EPA-600/3-76-039
April 1976
Ecological Research Series
LIMNOLOGICAL STUDIES OF
FLATHEAD LAKE MONTANA:
A Status Report
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. 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.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-76-039
April 1976
LIMNOLOGICAL STUDIES OF FLATHEAD LAKE
MONTANA: A STATUS REPORT
Arden R. Gaufin, Gerald W. Prescott, John F. Tibbs
University of Montana
Missoula, Montana 59801
and
State of Montana Department
of Health and Environmental Science
Helena, Montana 59601
Contract No. F.W.Q.A. and E.P.A.
Training Grant 1-F1-WP-26, 212-1-4 (Univ. of Utah)
Project Officer
Thomas E. Maloney
Assessment and Criteria Development Division
Corvallis Environmental Research Laboratory
Con/all is, Oregon 97330
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
CORVALLIS, OREGON 97330
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DISCLAIMER
This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products consti-
tute endorsement or recommendation for use.
n
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ABSTRACT
Flathead Lake, a dimictic oligotrophic lake located in western Montana
has been the subject of several investigations beginning with Forbes1
study of aquatic invertebrates in the lake in 1893- Young in 1935 pre-
sented the results of four years of data collecting on the chemistry and
biology of the lake. During the last ten years (1964-1974) a number of
limnological studies have been conducted dealing with the physical,
chemical, and biological characteristics of the lake. The objectives of
these studies have been to determine the standing crop of phytoplankton
and zooplankton during all seasons of the year, to observe the succession,
distribution and diversity of planktonic forms, to determine the role of
chemical nutrients in relationship to phytoplankton productivity, and to
study fish population trends, life histories and seasonal fish distribu-
tion of the Flathead Lake system.
The composition of the algal flora of Flathead Lake in number of species
so far reported is Chlorophyta 102 species (17-5%); Cyanophyta 40 species
(7?); Chrysophyceae 12 species (2.1%); Baci1lariophyceae 399 species and
varieties (69.8%); Pyrrhophyta 13 species (2.0%); Xanthophyceae 4 spe-
cies; Euglenophyta 1 species; and Cryptophyta 2 species. The Chryso-
phyta as a phylum (Diatoms and Chrysophyceae) thus constitutes by far
the dominant floral group. In this respect the lake shows an oligo-
trophic character remindful of the oligotrophic flora in arctic lakes.
Nitrates and phosphates are relatively low as might be expected. Levels
of these critical nutrients that have been reported are high enough to
occasionally support plankton blooms. That extensive blooms do not occur
is possibly due to oligotrophic features such as low temperatures and
low concentrations of organic acids and vitamins.
The more common forms of zooplankton found in the lake, Daphnla spp.,
Kellicottia longispina, Keratella cochlearis, Cyclops tHcuspidatus
thomasi, and Diaptomus ashlandi, compose a community similar to that
described by Sheffer and Robinson (1949) for Lake Washington. The
distribution of Daphnia spp. in the lake has been of particular interest
because their temporal and spatial distributions seem to be influenced
primarily by temperature.
A total of 8,912 fish were collected in 163 net sets during the fish
sampling program on the lake from November 1967 through December 1971.
Fifteen major fish species were collected with the lake whitefish,
kokanee salmon, Dolly Varden, and lake trout being the most common game
species in that order of abundance.
This report was submitted in fulfillment of Training Grant No. 1-F1-
WP26, 212-1-4, by the University of Montana Biological Station, under
the sponsorship of the Federal Water Quality Administration and Environ-
mental Protection Agency. Work was completed as of June 1973-
111
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ACKNOWLEDGMENTS
This project was directed by the following three principal investigators:
Arden R. Gaufin, Department of Biology, University of Utah and Montana
University Biological Station; Gerald W. Prescott, Resident Biologist,
University of Montana Biological Station, Bigfork, Montana, and John F.
Tibbs, Director, University of Montana Biological Station, Bigfork,
Montana.
Each of the principal investigators also participated in several aspects
of the research conducted during the course of the project.
The work on the distribution, ecology, and production of phytoplankton
in the lake was conducted principally by Fatiman Moghadam, Garth R.
Morgan, and Thomas Ivory, graduate students at the University of Utah
and Montana Biological Station. This work served as a basis for Ph.D.
theses presented to the University of Utah, Salt Lake City, Utah. With-
out their untiring efforts the research conducted on the phytoplankton
could not have been completed.
Special thanks are extended to Dr. William Vinyard, Professor of Botany,
California State University at Humboldt, Arcata, California, and to Dr.
Ruth Patrick of the Academy of Natural Sciences of Philadelphia,
Pennsylvania, for their help in the identification of diatoms from the
lake.
David S. Potter, a graduate student at the University of Montana, has
conducted a study of the zooplankton of the lake during the last three
years and is to be credited for the section of the report dealing with
the systematics and ecology of zooplankton in the lake.
The section of the report entitled the Fish Population of Flathead Lake
was contributed by Delano A. Hanzel of the Montana Fish and Game Depart-
ment and represents the work of him and his associates over a period
of ten years (1962-72). The principal investigators especially ack-
nowledge Mr. Hansel's contribution and wish to thank the Montana Fish
and Game Department for their help and cooperation.
iv
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CONTENTS
Sections Page
I Conclusions ]
II Introduction 3
III Review of Water duality Studies 12
IV Study Objectives and Approach 14
V Methods of Sampling 16
VI Phytoplankton Productivity 17
VII Physical Characteristics of Flathead Lake 19
VIII Chemical Characteristics of Flathead Lake 21
IX Phytoplankton Distribution in Flathead Lake 23
X Algal Flora of Flathead Lake 29
XI Higher Aquatic Plants in Flathead Lake kk
XII Rotifer and Crustacean Plankton Communities of
Flathead Lake 48
XIII Fish Population of Flathead Lake 53
XIV References 63
XV Appendix 69
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FIGURES
No.
1 Counties of the Flathead Drainage k
2 Flathead River System 6
3 Map of Flathead Lake 15
5 Daphnia in Lake 49
6 Species of Fish Netted in Flathead Lake 59
vi
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TABLES
No. Page
1 Mean Temperature Values 10
2 Total Precipitation 11
3 Flathead Lake Water Chemistry - Forty Year Span 22
4 Rank of Phytoplankton Species According to
Mean Population 27
5 Turbidity J.T.U. 30
6 Thermal Readings 32
7 Nitrate Nitrogen in the Photosynthetic Zone of
Selected Stations in Flathead Lake - Monthly Averages 35
8 Ortho-phosphate at Selected Stations in Flathead Lake 36
9 Total Hardness in the Photosynthetic Zone at Selected
Stations in Flathead Lake - Monthly Averages 37
10 pH in the Photosynthetic Zone of Selected Stations -
Flathead Lake - Monthly Averages 40
11 Plankton Counts at Selected Stations in Flathead
Lake - Early June 41
12 Plankton Counts at Selected Stations in Flathead
Lake - September 21 42
13 Plankton Counts at Selected Stations in Flathead
Lake - December 43
14 Tentative Check List of Aquatic and Marginal Plants
in Flathead Lake 46
15 Preliminary Seasonal and Depth Distributions for
Rotifera and Crustacea in Flathead Lake, Montana 51
16 Native and Exotic Fish Species in Flathead Lake 54
17 Fish Species and Other Netting Data for Flathead
Lake, Winter 1967 Through Fall 1970 60
18 Size and Weight of Fish Species Collected from
Flathead Lake, October 1966 through December 1970 61
vii
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SECTION I
CONCLUSIONS
Flathead Lake is of such a quality that it is presently classified as an
A-open D| lake by the Montana Water PollutJon Control Authority. Under
the present classification water may be used for drinking, culinary and
food processing purposes for use after simple disinfection treatment and
removal of natural impurities. Coliform bacteria concentrations obtained
near the shores by Bauer' and Hern^ often exceeded the state standard for
the lake (50 coliforms per 100 ml). Samples taken away from the shore-
line were consistently low, and no fecal coliforms were found.
Various studies conducted on the lake have clearly demonstrated that it
is a cold dimictic take exhibiting submerged depression individuality.
While much of the lake stratifies thermally, there are several extensive
shallow bays such as Poison Bay which do not do so.
The algal flora of Flathead Lake, both quantitatively and qualitatively,
reflects its Umnological and hydrographic uniqueness. Very low turbid-
ity, a strong channel current from the Flathead River, a distinctly
fluctuating water level, and a relatively deep basin which contributes
to and maintains low temperatures all contribute to the oligotrophic
characteristics of the lake.
The algal flora can be classified as a Diatom-Cyanophyte moderately
hardwater type. However, the cyanophyte element is not only lower in
number of taxa, but is also more weakly developed than lakes which fall
within such a classification. The diatoms comprise the dominant flora
at all times of the year with 399 species and varieties in k2 genera
having been reported.
Nitrates and ortho-phosphates are relatively low as might be expected.
However, the development of blue-green algal blooms during recent years
in shallower bays as Yellow Bay and Hell Roaring Bay indicate that such
sections of the lake are gradually undergoing eutrophication.
The Flathead Lake fishery is dependent on the natural reproduction in
the lake and recruitment from the tributary system above the lake. A
total of 8,912 fish were collected in 163 gill net sets during a sam-
pling program conducted by the Montana Fish and Game Department from
November 196? through December 1970. The dominant game fish taken were
cutthroat trout, Dolly Varden, kokanee, lake trout, mountain whitefish,
and lake whitefish.
The future of the Flathead Lake fishery is dependent on the natural
reproduction in the waters of this complex system. The quality of the
fishery available will be dependent on the quality of the aquatic
habitat. Changes caused by natural variations in the environment, as
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well as the results of man's activities in water development projects,
housing projects, lumbering or a combination of many factors will be
reflected in the fish populations of this drainage system.
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SECTION II
INTRODUCTION
FLATHEAD LAKE
Flathead Lake is located in the northern portion of a large glacial
valley in Northwestern Montana, near Glacier National Park. The lake is
a remnant of a much larger lake which occupied the area during Tertiary
times.
During the late Wisconsin stage, approximately 10,000 years ago, a
glacier filled Flathead Valley. The retreat of the glacier deposited a
terminal moraine near Poison, Montana, and left the Flathead Valley par-
tially filled with sand, clay, and silt. This moraine at present forms
the southern boundary of Flathead Lake (Ross,3).
Flathead Lake is the largest natural body of fresh water west of the
Mississippi River. It is 56.4 kilometers by 25-8 kilometers in its ex-
tremes of length and width, and it has a maximum depth of 112 meters.
The lake has a shoreline of 185 kilometers more than half of which is
composed of rock (quartzitic argil lite, quartzite, and carbonate) and
gravel which extends lakeward to a depth of approximately 30 meters
(Moghadam,^). At the extreme northern and southern portions of the lake
the rock and gravel bottom gives Way to sand or an ooze consisting of
sand, clay, and organic detritus. Nearly half of the shoreline is com-
posed of rocky cliffs, and the remainder is sandy or rocky beach.
Flathead Lake is bounded on the east shore by the Mission Mountains whose
steep slopes arise almost at the water's edge. On the west shore the
mountains are lower and are intermittently cut by valleys. The steep-
ness of much of the drainage area and its close proximity to the lake
greatly limits the amount of drainage into the lake.
DRAINAGE AREA
The drainage area of Flathead Lake at Poison encompasses approximately
7,010 square miles in Montana and Canada. The North Fork of the Flat-
head River at the international border has a drainage area of about 450
square miles in Canada, with an additional 175 square miles of drainage
in Canada that flows into tributaries that enter the North Fork below
the border. Of approximately 6,375 square miles of the drainage in
Montana, 4,550 are in Flathead County and 850 square miles are in Lake
County. Powell, Missoula, Lincoln and Lewis and Clark Counties contain
about 425, 410, 90, and 65 square miles of the Flathead drainage,
respectively (Fig. 1). All of Glacier National Park west of the divide,
or 875 square miles, and most of Flathead National Forest's 3,680 square
miles are located in the drainage. Three major rivers, the South, North,
and Middle Forks of the Flathead River, join to form the main stream at
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Figure 1. Counties of the
Flathead Drainage
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Hungry Horse, Montana. The Whitefish and Stillwater Rivers merge and
empty into the Flathead River below Kali spell (Fig. 2).
An average of 8,405,000 acre feet of water flow through the gauging
station near Poison yearly (11,610 cfs average). The average flow of the
Flathead River below Kalispell before it empties into the lake is gauged
with the flow averaging between 9,500 and 11,000 cfs. A major tributary,
the Swan River, near Bigfork discharges an average of 1,127 cfs to
Flathead Lake.
The largest tributary of the Upper Flathead River is the South Fork,
which discharges an average of 3,523 cfs as modi fed by Hungry Horse Dam.
Next largest is the North Fork, discharging an average of about 3,000
cfs over the year. The Middle Fork discharges about 2,920 cfs average
at the junction with the North Fork, forming the Flathead River Main-
stem. The Stillwater and Whitefish Rivers discharge estimated averages
of 350 cfs and 200 cfs respectively as they empty into the Flathead
River.
EFFECTS OF GLACiATlON
During the last great glacial advance, the Flathead Glacier, in its move-
ment down the Rocky Mountain Trench, deposited not only the "Poison
Moraine" at the south end of Flathead Lake but also various moraines in
the Big Arm embayment. Near the middle of the lake, the ice moving
southward split into two parts. One lobe continued south into Poison
Bay. The other turned to the west and moved into the Big Arm embayment.
The Big Arm ice split again into three smaller lobes; these, in turn,
pushed into the Dayton, Big Draw, and Big Arm Valleys. These three
smaller lobes deposited terminal moraines in each valley and these
moraines are believed to be of the same age as the Poison Moraine.
Throughout the glacial period, glacial till accumulated in large volumes
and buried much of the preglacial topography. These accumulations have
resulted in many unusual land forms. As the ice released its load of
till, great amounts of meltwater carved many features of unique shape
into the local landscape. During the ice retreat several small pre-
glacial lakes evolved, existed for a short time, and then drained as
their ice dams melted. The present topography has had little modifica-
tion since the glacial period. Many of the land forms found today still
exhibit large volumes of glacial till and show the scars of fluvial
erosion that resulted from the ice age.
HISTORY OF THE REGION
White settlement of the region around Flathead Lake occurred relatively
late in the 19th century. Prior to the l820's, the land was wilderness
and belonged to Indians of the Salish Tribal Nation. The rate of
settlement was slow but steady and was enhanced by the coming of the
Great Northern Railroad in 1891. Lumber was, and remains, a principal
industry of the area. The Stillwater, Whitefish, Flathead and Swan
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CANADA
u s.
Figure 2.
Flathead River System
SCAli MlltS
MART RONA
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Rivers served as transport systems for the earliest lumber center at
Somers, located on the northwest shore of Flathead Lake.
Flathead Lake served as a transport system from Poison to points north
until a road (now highway 93) was built along the west side of the lake.
Steamboats carried passengers and cargo to points along the lake and
upper Flathead River. As a result, almost all virgin timber around the
lake was cut to fuel these boats. The land now occupied by the University
of Montana Biological Station represents the largest tract of relatively
pristine forest along the lake.
The Flathead River system remained largely unmodified until the con-
struction of Kerr Dam below Poison in 1938. The dam regulates the upper
ten feet of Flathead Lake and has a capacity of 1,219,000 acre-feet
(Montana Water Resources Board,->).
