influence
of DO on hatching time and size of selected, repre-
sentative species of fishl/ at the lowest water
velocities and highest temperatures to which their
embryos are likely to be frequently exposed in nature^
are needed.
9.4.A. Reduced DO levels below which hatching size of larvae is reduced
or hatching is delayed are not reliable and useful indices of
DO concentrations necessary for adequate reproduction in
nature. See Prop. 9.5.
9.5. DO requirements for adequate natural reproduction can be
determined experimentally under more or less natural conditions:
The influence of DO on reproduction (i.e., spawning, pro-
duction of young, and survival through early developmental
stages) in nature is reliably determinable through controlled
experiments performed under simulated natural conditions in
the laboratory or nearly natural conditions in the field.
See Conclusion XIV.
Conclusion XIV: Studies of the effects of reduced
DO on the reproduction of selected* representative
fish speciesz/ under simulated natural conditions
in the laboratory or nearly natural conditions in
the field and at lowest water velocities and
highest temperatures to which embryos and larvae
are likely to be exposed frequently in nature-'
are needed.
9.5.A. The influence of DO on reproduction in nature cannot be reliably
determined experimentally. See Conclusion XV.
Conclusion XV : The DO requirements of fish must
be inferred from observations on reproduction of
selected, representative fish species^ (abundance
of young, etc.) under varying, uncontrolled con-
ditions in natural habitats.
87
-------
10. Fish are at least as sensitive to organic pollution as their
food resources: Reduction of DO by oxygen-depleting organic
wastes reduces the food supply of fish only at levels at
which exploitation by the fish of normally available food
resources is materially impaired. See Prop. 11.
10.A. The food supply of fish is considerably reduced at reduced
DO levels having no material direct effect on the feeding
and growth of the fish. See Prop. 10A.1.
10.A.I. Effects of organic pollutants on the food resources of fish are
- uniformly related to their effects on DO levels: Although
putrescible organic pollutants have variable nutritive proper-
ties, contributing directly or indirectly to the production
of some fish food, the effect on the abundance of fish food
of organic pollution having a given effect on DO levels is
reliably predictable on the basis of knowledge only of the
DO requirements of representative fish-food organisms.
See Conclusion XVI.
Conclusion YNI:Studies of the DO requirements of
fish-food organisms and their foods are needed.
The proposed scheme pertaining to investigation
of the DO requirements of fishes can "be used*
with some modifications* for determining also the
nature of needed laboratory studies on the fish-
food organisms.
10A.1A. Even when effects on DO levels are known, the effects of
"organic enrichment" of waters on the food supply of fish
cannot be reliably predicted on the basis of knowledge of
the DO requirements of representative fish-food species, the
relation between DO depression and reduction of food resources
being highly variable. See Conclusion XVII.
Conclusion XVII: Studies of the effects of varying
degrees of contamination of water with different
putrescible organic wastes on various complex
" aquatic communities and on the production of fish
foods under otherwise nearly or entirely natural con-
ditions are essential.
11- Reduction of the metabolic "scope for activity" of fish
indicates growth impairment: Any reduction of the maximum,
active oxygen uptake (metabolic) rate of a fish and its "scope
for activity" (difference between the active and resting rates),
or reduction of the scope by some definite fraction (e.g., by
one-half) but not by a lesser amount, due to depression of DO
will result in material reduction of the food consumption and
growth, if not the length of life, of the fish in nature.
See Conclusion XVIII.
88
-------
Conclusion XVIII: Studies of the influence of
DO on the active oxygen uptake of selected
representative fish speciesl/in suitable res-
pirometers and on their scope for activity at
maximum habitat temperatures^/ are needed.
11.A. The restriction of the food consumption and growth rates of
fish by reduction of DO is not simply related to the restric-
tion of their active oxygen uptake rate or their scope for
activity. See Prop. 12.
12. Food abundance is usually the factor limiting food consumption
and growth of fish in nature.See Prop. 12.1.
12.A. Food in nature is usually so abundant that its availability
is not a factor limiting food consumption and growth of fish
under natural conditions. See Conclusion XIX.
Conclusion XIX: Laboratory aquarium*tests in which
selected representative fish species— are fed
unrestricted food rations to determine critical DO
levels below which appetite and growth are markedly
impaired at maximum habitat temperatures^/ are needed
and adequate.
12.1. Reduced DO levels at which the food intake and growth begin to
be markedly restricted (oxygen-dependent) in laboratory aquaria
and under natural conditions are nearly the same.
Conclusion: See Conclusion XIX dbove3 under Prop.
12. A. Acceptance of Prop. 12.1 leads to the same
conclusion.
12.1.A. Critical DO levels below which food consumption and growth
rates of fish will be restricted in nature cannot be predicted
from results of laboratory experiments in which fish are fed
unrestricted food rations in simple aquaria. See Conclusion XX.
Conclusion XX: Effects of DO reduction on the food
consumption and growth of selected^ representative
fish species^at maximum habitat temperatures^/ and
different levels of food availability under simulated
natural conditions must be determined. Food density
and intake rate can be controlled by artificial
stocking of the environment or by varying fish biomass
levels in environments in which food is produced
naturally (e.g., in laboratory streams). The DO ^
requirements for unimpaired growth of the fish will
depend on the food availability and consequently will
tend to vary with the growth rates of the fish;
89
-------
howevers the maximum natural food availability3
rathe? than the average availability, in a
given fish habitat may be the factor determining
the critical DO level for that habitat3 if the
periods of highest food availability and of
seriously reduced DO coincide.
90
-------
APPENDIX III
xm c?AX,nAnEcAPPR°ACH T° ™E FORMULA™ OF DISSOLVED OXYGEN CRITERIA
AND STANDARDS FOR THE PROTECTION OF FISHERIES RESOURCES
Reprinted with permission of
Food and Agriculture Organization of the United Nations
Pages 255-275 from
Doudoroff, P., and D. L. Shumway. 1970.
Dissolved Oxygen Requirements of Freshwater
Fishes. Food and Agricultural Organization
of the United Nations. FAO Fisheries
Technical Paper No. 86. 291 p.
SOME CONSIDERATIONS BASIC TO THE
FORMULATION OF CRITERIA OR STANDARDS
The difference between the air-saturation level of 02 and 50% of the
air-saturation level may appear to be a large difference, amounting to
about 4 to 7 mg/1 at ordinary water temperatures. When viewed from a
physiological standpoint, however, it is seen not to be actually a
very large difference. The logarithmic scale is generally, and with
very good reason, accepted as being biologically the most appropriate
scale to use in considering differences of concentration or of
exposure time. On this scale, the range between 100% and 50% of
saturation represents only a modest fraction (less than a quarter) of
the total range of 02 levels to which fish are sometimes exposed in
nature and that most fish are able to tolerate at moderate temperatures.
It is less than one half of the portion of the tolerable range that
lies below the air-saturation level even at ordinary summer tempera-
tures, and a smaller fraction at winter temperatures. When considered
in this light, 02 concentration differences of 1 mg/1 within the
range of concentrations above 50% of air-saturation are seen to be quite
small. This can account for inability of biologists definitely to
decide, for example, whether some adverse effect on fish of reduction
of 02 begins at a concentration of 6 mg/1 or at 5 mg/1. Any serious
disputation concerning such a question would be hairsplitting from a
biological standpoint. Even the difference between 7 mg/1 and 5 mg/1
is not a large difference and its ecological importance consequent!/
may not be readily demonstrable.
Yet, the cost to industry and municipalities of improving waste
treatment so as to raise 02 concentrations in receiving waters by only
an extra 1 mg/1 would amount to untoH millions of dollars. The
conscientious and well-informed biologist who is charged with recommending
water quality criteria or standards for the protection of fisheries thus
is faced with a dilemma. He can see that any large reduction of 02
below natural levels may prove detrimental to fish production in
some waters that support fisheries of immense value. He must not
91
-------
yield to pressure from those who would destroy valuable natural
resources for profit or advancement of other personal ends. Yet,
having thought deeply upon the problem, he knows also that he cannot
honestly assert that the difference between 02 levels clearly harmful
and harmless for fish is as small as 1 mg/1. How, then, can he insist
on a particular 02 level as a minimum acceptable level for all waters
that support fish life of some value when faced with the argument that
a level only 1 or 2 mg/1 lower could be maintained at much less cost to
the public? Ultimately, it is the public that must bear the cost of all
waste treatment,and this is a fact that a biologist who is a public
servant should not forget.
For the biologist's dilemma there is a solution, we suggest, and that
solution lies in the adoption of a sound philosophy and system of water
quality regulation properly attuned to socio-economic realities. The
difficulty with which we are here concerned stems, perhaps, from wide
acceptance of the scientifically indefensible proposition that thin
lines can be drawn that separate water quality alterations that are
virtually harmless to aquatic life from those that are decidedly harm-
ful and therefore unacceptable to an enlightened society. Actually,
there are no such lines, but only broad zones of gradual transition
from quite unimpaired productivity of waters to total destruction of
populations of all valuable aquatic organisms. In the case of dis-
solved 02 concentration, we have seen that the zone in question may
extend all the way from quite undiminished, natural levels of 02 to a
level as low as 2 mg/1 or less. Within such a broad zone, a limit
or limits must be defined for administrative purposes. However, such
a limit cannot be based on biological judgments alone; social and
economic considerations must somehow enter into its determination.
Some waters support or are capable of supporting fisheries of great
commercial or recreational value. This value can be easily destroyed by
a single improperly located or carelessly designed industrial enter-
prise of relatively small value to society. But even the slightest
risk of serious impairment of a very valuable fishery should be unac-
ceptable to society if it can be avoided at a small cost, a cost that
is but a fraction of the possible loss. On the other hand, there
are, in densely populated and highly industrialized regions, some
naturally unproductive waters supporting fisheries that are and always
were of minor importance, because of natural characteristics of the
habitats. A high level of protection of these minor fisheries is
usually attainable only at a cost to society far in excess of any
possible benefits. There are also many waters of intermediate status,
whose moderately valuable fishery resources can be given a corres-
ponding, moderate level of protection at a reasonable cost to society.
The productivity of these waters can usually be maintained at a high
level, but some impairment or risk of impairment of this productivity
unfortunately must be accepted as an unavoidable accompaniment of growth
of population and industry.
The sooner we squarely face the fact that we are concerned not with
92
-------
a choice between protecting and not protecting fisheries--between
white and black-but with a choice of appropriate levels of protection,
the sooner will rapid progress be made in the development of sound
water quality criteria and standards for the protection of fisheries.
This recognition involves the establishment of an appropriate formal
or informal system of "use classification" of waters. Use classifi-
cation of waters can be defined as any administrative classification
done with the avowed intention that all waters assigned to a given
class shall be maintained in, or returned to, a condition suitable
for the same beneficial use or uses through the enforcement of appropri-
ate water quality standards. Various formal systems of use classification
of waters are now in use. We have yet to find, however, one that
clearly and unequivocally acknowledges the need for different levels of
protection of each use, to be determined independently of the levels of
protection of any other approved uses of the same waters. Therefore,
the need also for different criteria or standards of water quality,
appropriate to the different levels of protection of fisheries or
other beneficial uses of water, seems not to have been acknowledged.
This lack of recognition of the need for more than one level of pro-
tection of fisheries, and of most other uses of water too, seems to be
reflected in most of the existing water quality standards and criteria
of a formal nature.
Criteria of suitability of water for different uses differ widely,
and the use that has the highest water quality requirement (with
respect to a given measure of water quality) when protection is
maximal is not necessarily the most important use of a given water.
The requirements of fish life have little relation to those of
domestic or agricultural uses of water, for example. Only aquatic
life needs much dissolved 62- Fisheries can be very important and
can require the highest degree of protection where domestic and
agricultural uses of water are of minor importance and require pro-
tection of a lower order. Elsewhere they can be relatively unimpor-
tant and require less protection than do the other uses mentioned.
Existing classification systems generally are too rigid to provide for
protection of each use commensurate with its relative importance
locally, and therefore most appropriate to local needs.
As we have indicated already, use classification of waters, formal
or informal, must be based on socio-economic considerations--on
public desires and willingness to bear—directly or indirectly, the
costs of satisfying these desires. Once the objectives of waste
treatment or other pollution control measures have thus been adequately
defined, science perhaps will be able to go to work more effectively
in providing suitable criteria of water quality that are founded on
the best available technical information and judgment.