The Flathead drainage system was significantly modified by the Hungry
Horse Reservoir. This dam began operation in 1953 on the South Fork of
the Flathead River; the dam has a capacity of 3,^68,000 acre-feet. The
dam regulates much of the spring runoff on the South Fork, reducing the
flow of the Flathead River during this period. Conversely, the dam dis-
charges water during other periods of the year, correspondingly increas-
ing the volume of the Flathead River.
INDUSTRIES AND MUNICIPALITIES
At present there are very few industries located on the tributaries of
Flathead Lake and its surrounding shoreline areas. Anaconda Aluminum
Company, located on the Flathead River at Columbia Falls, Montana, is
the largest industry utilizing the river's water. The effluents from
this industry are ponded or placed in dry wells on the company's prop-
erty. Wood-product industries have used the main rivers and tributaries
since the turn of the century. Agricultural practices are conducted
throughout the lower valley areas of the two main tributaries. This in-
cludes practices such as grazing and watering of livestock, irrigation
and runoff back into the streams.
The permanent population of the communities surrounding the immediate
area of Flathead Lake is estimated at 7>000. Approximately 90 per cent
of the population is served by municipal sewage treatment. The popula-
tion of the Flathead Lake area is estimated to increase in summer to
three times the permanent population. Summer residents reside in summer
homes, trailers, campgrounds, motels and lodges. Most of these facili-
ties use septic tank systems for sewage treatment. The population along
the rivers studied consists of scattered homes plus three communities
totaling 16,000 people. Kali spell with a population of over 10,000 is
served by primary sewage treatment with post-chlorination but no reten-
tion time and discharges into Ashley Creek which eventually enters the
Flathead River. Columbia Falls with a population of 2,132 has an aerated
lagoon and Whitefish with 3,936 people uses a sewage lagoon system.
Bigfork, population 500, is located on the Swan River at its point of
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entry into the lake. This community utilizes secondary sewage treat-
ment with chlorination but no retention time for disinfection. The
sewage effluent of Bigfork enters directly into Bigfork Bay.
WATER QUALITY CLASSIFICATION OF LAKE
Flathead Lake is presently classified as an A-open Dj lake by the
Montana Water Pollution Control Authority. Under the present classifica-
tion water may be used for drinking, culinary and food processing pur-
poses suitable for use after simple disinfection treatment and removal of
natural impurities. The water quality must also be maintained suitable
for swimming and recreation.
The Flathead River above the lake is presently classified by the Montana
State Water Pollution Control as B-Dj. This classification is strict
enough to maintain the water for swimming, boating, growth and propaga-
tion of salmon id fish and other associated aquatic life, such as water-
fowl and furbearers.
On October 5, 1967, the state of Montana adopted the following water
quality criteria for Flathead Lake (Brink,6):
"Concentrations of chemical constituents shall comform with
the 1962 U.S. Public Health Service drinking water standards.
Induced variation within these standards shall be limited to
an increase of not more than ten per cent of the concentration
present in the receiving water. The pH should be in the range
of 6.5 - 8.5. Turbidity should be none. No evidence of
matter other than that naturally occurring should be found,
except real color shall not be increased more than two units
above that naturally occurring.
"Organisms of the coliform group by the most probable
number (MPN) or equivalent membrane filter methods, during
any consecutive 30-day period and using a representative
number of samples, shall: average less than 50/100
mi 11iliters (ml) when demonstrated by sanitary survey to
be a result of domestic sewage."
With these stringent classifications of Flathead Lake and Flathead River,
guidelines for controlling polluted effluents entering the lake are
necessary.
CLIMATOLOGY
Monthly temperatures and precipitation for various stations in the drain-
age have been recorded for over fifty years at some locations. Precipi-
tation records for Kalispell were initiated in 1897.
Mountain ranges are responsible for varying local climatological differ-
ences. The western side of the lake is in a rain shadow and receives
less rainfall than the comparable altitudes on the east side of the lake.
8
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The growing season varies from about 150 days at Kalispell to an estimated
30 days in the high mountainous areas.
Flathead Lake can be shown to modify local weather conditions somewhat,
especially on the east side of the lake. Bigfork, Montana has the warmest
annual temperatures and is cooler in the summer and warmer in the winter
than other stations in the drainage. Weather modification by the lake,
then, is responsible for the ability of the east side to support a local
cherry orchard industry.
A summary of monthly mean values for temperature and precipitation is as
follows:
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Table 1. MEAN TEMPERATURE VALUES
Years on
Location record
Blgfork
Hungry
Horse Dam
Kalispell
Po 1 son
Airport
West
Glacier
21
13
38
47
46
Jan.
26.2
19.5
21.4
24.1
20.8
Feb.
29.8
24.7
25.2
27.7
24.6
Mar.
35.2
29.9
33-1
33-2
31.7
Apr.
45-2
40.8
43-7
44.7
41.8
May
53.5
51.1
52.0
52.7
50.5
Jun.
59.1
57.6
58.4
59-9
57.0
Jul.
61.5
65.0
68.4
67.5
64.5
Aug.
65-9
63-1
63-3
65.8
62.5
Sep.
57.1
54.3
54.0
56.2
53.2
Oct.
47.0
43.1
43.9
46.1
42.9
Nov.
35.3
31.4
32.2
34.7
30.9
Dec.
31.0
26.2
24.9
28.6
24.3
Ann
46.1
42.2
43.2
45.1
42.1
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Table 2. TOTAL PRECIPITATION
(inches)
Years on
Location record Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Ann
Blgfork 22 1.86 1.42 1.15 1-75 2.46 3-18 1.28 1.31 1-58 1.91 2.09 1.92 21.91
Hungry 13 3.65 2.71 1-93 2.02 2.49 2.94 1.58 2.05 2.13 3-33 3-29 3.02 31.14
Horse Dam
65 1.51 1.12 0.92 0.87 1.51 2.05 1.13 1.00 1.17 1.08 1,36 1.42 15.14
Kail spell 13 1.28 1.14 0.81 1.17 1.71 2.02 1.26 1.52 0.87 1.18 1.40 1.31 15.67
52 1.57 1.11 0.95 0.80 1.46 2.06 1.10 0.87 1.24 1.06 1.35 1.45 15.02
Poison 49 1.11 0.93 0.91* 1.17 1-74 2.24 1.02 0.94 1.32 1.23 1.26 1.24 15.14
Airport
Kerr Dam 30 1.07 0.91 0.78 1.23 2.03 2.44 0.99 1.08 1.35 1.20 1.28 1.18 15.51*
West 45 3.10 2.3** 1.7^ 1-73 2.20 2.83 l.M 1.39 2.02 2.64 2,91 3.24 27.58
Glacier
Whitefish 21 2.13 1.80 1.34 1.58 2.29 2.88 1.39 1.46 1.46 1.74 2.19 1,97 22,23
NW
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SECTION III
REVIEW OF WATER QUALITY STUDIES
Flathead Lake has been the subject of several investigations beginning
with Forbes1 study of aquatic invertebrates in the lake in 1893,'. Elrod,8
discussed the geology and topography of the lake in his study of the
zooplankton. "The Life of Flathead Lake" by Young° presented the results
of four years of data collecting on the chemistry and biology of the lake.
The data he collected constitute a very comprehensive basis for inter-
pretation of changes which have occurred in the lake during the last half
century.
Five papers have been published on the microbiology of Flathead Lake.
Graham and Young,'^ studied bacteria of the lake and concluded that the
fewest bacteria occurred on the surface and gradually increased toward
the bottom. He found a heterogenous group of bacteria in the lake.
Potter and Baker,''»'2 studied the chemistry and microbiology of Flathead
Lake including the bacteria and fungi. Ninety-eight species of fungi
were identified and the dominant types of bacteria were reported as Gram
negative rods. Bauer, investigated the occurrence of bacteria of the
coliform group in the lake and Hern,2 studied the relations of enteric
bacteria to the water quality of the lake. Bauer found that coliform
bacteria concentrations obtained near the shores often exceed the state
standard for the lake (50 coliforms per 100 ml). Samples taken away from
the shoreline were consistently low, and no fecal coliforms were found.
"Septic tank seepage into the lake was shown to be capable of producing
total coliform populations greatly exceeding the state standard." Hern's
conclusions were very similar to those stated by Bauer. Data on coli-
form bacteria also have been obtained from 1966 to the present by the
Lake County Sanitarian personnel (Robertson, unpublished data). These
data also indicated high coliform concentrations near the shores, with
late August, early September being the period of highest contamination.
Intensified studies of the phytoplankton, zooplankton, fisheries and
chemical and physical characteristics of Flathead Lake have been con-
ducted by a number of individuals and agencies since 1966 and have pro-
duced an abundance of data. Bjork, ^ studied the zooplankton of the
lake and reported 25 species of crustaceans and rotifers during the
summer months. The Montana Fish and Game Department has studied the
distribution, movements, and composition of fish populations along with
physical and chemical characteristics of the lake since 1964, Hanzel,
•5-25. Potter has been studying the zooplankton distribution and
ecology during the last ,two years (1971-1973, ).
Most of the recent works on the chemical and physical characteristics
and the phytoplankton and zooplankton of Flathead Lake have been par-
tially or wholly supported by grants from the Federal Water Quality
Administration and its successor, the Environmental Protection Agency.
A number of theses and research papers supported by these agencies are
12
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by MoghadamA Hern,2, Morgan,2?»28, Ivory,3°, and Potter,26.
While not supported directly by federal grant funds, the work of Dr.
Gerald Prescott on the higher aquatic plants of Flathead Lake, that of
Dr. Prescott and Dr. William Vinyard on the algae of Flathead Lake, and
the work of D. A. Hanzel and his associates of the Montana Fish and Game
Department on the fishes have contributed significantly to our knowledge
of Flathead Lake. The results of their research will also be included
in this report.
13
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SECTION IV
STUDY OBJECTIVES AND APPROACH
OBJECTIVES OF STUDIES
The objectives of the studies conducted by Moghadam, \ Morgan, '', and
Ivory,30 were: (i) to determine the physical and chemical characteristics
of the water, (2) to determine the standing crop of phytoplankton present
during all seasons of the year, (3) to correlate these characteristics
with the phytoplankton productivity of the lake, (k) to observe the
succession, distribution, and diversity of the phytoplankton forms, (5)
to determine the role of chemical nutrients in the relationship to the
phytoplankton, and (6) to help establish guidelines for the chemicals
dissolved in the lake's water during the different seasons of the year.
SAMPLING STATIONS
Due to the large size of Flathead Lake the studies conducted by Moghadam,
Morgan, and Ivory were limited to sections of the lake most affected by
man's activities. Stations where sampling was done are marked on the
map (Plate 1) by triangles directed toward shoreline landmarks. The
stations selected for sampling by Moghadam and Morgan were as follows:
1. Flathead River at Holt Bridge
2. Swan River at Ferndale Bridge
3. Mouth of Flathead River
4. Bigfork Bay
5. Mid-Lake Station between Angel Point and Yenne Point
6. Yenne Point southwest of Bigfork Bay
7. Wood Bay
8. Deep Water Station between Yellow Bay and Wildhorse Island
9. Yellow Bay
Moghadam's ecological and systematic study of plankton diatom communities
in the lake covered an eight-week period during the summer of 1967.
Weekly samples were collected from each station at four depths. For
comparative purposes qualitative samples of phytoplankton were taken from
five additional stations on a more limited basis. Morgan's study of
phytoplankton productivity and dissolved nutrient levels was confined to
the nine major sampling stations listed but in addition to the summer of
1967 comprised an intensive sampling period from June 18, 1968, through
September, 1969. Ivory's study of phytoplankton productivity was con-
fined to six sampling stations in Poison Bay during the period from
June, 1970, through September, 1972.
-------
\ I C^** i»r V I •
FLATHEAD LAKE
MONTANA
15
-------
SECTION V
METHODS OF SAMPLING
Temperature measurements were obtained by means of a Foxboro conductivity
thermometer. Light transmission was measured by a Secchi disc and a
Gemware submarine photometer. Water samples were taken with a Kemmerer
water bottle and a Van Dorn water sampler. The Van Dorn sampler was used
for obtaining water for the light and dark bottle experiments to prevent
metal contamination of the living organisms. Water samples were taken
from the surface, 3 m, 10 m, 20 m, and 30 m depths except in Poison Bay
where the depths were limited. Ivory limited his sampling to the surface,
3-meter and 5-meter depths.
CHEMICAL ANALYSES
Analytical procedures described in the Hach Chemical Engineers Kit,
Model DR-EL, were used on the boat in determining alkalinity, carbon
dioxide, dissolved oxygen, pH, and turbidity. In the laboratory 500 ml.
samples of water were filtered through a mi 11ipore filter (R) having a
0.45 micron pore size. Analyses of the filtered water for chloride,
fluoride, dissolved iron, nitrate, ammonia, orthophosphate, sulfate,
silica, calcium and magnesium hardness were made in accordance with the
procedures described by the American Public Health Association (1965)
and modified in some cases by the Hach Chemical Company in their
Engineer's Laboratory, Methods Manual 29.,3'.
16
-------
SECTION VI
PHYTOPLANKTON PRODUCTIVITY
OXYGEN EVOLUTION METHOD
As one means of measuring phytoplankton productivity both Morgan and
Ivory in their studies utilized the light and dark bottle evolution tech-
nique as described by Strickland,32 for at least one summer during their
research. Due to the oligotrophic nature of Flathead Lake the results
were too variable to have significant value. Vollenweider,33 indicated
that, in deference to statistical considerations, there must be an
arithmetical difference of at least 0.15 mg 02/1 between the light and
dark bottles for the data to be considered significant. Utilizing
incubation periods of from k to 2k hours both Morgan and Ivory found that
very often such a difference in the content of dissolved oxygen did not
occur.
CARBON H (C1/J) UPTAKE
The assimilation of Carbon 14 (C ) is a direct measure of the photo-
synthetic activity or organic productivity taking place in the aquatic
environment. Steemann-Nielson,3**>35 developed this method for assessing
algal productivity in the marine environment. The procedure is very
similar to that of the oxygen evolution method, the difference being the
injection of a specific quantity of radioactive C^ in the form of sodium
carbonate (Na2C'^0-j) in the light and dark bottles.
The field procedure involved taking water samples from various depths at
each station with the Van Dorn bottle. Each sample was then used to fill
two light and one dark bottles which were kept in a darkened area until
the Cl** solution was introduced into them. The bottles were left in the
water to incubate for periods from k to 6 hours.
In the laboratory a 200 ml. aliquot of each sample was filtered through
a 22 mm membrane filter using a field isopor filtration kit. The
measurement of radioactivity of c'^ labeled algae on the membrane fil-
ters was performed with a Geiger-Mueller counter by Morgan. Ivory in
his work had access to a liquid scintillation spectrometer which proved
to be considerably more efficient as a counting device.
PHYTOPLANKTON STANDING CROP
One-liter samples of water for phytoplankton analyses were taken at the
various depths at each station. These samples were refrigerated until
they could be concentrated and preserved. Phytoplankton was concen-
trated through the use of a Foerst continuous flow centrifuge. A 500 ml.
aliquot of the sample was centrifuged for k minutes and the resulting
concentrate was then diluted to 10 ml. and preserved in Transeau's
17
-------
Solution consisting of water, 95% alcohol, and formaldehyde in a 6:3:1
proportion. The concentrated samples were stored in 6-dram vials until
identification and enumeration of the plankton could be accomplished.
Plankton counts were made with a Whipple disc and Sedgewick Rafter count-
ing slide, using ten randomly selected fields. After ten fields were
enumerated a strip count was made to include any genera which were too
scarce to be detected in the Whipple disc counts. Species determinations
were made by examining a drop of the plankton concentrate under 450X
magnification. Raw counts were then converted to number per liter of
lake water.
18
-------
SECTION VII
PHYSICAL CHARACTERISTICS OF FLATHEAD LAKE
TEMPERATURE
The various studies that have been conducted on the lake have clearly
demonstrated that it is a cold dimictic lake exhibiting submerged
depression individuality. There are various bays and depressions in the
lake each of which may have its own thermocline that differs in position
and thickness in the different depressions, and each depression may have
its own individual seasonal history. Furthermore, while much of the lake
stratifies thermally, there are several extensive shallow bays such as
Poison Bay which do not do so.
Morgan,27«2° found considerable variation in temperature between the
stations which he studied. Temperatures at the surface during the peak
summer stratification on August 6, 1968, reached a high of 21°C at four
of nine stations, with the remaining stations ranging from 17°C in the
Flathead River to 20.5°C at the Mid-Lake Station. Hypolimnion tempera-
tures reached 9.0°C at the 35-meter depth in the bay stations and mouth
of the Flathead River. The deep H20 and Mid-Lake stations reached 7.0°C
during the peak period. Water samples taken at the deep H20 Station,
June 20, 1969, from the 40-meter, 50-meter, and 60-meter depths had
temperatures of 4.3°C, 4.6°C, and A.7°C respectively.
Whereas a distinct thermocline can be found in various depressions of the
lake each summer, its depth, period of formation, and the spring and fall
overturns vary considerably from year to year. In 1968 the thermocline
began forming the last week in June and persisted until the beginning of
October of that year in the deep H£0 Station. The fall overturn began
during the last week of September. This mixing continued until the first
week of November when the lake was homothermous from top to bottom.
Inverse stratification of the lake began in late December, 1968. The bay
areas of the lake began freezing over, a normal occurrence for the lake
at this time. Extreme cold persisted with air temperatures reaching as
low as -37°C during the months of December and January. The lake proper
began freezing over during the month of January and had a complete ice
cover from the last week of January until the first week of April when
the ice cover began to break up. The formation of a complete ice cover
is uncommon on the lake. This was the first complete icing of Flathead
Lake in 23 years.
The spring turnover began shortly after the ice break-up with homo-
thermous conditions occurring during the middle of May. The lake did
not stratify during the summer of 1969 until the first week of July.
19
-------
LIGHT TRANSMISSION
The oligotrophic waters of Flathead Lake offer little interference to
light waves impinging on the lake's surface. Low levels of dissolved
solids and color-producing compounds plus limited plankton allow measur-
able light to penetrate to depths of 60 meters. During a calm period on
July 23, 1969, Morgan found 1\% light transmission at a depth of 10
meters and k% transmission at 50 meters at a deep H20 Station.
The lower limit of the euphotic zone as defined by Reid,3° is that point
at which only 1% of the total incident surface radiation is measurable.
The transmittance of light in Poison Bay, which during the summer months
is often much more turbid than the lake proper, was found by Ivory,30 to
range from 100.0% near the surface to 6.7% near the bottom (7 meters).
Thus even more shallow freely mixing areas of the lake appear to be well
within the euphotic zone.
20
-------
SECTION VIII
CHEMICAL CHARACTERISTICS OF FLATHEAD LAKE
The dilute chemical composition of the waters of Flathead Lake might be
expected considering the drainage basin which is composed of sedimentary
rock with thin soils and subsoils of gravelly glacial debris and
impermeable bedrock. Furthermore, the streams draining into the lake are
relatively short and arise from snow and ice melt and from cold mountain
springs. Consequently, there is little opportunity for the inlet waters
to have gathered high concentrations of solutes.
In 1929 Howard, working with Clapp, Elrod, Young, and Shallenburger,
conducted a survey of the lake (Clapp, C. H. et al.,2?). Dr. Howard was
responsible for the chemical determinations during the study. Morgan,2°
summarized the results of chemical analyses of the lake conducted at
various times since Howard's work. The summary (Table 1) indicates that
little change has occurred in the chemical composition of the waters of
the main body of the lake over the last forty years.
The results of Ivory's study of Poison Bay are included in Table 3 for
comparative purposes. Concentrations of some nutrients as ammonia and
nitrate nitrogen were slightly less than in other areas of the lake. This
may have resulted from nutrient utilization by Chara and higher aquatic
plants which occur abundantly in the shallow waters of the bay.
21
-------
Table 3- FLATHEAD LAKE WATER CHEMISTRY
Forty Year Span
(mg/1)
NJ
Aluminum
Ammonia-Nitrogen
Bicarbonate
Carbon Dioxide
Carbonate
Chloride
Dissolved Oxygen
1 ron Tota 1
Nitrate-Nitrogen
Nitrite-Nitrogen
Phosphate-Ortho
Silicate
Sulfate
PHC
Howa rd
1929
9.3
0.13
-
2.0
20.5
0.32
8.0
0.02
Trace
-
Trace
8.2
24.9
8.4C
Potter &
Baker
1961
a
o.ot
10.2-85.7
0.0
4.0
a
11.0
0.60
0.05
Trace
0.20
a
a
8.0C
Morgan
1967
0.04
0.32
80.0
Trace
10.0
0.50
10.3
0.10
0.16
Trace
0.16
5.0
5-5
8.3-8.7°
Morgan
1968
0.04
0.25
80.0
0.0b
7.5
1.00
10.8
0.05
0.12b
Trace
0.11
4.7
7.0
8.2-8.7c
Morgan
1969
0.03
0.23
75.0
0.0
5.0
0.75
10.5
0.05
0.19
Trace
0.15
4.5
6.8
8.3-8.8C
Ivory
1971-72
a
0.04
81.0
0.8
2.8
a
9.0
0.02
0.06
Trace
0.035
4.6
5.4
8.0-8.4C
.Not determined by researcher
Denotes extremes not included
cpH expressed in unfts
-------
SECTION IX
PHYTOPLANKTON DISTRIBUTION IN FLATHEAD LAKE
4
Dr. Moghadam, in her systematic study of the diatom communities of Flat-
head Lake identified 337 different taxa of which five species and two
varieties were new. Dr. Morgan,27»28 jn njs studv of phytoplankton pro-
ductivity of the lake identified a total of 199 species and varieties.
Five divisions of algae were encompassed in his enumeration. Deletion of
species common to both studies yields a combined total of 503 different
species and varieties of algae found in Flathead Lake's phytoplankton
population.
DOMINANT SPECIES OF CHRYSOPHYTA
The planktonic algae which exhibited dominance throughout Morgan's study
were almost entirely of the subdivision Baci1lariophyceae. The genera
most frequently encountered were: Asterionella, Fragilaria,
Rhizosolenia, Synedra, and Tabellaria, with occasional appearances of
Cyclotella, Navlcula, Cymbella, Campylodiscus, Surirella, Gyrosigma, and
Eunotia. Other algae encountered frequently of the same division,
Chrysophyta, subdivision Chrysophyceae, were four species of the same
genera: D i nobryon bavaricum Imhof, D. djyergens Imhof, IK sertujaria
Ehrenberg, and JD. sociale Ehrenberg. Other genera of the same sub-
division, but which occurred less frequently, were Mailomonas,
Rhizochrysis, and Synura. The total number of species identified in the
order Chrysophyta was 109.
The Cyanophyta or blue-green algae most often found were Chroococcus,
Gomphosphaer i a, Gloeocapsa, Microcystis, Merlsmopedia and on occasions
Spirulina, Anabaena, Aphanocapsa, and Aphanizomenon. Aphanizomenon
occurred one time only in the phytoplankton of Flathead Lake. The blue-
green algae did not exhibit any dominancy except for one bloom of
Aphanizomenon flos-aquae Ralfs in late summer. The bloom occurred just
to the west of Bigfork Bay. This area is relatively shallow (2-8 m) and
is exposed to the diurnal mixing action of the south wind. The contin-
ual eddying returns the nutrients from the sediments to the water above
for algal utilization.
The blue-green algae occurred most frequently in the late summer and
early fall when the nutrients were at their lowest concentrations.
Chroococcus limnetica Lemmermann, C_. prescotti i Drouet & Daily, and
Aphanocapsa elastista G. M. Smith were the most common species found in
the pelagic zone of the lake.
A total of 25 species was identified during the study of which 10 were
rather rare in occurrence. Genera, such as Dactylococcus, Eucapsis,
Gloeotrichia, Lyngbya, and Synechococcus appeared rarely and then only
in limited numbers.
23
-------
The division Chlorophyta (green algae) was even less frequently found
in the planktonic samples of Flathead Lake. Oocyst is spp. were the most
frequent, followed by Spaerocystis, Cosmarium, Pediastrum, and
Staurastrum. Dictyosphaerium pulchellum Wood was often found in samples
containing Chroococcus spp. during the late summer months. The remaining
species were infrequent and were transported largely from areas along the
shoreline or rivers to the pelagic region of the lake. Filamentous spe-
cies, such as Mougeotia genuflexa (DUlw.), Zygnema pectinatum Fritsch £
Stephens represent such transported species. These species are sessile
forms commonly found along the shore areas.
Sixty-three different species of green algae were found in the plankton
samples during the study.
The small division Pyrrophyta was well represented with five genera and
\k species. Most commonly encountered were the species Ceratium
hirundinella, Glenodinium kulczynskii (Wolosz.) Schiller, and Peridinum
cinctum var. tuberosum (Meunfer) Linderman. This division is limited in
numbers during the spring. The increased temperatures of summer and
possibly the increased organic compounds (Hutchinson,38) released by
previous plankters facilitate these plankters1 growth and reproduction.
The fifth and smallest division Euglenophyta was represented by only one
genera, Trachelomonas sp., at the Bigfork Bay Station. This division
undoubtedly has many more species in the shoreline areas where more or-
ganic matter is available for their use.
ECOLOGICAL RELATIONSHIPS
In planktonic studies of algae certain species appear to be associated
with one another. The name of the dominant species or sometimes the
dominant and subdominant are used as designations for the association.
Hutchinson,3" uses this form naming the dominant species and then the
subdominant, e.g., Fragilaria-Asterionella; Fragilaria being the domi-
nant and Asterionella the associated subdominant. One or more sub-
dominants may be associated. This type of association was used in
showing relationships between genera found during the study.
The species showing dominance during the study were Tabe11 aria quadri-
septa Knudson, Fragilaria crotonensis Kitton, Rhizosolenia ertensis H.
L. Smith, Dinobryon divergens, Stephanodiscus sp., Asterionella formosa.
Each of these genera showed pulses during the study but none were strong
enough to exhibit a bloom.
Tabellaria quadrisepta occurred in its greatest numbers during June and
early July. The largest population of this species, 186, 189 per liter,
occurred at the Deep h^O 30 m level. Computer data indicates this spe-
cies as being a cold water, high nutrient requiring species.
Fragilaria crotonensis exhibited a pulse during late June in 1968 and
1969.This species exhibited another pulse shortly after the fall turn-
2k
-------
over each year.
Dinobryon bavaricum and _D_. sociale showed preference for colder tempera-
tures and higher nutrient levels than D. divergens or £. sertularia.
Silicon dioxide levels are known to limit £. divergens.
Rhizosolenia eriensis, a diatom of the order Centrales, showed high popu-
lation figures shortly after the ice breakup in the spring of 19&9-
Another pulse was detected during the summer when nutrients are more
limited. Pearsal1,39 reported R. eriensis as requiring less nutrients
than Asterionella formosa, Fragilaria crotonensis and Tabellaria
fenestrata.
Asterionella formosa, a pennate form of the family Fragilariaceae, was
found throughout the study. Asterionella formosa is considered to be a
cold water form requiring high nutrient levels. This species during the
summer is a subdominant associated with all the species described pre-
viously. Concentration of A_. formosa fluctuated throughout the study
with a general increase being noted after late August. The increase of
A. formosa can be attributed to increase of dissolved nutrients two weeks
prior to the pulse.
Synedra delicatissima W. Smith and Su fasciculata var. fasciculata (Ag.)
Kuts. were found in numbers totaling 17^,000 and 3^,800 per liter
respectively during and shortly after the spring thaw of 1969- The
Synedra spp. showed a decline with the decreasing of silica, nitrate and
sulfate in the summer months. S^. acus var. acus Kutz. was limited mainly
to the rivers and those stations more directly influenced by the rivers.
Other diatoms of the order Pennales that appeared commonly in the plank-
ton samples were the genera Amphora, Cymbella, Navicula and Pinnularia;
other pennale genera were identified but occurred less frequently.
Cymbe11 a and Navicula appeared in minor concentrations throughout the
study. Both general, although usually free-floating, are often found
attached to submerged objects, which accounts for limited numbers in
plankton samples. Both genera were found in plankton samples at each
station sporadically.
Cyclotella and Melosira, of the order Centrales, occurred at all sta-
tions and the various depths sampled. Melosira, a diatom forming a
filamentous chain, is considered to be a cold water, high nutrient-
demanding diatom. Melosira occurred in limited numbers at all stations
and depths. The nutrient level required, plus the physiological struc-
ture influenced by density, limits Melosira to periods of seasonal
overturn. Cyclotella appeared in increased numbers during the late
summer and fall periods similar to the distribution patterns of
Stephanod i scus.
Dr. Ivory,^O conducted his 1imnological studies of Poison Bay from June
1970 to September 1972 and encountered phytoplankton populations some-
25
-------
what different than those found in the upper deeper sections of the lake
by Morgan. Poison Bay is located in the southern end of Flathead Lake
and has a gently sloping muddy bottom and a maximum depth of only 7 meters.
Much of the bottom is covered with sizeable growths of Chara, Potamogeton,
Ceratophyllum, and Myriophyllum. During the fall and winter months much
of the bottom area is left dry and exposed by the receding waters of the
lake.
Ivory reported 67 genera and 94 species of algae in Poison Bay. The
Bacillariophyceae and the Chlorophyceae were the most abundant groups,
and the diatoms contributed more than 50% of the total population during
each year of the study. The composition of the phytoplankton varied some-
what from year to year as did the size of the standing crop, but no
definite pattern of change in productivity was evident. Populations
trends during the spring and summer periods of the three years appeared
to follow a similar pattern with an increase in the population size in
late spring or early summer. This increase was followed by a steady de-
cline in the population until early autumn. During 1970 a definite fall
maximum was observed; during 1971 the seasonal sample obtained in October
indicates that such an autumnal increase had probably occurred somewhat
earlier. In 1972 sampling was terminated in late August before any such
seasonal increase in population had occurred.
During the three-year period, the concentration of phytoplankton appeared
to be slightly greater at depths of 3, 5, or 7 meters than near the sur-
face, but no station had a consistently greater plankton population than
any other.