Another important consideration is the biological fact that fish
faunas that are to be found in natural, unpolluted waters and the
production rates of these fishes of value to man vary widely with
93
-------
the highly variable natural quality of these waters. The degree of
impairment of fish production that will result from reduction of the
02 content of water to some uniform level cannot be independent of
the water's natural 03 content. It should be obvious that no fish species
will thrive in any water whose natural 62 content is intolerable or
only barely tolerable for it. Therefore, the abundant species whose
production must be protected in a naturally 02-deficient water will
be species that have 02 requirements quite different from those of
some of the valuable species that may need protection in waters
naturally rich in 02- Large differences in 02 requirements even
between populations of fishes of the same species found in, or
acclimatized to, naturally very different waters have been reported,
and these may have, at least in part, a genetic basis. Living organ-
isms have widely different environmental requirements because they
are adapted for life in different natural environments; the variety of
these requirements and environments is the principal reason for the
variety of biological communities.
Yet, apparently for the sake of engineering and administrative sim-
plicity, these well-known biological truths have been too often over-
looked in the formulation of criteria and standards of water quality
designed for the protection of aquatic life. In a sincere effort to
accommodate engineers and administrators in the field of water pollution
control, and doubtless with some misgivings, biologists have for years
been willing to assert, for example, that warmwater fish populations
or faunas require some minimal 02 concentration, or a pH within some
stated range. Such a criterion clearly implies that all warmwater
fish populations or faunas of unpolluted waters are much alike and
have essentially the same requirements for their preservation. Yet,
we are sure that few biologists would be willing to defend such a
thesis.
It is important to note that the variety of environmental requirements
of fish faunas has not been usually disregarded, or at least is not
now being disregarded, in regulating thermal pollution. The National
Technical Advisory Committee on Water Quality Criteria (U.S.A.)
stated, for example, in its recent report (Federal Water Pollution
Control Administration, 1968) that "no single temperature requirement
can be applied to the United States as a whole, or even to one State;
the requirements must be closely related to each body of water and its
population." These noteworthy additional comments follow: "To do
this a temperature increment based on the natural water temperature
is more appropriate than an unvarying number. Using an increment
requires, however, that we have information on the natural temperature
conditions of the water in question...."
One can only wonder why the same principle that was so firmly stated
in connection with recommended temperature criteria was not considered
pertinent to dissolved 02 criteria, and also to criteria or recommen-
dations pertaining to alterations of the pH and the turbidity of
94
-------
fresh waters. Interestingly, a recommendation against introduction
into coastal waters of materials "that extend the normal ranges of
pH at any location by more that +0.1 pH unit" is included in the
section of the committee's report that deals with marine and estuarine
organisms. For fresh waters, however, only upper and lower limits
(pH 6.0 and 9.0) are recommended; these are well within the range of
extreme natural variation. Presumably, any naturally more acid or more
alkaline waters should not be rendered still more acid or alkaline even
in small degree, according to these recommendation.
The committee's recommendations are not fundamentally very different
from long-established practice. But it is this long-established
practice that we here propose to reject in favor of one that we believe
to be more easily defensible biologically. Without such a departure
from precedents, we feel that we could contribute little of practical
value, certainly no very solid recommendations, on the basis of our
detailed study of background information.
RECOMMENDED CRITERIA AND THEIR APPLICATION
As we have already indicated, the criteria that we are recommending
here differ in two important respects from those now widely used.
Firstly, they are not fixed values independent of natural conditions.
Secondly, by offering a choice, they provide for several different
levels of protection of fisheries, the selection of any one of which
would be primarily a socio-economic decision, not a biological one.
The criteria can best be presented graphically (Figure 1). Their
formulation admittedly required much exercise of personal judgment,
and they may therefore be deemed arbitrary. However, they do derive
from conclusions to which our own research and our detailed study of the
results of other research that are reviewed in this treatise have led
us. We think that they are probably somewhat more accordant with
pertinent biological principles and results of recent research than
are other comparable criteria pertaining to dissolved 02 now used in
connection with water pollution control.
Each line or curve in Figure 1 depicts the relation between estimated
natural 02 concentration minima in fresh waters for any given season
of the year and the seasonal minima that we judge compatible with a
specified level of protection of fisheries in the same waters. In
other words, each shows the level to which we suppose the dissolved
02 can be depressed below the estimated natural minimum for the same
season of the year while still providing the stated level of protection
for local fisheries. The five lines or curves thus are supposed to
represent,'or to be appropriate to, different levels of protection of^
fisheries. One of these levels or another may be selected on the basis
of socio-economic considerations, in classifying a water according to
its intended best uses.
95
-------
IE
O
U
ill
O
>-
X
O
O
V)
<
UJ
OT
Ul
_l
01
Q.
liJ
U
U
1 I ' I ' I ' I I I I I ' I I I ' I ' I ' I '
4 -
3 -
2 -
I -
01 2 3 4 5 6 7 8 9 10 II 12 13 14 15
ESTIMATED NATURAL SEASONAL MINIMUM OXYGEN CONCENTRATION (MG/L)
Figure 1. Proposed dissolved oxygen criteria for protection of
freshwater fisheribs: Curves relating "acceptable" seasonal dis-
solved oxygen minima, or minimum leveis that are deemed appropriate
to different, specified levels of protection of fisheries, to
estimated natural seasonal minima. Curves or lines designated A,
Bj, B, C, and D correspond to levels of protection described in the
text.
-------
As used here, the word "season" means a period, defined with attention
to local climatic and hydrologic conditions, during which the natural
thermal and dissolved 02 regime of a stream or lake can be expected
to be fairly uniform. Usually, division of the year into four equal
(3-month) periods, such as December-February (winter), March-May
(spring); June-August (summer), and September-November (fall) probably
will be satisfactory. However, under special conditions, the designated
"seasons" can be periods longer or shorter than three months; they
need not necessarily be equal in length.
The oblique, straight line designated A in Figure 1 represents no
depression of the 02 concentration in any season of the year below
the estimated natural minimum level for the same season. Thus,
it represents nearly maximal protection of fishery resources. Protection
at this high level can be appropriate for some prime spawning grounds on
which major fisheries are dependent in large measure, and it will
almost fully ensure unimpaired productivity of the protected waters.
This degree of protection is exceeded only by total exclusion of
putrescible organic wastes and therefore no reduction of 02 concentra-
tion below natural levels at any time. It requires, of course, either
complete suspension of waste-producing operations or storage of all 02-
demanding wastes whenever the estimated natural seasonal minima occur
naturally. Such periodic interruption of waste discharges is not
often feasible, and for this reason we doubt that the level of protection
represented by line A will be often chosen in preference to the mainten-
ance of natural 02 levels at all times, the highest possible level of
protection.
The curves designated B and BI are appropriate, we suppose, to a high
level of protection of fishery resources of such dominant importance
that no uses of the water that are likely to cause considerable
reduction of fish production can be approved. Some impairment of fish
production doubtless is risked even when this high level of protection
is provided, but the damage is not to be expected and can never be
great, in our opinion. Curve B is intended for general application
and curve BI for application to major spawning grounds of salmonid
fishes during the months when embryos or larvae are in the gravel.
Curve C is supposed to be appropriate to moderate protection of
fisheries that are highly valued but cannot be given more protection
because they must coexist with major industries or a dense human
population, or with both of these. With this level of protection, we
would expect existing fisheries to persist and usually to suffer no
serious impairment, but some reduction of fish production is likely
to occur often, in our opinion.
Curve D is deemed appropriate to a low level of protection of
fisheries that have some commercial or recreational value but are
so unimportant, in comparison with other water uses, that their
maintenance cannot be a major objective of pollution control. This
level of protection is likely, we suppose, to permit the persistence
97
-------
of sizeable populations of some of the more tolerant species and
successful passage of most migrants. However, we would expect much
reduced production or even complete elimination of other, resident
fishes, often the more desirable ones. Furthermore, use of this
curve is not deemed appropriate when successful passage of the most
sensitive migrants, such as the anadromous salmonids, must be ensured.
Whenever unobstructed migration routes for such fishes are essential
to the persistence of important fisheries, use of curve C or of an
interpolated curve intermediate between curves C and D is recommended.
In our opinion, interpolated values (acceptable 02 concentration minima)
about half-way between those obtained by using curves C and D will
usually be adequate to ensure normal migration of salmonid fishes
through lower reaches of most streams where the current velocity is
moderate.
To apply the proposed criteria, it would be necessary, of course, to
determine the natural, seasonal C>2 minimum from which the acceptable
minimum is to be derived by reference to the appropriate curve in
Figure 1. For waters that can be adequately studied before they are
materially altered from their natural condition, the relations between
season of the year, temperature, stream discharge volume, and 02 con-
centration can be determined by observation. We suggest that, from
these data, sufficiently reliable estimates probably can be derived of
natural 02 minima not only in these waters but also in other similar
waters in the same geographical region when waste discharges render
direct determination of natural 02 levels impossible.
Unfortunately, in many densely populated regions, all or most of the
larger streams and lakes have already been much altered from the
natural condition by waste discharges and other human activities.
If sufficient records of 02 concentrations in such waters before these
changes occurred are lacking, accurate determination of natural minima
may be no longer possible. This will probably be the principle
objection to the use of the proposed criteria as a basis for water
quality standards. However, it is our view that errors in the choice
of water quality standards that would result from incorrect estimation
of natural conditions could not be as great as errors that are likely
to result from total disregard of natural water quality differences.
When the need for sound estimation of natural properties of waters
receiving wastes if fully recognized, the necessary basic data and
reliable methods doubtless will be developed. Some standardization of
the methods may be feasible and desirable, but regulatory agencies
will have to rely in large degree upon the judgment of groups (panels)
of experts charged with the responsibility of determining the probable
natural properties of particular waters. Members of these special
panels should be unbiased so that their decisions would be acceptable
to all interested parties.
98
-------
DERIVATION OF PROPOSED CRITERIA
The position of each of the several curves in Figure 1 has no demonstrable
relation to any particular experimental results. It represents merely
our best judgment broadly based on all of the pertinent information
now available to us. Our curves are admittedly tentative, and sub-
stitution of similar curves lying somewhat above or below them could
well be dictated by future experience in their application and by results
of additional research.
The shaping of the curves in Figure 1, however, did have some connection
with particular experimental data. Originally, these curves were drawn
by us with a variety of general considerations in mind. But having
drawn'the original curves, we decided to test their general accordance
with available data from laboratory experiments in which relative
magnitudes of various readily quantifiable responses of fishes to dif-
ferent reductions of 02 concentration had been reliably determined.
Therefore, we plotted some curves by a different procedure which is
indicated below, and we compared them with the original ones. It
was interesting to find that curves arrived at in the two different ways
very nearly coincided. We then decided to adopt the formal second
procedure for derivation of the curves in Figure 1, except curve B^.
Explanation of the shaping of these curves thus was facilitated. We well
realize, however, that the experimental data we have used have to do
only with a few selected typical responses of individual organisms to
reduction of 02 concentration under controlled laboratory conditions.
We do not wish to imply the assumption that quite different responses
of fish populations under natural conditions will generally parallel
these miscellaneous measured responses. We realize that natural pro-
duction rates of fish populations, for example, cannot be reasonably
assumed to vary with 02 concentration in the same way as do growth
rates of fish fed unrestricted rations in the laboratory. Still, we
believe that our use of experimental data in deriving our own curves is
not unreasonable in the absence of more relevant quantitative infor-
mation.
In Figure 2, the experimental data that we decided to use, all obtained
at moderately high temperatures, have been plotted together, and
curves have been fitted by eye to the data. These curves show how
the rates of growth on unrestricted rations and the sustained swimming
speeds of coho salmon and largemouth bass, and also the weights of newly
hatched coho salmon and steelhead trout alevins, were related to dis-
solved 02 concentrations (or, strictly speaking, to their logarithms).
The data used in plotting these curves are believed to be some of the
best available data showing marked responses of experimental animals to
moderate reductions of 02 below air-saturation levels. They are all
values (actual observations or values obtained by interpolation)
reported in the text of this treatise. In graphing each set of data,
the mean growth rate, swimming speed, or size at hatching at each
99
-------
Figure 2. "Impairment-of-performance responses" of freshwater fishes to
reductions of oxygen concentration: Hypothetical "average" concentration-
response curve (heavy line) generally agreeing with some plotted, repre-
sentative relations between oxygen concentration and indices of relative
"performance" (growth rate, swimming speed, or weight at hatching) of
largemouth bass, coho salmon, and steelhead trout. The plotted points are
included mainly to facilitate identification of curves; they are all data
reported somewhere in the text] some are actual observations, but most
are estimates obtained by interpolation or by integration of experimental
results. The significance of the ordinates ("relative performance
indices") is explained in the text; they are percentages of values
obtained at the air-saturation level of dissolved oxygen, except that in
the case of the hypothetical concentration-response curve, the ordinates
have no definite meaning. The indicated average oxygen concentration
corresponding to no growth of coho salmon (zero ordinate) is a crude
estimate.
100
-------
110
100
90
X
UJ
Q 80
U
70
ir eo
e
£ «
Q.