During July 1970, increases in the populations of Dinobryon divergens,
Tabellaria quadrisepta, and Cyclotella spp. led to a phytoplankton maxi-
mum, in September and October another maximum was observed. During
this autumn maximum, many of the organisms reached their greatest abun-
dance. Thus, Tabellaria quadrisepta, Cyclotella spp., Fragilaria
crotonensis, Navicula spp., Rhizosolenia eriensis, Gomphosphaeria aponina
Kuetz, Gomphosphaeria lacustris Chodat, Mailomonas pseudocoronata
Prescott, Mailomonas alpina Pascher and Ruttner, Ceratium hirudinella,
and Synedra spp. attained their maximum abundance during the fall. The
organisms which dominated the fall maximum were Tabellaria quadrisepta
Knuds, Cyclotella spp., Gomphosphaeria aponina, G. lacustris, Dinobryon
divergens Bachm., and Fragilaria crotonensis Kitton.
A rank of the most abundant species during each year of the study is
given in Table 4.
Although the overall population patterns appeared to be similar from year
to year, the absolute abundance of the standing crop and the dates at
which maxima and minima occurred were slightly different from year to
year. Thus, the absolute abundance of phytoplankton during the spring-
summer maximum of 1971 was considerably larger than the maxima of 1970
or of 1972, and it occurred at a siightly different date than either of
the others.
26
-------
Table 4. RANK OF PHYTOPLANKTON SPECIES ACCORDING
TO MEAN POPULATION
(number of organisms/1 x 102)
Taxon
Dinobryon divergens 1 970
Tabellaria qjuadrisepta "
Gomphosphaer ia spp. "
Cyclotel la spp. "
Navicula spp. "
Fragilaria crotonensis "
Tabellaria quadrisepta 1971
Cyclotel la spp. "
Dinobryon divergens "
D. bavaricum "
Navicula spp. "
Chroococcus spp. "
Synedra spp. "
Cyclotel la spp. 1972
Dinobryon divergens "
Synedra spp. "
Dinobryon bavaricum "
Tabellaria quadrisepta "
Rhizosolenia eriensis "
Chroococcus spp. "
Mean
222.0
183.0
113-0
91.0
65.6
50.8
577.0
467.0
212.0
111.0
109.6
102.8
93.9
396.0
229.0
132.0
124.0
116.0
87.0
56.5
Max i mum
1183.0
833.0
482.0
351.0
482.0
438.0
1464.0
2063.0
499.0
766.0
2463-0
300.0
900.0
1281.0
525.0
854.0
493-0
493.0
296.0
1478.0
27
-------
The composition of the phytoplankton standing crop also differed some-
what from year to year. Thus, the Myxophyceae comprised a larger per-
centage of the total population in 1970 than in either 1971 or 1972. On
the other hand, the Dinophyceae contributed a larger percentage of the
population in 1972 than they did in 1970. Such yearly differences in the
composition of the standing crop may result in part from a sampling bias
since the early and late sampling periods of each year do not coincide
exactly. Also, slight differences in such environmental parameters as
temperature and light probably account for such differences in composition.
28
-------
SECTION X
ALGAL FLORA OF FLATHEAD LAKE
The algal flora of Flathead Lake, both quantitatively and qualitatively,
reflects its limnological and hydrographic uniqueness. This is not-
withstanding that every lake possesses its own combination of physio-
chemical characteristics. But these hydrographic and physiographic fea-
tures seem to have some significant influences which help to explain the
somewhat unusual biotic composition and distribution of algae throughout
the lake.
First, it is seldom that a lake with the volume of the Flathead lies so
near the headwaters of its tributaries. In this instance the streams
draining into the lake are relatively short, and they arise from snow and
ice melt and from cold mountain springs. Accordingly the inlet waters
1) are relatively cool, and 2) have little opportunity to become heavily
silted or to have gathered high concentrations of solutes. The turbidity
readings for the two principal tributaries (Swan River, Flathead River)
for example are relatively low (Table 5) and in general are much less (at
the same time of year) than at many stations throughout the lake. Like-
wise, phosphates and nitrates are low, those for the Flathead River being
slightly but not significantly greater than in the Swan River. The tem-
perature of inlet waters averages slightly higher than at stations
throughout the lake during the spring run-off (Table 6). Throughout the
lake the surface layer temperature seldom reaches 20°C throughout the
summer, whereas at 30 M, where the algal population is often greater in
numbers of individuals than at the surface, the temperature does not rise
above 13°C and seldom reaches that level. The relatively deep basin con-
tributes to and maintains the low temperature of Flathead Lake (Table 6)
and determines some of the oligotrophic features of the lake.
Secondly, Flathead River which flows into and out of the lake produces
a strong channel current. This has an unknown effect on the systems of
currents both vertical convection and horizontal. But it seems obvious
that the distribution pattern of phytoplankton species is influenced by
and determined in part by currents. For example, it is likely that the
unusual density of plankters in the 25-30 M zones is related to lake
currents (Tables 11-13). In addition to currents influenced by channel
flowage, distribution is influenced (to an unknown extent) by strong and
frequent wind action which produces oceanic effects in the surface
waters periodically. Such action also has a bearing on water mixing and
the level of the thermocline which in turn has both direct and indirect
effects on the distribution of organisms.
Another factor which has interacting effects is the fluctuation of the
water level in Flathead Lake, Operation of a power dam in the outlet
causes the lake level to drop from 10 to 12 feet during the winter and
early spring months, in all about 7 months of the year. This has an
29
-------
Table 5. TURBIDITY J.T.U.
Station
Swan
River
Flthd
River
Mth of
Flthd
Blgfork
Bay
Mid-Lake
Yenne
Point
Depth
(m)
Sa
3
Sa
3
9
Sa
3
10
20
30
sa
3
4
Sa
3
10
20
30
Sa
3
10
20
30
1
5.0
6.0
15.0
18.0
19.0
10.0
14.0
15.0
16.0
15.0
14.0
14.0
11.0
15-0
11.0
13.0
12.0
16.0
16.0
11.0
10.0
8.0
7,0
2
7.0
4.0
8.0
5-0
4.0
3.0
3-0
8.0
3-0
12.0
5.0
6.0
18.0
13-0
17.0
16.0
17-0
17.0
10.0
10.0
8.0
4.0
6.0
3
0.0
8.0
5.0
0.0
0.0
20.0
8.0
18.0
20.0
20.0
22.0
23.0
17.0
2.0
0.0
2.0
5.0
1.0
5.0
10.0
11.0
1.0
1.0
4 5 6 7 8 9 10 11
4.0 3.0 5.0 7.0 12.0 8.0 9-0 4.0
10.0 6.0 5.0 5.0 12.0 7.0 10.0 8.0
4.0 7.0 7.0 4.0 6.0 4.0 5.0 25.0
8.0 6.0 4.0 4.0 6.0 6.0 4.0 28.0
6.0 5.0 4.0 5.0 7-0 5.0 5.0 25.0
8.0 12.0 8.0 4.0 1.0 5.0 1.0 20.0
10.0 13.0 8.0 4.0 9.0 9.0 2.0 22.0
14.0 10.0 12.0 3.0 8.0 13.0 8.0 23.0
9.0 9.0 6.0 1.0 7.0 9.011.026.0
30.0 d 19.0 8.0 4.0 9.0 1.0 33.0
9.0 10.0 26.0 7-0 1.0 20.0 2.0 26.0
20.0 25.0 28.0 9.0 3.0 22.0 3.0 27.0
14.0 17-0 21.0 7-0 3-0 20.0 5-0 38.0
1.0 2.0 2.0 5.0 7.0 12.0 2.0 9.0
19.0 1.0 4.0 8.0 7.0 13.0 5.0 12.0
15.0 1.0 9.0 4.0 1.0 15.0 8.0 10.0
13.0 1.0 5.0 8.0 2.0 13.0 6.0 15-0
11.0 1.0 10.0 0.0 3.0 8.0 7.0 21.0
17.0 10.0 6.0 7.0 8.0 10.0 19.0 22.0
12.0 5.0 7.0 3.0 10.0 3.0 21.0 24.0
17.0 14.0 8.0 3.0 9.0 5.0 16.0 21.0
8.0 9.0 14.0 12.0 8.0 5.0 17.0 14.0
1.0 2.0 7-0 1.0 8.0 3.0 16.0 14.0
12
1.0
2.0
17.0
17.0
18.0
17.0
15.0
7.0
10.0
8.5
11.0
10.0
17.0
7.0
8.0
5.0
10.0
13.0
10.0
12.0
7.0
5.0
8.0
13
5.0
0.0
10.0
9.0
13.0
0.0
0.0
0.0
0.0
2.0
3.0
3.0
0.0
9.0
9.0
8.0
9-0
1.0
0.0
1.0
1.0
2.0
1.0
14
5.0
5.0
4.0
1.0
4.0
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
15
10.0
11.0
7.0
8.0
10.0
12.0
8.0
5.0
2.0
3.0
4.0
2.0
5.0
8.0
10.0
8.0
1.0
3.0
4.0
4.0
2.0
2.0
3.0
16
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
-c
c
17
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
7.0
5.0
4.0
4.0
2.0
18
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
3-0
2.0
3.0
1.0
2.0
19
8.0
8.0
12.0
15.0
21.0
12.0
12.0
11.0
10.0
12.0
10.0
10.0
9.0
4.0
6.0
4.0
2.0
2.0
14.0
10.0
8.0
5.0
4.0
20
10.0
9.0
22.0
25.0
37-0
14.0
18.0
14.0
15.0
14.0
12.0
14.0
15.0
10.0
8.0
7.0
8.0
8.0
12.0
12.0
14.0
5.0
6.0
21
6.0
6.0
14.0
17-0
30.0
10.0
12.0
16.0
12.0
13.0
11.0
10.0
13.0
8.0
6.0
3-0
3-0
5.0
6.0
8.0
12.0
14.0
6.0
-------
Table 5 (continued). TURBIDITY J.T.U.
Station
Woods
Bay
Deep
H,0
2
Yellow
Bay
a Surface
Depth
(m)
Sa
3
10
20
30
Sa
3
10
20
30
Sa
3
10
20
30
» *. —..— .
1
7-0
7.0
8.0
5.0
6.0
8.0
8.0
8.0
4.0
8.0
3.0
2.0
3-0
3-0
3.0
2
10.0
8.0
5.0
9.0
9.0
9.0
7.0
8.0
6.0
8.0
2.0
4.0
5.0
6.0
3.0
3 A 5 6 7
0.0 2.0 12.0 18.0 3-0
3.0 3.0 10.0 9.0 6.0
5.0 10.0 8.0 9.0 7.0
0.0 0.0 9.0 10.0 8.0
0.0 0.0 7.0 7.0 4.0
8.0 10.0 8.0 8.0 7.0
2.0 17.0 12.0 8.0 8.0
7.0 9.0 15.0 11.0 6.0
6.0 7.0 11.0 12.0 18.0
7.0 5.0 1.0 k.O 2.0
2.0 1.0 2.0 4.0 2.0
5.0 1.0 5.0 8.0 1.0
7.0 5-0 10.0 6.0 6.0
8.0 1.0 10.0 4.0 1.0
4.0 4.0 9-0 4.0 5.0
8
6.0
7.0
8.0
8.0
8.0
3-0
3-0
3.0
0.0
4.0
10.0
10.0
7.0
6.0
8.0
9
3-0
2.0
5.0
1.0
3.0
10.0
12.0
15.0
10.0
10.0
11.0
10.0
8.0
5.0
7.0
10
10.0
8.0
8.0
9.0
10.0
1.0
4.0
5.0
2.0
1.0
10.0
2.0
5.0
4.0
1.0
11
0.0
2.0
0.0
3-0
8.0
3.0
6.0
7-0
3-0
7.0
8.0
4.0
4.0
8.0
4.0
12
8.0
7-0
6.0
4.0
4.0
5-0
3.0
5-0
5.0
4.0
9-0
4.0
5-0
5.0
5.0
13
4.0
4.0
1.0
2.0
6.0
12.0
9-0
10.0
9-0
9-0
6.0
8.0
4.0
8.0
4.0
14
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
15
4.0
6.0
1.0
7.0
10.0
15.0
10.0
8.0
4.0
10.0
7-0
7.0
6.0
6.0
3.0
16
c
c
c
c
c
c
c
c
c
c
c
• c
c
c
c
17 18
15.0 18.0
17.0 20.0
21.0 19.0
10.0 12.0
18.0 22.0
c c
c c
c c
c c
c c
5.0 1.0
6.0 8.0
4.0 15.0
14,0 16.0
13.0 20.0
19
0.0
1.0
1.0
0.0
0.0
6.0
5.0
5.0
10,0
7.0
5.0
2.0
4.0
2.0
1.0
20
1.0
8.0
10.0
8.0
10.0
1.0
3.0
6.0
3.0
4.0
4.0
3.0
5.0
1.0
3.0
21
2.0
2.0
3.0
4.0
1.0
4.0
4.0
7.0
1.0
1.0
2.0
2.0
2.0
4.0
4.0
c Beginning of continued ice cover
Too shallow
-------
Table 6. THERMAL READINGS
CO
oo
Station
Swan
River
Flthd
River
Mth of
Flthd
Bigfork
Mid-
Lake
Yentie
Point
Depth
(m)
Air
Sa
3
Air
Sa
3
9
Air
Sa
3
10
15
20
25
30
35
Air
Sa
3
l*
Air
Sa
3
10
15
20
25
30
35
Air
Sa
3
10
1 2 3 4 5 6 7 8 9 10 11 12
16.5 16.0 27.0 21.0 22.5 25.0 18.0 15-5 8.5 8.5 9-5 10.0
12.3 13.0 14.1 16.0 18.5 21,0 17-0 16.0 11.7 11.5 13-0 8.5
11.9 12.7 1*».3 16.8 18.0 21.0 16.5 16.5 13.0 12.0 13-0 8.5
15.0 16.0 27.0 22.0 25.0 26.0 24.0 25.0 22.0 18.0 10.0 10.0
9.5 10.0 11.0 12.0 13.0 17-0 21.0 20.0 17-0 16.0 14.0 8.5
9.3 10.0 10.5 12.5 12.0 16.5 20.0 20.5 16.0 16.0 13-0 8.0