UJ 40
_J 30
UJ
20 -
10 -
H BASS SWIM. SPEED. 25 C
*«••• BASS GROWTH RATE, 26°C
T SALMON GROWTH RATE, !8-2Cfc
e SALMON SWIM. SPEED, 10-20%
• TROUT HATCHING WEIGHT, IO°C
• SALMON HATCHING WEIGHT, IO°C~
.' . I . I . I . I . I . I . I . I i I i I,
6 7 8 9 10 II 12 13 1415
OXYGEN CONCENTRATION (MG/L)
101
-------
tested level of 02 has been plotted as a percentage of the correspond-
ing mean value for the air-saturation level. This percentage is
designated the "relative performance index." The most prominent curve
in Figure 2 (heavy line) is a curve that we have taken to be fairly
representative of the entire group of response curves fitted to the
plotted data. It is a generalized or "average" 02 concentration-
response curve representing no particular effect or response but
agreeing in general with the various experimentally derived curves
considered collectively. For this curve, the ordinates (relative
performance indices) represent percentages of "performance" at the 9.5
mg/1 level of 02, a value near the average of the air-saturation levels
of 02 at the various experimental temperatures. The curve has been
extended to the 14 mg/1 levels of 02, however, so that its highest ordinate
is slightly greater than 100 (i.e., 102.5). We shall not attempt to explain
here in detail the rather complex reasoning underlying the drawing of
this curve; we hope that enough of it will be apparent to the reader
after careful consideration of the matter. Admittedly, the depressing
effects of 02 reductions depicted by this curve probably are somewhat
greater than most of the effects that have been observed at average
temperatures of fresh waters of the Temperate Zone. As noted above,
the data plotted in Figure 2 were obtained at moderately high tempera-
tures. At low temperatures, some effects are evident only when reduc-
tions of 02 concentration from saturation levels are relatively large.
However, the bias resulting from the omission of low-temperature data
is intentional, our purpose being to devise criteria appropriate to the
protection of fish at the higher temperatures, and not only at average
and lower temperatures.
Comparison of any one of the curves in Figure 1 except curve B, with the
generalized response curve (heavy line) in Figure 2 will reveal a close
relationship between them, a relationship not immediately apparent.
Reductions of 02 (from estimated natural seasonal minima) that are
shown to be "acceptable" by curves A, B, C, and D in Figure 1 corres-
pond to the following constant (along each curve) per cent reductions
of ordinates in Figure 2: 0%, 3%, 9%, and 20%, respectively.
For example, let us consider curve C in Figure 1. It shows that a
reduction of 02 concentration from a natural seasonal minimum of 9.5
mg/1 to the 6.3 mg/1 level, or from a natural seasonal minimum of
6.1 mg/1 to the 4.8 mg/1 level is acceptable. Turning now to the
curve in Figure 2, we find that a reduction of 02 concentration (abscissa)
from 9.5 mg/1 to 6.3 mg/1 corresponds to a reduction of the ordinate
value from 100 to 91, or a 9% reduction. Likewise, a reduction of 02
concentration (abscissa) from 6.1 mg/1 to 4.8 mg/1 corresponds to a
reduction of the ordinate from 90 to 82, again about a 9% reduction
(90 x .09 = 8). The same relationship will be found between curve B
or curve D in Figure 1 and the generalized response curve in Figure
2, except that the percent reductions of Figure 2 ordinates will be
3% for curve A and 20% for curve D. For curve A, this reduction is,
of course, nil. For the lower portion of the curve B^ which was designed
especially for application to very valuable salmonid spawning grounds
102
-------
when embryos or larvae are in the gravel, the reduction is about 1.5%.
However, as noted earlier, this curve does not entirely conform to a
formula like that used in plotting the other curves; its upper portion
is less curved that it would have had to be to conform. Some special
considerations led to our deviation from the regular procedure in
shaping this curve.
In designing the proposed criteria, we have consciously disregarded in
large degree the known variations with temperature of the 02 require-
ments of fishes and of the solubility of 02 in water. We realize that
natural 02 concentration minima are likely to be relatively high when the
02 requirements of fishes are relatively low because of low water temp-
eratures. We have made no provision, however, for adjustment of the
acceptable 02 minima for different seasons of the year according to
temperature. Provision for such adjustment would have involved serious
complication of the criteria, and after careful consideration we have
decided that it is unnecessary.
The design of waste treatment and disposal facilities in accordance with
our proposed criteria must be based usually on the assimilatory capacity
of the receiving waters in summer, when the lowest 02 concentrations
are most likely to occur naturally. However, reduced 02 concentrations
that are acceptable in summer may be unsuitable for successful reproduction
of some valuable fishes during another season of the year when temperatures
are relatively low. That is, higher 02 concentrations may be required
during the cooler season to ensure successful spawning. Also most of
the growth of fish, and the most rapid growth, may well occur when
temperatures are not nearly maximal but natural foods and dissolved $2
are abundant. These considerations are the main reasons for our recom-
mendations that the acceptable 02 minimum for a given water and season
of the year be based on the estimated 02 minimum for the season, rather
than on the estimated annual minimum. They also had much to do with
our decision to recommend no adjustments for water temperature.
In our Introduction, we have already indicated the reason why inter-
actions between 02 deficiency and toxicity of various pollutants that
may be present in waters receiving putrescible organic wastes also
have not been considered in formulating the recommended criteria.
In our opinion, the disposal of toxic pollutants must be controlled so
that their concentrations would not be unduly harmful at prescribed,
acceptable levels of 02, temperatures, and pH values. The acceptable
02 levels, on the other hand, should be independent of existing or
highest permitted concentrations of toxic wastes, no matter what may
be the nature of interaction between these toxicants and 02 deficiency.
Our decision to prescribe acceptable 02 concentration minima, and not
acceptable average concentrations, is based on various considerations.
Among these are experimental data indicating that, when 02 concentra-
tions fluctuate widely about an apparently satisfactory mean level,
adverse effects on the growth of fish, as well as on survival, can be
103
-------
pronounced. Another pertinent consideration is the difficulty of
enforcement of water quality standards limiting average concentrations,
104
-------
APPENDIX IV
TABLES FOR RESEARCH CONDUCTED FROM SEPTEMBER 1, 1968
THROUGH AUGUST 31, 1971
105
-------
Table 1. Initial and final weights, growth and food consumption rates, and gross food conversion efficiencies of juvenile largemouth bass
held in 12-gal bottles at different dissolved oxygen concentrations and temperatures. The bass were fed to repletion on small fish
or tubificid woms.
Dissolved
oxygen
concentration
(mg/liter)
Experiment 1,
2.4
3.7
5.4
9.0
11.3
11. lV
Experinent 2,
2.3
3.4
4.8
7.1
10.0
9.l£/
Experiment 3,
2.5
3.2
4.6
7.2
10.3
10. £'
Experiment 4,
2.4
3.3
4.4
6.2
9.0
9.4S/
Experinent 5,
6.3
5.3
4.9
4.0
3.7
2.8
Experiment 6,
8.0
6.0
5.2
4.6
3.7
2.8
i /
Total wet weight
Initial Final
uitterenc
IOC, 6 fish, 30 days, April
49. 98 54. 84
48.96 56.28
50. 16 58. 56
51.24 57.84
48.96 55.80
49.50 57.54
4.86
7.32
8.40
6.60
6.84
8.04
15C, 6 fish, 25 days, April
57.12 73.14
58.38 82.38
59.46 82.68
55.68 76.56
58.50 82.44
58.74 81.06
16.02
24.00
23.22
20.88
23.94
22.32
ISC, 6 fish, 25 days, July
SI. 60 99.72
81.24 107.04
80.82 109.26
81.90 114.24
82.92 108.50
83.33 104.66
18.12
25.80
28.44
32.34
25.58
21.33
20C, 6 fish, 20 days, July
82.94 117.59
85.62 127.80
83.82 135.42
83.94 147.24
84.84 152.16
82.08 122.52
29. 3C, 7 fish, 17
37.42 —
34.87 --
38.07 —
39.88 —
37.79 —
37.57 —
24. 1C, 7 fish, 17
34.60
39.78 -
41.53 -
38.16 —
43.60 —
40.71
34.65
42.18
51.60
63.30
67.32
40.44
. Food .. Mean ,.
Total dry weight consumption rate- growth rate^
_ (g) (ne/8/davl (mo/5/davl
e Initial
10, 1969
12.31
12.05
12.36
12.61
12.05
12. 19
23, 1969
14.39
14.69
14.98
14.03
14.73
14.79
14, 1969
20.82
20.72
20.60
20.88
21.14
21.24
14, 1969
21.15
21.84
21.37
21.41
21.64
20.93
days, Septenber 13,
..
„
--
8.87
8.26
9.02
9.45
8.96
8.90
days, Septenber 13,
„
_.
--
8.20
9.43
9.84
9.04
10.33
9.65
Final
13,52
13.85
14.25
14.40
13.85
14.58
17.94
20.77
20.48
19.22
20.45
21.06
26.04
27.55
28.35
29.72
28.28
27.32
29.67
33.62
35.63
39.10
41.19
34.10
197<4/
29.11
25.40
23.82
14.41
24.47
19.87
19705/
23.49
27.68
26.28
22.57
24.09
21.55
Difference
1.21
1.80
1.89
1.79
1.80
2.39
3.55
6.08
5.50
5.19
5.72
6.27
5.22
6.83
7.74
8.84
7.14
6.08
8.52
11.78
14.26
17.69
19.55
13.17
20.24
17.14
14.80
4.96
15.51
10.97
15.29
18.25
16.44
13.53
13.76
11.90
Dry
12.7
15.6
15.7
14.1
15.3
22.7
24.9
32.0
32.2
31.3
32.2
42.5
20.0
25.3
29.6
31.9
26.8
42.2
37.9
42.3
47.6
56.7
58.8
82.8
111.1
112.1
100.9
83.6
94.2
96.4
103.4
101.1
94.6
95.6
86.1
86.3
Wet
3.08
4.71
5.09
4.03
4.28
5.01
9.83
13.68
13.08
12.47
13.57
12.87
7.89
10.93
11.92
13.02
10.50
9.00
17.22
19.66
24.44
29.10
28.21
19.70
--
--
—
—
--
--
-
--
--
—
--
.final weight
DrF
3.06
4.64
4.67
4.50
4.47
5.94
8.71
13.67
12.50
12.30
12.97
13.95
8.83
11.77
12.54
13.71
10.96
10.36
16.68
21.16
24.90
29.28
30.98
23.90
62.7
59.9
53.0
24.5
54.6
44.8
56.7
57.8
53.5
50.3
47.0
44.9
plus
Gross ,
efficiency— Mean growth rate
(t) Standard error USD. 051'
Dry
24.6
29.9
29.9
31.3
30.5
26.2
3S.1
37.0
38.9
39.7
40.4
32.8
44.6
44.7
42.7
43.8
43.1
23.7
44.2
50.1
52.6
51.6
52.9
28.9
56.4
53.4
52.5
29.3
58.0
46.5
54.8
57.2
56.6
52.6
54.6
52.0
initial w<
Wet
0.36
0.53
0.39
0.49
0.45
0.49
0.83
0.63
0.91
0.90
1.09
0.82
0.95
0.60
1.02
0.94
2.19
0.74
1.40
1.05
1.40
1.52
l.OS
1.70
Ei^i oer d.
Dry Wet Dry
0.41
0.44
0.79
0.55
0.54 .,.,. n.s.
0.63
0. 59 • "
0.66
0.93
0.87
1.20 2.58 2.57
0.78
0.81
0.82
1.27
1.42
2.05 ... > n.s
0.99
1.36 • *
1.17 • •
1.25 • •
1.07
0.99 3.75 3.39
1.23
iv.
Mean values are based on individual growth rates expressed as tissue elaborated in milligrams per mean gran of tissue (•
per day. In experiments 5 and 6, total weights of bass were used in determining mean growth rates.
Gross food conversion efficiencies were determined using total weights of tissue elaborated and food consumed.
Asterisk indicates growth rates that are significantly different from those of btus reared at near air-saturation and fed sttall fish.
All fish died during the evening of the last test day; therefore, wet weights were not determined.
Bass were fed live tubificid wore in this treatment, whereas those in other treatments were fed snail fish.
final weight plus initial weight)
107
-------
o
oo
Table 2. Initial and final weights, weight gained, food consumption and growth rates, and gross food
conversion efficiencies of juvenile largemouth bass held for 10 days at 20°C in 12-gal
bottles. One, five, and ten fish were held in separate bottles and fed to repletion on
small fish. All values are based on wet weights.
Number of
bass per
chamber
1
1
5
5
10
10
— Growth
* tn'tTl'im
Total weight
(R)
Initial
8.64
10.65
42.30
41.34
85.56
74.98
Final
11.18
15.04
50.39
55.87
107.75
100.25
and food consumption
Carrie -r\*aT» mo ar* nrT»am /^-P
Food , , , , Gross
consumption rate— Growth rate— e f ficiency
Difference (mg/g/day)
2.54
4.39
8.09
14.53
22.19
25.27
rates are
•f- 1 c cuo -r\f-t
73.97
89.33
63.53
81.34
68.42
78.56
expressed as tissue
,enm. rfinal wei§ht
(mg/g/day)
25.63
34.19
17.46
29.95
22.96
28.84
elaborated (or food consumed)
plus initial weight, ,
(%)
34.6
38.3
27.5
36.8
33.6
36.7
in
-------
Table 3.
"tes and *ross food Aversion efficiencies of
sir-"- oxygen
Dissolved
oxygen
concentrati
(mg/liter)
Experiment
10.7
8.3
6.4
4.9
3.9
3.1
Experiment
11.3
9.1
7.0
5.4
4.2
3.1
Experiment
10.8
8.4
6.4
5.2
3.9
3.3
Experiment
9.1
7.4
6.1
4.6
3.7
3.9
Experiment
7.3
6.7
S.4
3.8
3.3
Experiment
7.8
7.3
5.7
4.9
4.1
3.3
y Growth
CTfan n
on
Total wet weight Total dry weight
Initial rinai uitterence Initial
1, 13. OC,
21.
21.
21.
20.
20.
21.
2, 8.4C,
20.
20.
19.
19.
unal Difference
Food
consumption
ratei/
(mg/E/day)
Net
Dry
Growth rate!'
(mg/g/davl
Wet
Dry
Gross
efficiency
10 fish, 20 days, March 28, 1970
0 52.0 31.0
4 51.5 30.1
0 50.3 29.3
6 49.5 28.9
S 47.0 26.5
3 43.3 22.0
10 fish, 20 days, March 28
2 37.5 17.3
S 38.7 18.2
9 37.8 18.0
9 37.2 17.3
19.9 36.3 16.4
20.
3, 13. 2C,
7.
7.
7.
7.
7.
7.
4, 17.8C,
7.
7.
7.
7.
6.
6.
5, 21. 7C,
14.
14.
15.
15.
80
6, 18. 6C,
16.
IS.
10.
16.
IS.
60
and food
f tissue
4 33.0 12.6
9 fish, 20 days, June 7,
2 18.6 11.4
4 19.7 12.4
2 17.7 10.5
4 16.9 9.5
3 14.9 7.6
2 13.9 6.7
9 fish, 20 days, June 7,
2 24.3 17.1
1 23.9 16.8
0 20.2 13.2
0 19.8 12.8
9 13.6 6.7
3 10.1 3.8
4.2
4.3
4.2
4.2
4.1
4.3
, 1970
4.1 '
4.1
4.0
4.0
4.0
4.1
1970
1.3
1.3
1.3
1.4
1.3
1.3
1970
1.3
1.3
1.3
1.3
1.3
1.1
11.7
11.6
11.3
11.1
10.4
9.7
8.0
8.3
8.1
8.0
7.8
7.2
4.0
4.3
3.7
3.5
3.1
2.8
5.6
5.5
4.6
4.5
2.8
2.0
7.4
7.3
7.0
6.9
6.3
5.3
3.9
4.2
4.1
4.0
3.8
3.1
2.7
3.0
2.4
2.2
1.8
1.5
4.2
4.2
3.3
3.2
1.6
0.9
157
155
155
151
142
121
108
111
111
111
103
89
183
171
162
160
136
124
201
199
189
176
135
105
117
US
116
113
106
90
83
86
85
82
80
67
177
165
161
161
138
126
186
182
177
166
136
110
43.0
41.3
41.1
41.2
39.3
34.1
30.0
30.8
31.1
33.8
29.2
23.6
44.2
45.6
41.9
39.1
34.1
31.5
54.2
54.1
48.6
47.7
32.6
23.0
46.6
45.8
45.3
45.4
43.2
38.3
32.6
33.4
33.7
33.1
31.8
27.1
50.9
52.3
47.8
44.5
39.8
36.5
61.8
61.6
56.5
55.6
38.0
27.1
27.3
26.7
26.5
27.3
27.7
28.2
27.8
27.6
28.1
31.6
28.2
26.6
24.1
26.7
25.9
24.4
25.0
25.5
26.9
27.2
25.7
27.1
24.1
21.9
39.8
39.9
39.2
40.2
42.6
42.4
39.1
38.8
39.6
40.2
. 39.8
40.3
28.8
31.7
29.6
27.7
28.9
29.0
33.3
33.8
31.9
33.5
27.9
24.6
10 fish, 20 days, July 13, 1971
5 27.9 13.3
7 30.4 15.8
8 25.6 9.9
3 18.8 3.5
2.7
2.7
2.9
2.8
percent mortality occurred during
10 fish, 20 days, July 13
4 41.0 24.6
S 38.2 22.7
9 23.1 12.3
S 29.3 12.8
4 24.8 9.4
percent mortality occurred
, 1971
3.0
2.9
2.0
3.0
2.8
during
6.0
6.6
5.4
3.8
the test
9.2
8.6
5.0
6.4
5.3
the test
consumption rates are expressed as tissue
final weight plus Initial weight^
3.3
3.9
2.6
1.0
•
6.2
5.8
3.1
3.4
2.5
•
elaborated
per day.
183
191
147
121
184
185
168
152
140
(or
147
151
119
102
141
141
132
121
113
29.0
33.3
22.7
9.9
40.8
40.2
34.3
26.5
22.3
food consumed) in
36.7
40.3
29.4
14.5
48.6
48.1
41.5
33.3
29.1
milligrai
15.8
17.4
15.5
8.2
22.2
21.8
20.5
17.4
16.0
is per
25.0
26.6
24.7
14.2
34.4
34.0
31.4
27. S
25.7
mean
109
-------
Table 4. Experimental conditions, weights, food consumption rates, growth rates, and gross food
conversion efficiencies for juvenile Chinook salmon during cyclic ration feeding studies.
Ten fish were held in each test chamber.
Mean
dissolved
oxygen Feec
(mg/1) lev«
Experiment
10.4
5.1
3.1
10.3
5.0
2.9
Experiment
9.1
4.9
3.3
9.0
4.5
3.2
1,
L
L
L
H
H
H
2,
L
L
L
H
H
H
Total wet weight
ling (g)
sli' Initial
12C, Chinook
18.65
18.87
18.33
19.65
19.02
18.89
17C, chinook
20.17
20.62
19.68
19.72
20.44
20.87
Final
salmon
21.22
21.06
20.06
27.43
24,37
22.06
salmon
24.90
25.96
24.58
29.02
30.69
30.57
Diff.
, 14
2.57
2.19
1.73
Total dry weight
CK)
Initial Final
days, March
3.51
3.55
3.45
5.03 3.69
5.35
3.17
, 21
4.73
5.34
4.90
9.30
10.25
9.70
3.58
3.55
days, April
3.87
3.96
3.78
3.78
3.92
4.00
20,
3.95
3.97
3.85
4.90
4.88
4.35
9,
4.59
4.91
4.68
5.73
6.16
6.18
Diff.
1971
0.44
0.42
0.41
1.21
1.30
0.80
1971
0.72
0.95
0.91
1.95
2.24
2.18
Food
consumption
rate
(mg/g/day)
Wet Dry
57.2
51.8
44.8
74.5
76.1
55.8
83.3
78.8
73.9
105.9
98.9
91.9
52.1
52.8
49.9
70.1
71.0
54.3
75.8
72.1
6§l1
98.4
87.3
80.8
Growth rate
(mg/g/day)
Wet
9.2
7.8
6.4
16.3
17.3
11.1
9.9
10.9
10.5
18.2
19.1
18.0
Dry
8.4
8.0
7.8
20.1
22.0
14.5
8.1
10.2
10.2
19.5
21.1
20.4
Gross
efficiency
%
Wet
16.1
15.1
14.3
21.9
23.2
19.9
12.0
13.8
14.7
17.1
19.3
19.5
Dry
16.1
15.2
15.6
28.7
30.9
26.7
10.7
14.1
15.7
19.8
24.7
25.2
-------
Table 4. Continued
Mean
dissolved
oxygen
Experiment
10.7
5.0
3.3
10.6
5.0
3.0
Feeding
level!/
2, 12 C,
L
L
L
H
H
H
Total wet weight
fg)
Initial
chinook
19.62
21.00
20.20
18.32-/
/") /•) ty ry ** /
£.£.. OO—
20.94
Final
salmon,
25.21
27.64
26.32
28.87
34.20
31.77
Diff.
21 days
5.59
6.64
6.12
10.55
11.87
10.83
Total dry weight
(g)
Initial
, April
3.76
4.03
3.87
3.63
4.42
4.02
Final Diff.
9, 1971
4.75 0.99
5.32 1.29
5.15 1.27
5.79 2.16
6.78 2.36
6.31 4.44
Food
consumption
rate
(mg/g/day)
Wet ' Dry
71.5
65.6
63.0
91.5
79.4
81.0
65.6
59.4
56.6
83.3
73.3
70.0
Growth rate
(mg/g/day)
Wet Dry
11.9
13.0
12.6
21.3
20.0
19.6
11.0
13,1
13.4
23.0
21.0
21.1
Gross
efficiency
Wet
16.6
19.8
19.9
23.3
25.2
24.8
Dry
16.8
22.1
23.7
27.6
28.6
30.1
— Daily ration fed each week: L= 0, 1, 3, R, R, 3, and 1%
H= 3, 4, 6, R, R, 6, and 4% of initial wet weight of
salmon (R= repletion)
2/
— Nine fish were placed in the bottle at the oxygen concentration of 10.6 mg/1; eleven fish were
placed in the bottle held at 5.0 mg/1 of oxygen. The error was not discovered until the
termination of the experiment.
-------
Table 5. Initial and final weights, food consumption and growth rates, and food conversion efficiencies of juvenile
coho salmon held in 12-gal bottles at various dissolved oxygen concentrations and temperatures. The
salmon received an unrestricted supply of live tubificid worms.
Dissolve!
oxygen
concentrati
Cmg/ liter;
Experiment
3.0
3.7
5.4
8.3
10.9
21.5
Experiment
3.0
3.8
5.2
6.9
9.6
20.8
Experiment
10.8
8,3
6.6
5.1
3.9
3.1
Experiment
11.8
9,4
7.1
5.5
4.1
3.1
Experiment
9.2
7.0
5.5
4.9
3.6
3.1
Experiment
7.2
5.8
5.1
4.0
3.1
9.7
Experiment
8.9
7.9
5.9
4.8
3.8
3.4
1 ',
Total wet weight Total dry
'»» l£) fn)
1 initial Final Difference Initial Final
1, 13. OC, 6 fish, 18 days, October 1, 1969
34.40 44.40 10.00 7.62 10.69
33.20 45.80 12.60 7.34 11.27
34.60 53.40 18.80 7.67 13.22
34.10 57.50 23.40 7.56 14.47
33.70 57.40 23.70 7.46 14.58
33.00 56.50 23.50 7.30 14.30
2, 18. OC, 6 fish, 13 days, October 1, 1969
40.00 44.90 4.90 8.90 10.20
39.50 48.80 9.30 8.80 11.50
40.40 51.60 11.20 8.90 12.80
39.40 54.30 14.90 8.70 13.40
40.70 60.00 19.30 9.00 14.70
40.50 58.50 18.00 9.00 14.60
3, 12. 9C, 10 fish, 20 days, May 9, 1970
10.23 26.50 16.27 1.85 6.04
9.71 27.16 17.45 1.76 6.12
9.76 23.49 13.73 1.77 5.37
9.88 24.16 14.28 1.79 5.44
10.15 20.91 10.76 1.84 4.68
10.05 17.85 7.80 1.82 3.95
4, 8.6C, 10 fish, 20 days, May 1, 1970
12.0 23.1 11.1 2.3 4.9
12.7 25.0 12.3 2.4 5.3
12.4 23.5 11.1 2.4 5.0
12.3 2.2.9 10.6 2.3 4.9
12.5 21.8 9.3 2.4 4.6
12.4 2D.O 7.6 2.4 4.2
5, 21. 6C, 7 to 9 fish, 20 days, July 22, 1970^
2.53 3.91 1.38 0.52 0.97
2.28 3.34 1.06 0.47 0.77
1.79 3.07 1.28 0.37 0.71
2.20 3.48 1.28 0.45 0.84
2.53 2.09 -0.44 0.52 0.46
all died within the first ten days of the
6, 18.0C, 7 to 9 fish, 20 days, July 22, 1970^
2.32 3.74 1.42 0.47 0.90
2.19 3.78 1.59 0.45 0.91
2.47 4.23 1.76 0.50 1.03
2.14 3.56 1.42 0.44 0.8S
2.18 3.00 0.82 0.44 0.71
2.06 3.60 1.54 0.42 0.85
7, 21. 8C, 9 fish, 20 days, June 15, 1971
5.27 17.79 12.52 0.92 3.88
S.10 15.75 10.65 0.88 3.32
5.10 17.97 12.87 0;88 3.88
4.05 10.95 6.90 0.70 2.21
5,60 15.51 9.91 0.97 3.02
S.OO 11.14 6.14 0.87 2.27
weight
Difference
3.07
3.93
5.55
6.91
7.12
7.00
1.30
2.70
3.90
4.70
5.70
5.60
4.19
4.36
3.60
3.65
2.84
2.13
2.6
2.9
2.6
2.6
2.2
1.8
0.45
0.30
0.34
0.39
-0.06
test
0.43
0.46
0.53
0.41
0.27
0.42
2.96
2.44
3.00
1.51
2.05
1.40
Food
consumption
rate!'