8.7 9.0 10.5 12.5 12.0 15-0 20.0 20.0 16.0 16.0 13.0 8.2
16.8 16.2 34.0 30.6 23-9 23.0 21.0 33-0 16.0 19-0 18.0 5.0
11.2 12.8 14.4 18.9 17.9 21.0 18.0 19.5 19.0 11.0 12.5 8.0
8.7 12.2 13-1 16.7 16.1 21.0 18.0 19.0 19.0 13.0 12.5 8.3
6.2 10.0 9.0 7-8 14.4 20.0 18.0 19.0 18.5 12.0 12.5 8.5
4.6 5-6 6.2 6.1 10.6 16.2 16.5 18.7 18.3 13-0 12.5 8.5
3.9 3-9 5-6 5.6 8.9 11.4 10.0 18.5 18.0 15.0 12.0 8.5
3.8 3.9 4.6 5.6 7.2 10.3 9-3 15.0 15-5 13.0 12.5 8.2
3.8 3.8 4.0 5.6 d 10.0 9.0 12.0 13.0 9.0 12.5 8.0
3.8 3.8 4.0 5.6 d 7.8 6.1 8.0 9.0 9-0 9.0 8.0
18.0 15.4 32.0 29.0 25.0 24.0 18.0 27.0 18.0 8.5 18.0 11.0
12.3 12.1 15.2 18.0 18.0 20.0 18.0 18.0 17.0 11.0 11.5 8.0
10.8 12.0 14.3 17.5 15.5 21.0 18.0 18.0 17.0 12.0 11.0 8.5
10.8 11.7 14.3 15.0 15.0 20.5 18.0 18.0 17.0 9-0 11.0 8.0
17.0 16.1 37-2 24.4 24.0 23-5 21.0 30.0 17-0 19-0 16.0 7-0
11.7 14.4 18.9 20.0 19.0 20.5 20.1 19.0 19.0 13.0 12.7 8.2
10.6 13-9 16.7 18.3 18.0 20.0 19.7 19.0 19.0 13-0 12.5 8.5
6.7 7.8 12.8 14.4 16.0 15-0 18.0 18.0 18.5 12.0 12.5 8.5
5.8 6.1 10.0 8.9 11.5 10.9 12.8 15.0 18.5 12.0 12.5 8.5
5.0 5.0 8.3 7-2 11.0 10.0 11.8 12.0 18.5 12.0 12-5 8.5
4.8 4.4 7.2 6.1 9-6 8.6 8.9 8.7 9.6 11.5 11.8 8.3
4.0 4.4 6.1 5.7 8.0 7.0 8.0 8.0 9.0 11.0 9.5 8.0
4.0 3.8 5.5 5.0 5.0 6.0 6.8 5.6 6.0 6.8 7-2 7.0
18.9 16.1 17.8 28.9 17-8 19.5 18.0 21.0 17.0 9-5 13.0 6.0
15.6 16.7 18.0 19.4 15.6 21.0 18.0 18.0 19.0 13-5 12.5 8.0
15.0 16.1 17.0 18.3 15.0 20.0 19-0 18.0 19.0 14.0 12.0 8.0
11.7 10.6 12.0 12.2 13-9 18.0 19.0 17-0 18.0 13-0 12.5 8.5
13
-2.0
6.5
6.5
-5.0
7.0
7.0
7.0
2.0
7.0
7.5
7.5
7-5
7-5
7.8
8.0
8.0
0.0
7.0
7.5
7.5
0.0
6.8
6.8
6.8
6.8
6.8
7.0
7.0
7.0
2.0
6.0
6.0
7.0
14
2.0
6.0
6.0
2.0
7.5
6.8
7.0
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
15
-4.0
4.8
4.0
-5.0
3.4
4.0
4.8
3-7
6.3
6.3
6.0
6.0
5.8
5.8
5-8
5-8
-2.0
2.5
2.8
3.2
-10.0
5.5
5.5
5.8
5-8
5.9
6.0
6.0
6.0
1.7
5.0
5.5
5.7
16
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
17
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
-12.0
0.0
1.2
1.6
18
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
-7.0
0.0
1.2
1.5
19
9.0
5.0
5.1
9.0
5.7
5.7
5.7
14.0
2.9
2.9
3.0
3.9
3.9
4.0
4.0
4.0
13.0
5.0
5-2
4.8
15.0
3.0
3.0
3.8
3-9
4.0
4.0
4.0
4.0
19.0
3.0
3.0
3-1
20
22.0
11.8
12.4
22.0
9-1
8.7
9-0
23.9
10.0
6.1
3-9
3-9
3-9
3.9
3.9
3-9
20.0
14.0
14.0
14.0
24.4
10.0
7.2
4.4
3-9
3.9
3-9
3-9
3-9
22.0
13.0
9.0
5.9
21
8.0
10.8
11.5
6.9
10.0
10.0
9.8
17.0
12.8
12.7
9.0
6.0
5-3
3.8
3.8
3.8
14.0
12.0
11.5
10.8
16.0
12.8
12.0
9.2
7.2
5.3
5.0
3-9
3.9
12.0
11.0
8.0
5.0
-------
Table 6 (continued). THERMAL READINGS
Station
Yenne
Point
Woods
Bay
Deep
H.O
2
Yellow
Bay
Depth
(m)
15
20
25
30
35
Air
§a
3
10
15
20
25
30
35
Air
Sa
3
10
15
20
25
30
35
Air
Sa
3
10
15
20
25
30
35
12345678910 11
10.0 7.8 11.0 9-4 10.6 10.8 11.0 12.5 12.7 12.5 12.5
8.3 7-2 8.0 7-8 7-8 9-4 10.0 11.0 11.2 8.5 9-0
7.2 6.7 7.4 6.7 7.4 9.0 9.0 9.2 8.5 8.5 8.5
5.0 6.1 6.0 6.1 6.7 7-2 8.2 8.5 8.3 8.4 8.3
5.0 6.1 6.0 5.5 5.6 6.0 7-0 7.2 7-6 7-6 7-3
19.0 16.5 23.3 17.2 21.7 17-0 20.0 22.0 19-0 9-5 13-0
15.0 17.0 18.3 17-2 16.7 21.0 20.0 20.0 19.0 13.0 12.5
13.8 16.1 16.1 16.8 16.1 20.0 19.0 19.0 19-0 13-5 12.5
7.8 10.6 12.2 12.2 13.0 15.0 18.0 18.5 19.0 13-5 12.5
7.2 7.2 10.0 10.5 10.0 10.0 13-0 13.0 18.5 13-5 12.5
6.7 6.7 8.9 8.3 9-4 9.4 11.0 11.0 17.2 13-5 12.0
5.7 6.1 8.3 8.3 7.8 9.0 10.0 10.6 15.0 13.5 12.0
5.2 5.2 7.2 7.2 6.8 7.2 9-0 9.0 10.0 12.0 12.0
5.0 5.2 6.7 6.7 5.6 6.1 7-0 7-2 9.0 9.0 9-0
18.3 27.8 17.8 26.1 20.0 24.0 20.0 20.6 16.0 6.0 12.5
15.6 18.9 16.7 19.4 20.0 20.0 20.0 19.0 17.0 12.0 12,0
14.4 16.1 15.6 18.3 19.0 20.0 20.0 19-0 17.0 12.0 12.0
10.6 11.1 11.7 15.6 18.0 19.0 19-0 19-0 17-0 13-0 12.0
7.8 11.1 9.4 10.6 13.0 15.0 15-6 16.1 15-5 13.0 12.0
7.2 7.2 6.7 7.2 12.0 14.0 14.0 14.4 14.0 13-0 12.0
6.7 7.2 6.1 6.7 7.2 9.4 9.0 9-4 9-4 9.0 9.0
5.7 6.1 5.7 5.6 6.7 8.0 8.2 8.2 8.2 8.0 9.0
5.0 5.0 5.0 5.0 5.5 6.1 7-0 7-0 7-0 7-0 7.0
18.3 16.8 20.0 23.9 18.3 20.5 11.0 20.0 21.0 9-5 13-0
15.0 16.7 20.0 18.3 17.8 20.0 18.0 19.0 19.0 12.5 12.5
11.1 15.6 19-8 18.3 17-2 16.0 18.0 19.0 18.0 13.0 12.2
8.3 10.0 18.0 16.7 16.1 11.1 11.7 13.0 18.0 13-0 12.2
6.7 8.9 12.0 12.2 13.9 10.0 10.0 11:7 17.0 13-0 13-0
6.1 7-8 9.0 9.8 9.4 9.4 9.0 10.0 12.2 13.0 13.0
5.2 6.7 6.7 6.7 8.9 8.9 8.9 9.0 10.0 12.0 9.0
5.2 6.1 6.7 6.7 8.3 8.3 8.0 9.0 9.0 9.0 9-0
5.2 5-2 6.5 6.5 6.7 7-2 8.0 8.7 8.7 8.7 8.7
12
8.5
8.5
8.5
8.3
7.3
7.0
8.0
8.0
8.5
8.5
8.5
8.5
8.3
8.0
7.0
8.0
8.0
8.5
8.5
8.5
8.3
8.3
7.0
7.0
8.0
8.5
8.5
8.5
8.5
8.7
8.7
8.7
13
7.0
7.0
7.5
7.5
7.0
2.0
6.5
6.5
7.0
7.0
7.0
7.0
7-0
7-0
2.0
6.0
6.0
6.5
7.0
7-0
7.0
7.0
7.0
1.0
6.5
6.5
7.0
7.0
7-5
7.3
7.3
7.0
14
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
15
5.5
5.5
5.5
5.6
5.8
-10.0
5-5
5.5
5.8
5.8
5.9
6.0
6.0
6.0
5.0
5.0
6.0
6.0
6.0
6.0
6.0
6.0
6.0
2,0
6.0
6.0
6.0
6.0
6.0
6.0
6.0
6.0
16
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
17
3-0
3.5
3-5
4.0
4.0
-12.0
0.0
1.1
1.5
2.8
3.8
3.8
4.0
4.0
c
c
c
c
c
c
c
c
c
-10,0
0.0
1.7
2.8
3.3
3.3
3,9
4.0
4.0
18 19
2.8 3-1
3.1 3-7
3.1 4.0
4.0 4.0
4.0 4.0
-7.0 19.0
0.0 2.9
1.2 3-1
1.7 3.1
3.0 3.1
3.5 3.1
3-8 3-7
4.0 4.0
4.0 4.0
c 14.0
c 3-9
c 3-0
c 3.1
c 3.1
c 3-7
c 4.0
c 4.0
c 4.0
-7,8 14,0
0.0 2.9
1.7 2.9
2.8 3.0
3-3 3.0
3.3 3.8
3.9 4.0
4,0 4.0
4.0 4.0
20
5.7
5.5
5.2
5-0
4.0
23.0
19.0
10.0
5.9
5.7
5.5
5-2
5.0
4.0
20.0
13-9
11.1
8.9
7.1
6.0
5.2
4.0
4.0
14.0
6.0
5-3
5.0
5.0
5.0
5.0
4.0
4.0
21
4.5
4.5
4.5
4.5
4.5
12.5
10.0
9.0
9.0
7.0
5.5
5.5
5.5
4.0
13-5
12.8
12.2
10.0
9-0
7-8
6.0
5.0
4.4
17.0
13.3
13-1
9.5
6.8
5.3
5.2
5.2
4.0
Surface
b . .
t_
Beginning of continued ice cover
Too shallow
-------
unknown but pronounced influence on concentration of solutes and
development of algal populations.
The hydrography of the lake includes a highly irregular shore line with
many inlets, islands and bays. The margins of several bays is shallow
and marshy, hence the water is warmer and solutes are more highly concen-
trated. Thus some eutrophic features probably explain, at least in part,
the development and/or occurrence of certain eutrophic floral elements in
this semi-oligotrophic lake.
Still another important condition is that of pollution. In a relatively
short inlet flowage an unusual amount of pollution occurs from several
sewage treatment plants discharging into the Flathead River. In addition,
communities, resort areas and private homes around the lake contribute
pollution from septic tank drainage. There is a moderate amount of drain-
age from agricultural and cultivated lands. In all, concentrations of
nutrients (nitrates, phosphates, chlorides, sulphates) are maintained at
relatively high levels for a semi-oligotrophic lake (Tables 7, 8, 9).
Related to the above mentioned conditions is an algal flora which well
might be classified as a Diatom-Cyanophyte, moderately hardwater type.
But the cyanophyte element is not only lower in number of taxa but also
more weakly developed than in lakes which fall within such a classifica-
tion. The Bacillariophyceae, in contrast comprises the dominant flora at
all times of the year, becoming especially abundant in numbers of indi-
viduals during the fall and winter phytoplankton peaks. There are 399
species and varieties of diatoms in 42 genera as compared with 40 species
of blue-green algae in 26 genera. In contrast the Chlorophyta are much
fewer in number of individuals, but show the largest number of genera
(70) of any of the phyla in Flathead Lake plankton. In surface collec-
tions at the confluence of the Flathead River, for example, diatom counts
(early June) showed 43,632 organisms per L. as compared with zero blue-
green and zero green algae. A late September collection showed 8,228
diatoms per L. at the same station in contrast to a zero count for
Cyanophyta and Chlorophyta. It may be significant, however, that at this
station in September the green algae showed a count of 3,276 organisms
per L. at 30 M (Tables 11, 12, 13).
The composition of the algal flora of Flathead Lake in number of species
so far reported is Chlorophyta 102 species (17.5$); Cyanophyta 40 spe-
cies (7%); Chrysophyceae 12 species (2.1%); Bacillariophyceae 399 species
and varieties (69.8%); Pyrrhophyta 13 species (2.0%); Xanthophyceae 4
species and Euglenophyta 1 species; Cryptophyta 2 species. When the
Nygaard ratio is applied to the percentages of species composition in
Flathead Lake, the quotient index is well above 1.0, thus indicating a
eutrophic character.
As mentioned previously, the Chrysophyta as a phylum (Diatoms and
Chrysophyceae) constitute by far the dominant flora group (Table 11).
In this respect the lake shows an oligotrophic character remindful of
oligotrophic floras in Arctic lakes. Nine genera of diatoms comprise
34
-------
Table 7. NITRATE NITROGEN IN THE PHOTOSYNTHET1C ZONE OF
SELECTED STATIONS IN FLATHEAD LAKE
Monthly Averages
(mg/1)
Month
JUNE
JULY
AUG.
SEPT.
OCT.
NOV.
DEC.
JAN.
FEB.
MAR.
APR.
MAY
Flathead R.
Confluence
0.165
0.09
0.15
0.17
0.12
0.16
0.16
—
—
—
0.23
0.1**
Swan R.
Confluence
0.155
0.12
0.17
0.24
0.25
0.11
0.10
—
—
—
0.3
0.17
Mid Lake
0.10
0.185
0.11
0.09
0.13
0.18
0.13
--
—
—
0.24
0.10
Yenne
Point
0.145
0.10
0.10
0.13
0.15
0.145
0.15
—
—
0.20
0.18
0.12
Yellow
Bay
0.10
0.90
0.08
0.095
0.13
0.135
0.2
—
0.17
0.28
0.18
Woods
Bay
0.10
O.T06
0.063
0.115
0.09
0.115
0.13
—
—
0.18
0.07
0.09
Deep
Hole
0.065
0.016
0.116
0.125
0.14
0.12
0.03
—
—
—
0.26
0.10
-------
Table 8. ORTHO-PHOSPHATE AT SELECTED STATIONS IN FLATHEAD LAKE
(mg/1)
Month
JUNE
JULY
AUG.
SEPT.
OCT.
NOV.
DEC.
JAN.
FEB.
MAR.
APR.
MAY
Flat head R.
Confluence
0.1A
0.125
0.14
0.10
0.15
0.06
0.11
—
—
—
0.17
0.2
Swan R.
Confluence
0.08
0.15
0.153
0.065
0.17
0.04
0.14
—
—
—
0.21
0.12
M!d Lake
0.10
0.156
0.05
0.08
0.06
0.08
0.04
—
—
—
0.14
0.11
Yenne
Pofnt
0.085
0.116
0.05
0.05
0.05
0.07
0.04
—
0.08
0.15
0.16
0.09
Yellow
Bay
0.165
0.133
0.106
0.086
0.08
0.155
0.10
—
0.12
0.27
0.26
0.20
Woods
Bay
0.07
0.17
0.83
0.07
0.08
0.12
0.11
--
0.13
0.21
0.16
0.14
Deep
Hole
0.09
0.163
0.03
0.085
0.16
0.075
0.10
--
—
—
0.16
0.21
-------
Table 9. TOTAL HARDNESS IN THE PHOTOSYNTHETIC ZONE AT
SELECTED STATIONS IN FLATHEAD LAKE
Monthly Averages
(mg/1)
Month
JUNE
JULY
AUG.
SEPT.
OCT.
NOV.
DEC.
JAN.
FEB.
MAR.
APR.
MAY
Flathead R.
Confluence
81.0
76.0
76.0
77.0
80.0
91.0
78.0
—
—
—
78.0
90.0
Swan R.
Confluence
73-0
66.33
74.0
78.0
96.0
87.0
80.0
—
—
—
90.0
88.0
Mid Lake
78.0
78.6
78.0
88.0
88.0
94.0
90.0
—
—
—
76.0
90.0
Yenne
Point
73.5
74.6
79.3
81.0
82.0
92.0
88.0
—
82.0
78.0
84.0
84.0
Yel low
Bay
74.0
72.6
75-3
84.0
82.0
91.0
89-0
—
88.0
78.0
80.0
82.0
Woods
Bay^
77.0
75.3
77.3
85.0
80.0
92.0
86.0
—
90.0
92.0
88.0
88.0
Deep
Hole
80.0
76.6
74.6
79-0
84.0
93.0
88.0
—
—
—
82.0
80.0
-------
the majority of the group and these are found in large numbers in mid-
winter appearing more abundantly at 20 or 30 M than in the photosynthetic
zone. Repeated sampling shows populations of all algal groups is gener-
ally greater in late summer and earty fall (September readings, Table 12).
The unusual large numbers of individuals at 20 or 30 M as compared with
the surface and photosynthetic zone are considered to be related to the
peculiar currents through Flathead Lake.
It is needed to be learned how much and how many of the algal components
are developed within the lake, and how much of the flora represents
transients contributed by inlet streams. When numbers of species carried
into the lake by the Swan River are compared with numbers at Mid-Lake (for
example) it is seen that the river count is significant (Table 11). It
is suggested that many elements of the Chlorophyta, especially desmids,
are 1) transients, or 2) drifters from back waters and shallow, marshy
areas which are conducive to the multiplication of soft-water or acid-
loving species. It is noteworthy that there is such a nearly uniform
horizontal distribution of phytoplankton, quantitatively and qualitative-
ly. The charts show these numbers in selected stations at three times of
the year (June, September, December).
Nitrates and ortho-phosphates (Tables 7» 8) are relatively low as would
be expected. But it is significant that these critical nutrient sub-
stances are high enough to support a much richer algal flora, and even
algal blooms. That blooms do not occur is explained by the oligotrophic
features such as 1) low temperatures, 2) low concentrations of organic
acids and vitamins. That the lake is gradually (perhaps too rapidly)
undergoing eutrophication is indicated by the development of slight blue-
green algal blooms during the past 20 years of observation. In August
there appears a profuse growth of Anabaena flos-aquae, a reliable indi-
cator of eutrophication (and/or pollution), at least when this species
appears in combination with certain other cyanophytes such as Aphanizo~
menon flos-aquae. This suggests that in Yellow Bay, HeII-Roaring Bay,
and others the higher temperatures of shallow water combined with a
higher concentration of nutrients (possibly from pollution) are suffic-
iently greater than in the years previous to 1950 to permit cyanophyte
blooms to develop. These blooms are accompanied by peak numbers of
Ceratium hirundlnella and Dinobryon spp. It is significant that there
are records of other cyanophyte species which are notable indices of
eutrophy but their numbers are scant and there has been no tendency to
form objectionable blooms. The evidences of eutrophy are clear enough
that 1) monitoring of the algal flora is warranted, and 2) studies re-
lating to pollution sources are needed for remedial practices.
38
-------
CO
Table 10. pH IN THE PHOTOSYNTHETIC ZONE OF SELECTED STATIONS
FLATHEAD LAKE
Monthly Averages
Month
JUNE
JULY
AUG.
SEPT.
OCT.
NOV.
DEC.
JAN.
FEB.
MAR.
APR.
MAY
Flathead R.
Confluence
8.35
8.5
8.5
8.6
8.4
7.45
8.3
—
—
—
8.3
8.3
Swan R.
Confluence
8.65
8.0
8.5
8.45
8.5
8.35
8.3
—
—
—
8.4
8.5
Mid Lake
8.55
8.4
8.5
8.55
8.4
8.25
8.3
—
--
--
8.5
8.6
Yenne
Point
8.45
8.46
8.55
8.55
8.5
8.4
8.3
8.3
8.4
8.6
8.4
—
Yellow
Bay
8.45
8.54
8.5
8.55
8.5
8.35
8.4
8.3
8.3
8.4
8.4
--
Woods
Bay
8,55
8.55
8.54
8.6
8.5
8.45
8.3
—
8.3
8.4
8.4
8.5
Deep
Hole
8.65
8.65
8.53
8.55
8.5
8.4
8.3
—
—
—
8.4
8.3
-------
Table 11. PLANKTON COUNTS AT SELECTED STATIONS IN FLATHEAD LAKE
EARLY JUNE
(no/1)
DIATOMS
CHRYSOPHYCEAE
PYRRHOPHYTA
CHLOROPHYTA
CYANOPHYTA
S
30M
S
30M
S
30M
S
30M
S
30M
Flathead R.
Confluence
43,632
92,920
5,220
15,324
—
—
—
Swan R.
Confluence
97,440
99,544
56,616
39,820
468
468
—
Mid Lake
30,548
87,000
26,100
12,180
6,960
—
Yenne
Point
101,548
66,120
8,700
5,220
—
—
—
Yellow
Bay
71,808
111,360
5,220
10,440
468
1,740
—
Woods
Bay
125,280
205,314
71,340
40,026
—
3,480
—
Deep
Hole
69,364
133,446
14,856
22,620
—
936
--
Swan
River
41,994
44,436-3M
468
I, 740- 3m
936
468-3M
—
-------
Table 12. PLANKTON COUNTS AT SELECTED STATIONS IN FLATHEAD LAKE
SEPTEMBER 21
(no/1)
DIATOMS _0jj
CHRYSOPHYCEAE *
PYRRHOPHYTA *
CHLOROPHYTA *
CYANOPHYTA *
Flat he ad R.
Confluence
8,228
50,602
4,316
468
936
3,276
—
Swan R.
Confluence
51,028
49,188
4 M
14,288
5,220
1,740
1,740
6,960
936
1,740
3,480
Mid Lake
21,924
88,440
5,220
10,440
6,960
3,168
5,520
3,948
Yenne
Point
42,272
52,200
12,180
5,220
1,740
2,208
1,740
—
Yellow
Bay
21,916
33,996
13,920
468
6,960
3,480
2,076
2,208
3,480
2,808
Woods
Bay
35,064
60,588
10,440
5,220
468
10,440
2,208
1,740
936
6,960
Deep
Hole
18,680
22,854
3,948
8,700
10,908
1,740
468
5,140
936
Swan
River
60,664
50.392-3M
5,220
468
5,220
3,612
—
-------
Table 13- PLANKTON COUNTS AT SELECTED STATIONS IN FLATHEAD LAKE
DECEMBER
(no/1)
ro
DIATOMS
CHRYSOPHYCEAE
PYRRHOPHYTA
CHLOROPHYTA
CYANOPHYTA
S
30M
S
30M
S
30M
S
30M
S
30M
Flathead R.
Confluence
47,112
30,180
6,960
5,220
1,740
3,480
3,480
468
Swan R.
Confluence
909,620
78,900
1,740
2,208
4 M
468
1,740
—
Mid Lake
36,204
54,244
1,740
2,406
~
1,740
468
Yenne
Point
29,580
28,776
8,700
~
5,220
--
Yellow
Bay
39,684
6,204
3,948
2,208
—
1 ,740
—
Woods
Bay
57,552
27,082
3,480
2,208
468
1,740
1,740
--
Deep
Hole
19,272
46,980
936
1,740
--
--
2,208
Swan
River
117,048
155.576-3M
3,480
1.740-3M
1.740-3M
3,948
--
-------
SECTION XI
HIGHER AQUATIC PLANTS IN FLATHEAD LAKE
Higher plants (water weeds) play an important role in aquatic environ-
ments inasmuch as they: 1) are involved in fish biology (food and
shelter), as well as for other animals (birds and mammals); 2) provide a
habitat and support many kinds of fish-food organisms; 3) influence water
chemistry and the composition of solutes; k) are factors in aging of
lakes, leading to eutrophlcation; 5) often interfere with recreation
uses and 6) spoil domestic water supplies.
Because of its hydrography and morphometry (mostly oligotrophic) Flathead
Lake does not provide suitable substrates for a conspicuous flora at
this time. But there are a few sectors where aquatic plants show an
increasing amount of limnological concern. It is planned that a complete
inventory of aquatic plants in Flathead Lake will be taken, with quali-
tative and quantitative mapping of certain sectors. It is appropriate
to monitor the development of weed beds because of the several relation-
ships mentioned above. Whereas no complete survey of the lake has been
undertaken to date, exploratory samplings permit a tentative listing and
an appreciation of what the vegetation is doing for and to the lake.
This is particularly true for some bays and shallows where nutrient-
bearing sediments provide a suitable substrate.
In the zones lateral to the delta area where the Flathead River enters
the lake, there is a normal build-up of sedimentary reefs quite unlike
the rocky shores which characterize most of the lake. Accordingly, the
flat margins and the shallow water in the north part of the lake permit
the development of an aquatic flora. It can be predicted that the in-
definite lake margin on the north shore will be extended and built up
by encroaching semi-aquatic plants, expanding the marsh lands lakeward.
In Hell Roaring Bay (a lobe of the Poison Bay sector in the south sector
of the lake) occurs an example of the ability of aquatic plants to
contribute to the aging of a lake. The lake in the southern part is
relatively very shallow in any event; the margins are low and marshy,
being formed by debris and outwash from the lateral and terminal morains
which bound the lake on the south. Lake currents, wind action, and the
configuration of the shore line combine to produce deep sediments and
flat beaches. During the past 25 years the lakeward extension of the
marshes by aquatic and marginal plants has been observable along the
north and south shores of Hell Roaring Bay. Also as a result of wind
and wave action and peculiar currents, a reef has been formed on the
north side of the bay which has resulted in a large lagoon. Here aquat-
ic plants have a suitable basin for profuse growth and their 'fill-in1
activity is very obvious. It is a truism that the aging of a lake pro-
ceeds logarithmically under the influence of aquatic plants. For as
sediments accumulate, more and more favorable substrates are formed for
43
-------
aquatics; the more profuse the aquatic plants, the greater and the more
rapid the accumulation of organic, fertilizing debris that supports
greater plant productivity.
The reef that has produced the lagoon is populated with several species
of Salix that have recently migrated there, also Cornus stolon ifera, and
other shrubs. The soil is under bind with Equisetum spp. and a variety of
terrestrial and semi-aquatic phanerogams.
On the north shore of Hell Roaring Bay is a migrating marsh composed of
Typha latifolia, Scirpus validus and several species of Carex. The lake
margin and the lagoon have become gardens of Polygonurn natans, P_.
coccineum, Elodea occidental is, Potamogeton pusi11 us, Potamogeton natans,
Hype ri cum sp., Ceratophyl lum denier sum and Myriophyl lum exalfaescens.
The south shore is invaded by a dense stand of Typha and Scirpus, inter-
mingled with Acorus calamus and semi-aquatic species of Carex, Eleocharis
and Juncus. Very sparse and rarely found are plants of Indian Rice,
Zizania aquatica, apparently the remains of plantings attempted by sports-
men to introduce duck-food plants. Butomus umbellatus along the north
shore of the lake in the delta region is another such introduced plant.
The fluctuating level of the water in Flathead Lake (because of impound-
ment operations) is a decided determiner of the kind, amount and
1imnological aspects of aquatic vegetation. The rather unique situation
presents some biological problems which invite surveys and monitoring.
44
-------
Table 14. TENTATIVE CHECK LIST OF AQUATIC AND MARGINAL
PLANTS IN FLATHEAD LAKE
Typhaceae
Typha latifolia (L.)
Sparganiaceae
Sparganium chlorocarpum Rydb.
Najadaceae
Najas flexilis (Willd.)
Potamogeton gramineus (L.)
Potamogeton natans (L.)
Potamogeton pectinatus (L.)
Potamogeton pusillus (L.).
Alismaceae
Alisma plantago-aquatica (L.)
Sagittaria latifolia (wTlld.)
Hydrocharitaceae
Anacharis occidental is (Pursh.) Victoria
Butomaceae
Butomus umbellatus (L.)-
Gramineae
Beckmania syzigachis (Steud.) Fernald
Glyceria fluitans (L.) R. Br.
Glyceria grand is Wats.
Zizania aquatica (L.)
Cyperaceae
Carex lacustris Willd.
Carex rostrata Stokes
Carex stipata Muhl.
Carex vulpinoidea Michx.
Eleocharis tenuis (Willd.) Schultes
Eleocharis parvula (R. £ S.) Link.
Scirpus acutus Muh1.
Scirpus validus (Vahl.)
Araceae
Acorus calamus (L.)
Lemnaceae
Lemna minor (L.)
Lemna tri sulca (L.)
Spirodela polyrhiza (L.) Schleid
45
-------
Table \k (continued). TENTATIVE CHECK LIST OF AQUATIC
AND MARGINAL PLANTS IN FLATHEAD LAKE
Juncaceae
Juncus balticus (WMId.)
Juncus mi 1itar is Bigel.
Iridaceae
Iris pseudacorus L.
Salicaceae
Salix long!folia Muhl.
Salix serissima (Bailey) Fernald
Salix amygdaloides Anders
Betulaceae
Alnus sinuata ?
Polygonaceae
Polygonum coccineum Muhl.
Polygonum hydropiperoides Michx.
Polygonum nat_a_ns_ Eaton
Polygonum persicaria (L.)
Ceratophyllaceae
Ceratophyllum dernersum L.
Ranunculaceae
Ranunculus septentrional is Poir.
Ranuncu1 us t r i chophy11 us Chaix.
Crue!ferae
Rorippa palustris (L.) Bess
Callitrichaceae
Callitriche palustris L.
Hypericaceae
Hypericum elliptlcum f. aquaticum ?. Fassett
Haloragidaceae
Myriophyllum exalbescens Fernald
Umbelliferae
Siurn suave Walt.
Cornaceae
Cornus stolonifera Michx.
Primulaceae
Lysimachia thyrsi flora L.
Labiatae
Scutellaria epilobiifolia Hamilton
Solanaceae
Solanurn dulcamara L.
46
-------
SECTION XII
ROTIFER AND CRUSTACEAN PLANKTON COMMUNITIES OF FLATHEAD LAKE
The zooplankton fauna of Flathead Lake has been surveyed several times
since Forbes made his preliminary investigations in 1891. The reports
of El rod, ^O*^', Young,°, and Bjork,'* demonstrated the dynamic nature of
the Flathead fauna since Forbes1 collection. The Montana Fish and Game
Department has taken a number of surface samples of zooplankton at all
seasons of the year since 1967 in connection with their fisheries investi-
gations. Potter and Tibbs since 1971 have been studying the systematics,
distribution, and ecology of zooplankton in the lake. The objectives of
their study have been to determine the diel and other temporal variations
of density and spatial distribution of zooplankton as influenced by
physical and chemical features of the lake. Their work has been closely
coordinated with that of Hanzel of the Fish and Game Department and with
Ivory in Poison Bay.