(mg/ a/day]
wet Dry
179.7
175.3
166.8
160.1
141.6
124.0
130.0
112.8
113. C
112.6
105.0
96.8
149.7
149.8
161.5
137.2
128.6
136.4
134.0
120.9
115.7
150.7
243.1
239.7
230.9
236.8
200.9
190.2
71.3
78.7
97.2
109.8
116.5
1.19.9
93.4
93.5
125.3
125.6
140.6
137.8
159.6
156.7
148.4
143.8
128.8
114.3
119.9
108.5
104.5
103.7
98.3
91.0
107.6
114.1
122.1
101.4
_
95.5
100.7
98.5
89.7
61.3
113.5
161.1
164.4
154.5
168.0
146.4
135.0
Growth rate^'
(mg/i/day)
Wet Dry
14.10
17.72
23.74
28.38
28.91
29.17
8.88
16.20
18.72
24.46
29.48
27.97
44.3
47.3
41.3
42.0
34.6
28.0
31.5
32.7
30.7
30.3
27.2
23.5
21.4
18.9
26.3
22.5
9.5
23.4
26.6
26.3
24.9
15.8
27.2
51.7
48.6
S3.1
43.8
44.7
36.2
18.63
23.46
29.52
34.85
35.89
36.01
10.47
20.46
27.65
32.72
37.00
36.50
53.0
55.3
50.4
50.4
43.5
36.8
36.5
37.5
35.4
35.5
31.6
27.7
30.2
23.2
31.5
30.2
-6.1
31.4
33.8
34.6
31.8
23.5
33.3
58.7
55.3
60.0
49.2
48.8
42.5
Gross
efficiency
(%)
wet
_
24.6
27.0
24.7
26.2
24.5
22.5
24.2
27.8
27.2
26.9
25.9
24.3
14.3
12.6
16.3
16.4
18.2
19.5
19.6
20.6
13.7
18.0
21.3
20.3
23.0
18.5
22.2
19.0
ury
26.1
29.8
30.5
31.7
30.8
30.0
11.4
22.6
26.3
25.6
26.4
26.6
33.2
35.3
34.0
35.1
33.8
32.2"
30.4
34.6
33.9
34.3
32.2
30.4
28.1
20.3
25.8
29.8
32.9
33.6
35.1
35. S
38.3
29.3
36.4
33.6
38.8
29.3
33.3
31.5
Experiment 8, 18. 3C, 10 fish, 20 days, June 15, 1971
9.3
7.S
6.1
S.O
3.9
3.6
S',42 22.56 17.14 0.94 5.02
5.89 19.68 13.79 1.02 4.37
5.82 16.15 10.33 1.01 3.49
5.94 22.13 16.19 1.03 4.94
5.72 20.24 14.52 0.99 4.40
S.80 6.31 0.51 1.00 1.26
4.08
3.35
2.48
3.91
3.41
0.26
246.6
231.0
219.9
225.0
223.9
- 3/
- Growth and food consumption rates are expressed as tissue elaborated (or
gram of tissue present , final weight plus initial weight , per day.
2/ I 2
— The weights shown are mean weights. Mortality during
to sevf
-1 Pour fi
m or nine.
Afn*>0 <~m
i
acclimation
*ciintn4'if\n fat
reduced
»« UATA
159.8
151.0
148.1
145.9
148.5
— V
58.3
51.3
44.8
54.9
53.3
0.4
food consumed) in
65.2
59. 1
52.5
62.3
60.7
11.0
23.6
22.2
20.4
24.4
23.8
mil ligrams per
the initial number of fish
nnt Af*tf
ivmi nn/4
40.8
39.1
35.4
42.7
40.5
mean
per bottle
112
-------
Table 6.
Dissolved
oxygen Daily ,.
concentration food ration^
(•g/Uter) (»)
8.0
5.0
3.0
Sumer 1968
0
1
1
2
2
3
3
4
4
5
5
R
R
R
R
0
0
1
1
2
2
3
3
4
4
S
5
R
R
R
R
0
0
1
1
Z
2
3
Net weight £
•" ii • .I
1.10
1.08
1.15
0.91
1.38
0.84
1.05
0.91
1.17
1.19
1.29
1.08
1.40
1.31
1.09
0.82
1.39
1.62
1.19
1.04
0.86
1.27
1.46
1.31
1.04
1.04
1.16
1.18
1.65
1.12
1.05
1.01
1.01
0.87
1.43
1.08
1.12
0.96
1.33
0.88
1.02
0.72
1.01
1.11
1.33
1.12
1.31
1.35
1.91
1.83
5.03
2.10
3.00
2.59
2.44
2.27
2.96
3.63
2.53
1.66
2.89
2,34
2.44
2.10
2.94
1,85
2.66
2.45
2.54
2.30
3.18
3.14
2.53
3.56
3.01
2.65
2.11
2.28
1.91
1.94
2.54
2.95
2.15
3.22
3.13
1.84
1.99
2.50
— — ,^___
0.95
0.97
1.13
0.86
1.46
0.87
1.11
0.97
1.36
1.34
1.53
1.27
2.09
1.69
1.40
1.12
1.29
1.46
1.15
1.00
0.86
1.31
1.60
1.41
1.22
1.15
1.40
1.44
2.27
1.45
1.49
1.32
0.94
0.80
1.43
1.05
1.16
0.98
1.38
0.95
1.16
0.83
1.18
1.27
1.66
1.28
1.63
1.60
1.63
1.56
2.93
2.01
3.00
2.60
2.71
2,45
3. 52
4.07
3.11
1,97
4.07
3.26
3.37
2.90
2.60
1.60
2.56
2.37
2.65
2.30
3.45
3.48
2.94
4.18
3.80
3.27
2.68
3.09
2.72
2.96
2.22
2.65
2.07
2.94
3.22
1.88
2.18
2.79
Difference
-
-0.15
-0.10
-0.03
-0.05
0.08
0.02
0.05
0.06
0.19
0.15
0.24
0.18
0.70
0.37
0.31
0.31
-0.10
-0.16
-0.04
-0.04
0.01
0.04
0.14
0.10
0.18
0.11
0.24
0.26
0.62
0.32
0.44
0.31
-0.07
-0.07
0.00
-0.03
0.04
0.02
0.05
0.07
0.14
0.11
0.17
0.15
0.33
0.17
0.32
0.24
-0.28
-0.27
-0.10
-0.09
0.00
0.02
0.27
0.18
0.56
0.44
0.59
0.31
1.19
0.92
0.94
0.81
-0.34
-0.25
• 0.10
-0.07
0.11
-0.01
0.26
0.34
0.42
0.62
0.79
0.62
0.58
0.81
0.81
1.02
-0.32
-0.30
-0.08
-0.28
0.09
0.04
0.18
0.30
Initial
• '
0.24
0.23
0.25
0.20
0.30
0.18
0.23
0.20
0.25
0.26
0.28
0.23
0.30
0.29
0.24
0.18
0.28
0.33
0.24
0.21
0.18
0.26
0.30
0.27
0.21
0.21
0.24
0.24
0.34
0.23
0.21
0.21
0.22
0.19
0.31
0.23
0.24
0.21
0.29
0.19
0.22
0.16
0.22
0.24
0.29
0.24
0.28
0.29
0.40
0.33
0.63
0.44
0.62
0.54
0.51
0.47
0.61
0.75
0.52
0.34
0.60
0.48
0.50
0.43
0.61
0.38
0.55
0.51
0.53
0.48
0.66
0.65
0.52
0.74
0.62
0.55
0.44
0.47
0.40
0.40
0.53
0.61
0.45
0.67
0.65
0.38
0.41
0.52
)ry weight
(!)
Finaf-
0.16
0.18
0.24
0.16
0.30
0.18
0.23
0.20
0.29
0.29
0.32
0.28
0.47
0.41
0.31
0.24
0.23
0.29
0.23
0.19
0.17
0.28
0.34
0.30
0.27
0.26
0.31
0.32
0.52
0.33
0.33
0.33
0.18
0.16
0.28
0.21
0.24
0.19
0.29
0.20
0.26
0.16
0.25
0.28
0.36
0.27
0.37
0.36
0.31
0.25
0.56
0.43
0.61
0.52
0.57
0.49
0.74
0.91
0.68
0.41
0.91
0.72
0.80
0.70
0,53
0.29
0.46
0.53
0.53
0.46
0.73
0.78
0.63
0.88
0,87
0.71
0,63
0.71
0.58
0,68
0.39
0.54
0,41
0.54
0.67
0.39
0.47
0.60
Difference
^ j
-0.08
-0.06
-0.01
-0.03
0.01
0.00
0.01
0.01
0.03
0.03
0.04
0.05
0.17
0.12
0.08
0.06
-O.OS
-0.04
-0.01
-0.02
-0.01
0.02
0.04
0.04
0.05
0.04
0.07
0.07
0.18
0.10
0.11
0.12
-0.04
-0.03
-0.03
-0.02
0.00
-0.01
0.00
0.01
0.04
0.00
0.03
0.03
0.07
0.03
0.08
0.07
-0.09
-0.13
-0.08
-0.01
-0.01
-0.02
0.06
0.02
0.13
0.16
0.14
0.07
0.31
0.23
0.30
0.26
-0.08
-0,0
-0 09
0.03
0,01
-0.12
0.07
0.13
0.11
0.14
0.24
0.16
0.20
0.24
0.19
0.28
-0.14
-0.07
-0.03
-0.13
0.03
0.00
0.06
0.08
Food
consiupUon
0
0
11.0
10.5
19.8
20.2
31.2
28.9
37.3
37. S
45.9
46.6
97.2
75.8
65.7
79.3
0
0
10,9
10.1
19.9
19.6
29.3
28.9
37.7
38.8
45.4
45.5
78.8
71.8
78.3
80.0
0
0
10.0
10.6
19.9
19.9
29.8
29.1
37.0
35.0
42.2
47.8
56.1
41.4
58.4
44.9
0
0
10.2
10.3
20.3
20.8
28.3
29.0
36.6
37.8
45,7
45.7
65.0
67.3
64.0
65.1
0
0
10.6
10.3
20.8
29.2
29.0
37.2
37.8
44.5
45.7
56.3
61.5
59.6
77.8
0
0
10.8
10.5
29.9
20.2
29.2
28.7
0
0
11.1
12.2
20.7
31.8
31.8
37,7
40.6
46.9
49.3
93.4
74.1
62.6
84.6
0
0
12.6
11.9
23.3
21.8
32.8
32.0
41.4
42.1
49.3
49.9
81.9
75.2
81.7
80.0
0
0
11.3
11.9
21.8
22.4
32. S
31.7
39.0
39.8
46.3
51.0
59.1
44.8
62.6
45.9
0
0
15.9
15.6
30.7
31.9
42.5
57.4
54.1
54.6
67.4
68.4
92.5
95.4
S7.S
90.6
0
0
17.1
14.7
32.1
43.1
41.2
54.6
55.1
63. 4
65.9
76.5
86.1
88.1
107.6
0
0
16.5
16.9
30.0
30.6
43.0
42.3
-_ _
Growth rate-'
9.9
7.1
1.8
3.9
4.2
3.5
4.6
10.7
8.5
12.2
11.0
28.5
17.8
17.5
22.5
5.5
7.2
-2.3
3.0
0.4
2.4
6.6
5.3
11.2
7.0
13.2
13.9
22.7
17.9
24.8
19.1
5.2
6.0
0.2
0.2
2.4
1.2
2.4
5.6
8.9
10.3
11.1
9.1
15.8
10.1
15.6
11.8
-11.3
-11.4
- 2.5
3.2
0.0
10.4
7.6
5.4
12,3
8.1
14.8
12.2
24.4
23.5
23.0
23.1
8.7
-10.5
2.8
2.2
- 0.2
5.6
7.3
10.9
11.4
16.6
15.0
17.2
21,5
24.9
29.7
- 9.6
7.8
2.7
- 6.5
2.1
1.6
6.3
8.0
-27.1
-19.6
2.3
-13.0
1,2
1.6
2.5
9.0
7.9
9.4
13.0
31.3
25.3
20.0
21.1
-14.4
9.2
- 2.6
7.0
3.7
4.2
8.5
9.0
IS. 2
13.3
18.8
18.9
30,6
26.4
29.6
32.4
-13.6
-11.5
- 7.0
7.7
0.0
5.0
- 0.5
3.3
10.4
1.8
8.6
9.4
15,6
7.3
18.2
IS.O
-17.2
-29.0
9.3
l.S
1.1
2.6
8.3
3.1
13.6
13.6
17.1
14.1
29.5
27.6
32.6
33.3
9.4
-18.8
-13.2
3.6
2.8
7.6
12.7
13.7
12,9
23.3
18.1
26.4
28.4
27.4
35.8
-22.1
8.4
5.5
-IS. 4
2.4
0,7
8.9
10.0
Cross
efficiency
«et Dry
21.0
11.3
16.1
28.6
22.7
26.5
23.6
29.3
23.4
26.6
28,4
2.1
11.3
22.6
18.2
29.6
18.2
29.0
30. S
28.8
24.9
31.6
23.8
-
11.9
5.9
8.2
19.3
23.9
29,6
26.4
19.1
28.2
24.3
26.7
26.4
2.0
26.7
18.7
33.6
21.5
32.5
26.7
37.5
35.0
35.9
35.5
19.3
25.8
29.4
30.9
37.2
33.5
30.6
34,9
41.7
38.2
10.3
7.8
21.5
27.8
5.4
4.5
7.9
22.1
19.5
18.5
26.4
31.2
34.2
29.3
24.9
19.5
26.0
28.1
36.7
31,7
38.1
37.9'
37.3
35.0
36.5
40.5
-
10.3
26.7
4.5
18.5
18.4
26.5
16.3
29.0
32.7
-
-
-
19.4
5.4
25.1
24.9
25.4
19.6
31.9
29.0
37.3
36.8
-
24.3
4 n
*,u
17.6
30.8
25.1
23,1
36.8
27.5
34.6
33.1
31.1
33.8
9.0
2.4
20.8
23.7
113
-------
Table 6. Continued
Dissolved
oxygen Daily ..
concentration food ration-'
(•(/liter) (%)
3.0
8.0
5.0
3.0
Fall 1968
4
4
5
5
R
R
R
R
Spring 1969
0
0
1
1
2
2
3
3
4
4
5
S
R
R
R
R
0
0
1
1
2
2
3
3-
4
4
5
S
R
R
R
R
0
0
1
1
2
2
3
3
4
4
5
5
R
R
R
R
Net neigh!
(l)
Initial
4.10
3.2S
3.20
2.66
1.94
1.9S
2.69
3.31
5.S2
4.68
4.74
4.93
4.91
5.30
5.90
6.15
4.63
4.04
6.08
6.73
4.49
4.67
7.42
6.72
4.03
4.44
4.64
4.95
4.58
5.73
5.44
5.32
4.83
3.65
4.87
4.39
4.89
4.77
6.70
6.20
4.90
4.72
4.88
4.81
4.31
4.98
4.74
5.07
3.90
5.56
5.97
5.70
3.60
4.11
7.73
7.02
Final
4.61
3.64
3.74
3.14
2.47
2.33
3.53
4.06
4.93
3.82
4.52
4.69
5.00
5.34
6.38
6.53
5.26
4.64
7.16
8.14
5.86
6.32
9.39
10.35
3.36
3.97
4.37
4.70
4.74
5.80
5.84
5.72
5.51
4.14
5.86
5.09
7.30
6.94
S.85
8.90
4.29
Dead
4.51
4.61
4.34
5.03
5.12
S.38
4.40
6.29
6.82
6.25
4.80
4.95
11.01
8.05
Difference
0.52
0.39
0.54
0.48
0.53
0.38
0.84
0.75
-0.59
-0.86
-0.22
-0.24
0.09
0.04
0.48
0.38
0.63
0.60
1.08
1.41
1.37
1.65
1.97
3.63
-0.67
-0.47
-0.27
-0.25
0.16
0.07
0.40
0.40
0.68
0.49
0.99
0.70
2.41
2.17
2.15
2.70
-0.61
-0.37
-0.20
0.03
0.05
0.38
0.31
0.50
0.73
0.85
0.55
1.20
0.84
3.28
1.03
Dry weight
Initial
0.85
0.67
0.66
0.55
0.40
0.41
O.S6
0.69
1.10
0.94
0.95
0.99
0.98
1.06
1.18
1.23
0.93
0.81
1.22
1.35
0.90
0.93
1.48
1.34
0.81
0.89
0.93
0.99
0.92
1.15
1.09
1.06
0.97
0.73
0.97
0.88
0.98
0.95
1.34
1.24
0.98
0.98
0.96
0.86
1.00
0.95
1.01
0.78
1.11
1.19
1.14
0.72
0.82
1.55
1.40
final
1.06
0.80
0.84
0.71
0.58
0.50
0.77
0.90
0.87
0.63
0.94
0.90
.04
.15
.39
.31
.11
.03
.70
.08
.37
.58
2.18
2.57
0.66
0.7*
0.89
0.96
0.97
.29
.28
.28
.26
.90
.39
.12
.76
.71
2.09
2.28
0.81
1.00
0.91
0.93
.08
.08
.22
.00
.48
.45
.35
.09
.13
2.59
1.93
Difference
0.22
0.13
0.18
0.16
0.17
0.09
0.22
0.22
-0.23
-0.31
-0.01
-0.09
0.06
0.09
0.21
0.08
0.18
0.22
0.48
0.73
0.47
0.65
0.70
1.23
-0.15
-0.13
-0.04
-0.03
0.05
0.14
0.19
0.22
0.29
0.17
0.42
0.24
0.78
0.76
0.75
1.04
-0.17
0.02
-0.05
0.07
0.08
0.13
0.21
0.22
-0.37
0.26
0.21
0.37
0.31
1.04
0.53
Food
consumption
rat«2/
(•t/i/day)
Wet Dry
37.7
38.0
43.9
43.3
67.4
54.2
57.1
46.8
0
0.4
10.3
10.4
20.2
20.3
29.0
29.2
37.9
37.7
46.6
45.7
72.0
70.1
63.5
82.1
0
0.3
10.4
10.5
20.1
20.4
29.4
29.4
37.7
38.0
46.0
46.5
80.0
76.4
65.3
74.4
0
10.7
10.4
20.3
20.7
29.1
29.5
37.9
37.7
47.1
44.9
61.3
51. S
63.8
44.0
53.4
55.0
62.6
60.9
93.4
79.0
82.4
66.2
0
0.6
14.5
15.4
28.4
28.1
39.9
41.8
52.7
51.0
60.6
57.0
94.5
88.4
83.6
103.1
0
0.4
14.7
14.9
28.6
27.6
40.4
39.7
50.5
52.4
59.9
63.3
102.0
96.4
85.0
91.6
0
14.6
15.1
28.3
28.6
40.8
39.8
50.7
49.7
65.5
61.7
82.1
69.1
82.9
57.3
Growth rate2/
(«/i/day)
»et
8.5
8.0
11.1
11.8
17.1
12.6
19. S
14.6
- 7.0
-14.5
3.4
3.6
1.3
0.5
5.6
4.3
9.1
9.9
11.7
13.6
18.9
21.5
16.8
30. 4_
-13.0
8.0
- 4.3
3.7
2.5
0.9
5.1
5.2
9.4
9.0
13.2
10.6
28.3
26.5
19.8
25.5
- 9.5
- 5.6
- 3.0
0.5
0.7
5.5
4.2
8.6
8.8
9.5
6.6
20.4
13.2
25.0
9.8
Dry
16.1
12.6
16.6
18.4
25.4
14.7
23.3
19.6
-16.8
-28.4
0.8
- 6.8
4.2
5.8
11.7
4.5
12.6
17.1
23.5
30.5
29.7
37.1
27.3
45.0
-14.8
-11.3
3.1
2.2
3.8
8.2
11.5
13.4
18.7
15.0
25.4
17.1
40.7
40.8
31.3
42.2
-13.6
1.4
- 3.8
5.6
5.5
9.2
13.5
17.7
20.5
14.1
12.1
29.4
22.8
35.9
22.8
Gross
efficiency
»et Dry
22.5
21.1
25.3
27.4
25.4
23.2
33.9
31.2
-
-
-
6.4
2.7
19.3
14.7
24.0
26.2
25.0
29.6
26.3
30.6
26.4
37.0
0
.
_
12.2
4.3
17.2
17.6
24.9
23.7
28.7
22.7
35.4
34.7
30.3
34.3
.
_
_
2.4
3.5
18.9
14.4
Z2.7
23.3
20.2
14.7
33.3
25.7
39.2
22.2
30.1
22. 8
26.6
30.2
27.2
18.6
28.3
29.6
-
- ,
-
-
14.9
20.8
29.4
10.8
24.0
33.5
38.8
53.5
31.4
42.0
32.7
43.7
0
-
_
_
13.3
29.7
28.4
33.8
37.0
21. 6
42.4
27.1
39.9
42.3
36.8
46.1
.
9.9
.
19.8
19.2
22.5
33.9
34.8
41.2
21.5
19.6
35.8
33.0
43.3
39.8
I/
II
"R" leans repletion. These fish were allowed to consuM as men food as they would at each daily feeding.
Growth and food consumption rates are expressed as tissue elaborated (or food consumed) in lilligravs per Bean gram of tissue present
(final weight plus initial weight^ .
114
-------
Table 7
of largemouth bass for the pond experiments Concentration, prey density, and lengths, weights and growth rates
Rxperiment
number
and date
I
10/13/70
2
11/18/70
3
9/25/70
4
4/12/71
S
5/6/71
6
5/26/71
7
9/ 3/70
8
6/15/71
7/3/71
10
7/24/71
Mean
temperature
arrange
13.3
(11.5-14.7)
13.3
(11.6-15.6)
13.3
(11.7-15.5)
13.9
(12.8-16.1)
16.0
(13.8-17.2)
16.6
(13.2-19.6)
16.6
(15.2-19.1)
16.8
(14.3-20.7)
18.4
(16.2-19.6)
19.0
(16.0-20.2)
17.7
(16.2-18.4)
18.5
(IS. 9-19. 2)
18.2
(15.4-20.2)
19.0
(IS. 6-21. 8)
23.0 ,
(18.3-25.5)
'
23.6
(19.4-25.8)
27. 2
(21.4-30.1)
27.6
(20.7-31.4)
26.5
(22.0-31.6)
26.8
(21.3-32.7)
Initial
Mean dissolved prey
oxygen and range density
0»g/i) (g/pond)
4.2 170
( 3.7- 5.4)
10.4 no
(10.2-10.9)
4.2 170
( S.8- 5.7)
10.3 170
(10.1-10.8)
4.7 170
( 3.7- 5.6)
9.6 170
( 9.4-10.4)
6.0 170
( 5.2- 7.1)
9.6 170
( 9.3-10.2)
4.3 170
( 3.4- 4.8)
9.7 170
( 9.1-10.0)
4.9 100
( 3.2- 5.2)
9.4 100
( 9.2- 9.8)
5.1 240
( 4.2- 6.2)
9. 3 240
( 8.9-10.1)
4.0 . 170
( 3.0- 4.6)
9.0 170
( 8.5- 9.3)
4.2 170
( 3.2- 4.7)
8.4 170
( 7.4- 9.1)
5.8 170
( 4.0- 6.6)
8.3 170
( 7.8- 9.2)
Total length
(cm)
Initial Fina!
11.9
11.9
11.7
11.6
11.7
11.8
11.7
11.6
11. S
11.6
11.6
11.7
11.5
11.8
11.8
11.7
11.8
11.6
11.4
11.6
11.8
11.7
11.5
11.7
11.5
11.5
11.6
11.6
11.6
11.5
11.7
11.7
12.5
12.2
12.2
12.2
12.3
12.3
12.1
12.5
11.7
11.9
11.8
11.6
12.1
11.9
11.8
11.6
11.4
11.5
11.5
11.6
11.9
11.7
11.4
11.4
11.4
11.2
11.3
11.4
11.2
U.I
11.2
11.1
11.2
11.2
11.2
11.1
10.8
11.0
10.9
11. 0
10.8
10.9
10.7
10.8
11.0
11.0
10.8
11.1
12.4
12.4
12.3
12.2
12.'