METHODS
Zooplankton samples were collected in the field with several types of
sampling gear. A Clarke-Bumpus plankton sampler was used to obtain sev-
eral series of horizontal collections. More numerous collections were
taken with a large, metered net towed near the surface. Such surface
collections were taken at all seasons and dates through the year 19&7~
1972 (Hanzel, Montana Fish and Game Department).
Vertical collections were taken by Potter through five meter intervals
with Wisconsin nets and Wisconsin closing nets. These net hauls were
usually through five meter intervals in the water column. Sample
collections were preserved immediately in the field or returned to the
laboratory for fixation or preliminary observation. Aliquot portions of
each sample were studied under a dissecting scope after specific deter-
minations had been completed at higher magnification.
Quantitative analysis of one milliliter aliquot portions was attempted
only on the Clarke-Bumpus collections and vertical Wisconsin net collec-
tions. Because these samples constituted the minority of material, the
information presented below indicates relative rather than absolute
abundance of any species.
Vertical temperature profiles were taken with a Foxboro portable thermo-
couple and light extinction curves were taken with a Gemware Submarine
Photometer. Several temperature profiles were obtained from the Montana
Fish and Game Department.
Chemical analyses were not conducted regularly because Morgan demon-
strated the relatively stable chemical composition of lake water. The
few tests routinely conducted by the Fish and Game Department indicated
47
-------
Figure 5. Daphnia in lake.
A. Daphnia rosea. mature female, Yellow Bay, 2 February,
197'; B. Daphnia longiremis, mature female, Yellow Bay,
30 January, 1971; C. Daphnia thorata, mature female,
Woods Bay, 21 July, ~
48
-------
the continuing stability of lake water chemistry.
RESULTS
A preliminary list of the Flathead Lake zooplankton appears in Table 15-
The table also presents the depth distribution of each species and
temporal occurrence. Abundance is relative as compared to other species
with consideration allowed for unusual temporal abundance of the more
common forms.
The more common forms of zooplankton found in Flathead Lake, Daphnia spp.,
Kel1icottia longispina, Keratella cochlearis, Cyclops bicuspidatus
thomas?, and Diaptomus ashlandi, compose a community similar to that
described by Scheffer and Robinson,^2 for Lake Washington. These forms
occur commonly across the lake; the less common forms display more speci-
fic preference for depth, temperature, and other factors associated with
open lake or bay environments.
The three species of Daphnia — JK thorata, 0. longiremis, and D_. rosea —
are of particular interest because temporal and spatial distribution
seem to be influenced primarily by temperature (Figure 5). Neither
Daphnia longiremis nor Daphnia rosea have been reported from the lake
though Bjork (1965, personal communication) mistakenly reported JX
longiremis to be JK longispina. We have not yet determined whether these
species have always been present or are recently introduced. Neither
species has been observed in the few recovered samples from collections
by Forbes and El rod.
Daphnia 1ongiremis is noted by Brooks,^3 to be a cold stenotherm. This
species does maintain an association with cold waters of Flathead Lake
and exhibits peak populations during late winter. At that season D_.
longiremis is the most abundant cladoceran in the lake and occurs from
the surface to depths of 50 meters. During summer and fall months when
the lake is stratified with warm surface temperatures D. longiremis
restricts itself to hypolimnetic depths. At that time it is common, but
it is not nearly as abundant as during winter months.
Daphnia rosea is the least abundant of the three species. It occurs at
all depths at all seasons with modest populations developing in spring.
Daphnia rosea has not previously been reported from the lake. It may
have been present earlier though not recognized as distinct from the
other species. It may be a recent introduction from other Flathead
Valley ponds where it is often abundant.
The most interesting temporal sequence is demonstrated by Daphnia
thorata. Early exephippial females appear in the plankton as water
temperatures reach five to seven degrees centigrade during April and
May. These early individuals appear in shallow bays and near shore.
The populations increase gradually through the summer. Daphnia thorata
replaces D. long? remis in surface waters as summer stratification
develops.
49
-------
Table 15. PRELIMINARY SEASONAL AND DEPTH DISTRIBUTIONS FOR ROTIFERA
AND CRUSTACEA IN FLATHEAD LAKE, MONTANA
Organ i sm
ROTIFERA
Asplanchna sp.
Brachionus sp. ?
Chromogaster sp.
Col lotheca sp.
Conochilus unicorn is Rousselet
Dissotrocha sp. ?
Euchlanis sp. ?
Filinia long? set a (Ehrenberg)
Kellicottia longispina (Kellicott)
Keratella cochlearis (Gosse)
Keratella quadrata (Multer)
Ploesma sp.
Polyarthra vulgaris Carl in
Trichotria sp.
Tylotrocha sp. ?
CLADOCERA
Acroperus harpae Ba 5 rd
Bosmina longirostris (O.F.Muller)
Chydorus sphaericus (O.F.Muller)
Daphnia loncjiremis Sars
Daphnia rosea Sars
Daphnia thorata Forbes
Eubosmina sp.
Eurycercus lamellatus (O.F.Muller)
Leptodora kindtii (Focke)
Scapholeberis king! Sars
Sida crystal! ina O.F.Muller
COPEPODA
Cyclops bicuspidatus thomasi
S.A. Forbes
Diaptomus ashlandi Marsh
Diaptomus leptopus S.A.Forbes
Epischura nevadensis Lilljeborg
Eucy clops agi 1 is (Koch)
Ergasiius sp.
Salmincola sp.
Depths
surface
surface
surface
surface
all depths
surface
surface
mid, deep
all depths
all depths
surface
surface
surface
deep
surface
surface
surface
surface
all depths
deep
all depths
surface
surface
surface
deep, surface
at night
surface
mid
all depths
surface, mid
surface
surface, mid
surface
deep
on fishes
1, spring; 2, summer; 3, autumn; 4, winter;
surface - epillmnion mid - metal imnion deep
Seasons
1.2.3M
2
2
2,3
l*.2*.3.«i
2
1
1*,2,3,4*
1*,2*,3M*
1*,2*,3M*
1*,2,3,4
2
1,2
1.*
1
2
K2.3.4
1,2,3,1*
!*,<•
2,3
1,2,3, A
1,2*, 3*. 4
1.2*,3,*
1,2,3,4
2*,3
1,2,3*,<»
2
1*,2*,3*,A*
1*,2*,3M*
2
1,2,3
2
1.*
1, 2, 3,4
*, abundant
- hypol imnion
50
-------
Highest densities occur in October and November when males appear in the
population. Sexual reproduction with the formation of ephippia persists
through early February, but populations begin to decline with cooling
water temperatures of mid-November. Between late February and April £.
thorata is absent from the Flathead Lake plankton community. ~"
These three species are much used as food by pygmy whitefish (Prosopium
coulter?, Eigenmann,^°) and landlocked silver salmon or kokanee
(Oncorhynchus nerka Waldbaum) (Hanzel,2^). Possibly predation is an
important influence on population size and particularly when females carry
ephippia and are most visible.
Other species important in fish diets are Leptodora kindtii and Epischura
nevadensis. Both are summer forms that display temporal periodicity
similar to Daphnia thorata. The seasonal occurrence of _L_. kindt? i in
Flathead is supported by observations of Chambers, Burbidge, and Van
Engel," who noted the species to be present only at temperatures near and
above ten degrees centigrade.
Leptodora displays distinct diel migrations. Individuals disperse between
five and thirty meters depth during the day and congregate in the top ten
meters of water during the night hours. Day distribution seems to be at
depth with light below twenty foot candles, yet the few individuals that
occur near the surface indicate that light may be only one influential
factor.
Epischura is a form commonly eaten by planktivore fishes, yet it is much
less common in the plankton than the cladocerans mentioned above. Impor-
tance as a food organism as compared to uncommon occurrence in the plank-
ton probably reflects selectivity of fish predators (Brooks,^3).
DISCUSSION
These few species displayed distinct periodicities in their occurrence
and seemed to be controlled by environmental factors. The perennial spe-
cies may be more tolerant of seasonal fluctuations or may display similar
population variations that will become evident when quantitative analyses
are completed.
Description of the modern plankton community and its comparison to earlier
investigations has indicated a few changes of community structure that
may have been influenced by accelerated eutrophication, fish introduction,
and other factors. We conclude that our efforts can profitably continue
with a comparison between present conditions and previous collections and
accounts. Analysis of sediment cores for plankton microfossils
(Deevey,^°) will be completed as another comparator.
51
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SECTION XIII
FISH POPULATION OF FLATHEAD LAKE
Flathead Lake is the state's largest and one of its most important sport
fishing lakes. The lake historically has been an important physical
feature of the area but very little information was written about the
fisheries of the lake prior to 1900. The available data are general notes
on specific fish as they were recorded by early investigators as
Evermann,^7; Eigenmann,^; Gilbert and Evermann,^9, and Evermann and
Smith,50. |n 1906, Henshall published a list of the fishes of the state
but his list was incomplete due to limited records in the western areas.
The first real fishery studies were initiated in 1916 by Elrod, et al.51
Their investigation provided the basis for describing the fish present,
their relative abundance and some historical notes on the introduction of
exotic fish. Elrod described nine of the ten native fish species, only
missing the small inconspicuous pygmy whitefish (Table 16).
First fish management efforts on the lake, other than the harvesting of
fish by fishermen, occurred before the turn of the century with the
introduction of largemouth bass in 1898. Early concern to replenish the
stocks of fish in the lake by the local citizens was exhibited in their
action when they petitioned the State Government to build a fish hatchery
at Somers. Fish plants and other information prior to the completion of
the Somers Hatchery were often incomplete or lacking in lieu of records
kept by the individual sportsman. Between 1905 and 1916, most of the
fish introductions made into this lake occurred; during this interval
thirteen exotic fish species were planted (Table 16). Since that time,
only two species of Pacific salmon have been added; the kokanee and coho
salmon. Five of these exotic species did not survive in the lake; they
were the small-mouth bass, white crappie, grayling, chinook and coho
salmon. The other species continue to live and reproduce their kinds
with varying degrees of success in this lake system.
Elrod, et al.5' described the blue-gill, a member of the sunfish family,
as being introduced into the lake in 1910 but it is believed that the
fish introduced was the pumpkinseed. No positive records of blue-gill
have since been found in the valley. All areas described for this fish
species are and have been occupied by the pumpkinseed. The only other
questionable species introduced in the lake was noted in the salmon plant
of 1916. To date, it is not known what species of salmon was planted.
Weisel,52 in his "Fish Guide for Intermountain Montana" and more recent
Brown,53 with his "Fishes of Montana" described in detail the species of
fish present in this lake and drainage area.
Early investigators found fish life in Flathead Lake to be quite scant
so their efforts were directed toward the establishment of other fish
species that might provide a commercial fishery. The maximum effort was
52
-------
Table 16. NATIVE AND EXOTIC FISH SPECIES IN FLATHEAD LAKE
Species
Native or
year of
introduction
Game - Nongame
Classification
Reference source
Cutthroat
Mountain whitefish
Pygmy whitefish
Dolly Varden
Northern squawfish
Peamouth
Longnose sucker
Largescale sucker
Red side shiner
SI imy sculpin
Largemouth bass
Lake trout
Lake whitefish
Pumpkinseed
White crappie
Small mouth bass
Black bul Ihead
Yellow perch
Brook trout
Cutthroat trout
Grayl ing
Rainbow trout
Salmond
Kokanee
Silver (Coho)
Native
Native
Native
Native
Native
Native
Native
Native
Native
Native
1898
1905
1909
1910
1910
1910
1910
1910b
1912
1913
1913
1914C
1916
1935
1969
Game
Game
Game
Game
Nongame
Nongame
Nongame
Nongame
Nongame
Nongame
Game
Game
Game
Nongame
Nongame
Game
Nongame
Nongame
Game
Game
Game
Game
Game
Game
Game
El rod, 1929
El rod, 1929
Hanzel, 1969
El rod, 1929
El rod, 1929
El rod, 1929
El rod, 1929
El rod, 1929
El rod, 1929
El rod, 1929
Biennial Report, 191 3-1 k
Biennial Report ,1905-06
Biennial Report, 1909- 10
El rod, 1929
El rod, 1929
El rod, 1929
El rod, 1929
Fish & Game Records
Biennial Report, 1911-12
Biennial Report, 191 3-1^
Biennial Report, 191 3-1 A
El rod, 1929
Biennial Report, 1917-18
Fish & Game Hatchery
Records (Poison)
Fish & Game Hatchery
Records (Anaconda)
Common names of fishes in this report are those given in American Fisher-
ies Society, 1970. A list of common and scientific names of fishes from
the United States and Canada. Spec. Pub. No. 6, Third Edition, 150 pp.
""introduction of this species not recorded but it was apparently included
in the mass introduction of warm-water fish during 1910.
"Year of first recorded plant; possible introduction as early as 1900.
This species purchased as Chinook or Quannat salmon from Oregon; surviv-
al reports from this plant indicate it included the Chinook salmon,
silver and kokanee. Apparently there was a mixture of eggs or question-
able identification.
53
-------
spent over a six-year period when 3 million lake whitefish fry were
introduced. The lake trout were introduced during the same period but
were considered a companion species that might provide a large sports food
fish. The first commercial netting program was attempted during the fall
of 1913 but yielded only Dolly Varden. The 1913-1914 "Montana Biennial
Report" describes the sale of thousands of pounds of Dolly Varden on the
Kali spell market for $.20 to $.25 per pound. Another attempt at fishing
commercially was tried in the fall of 1925, but was utter failure.
In 1907, a water development project was completed that undoubtedly had a
detrimental effect on the lake fishery. This power diversion dam on the
Swan River blocked spawning runs from one of the two major inlet streams
of Flathead Lake. These two streams provided the only spawning areas for
the Dolly Varden and cutthroat trout.
Another hatchery was built on the east shore of the lake in 1928 at
Station Creek, but was closed in 1959- Station Creek waters were too cool
to hatch and rear fish economically.
The first sport fishery for kokanee in the lake was noted in 1933 when
numerous salmon were creeled during the summer fishery. That fall large
numbers of salmon were found congregating along the shoreline. These
spawning populations were collected and canned in Poison with over 21,000
cans being distributed throughout Montana by the Relief Commission.
The second major water development project that directly affected the
fishes of the lake was the completion of Kerr Dam in 1938 at the outlet
of the lake. Although this structure did not block any fish migrations,
it did have an effect on the fish populations by the artificial manipula-
tion of the lake level. In an agreement between the federal, state, and
private principals, the lake levels are regulated to follow an annual
draw-down of ten feet. The maximum draw-down of the lake that is allow-
able by the present physical features of the outlet would be an addition-
al six feet. Structures of this type that impound water on existing deep
water lakes have seldom had any beneficial effect on the fish species or
the lake habitat.
Events relating to the fisheries of the lake during the war years of the
Forties were limited to the annual planting of salmon and trout and a
controversy over a water development proposal by the Corps of Engineers.