12.2
12.1
12.2
12.2
11.9
12.1
12.3
11.8
12.1
12.3
11.9
12.6
12.4
12.6
12.5
12.5
12.7
12.2
12.8
12.1
12.3
12.2
12.3
12.6
12.2
12.4
12.5
12.9
12.7
12.5
12.7
12.8
12.8
12.9
12.9
12.1
12.6
12.5
12.2
12.9
12.6
12.6
12.3
12.7
12.8
12.4
12.5
13.5
13.3
13.0
13.2
12.1
12.0
12.2
12.2
12.6
12.0
12.1
12.3
11.9
11.9
12.4
12.2
12.5
12,1
J2.6
12.9
11.8
12.1
11.7
12.6
12.5
12.5
12.4
13.1
Wet weight
(g)
Ini tial ' inal Difference
20.7
20.1
19.7
19.6
19.7
19.9
19.4
IS. 2
20.3
19.6
19.2
19.9
18.4
19.9
20.7
20.3
20.3
19.1
17.4
20.3
18.2
19.4
18.9
20.4
18.3
18.2
18.6
18.1
18.9
18.4
18.8
18.3
21.3
19.7
21.5
20.0
20.7
20.3
19.6
21.7
17.9
19.0
19.0
17.3
20.1
19.6
19.8
17.1
20.3
20.7
19.3
20.5
21.2
18.8
18.6
21.0
16.6
15.1
16.1
16.3
16.0
14.4
15.1
15.1
15,4
16.3.
15.3
15.7
14.2
55.2
14.6
15. S
13.7
14.9
14.0
14.1
15.6
13. 8
14.2
13.8
24.0
22.7
23.9
23.3
23.6
24.2
22.0
22.1
23.6
23.4
22.4
22.8
20.8
24.0
24.2
24.7
25.1
24.1
21.9
24.7
24.7
25.6
24.5
26.2
22.6
23.3
23.8
23.0
24.7
23.5
25.6
24.1
26.2
24.8
26.5
25.6
27.6
26.2
26.8
27.9
22.9
25.9
25.4
2S.9
28.8
27.9
29.4
23.9
27.6
28.5
26.7
26.9
33.3
32.5
29.7
30.6
22'. 0
22.8
22.7
23.3
26.7
21.7
22.1
26.2
20.9
23.1
23.3
24.0
25.3
23.2
25.6
28.8
20.3
24.0
20.0
24.2
25.6
22.7
22.8
27.4
3.3
2.7
4.2
3.7
3.9
4.3
2.6
2.7
3.3
3.8
3.2
3.0
2.4
4.1
3.5
4.4
5.0
5.0
4.5
4. 3
6. •
6.3
5.6
5.8
4.3
5.1
5.2
5.0
5.7
5.1
6.8
5.8
4.9
5.1
5.0
5.6
6.9
5.9
7.2
6.2
5.0
6.9
6.4
6.6
8.7
8.3
9.6
6.8
7.3
7.8
7.4
6.4
12.2
13.7
11.1
9.6
5.4
7.7
6.6
7.0
10.8
7.6
7.0
11.1
5.5
6.7
8.0
8.2
11. 1
8.0
11.0
13.3
6.6
9.1
6.0
10.1
10.0
8.8
8.6
13.6
Growth rate
rag/g/day
10.5
8.6
15.9
12.3
12.8
13.9
S.S
9.S
10.7
12.7
11.1
10.0
S.S
13.4
11.1
13.9
IS. 6
16.4
16.3
13.7
21.4
19.9
18.5
17.7
15.2
17.4
17.5
17.2
19.2
17.4
21.8
19.6
14.8
16.3
14.9
17.5
20.3
18.2
22.3
17.8
17.6
22.0
20.5
22.9
25.3
25.0
27.9
23.5
21.7
22.7
22.9
19.2
32.0
38.2
32.7
26.6
19.8
29.1
23.6
25.3
36.0
28.9
26.9
38.6
21.6
24.4
29.4
29.8
40.2
29.8
39.1
42.8
27.6
33.3
25.2
57.7
34.7
34.5
33.2
47.0
115
-------
Table 8. Initial and final densities, and sample weights and caloric values of mosquitofish used
in the pond experiments and estimated food consumption rates of bass.
Experiment
number
and date
1
10/13/70
2
11/18/70
3
9/25/70
4
4/12/71
5
5/ 6/71
6
5/26/71
7
9/ 3/70
8
6/15/71
9
7/ 3/71
10
7/24/71
Prey density
(g/pond)
Initial
170
170
170
170
170
170
170
170
170
170
100
100
240
240
170
170
170
170
170
170
Final Difference
123
127
113
113
115
106
119
107
124
106
47
26
154
117
94
73
96
69
90
72
47
43
57
57
55
64
51
63
46
64
53
74
86
123
76
97
74
101
80
9«
Food
consumption
rate of
bass
(mg/g/day)
36
36
46
48
46
51
47
56
35
48
44
57
66
85
70
"89
69
96
79
89
Initial Sample
wet
(g)
5.
5.
5.
11.
11.
13.
5.
13.
13.
14.
0
0
0
65
29
25
1
39
87
44
dry
(g)
1.34
1.38
1.32
1.93
2.05
2.89
1.28
3.08
3.17
3.97
caloric
(cal/g
dry wt)
5746
5518
5594
4784
4921
5053
5206
5112
5167
5182
Final sample
wet
(g)
5.02
5.07
5.0
5.0
5.0
5.0
10.86
11.06
11.06
11.15
11.74
12.37
5.0
5.2
10.31
11.74
14.15
14.26
14.43
16.62
dry caloric
(g) (cal/g
dry wt)
1.31
1.34
1.30
1.31
1.34
1.36
1.81
1.86
1.97
2.00
2.61
2.68
1.18
1.36
2.57
2.89
3.53
3.57
4.06
4.37
5463
5545
5020
5094
5661
5571
4934
4824
4947
5026
5127
5072
5248
5216
5087
5139
5136
5118
5214
5286
-------
Table 9. Statistical comparison between the growth rate values of bass reared at high and low dis-
solved oxygen levels in the experimental ponds. All values are based on wet weights.
Experiment
number
and date
1
10/13/70
2
11/18/70
3
9/25/70
4
4/12/71
5
5/6/71
6
5/26/71
7
9/25/70
8
6/15/71
9
7/3/71
10
7/24/71
Mean
dissolved
oxygen
(mg/1)
4.2
10.1
5.7
10.3
4.7
9.6
6.0
10.0
4.3
9.7
4.9
9.4
5.1
9.6
4.0
9.1
4.2
8.4
5.8
8.3
Mean
temperature
(C)
13.3
13.3
13.3
13.9
16.0
16.5
16.6
16.8
18.4
19.3
17.7
18.5
18.2
19.0
23.0
23.6
27.2
27.6
26, 5
26.8
Initial
prey
density
(g/pond)
170
170
170
170
170
170
170
170
170
170
100
100
240
240
170
170
170
170
170
170
Mean
growth
rate_/
(mg/1/day)
11.3
11.3
11.1
11.8
15.5
19.4
16.8
19.5
15.9
19.7
20.7
25 . 4
21.6
32.4
24.4
32.6
26.3
38.0
31.0
37.3
Reduction
in growth
rate
(%)
0
6
20
14
20
18
33
24
31
17
Standard
error
of the
mean
1.15
1.25
0.56
1.15
0.60
0.81
0.55
0.91
0.61
1.02
1.17
0-90
0.85
2.36
1.91
2.75
1.98
2.83
2.80
3.22
Variance
5.31
6.27
1.26
5.36
1.47
2.64
1.21
3.34
1.72
4.19
5.45
3.25
2.89
22.40
14.69
30.35
15.83
32.14
31.45
41.53
T2/
value
0.01
0.56
3.76
2.50
3.12
3.16
4.27
2.41
3.37
1.49
— Statistical samples consisted of the growth rate values of the 4 bass from each of the two
2/
experiment ponds,
— One-tailed T-table value at 95% confidence level with 6 degrees of freedom = 1.943.
-------
Table 10. Initial and final weights, growth rates and biomass of juvenile Chinook salmon held in laboratory streams and confronted with different food
densities at different oxygen concentrations and temperatures.
00
Stream
Experiment
N3
N6
S4
Nl
N4
S5
N2
N5
S6
Experiment
N3
N6
S4
Nl
N4
S5
N2
N5
S6
Experiment
N3
N6
S4
Nl
N4
SS
N2
N5
S6
Mean
D.O.
1, 9.5C,
11.0
11.0
11.0
5.3
5.2
5.0
3.2
3.3
3.3
2, 9.8C,
11.0
11.0
11.0
5.1
5.8
5.4
3.9
3.7
3.8
3, 11. 6C,
10.5
10.5
10. S
4.7
4.8
5.8
3.6
4.2
4.0
Wet
Initial
2 fish, 10
1.42
1.42
1.40
1.41
1.44
1.43
1.42
1.44
1.42
4 fish, 10
3.91
3.82
3.83
4.07
3.86
3.86
4.07
3.88
3.87
2 fish, 10
1.82
1. 65
2.09
1.89
2.10
1.59
1.81
1.73
2.04
weight—
(g)
Final
days,
1.99
1.89
1.92
1.86
1.92
1.97
1.82
1.84
1.61
days,
4.44
4.51
3.93
4.07
3.86
3.86
4.70
5.12
3.74
days,
2.48
2.37
2.83
2.55
2.75
2.30
2.39
2.27
2.49
Difference
April 8, 1970
0.56
0.48
0.52
0.45
0.48
0.54
0.40
0.40
0.19
April 21, 1970
0.53
0.68
0.10
0.73
0.50
0.81
0.63
0.72
-0.14
May 8, 1970
0.66
0.72
0.74
0.66
0.65
0.71
0.58
0.54
0.46
Dry
Initial
.239
.238
.235
.236
.242
.240
.238
.241
.238
.728
.711
.711
.756
.719
.717
.758
.722
.720
.318
.288
.366
.331
.367
.278
.316
.302
.356
weight-i/
Cg)
Final
.386
.361
.392
.349
.373
.437
.336
.346
.301
.819
.782
.684
.881
.777
.868
.851
.866
.634
.471
.474
.522
.494
.525
.451
.449
.421
.469
Difference
.147
.123
.157
.113
.131
.193
.098
.105
.063
.091
.071
-.027
.125
.058
.151
.093
.144
-.086
.153
.186
.156
.163
.158
.173
.133
.118
.113
Mean ,/
Growth rate-'
(mg/g/day)
Wet
33.2
28.7
31.4
27.6
28.5
31.7
24.9
24.3
12.7
12.6
16.4
2.7
16.5
12.2
18.9
14.3
16.0
- 3.6
30.8
36.2
30.1
29.8
27.0
36.2
27.8
26.9
20.1
Dry
46.9
41.0
50.0
38.7
42.5
57.3
34.1
35.8
23.3
11.8
9.5
- 3.8
15.3
7.8
19.0
11.6
18.1
-12.7
39.9
48.8
35.1
39.5
35.4
47.4
34.7
32.6
27.4
Individual ,,
growth rate^' Wet biomass
(mg/g/day) Benthos DriftT
45.9
39.2
53.1
35.3
45.7
60.4
31.8
44.4
31.8
37.5
47.7
34.5
33.3
41.3
42.2
39.4
28.6
36.6
Dry
48.4
43.1
46.9
42.7
38.4
53.7
36.0
48.2
12.7
39.6
50.2
35.8
44.6
31.0
51.9
29.8
38.5
16.4
(g/m )
2.3
2.9
5.2
2.0
4.7
4.4
0.8
3.6
2.8
4.2
3.9
5.0
2.7
4.0
8.9
3.8
4.8
2.3
S.I
5.2
6.7
2.9
3.1
8.1
6.1
4.5
4.0
(mg/nr)
4.7
3.4
6.2
0.5
0.9
7.6
2.7
1.3
•3.4
2.3
1.7
1.2
3.1
2.S
3.9
2.5
3.7
0.7
9.3
2.8
1.9
4.9
2.7
2.1
12.1
2.5
1.7
Fish
(g/m2!
1.10
1.07
1.07
1.05
1.08
1.10
1.04
1.09
0.98
2.83
2.90
2.49
2.86
2.65
2.75
2.83
2.90
2.45
1.38
1.29
1.58
1.43
1.56
1.25
1.35
1.29
1.46
-------
Table 10. Continued
Stream
Experiment
S4
Nl
N4
SSS/
N2-7
N5
S6
Experiment
N3
N6
54
Nl,.,
N4X/
SS^/
N2
N5
S6
Experiment
N3
N6
S4
N2
N4
S5
Nl
N5
S6
Mean
D.O.
Wet
(mg/1) Initial
4, 13. 5C,
10.1
10.1
10.0
5.4
5.0
S.7
3.8
4.4
3.3
5, 15. 5C,
9.8
9.9
9.9
5.3
S.O
5.3
3.6
3.8
3.3
6, 10. 4C,
10.6
10.6
10.5
S.O
4.0
4.8
3.0
3.7
2.6
2 fish,
2.04
2.06
2.06
2.03
2.00
2.06
1.48
1.99
2.07
4 fish.
3.00
3.76
3.40
3.12
2.42
2.74
3.02
3.37
3.08
4 fish,
7.52
7.89
7.84
7.86
7.44
7.98
8.10
8.00
7.77
weight-''
CK)
Final Difference
Dry
Initial
10 days. May 25, 1970
3.09 1.05 .353
2.68 0.62 .356
3.57 1.51 .356
3.11 1.08 .352
2.78 0.78 .346
3.40 1.34 .356
2.07 0.59 .256
2.50 0.53 .344
2. 54 0.47 .358
10 days
4.12
3.54
3.99
4.02
2.80
2.53
3.67
3.34
3.39
20 days
7.54
7.29
7.57
6.59
6.92
7.59
6.95
8.00
7.98
weight-i/
(K)
Final
.559
.466
.662
.563
.490
.647
.383
.441
.440
Mean 2/
Growth rate1-'
Cme/B/day)
Difference Jfet
.206
.110
.306
.211
.144
.291
.127
.097
.082
41.0
26.2
53.5
42.0
32.7
49.0
33.2
23.0
20.5
Dry
45.2
26.8
60.2
46.1
34.4
57.9
39.1
24.7
20.6
Individual j,
growth rate—
(mg/g/day)
Dry
Benth,c
(gAO
3.7
5.8
2.8
2.7
5.1
4.6
5.7
3.7
Wet biomass
,s Driflf Fish,
(mg/m-)
1.9
0.7
4.5
4.0
2.4
4.9
2.3
1.5
1.3
Cg/B J
1.65
1.53
1.82
1.66
1.54
1.77
1.14
1.45
1.49
, June 30, 1970
1.12
-0.22
0.59
0.90
0.38
-0.21
0.65
-0.03
0.31
, April 29,
0.02
-0.60
-0.27
-1.27
-0.52
-0.39
-1.15
0.00
0.21
.545
.685
.743
.570
.440
.500
.551
.572
.599
1971
1.430
1.500
1.490
1.494
1.414
1.517
1.540
1.521
1.477
.761
.606
.618
.736
.448
.450
.682
.560
.562
1.367
1.274
1.326
1.115
1.226
1.373
1.206
1.457
1.435
.216
-.079
.125
.166
.048
-.050
.131
-.012
.037
-.063
-.226
-.164
-.379
-.188
-.144
-.334
-.064
-.042
31.4
- 6.5
16.1
25.1
13.9
- 7.9
19.5
- 0.9
9.5
0.1
- 3.9
- 1.8
- 8.8
- 3.6
- 2.5
- 7.6
0.0
1.3
33.1
-12.3
18.4
25.4
10.3
-10.5
21.2
- 2.1
6.4
- 2.1
- 8.3
- 5.7
-14.1
- 6.8
- 5.2
-11.9
- 2.0
- 1.4
12.4
-14.4
35.1
9.0
5.9
-11. &
12.7
0.0
5.4
- 5.3
-10.0
- 1.5
-16.6
- 8.1
- 7.5
-13.3
- 4.6
0.1
42.7
-17.0
13.6
25.9
10.2
-20.2
27.2
- 3.5
8.3
- 3.1
1.2
-12.1
-14.1
- 9.9
- 0.1
- 9.9
- 1.2
- 4.3
32.5
-11.8
25.6
35.3
13.8
1.2
18.2
- 6.2
- y.6
- 3.7
-10.9
- 5.9
-16.0
- 5.9
- 3.1
-12.3
-11.3
- 0.1
35.2
5.8
- 0.6
20.6
-
_
20.7
1.2
13.3
2.7
-13.6
- 4.4
-11.1
- 4.8
- 1.9
-13.7
5.8
- 1.2
1.8
0.8
1.6
2.1
14.1
.
1.1
1.6
2.0
1.2
1.4
2.5
3.7
2.2
1.7
2.2
1.1
2.2
1.4
1.8
10.6
2.6
2.5
1.7
1.4
4.7
>100.0
2.2
2.3
1.5
0.5
4.3
1.5
2.8
2.5
4.4
2.29
2.36
2.38
2.30
1.67
1.70
2.16
2.16
2.09
4.86
4.90
4.97
4.66
4.63
5.02
4.92
5.16
5.09
-------
Table 10. Continued
N)
O
Mean Wet weight- Dry weight-
D.O. (g) (g)
Stream (mg/1) Initial Final Difference Initial Final
Experiment 7, 11, OC, 2 fish, 20 days, May 28, 1971
N3 10.4 3.87 4.23 0.37 .729 .711
N6 10.4 3.83 4.07 0.24 .743 .737
S4 10.4 3.72 4.43 0.72 .721 .792
N2 5.2 3.86 3.51 -0.36 .748 .591
N4 4.7 3.75 4.16 0.41 .739 .735
S5 5.0 3.73 3.75 0.02 .723 .630
Nl 3.2 3.87 4.23 0.37 .750 .644
N5 3.2 3.87 4.01 0.14 .751 .729
S6 2.8 3.73 3.89 0.16 .724 .683
Experiment 8, 14. 3C, 2 fish, 20 days, July 8, 1971
NJ^ 9.8 1.24 2.48 1.24 .243 .558
N6 9.8 2.32 4.12 1.80 .452 .885
S4 9.8 2.38 4.52 2.14 .484 .927
N2 4.9 2.40 4.81 2.41 .468 1.033
K4 5.2 2.37 3.09 0.72 .462 .646
S5 5.1 2.61 4.79 2.18 .508 1.030
Nl 3.1 2.64 3.99 1.35 .514 .877
NS 3.3 2.68 4.31 1.83 .523 .895
S6 3.1 2.66 3.68 1.02 .519 .804
Experiment 9, 13. 1C, 2 fish, 27 days, August 10, 1971
N3 10.5 3.18 2.17 -1.10 .668 .345
N6 10.6 3.32 '-.2.68 -0.64 .697 .505
S4 10. S 3.27 3.14 -0.13 .686 .532
N2 5.1 3.46 3.02 -0.44 .727 .461
N4 5.0 3.39 2.77 -0.62 .712 .457
S5 5.1 3.30 3.75 0.46 .692 .632
Nl 3.1 3.38 2.84 ' -0.54 .709 .488
N5 3.1 3.18 3.52 0.35 .667 .606
— Total weight of all salmon in each stream.
2/
— Mean growth rates are expressed as tissue gained or lost in
per day.
Difference
-.018
-.006
.071
-.157
-.004
-.093
-.006
-.022
-.043
.315
.433
.443
.565
.393
.522
.363
.372
.325
-.323
-.192
-.154
- . 266
-.256
-.060
-.221
-.061
milligrams per
Mean -,
Growth rate=-'
(mg/g/day}
Wet
4.5
3.1
8.8
4.8
5.2
0.2
4.5
1.8
2.1
33.3
28.0
31.0
33.4
13.0
29.5
20.5
23.3
16.1
15.2
8.9
1.5
S.O
13.5
4.8
6.4
3.8
mean
Dry
- 1.3
- 0.4
4.7
-11.8
- 0.3
- 7.0
- 0.4
- 1.5
- 3.0
39.3
32.4
31.3
37.6
16.6
33.9
26.1
26.2
21.5
-23.6
-11.8
- 9.4
-16.6
-16.2
- 3.4
-13.7
- 3.6
grant of
£ A dill V .L
Individual
growth rate^-' Wet biomass
(mg/6/day) Benthos Drift Fish.
- 8.7
0.5
1.5
-11.9
- 8.4
- 9.6
- 1.1
- 4.2
- 6.3
39.3
32.5
33.9
34.4
18.6
35.4
18.6
27.3
18.7
-24.1
-16.7
-13.5
-23.8
-21.1
- 1.8
-10.4
- 6.4
tissue in
— Individual growth rates are expressed as tissue gained or lost in milligrams per mean gram of tis;
A /
— One salmon trapped in export sample for up to 48 hours.
— One salmon was not recovered at end of test period.
Dry
5.2
- 1.4
7.1
-11.4
6.2
- 4.8
0.3
1.2
0.0
_
32.2
29.0
39.7
14.3
32.4
31.6
25.3
24.4
-23.3
- 6.9
- 6.6
- 9.9
-11.8
- 5.5
-19.4
- 1.3
(g/V)
1.0
1.4
1.4
0.5
1.4
1.7
0.9
1.0
0.5
2.6
2.9
2.0
1.7
2.1
3.0
2.1
2.5
1.8
2.9
2.0
2.2
1.5
1.7
1.8
1.0
3.2
each -trcam ffinal weisht vlus
sue ffinal
weight plus initial
2
(mg/m-
1.3
1.2
1.5
1.3
1.7
0.4
1.4
1.1
0.9
5.5
12.8
43.6
7.2
8.5
8.9
4.5
5.3
3.3
1.1
2.2
0.8
0.8
2.5
1.0
1,2
8.4
i initial
2
weight..
)
) (g/» )
2.61
2.55
2.63
2.38
2.32
2.41
2.61
2.54
2.46
2.18
2.07
2.22
2.33
1.76
2.39
2.13
2.25
2.05
1.72
1.94
2.07
2.09
1.03
2.27-
2.01
1.97
weight)
per day.
-------
Table 11. Statistical evaluation of the growth rates of coho
salmon held at high, intermediate, and low dissolved oxygen
levels in laboratory streams. Only experiments in which
growth rates appeared dependent on dissolved oxygen
concentration were compared. All values are based on dry
weights.
Experiment
number
1
3
8
Mean
dissolved
oxygen
Crag/1)
3.3
5.2
11.0
3.9
5.1
10.5
3.2
5.1
9.8
Mean
growth
rate
Ong/ g/ day)
34.2
46.1
45.2
30.6
42.8
39.5
24.3
29.1
34.4
Least
significant 2 ,
difference—
(.05) (.
11.33 9
9.47 7
*
8.6 7
10)
*
.33
*
.70
*
.1
- Mean values were calculated from six fish (two in each of the three
replicate streams) held at each of three dissolved oxygen levels.
Therefore any variance between the replicate streams contributed
to the error within each oxygen level.
-/ Asterisk indicates growth rate value significantly different from
that of salmon held at near air saturation.
121 *U.S. GOVERNMENT PRINTING OFFICE: 1973 514-154/Z60 1-3
-------
. Accession Number
w
f\ Subject Field & Group
06C
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Oregon State University, Corvallis, Oregon
Department of Fisheries and Wildlife
Title
DEVELOPMENT OF DISSOLVED OXYGEN CRITERIA FOR FRESHWATER FISH,
10
Authors)
Charles E. Warren,
Peter Doudoroff, and
Dean L. Shumway
16
Project Designation
EPA Program #18050 DJZ
21
Note
Environmental Protection Agency report
number, EPA-R3-73-019, February 1973.
22
citation Warren, Charles E. (Principal Investigator) 1971. Development of dissolved
oxygen criteria for freshwater fish. Terminal Report from Department Fisheries and
Wildlife, Oregon State University, Corvallis to U.S. Environmental Protection Agency
Washington n.r. nn Prnp-rani #1 Rj}E;nr).T7
~JoTOescriptors (Starred FirsT)
_—I *0xygen requirements, *Fish, *Fish growth, *Fish respiration, *Fish reproduction,
Salmon, Trout, Bass, Pollution (water), Aquatic productivity, Water quality
25
Identifiers (Starred First)
*Pacific salmon, *Steelhead trout, *Largemouth bass.
oxygen requirements of fish.
*Laboratory studies
stract
e research here reported has involved laboratory studies on the survival, develop-
ment, bioenergetics and growth, swimming performance, and avoidance behavior of chinook
and coho salmon, steelhead trout, and largemouth bass. Some of the studies have been
conducted under very simple laboratory conditions, as in aquaria or other apparatus,
but some of the studies on bioenergetics and growth have also been conducted under rather
natural conditions in laboratory streams and ponds. In some important cases, we have
found close correspondence between the effects of reduced oxygen concentration i~
aquarium studies of growth at maximum rations and its effects under more natural condi-
tions in laboratory streams and ponds. Some of the biological responses of the fish
studies were affected by any appreciable reduction in dissolved oxygen below the air
saturation levels, whereas others were affected only at levels below about 50 percent
the air saturation levels.
Abstractor
Charie<
Li.
Warr^n
Institution
Oregon
State
University
J»Fj:102 (REV. JULY 1969)
W AJ ER RE ^
WASHINGTON, D. C. 20240
* OPOI 1970-389-930
------- |