Bitter debate arose over the plan to raise the level of Flathead Lake
some 37 feet over the existing full pool level. This rise in water would
have placed the lakeshore at Kali spell and flooded most of the productive
land of the valley floor. This grandiose plan was shelved and replaced
by an alternate proposal for a multi-purpose flood and power dam on one
of the three major tributaries of the Flathead River. Hungry Horse Dam
was located on the South Fork of the Flathead River and completed in
1953- The 564-foot high dam blocked fish movements from Flathead Lake
and lost over 60 percent of the spawning areas that provide the annual
recruitment of trout to the lake. Water discharges from the dam have
also altered the aquatic habitat in the lower 50 miles of the Flathead
54
-------
River.
The first fisheries biologist for the Montana Fish and Game Department was
assigned to the area In 19*»9. His initial duties were to assess and
inventory existing fisheries resources, of which Flathead Lake is an impor-
tant part (Stefanich,5^-58). Assisting in this monumental job was the
fisheries work directed through the University of Montana and its
Biological Station located at Yellow Bay. Work on the lake included the
reports on growth of the kokanee by Brunson, Castle and Pirtle,59 fall
sampling of cutthroat trout by Brunson, Pennington and Biorklund,"^, and
life history aspects of the lake whitefish by Bjorklund,"', and Brunson
and Newman,"2.
In 1955f a large white sturgeon was reported to have been caught in Flat-
head Lake (Brunson and Block, 63). The catch climaxed the mystery sur-
rounding various reports of "monsters" being seen in the lake. There is
considerable question as to the origin of this fish which was reportedly
caught on May 28, 1955- This sturgeon measured 32 inches long and weighed
181 pounds and 1 ounce. Accounts of such sighting of large objects has
decreased but still are being reported.
The initial work during the 1950's established the need for further
detailed work in defining the role and importance of the tributaries
above Flathead Lake. The detailed work began in 1955 on the remaining
180 miles of free-flowing river system above the lake. The principal
investigators were Stefanich and Block.56- Block,6\ Stefanich,65-68.
Johnson,69,70; Rahrer,7l, and Hanzel,15-18. Tneir work defined the
spawning movements of the Dolly Varden and cutthroat trout in the Flat-
head River system above the lake.
They established that after hatching, cutthroat trout remain two years in
the lower 50 miles of the North and Middle Forks of the Flathead River.
During their third summer, they make a mass downstream migration. While
on the downstream journey, these fish concentrate in the larger, deep
pool areas of the lower 20 miles of the river above the lake. The time
taken by these fish to descend from these rivers varies from two weeks to
two months. During this period they move 50 to 80 miles. From late fall
through the winter months descending cutthroat reach and enter the lake.
They remain here until they reach maturity which is generally after one
and one-half years in the lake.
The predominance of immature fish in the Forks of the Flathead River is
evidenced by the average sizes of cutthroat trout measured in creel
census records taken on the North Fork. In 1955, Block stated the aver-
age total length was 8.5 inches. Eight and nine years later (1961 and
1962), the sizes were 8.A and 8.5 respectively.
Data from the extreme upper river areas indicate a year-around resident
cutthroat population. These mature cutthroat appear to be the non-
migratory type for fish tagged in the upper reaches have been recaptured
within five miles of the release point during three consecutive years.
55
-------
The recapture data also indicate a portion of the cutthroat trout popula-
tion in the North and Middle Fork Rivers are attracted to many of the
waters draining Glacier National Park. Fish tagged and released in these
rivers have been recovered in Kintla, Bowman, and McDonald Lake. This is
an upstream movement of 10 to 20 miles.
After the migrating type of cutthroat trout enter Flathead Lake, they
disperse along the entire shoreline and occupy an area near the surface.
An apparent winter concentration (November-December) occurs in the lake
near Dayton, Montana (Big Arm Bay-north of WMdhorse Island). With a life
expectancy of six years, cutthroat trout cannot be expected to make more
than two spawning runs into the upper river spawning areas during their
1ifetime.
There is an apparent escapement of cutthroat trout to the lower Flathead
River below Kerr Dam. Fish tagged in Flathead River above Flathead Lake
have descended the river into the lake, passed through the lake and have
been caught below Kerr Dam.
Studies of movements of the Dolly Varden have been considered on mature
fish only. All the data exemplify an inter-dependent relationship be-
tween the lake and river system. Four of the total thirteen recaptures
from the Middle Fork Tagging Site (Bear Creek weir-99 miles above the
lake) were caught in the lake. Fourteen of the total twenty-eight re-
captures from the North Fork Tagging Site (Trail Creek weir-105 miles
above the lake) were caught in the lake. Nine of the total fifty-five
returns from fish released in Flathead Lake were caught upstream on their
spawning run. Two of the lake-tagged fish were recaptured above the weir
sites on the Middle and North Fork Rivers. Movements within the lake
show constant traveling along the entire shoreline except during the
spring, when concentrations occur near the mouths of the Flathead and
Swan Rivers.
The Flathead Lake Fishery is dependent on the natural reproduction in the
lake and recruitment from the tributary system above the lake. The lake
and stream work defined the relationship of the lake as an integral part
of this lake-river system, each part being dependent upon the other to
provide the necessary environment for the production of the dominant game
fish. These species are the cutthroat trout, Dolly Varden, kokanee, lake
trout, mountain whitefish and lake whitefish. Since 1953, fisheries
management efforts and recommendations for Flathead Lake and the river
system above the lake have been directed toward principles that will
maintain and preserve the interdependent relationship of this lake-river
system.
Fishing pressure on Flathead Lake was measured by Robbins,'2 and his
estimates of 129,000 man days per year expresses the use of 1.03 man days
per acre per year. Nonresident fishermen represent nearly 25 percent of
the total fishing pressure. Catch rates varied with species and by
season. Creel composition for the entire year was 75 percent kokanee,
15 percent yellow perch, 3 percent cutthroat trout, 3 percent Dolly
56
-------
Varden and the remaining portion an aggregate of lake trout, largemouth
bass and mountain whitefish.
This lake-river system is located in an area that is rapidly developing
its natural resources; water, timber, and recreation. During the develop-
ment, it is very critical that further assessments be made on the fishery
of this river system as they would be affected by proposed water develop-
ment projects.
The Montana Fish and Game Department in 1966 initiated a special fisheries
study to determine fish population trends, life histories, and seasonal
fish distribution of the Flathead Lake system. Through the use of special-
ized gear, the horizontal and vertical distribution of the major fish spe-
cies in Flathead Lake were established in twelve major fish use areas
(Hanzel ,'9-24). A major portion of all fish were collected during the
summer seasons with the largest catches being taken in areas directly
influenced by currents. Seasonal variation in species composition and
length frequency distribution were determined for the twelve areas. These
areas represent twenty-one sample stations in the lake.
A total of 8,912 fish were collected in 163 net sets during the fish
sampling program on Flathead Lake, November 1967 through December 1970
(Table 17). The major fish species listed in order of relative numbers
were: lake whitefish, peamouth, kokanee, northern squawfish, Dolly
Varden, yellow perch, pygmy whitefish, mountain whitefish, longnose
sucker, large-scale sucker, lake trout, redside shiner, cutthroat trout,
coho salmon and largemouth bass. Species composition of the total net-
ting data represents the best year-around picture of the relative fish
abundance found in Flathead Lake, Figure 6. Significant changes were
found in species composition when comparing the deep (60 to 270 feet
depth) netting series (Nov. 1967 - August 1969) to the shallow (6 to 60
feet depth) water netting series. Shallow water sampling yielded more
than one and one-half times as many fish as the deep water sampling. Non-
game fish made up most of the increase with their numbers gaining four-
fold while the game fish numbers showed a slight drop (Table 17). The
size range and maximum weight of the major fish species taken from the
lake are present in Table 18.
Three main lake zones were used by the fish; near the bottom, near the
surface, and the open pelagic waters. All species collected preferred a
zone within 8 feet of the bottom, except the cutthroat trout and kokanee.
Cutthroat trout showed a distinct preference for the area near the sur-
face while the kokanee selected the open pelagic waters. The depth and
spatial distribution of the kokanee were periodically checked with the
use of a recording sonar. Light penetration, plankton concentration and
water temperature were the three factors affecting the kokanee distribu-
tion. Variations of these factors continually altered the kokanee distri-
bution.
Rough fish, such as northern squawfish, peamouth, longnose suckers and
largescale sucker, preferred the shore areas that ranged in depth from
57
-------
11/6? through 8/69
(deep water)
9/69 through 12/70
(shallow water)
Combined Netting Totals
Figure 6 Species of fish netted in Flathead Lake.
LNSu 1.8
I—C2u 1.1
1.1
0.7
0.5
0.1
0.0+
58
-------
Table 17- FISH SPECIES AND OTHER NETTING DATA FOR FLATHEAD LAKE, WINTER 196? THROUGH FALL 1970
(species as percent of total sample size)
en
10
PERCENT SPECIES COMPOSITION
FIRST PERIOD SECOND PERIOD
November '67 - August '69 September '69 -December '70
Fish Species Winter Spring Fall Summer Fall Winter Summer Fall
1967 1968 1968 1969 1969 1970 1970 1970
Lake whitefish 53-2 48.5
Peamouth 1
Kokanee
Northern squawfish 1
Dolly Varden 1
Yel low perch
Pygmy whitefish
Mountain whitefish
Longnose sucker
Largescale sucker
Lake trout
Redside shiner
Cutthroat trout
Coho salmon
Largemouth bass
Total fish
Stations Sampled
Predominant net length
Fish per net 3
1.0
3.0
1.0
2.0
0.6
3-0
2.0
1.3
1.2
0.1
1.6
702
22
350'
1.9
1.9
6.4
15.1
16.3
0.2
4.2
2.8
2.3
0.1
2.2
575
20
600'
28.8
31.3
6.5
19.4
12.7
14.5
2.2
8.7
0.4
2,2
0,6
1.5
1,088
19
600'
57.3
50.7
1.7
9.9
5.5
16.0
0.3
11.3
1.2
0.8
0.4
0.6
1.5
1,147
24
600'
47.8
7.3
24.0
28.1
15.4
7-7
2.3
0.9
6.2
1.6
1.4
1.6
2.5
0.6
0.3
0.1
2,584
27
350'
95-7
30.0
2.1
2.9
10.0
17.9
0.7
20.7
10.0
1.4
4.3
140
7
250'
20.0
11.2
29.1
0.4
16.4
4.9
31.2
0.9
1.4
2.3
2.0
0.2
1,325
20
125'
66.3
24.6
19-2
16.4
10.4
8.7
1.0
9.3
6.6
1.3
1.0
1.2
0.1
1,351
24
350'
56.3
First
Period
Tota 1 s
44.8
5-0
10.9
10.4
14.8
1.0
7-7
1.4
1.5
0.7
1,0
0.8
3,512
85
41.3
Second
Pe r i od
Totals
13.2
23-5
17-7
14.3
7.5
8.9
3.0
5.5
1.9
1.4
1.2
1.2
0.4
0.2
0.1
5,400
78
69.2
Total
Period
25-7
16.2
15-0
12.7
10.4
5.8
4.8
3.9
1.8
1.1
1.1
0.7
0.5
0.1
0.0+
163
54.7
-------
Table 18. SIZE AND WEIGHT OF FISH SPECIES COLLECTED FROM
FLATHEAD LAKE, OCTOBER 1966 THROUGH DECEMBER 1970
Size Range (T.L.)
Minimum Maximum
in. (mm) in. (mm)
Dolly Varden
Lake whitefish
Pygmy whitefish
Mountain whitefish
Lake trout
Cutthroat trout
Peamouth
Northern squawfish
Longnose sucker
Largescale sucker
Ye 1 low perch
6.6
5.5
3.1
5.3
7-8
8.5
4.7
3.4
4.5
6.4
5-2
(168)
"(140)
( 79)
(135)
(198)
(216)
(119)
( 86)
(114)
(163)
(133)
36.0
23.9
7-2
17.2
42.0
20.2
13-3
22.3
18.2
25.6
15.4
( 914)
( 606)
( 183)
( 437)
(1,067)
( 513)
( 338)
( 567)
( 462)
( 650)
( 390
Weight
Ibs. (g)
18.50
4.92
0.10
1.27
32.00
3-30
0.79
4.50
2.09
3.52
1.01
( 8,391)
( 2,233)
( . 45)
( 576)
(14,515)
( 1,497)
( 357)
( 2,128)
( 948)
( 1,597)
( 496)
Number
of
Fish
985
2,446
551
349
106
70
1,439
1,200
178
104
702
5,130
-------
the surface to 90 feet with the majority occurring in waters less than
60 feet deep.
Survivors of the latest introduction of an exotic fish species was the
coho salmon made in the lake during the spring of 1969. They were ob-
served in the lake for 18 months and then completely disappeared. Returns
of considerably less than one-half percent of the 240,000 smolt-sized
salmon were reported. Early growth rates were excellent but slowed after
eight months and then dropped off rapidly. Total lengths during the first
eight months increased to a maximum of 229 mm (9-0 inches). The largest
and last coho recorded as a "jack" salmon measuring 328 mm (12.9 inches)
and 3*»8 g (0.77 pounds) on November 3, 1970.
The future of the Flathead Lake fishery is dependent on the natural repro-
duction produced in the waters of this complex system. The quality of
the fishery available will be dependent on the quality of the aquatic
habitat. Changes caused by natural variations to this environment, as
well as the result of man's activities in water development projects,
housing projects, or a combination of all factors will be reflected in
the fish populations of this water drainage. The maintenance of a quality
sport fishery will be dependent upon the maintenance and preservation of
a high quality aquatic habitat in the lake-river system.
6.T
-------
SECTION XIV
REFERENCES
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]k. Hutchlnson, G. E. A Treatise on Limnology, Vol. 1. J. Wiley,
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15. Hanzel, Delano A. Survey of Cutthroat and Dolly Varden Trout in
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17- • Evaluation of Kokanee Spawning and Population Density in
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18. . Survey of Cutthroat and Dolly Varden Trout in the Flat-
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Montana Fish and Game Department. F-7-R-13, Job III. 8 pp. Multilith.
(1965)
19- • Survey of Cutthroat Trout and Dolly Varden in the Flat-
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Montana Fish and Game Department. F-7-R-14, Job III. 8 pp. Multilith.
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20. . Flathead Lake Investigations of the Fish Population and
its Chemical and Physical Characteristics. Comp. Report, Montana
Fish and Game Department. F-33-R-1, Job I. 5 pp. Multilith. (1968)
21. . Flathead Lake Investigations of the Fish Population and
its Chemical and Physical Characteristics. Comp. Report, Montana
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22. . Flathead Lake, Investigation of its Fish Population and
its Chemical and Physical Characteristics. Comp. Report, Montana
Fish and Game Department. F-33-R-3, Job I. 48 pp. Multilith. (1970)
23. • The Seasonal and Depth Distribution of the Fish Popula-
tion in Flathead Lake. Comp^ Report, Montana Fish and Game Depart-
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24. . The Seasonal and Depth Distribution of the Fish Popula-
tion in Flathead Lake. Comp. Report, Montana Fish and Game Depart-
ment. F-33-R-5, Job 'la. 14 pp. Multilith. (1972)
25. . Age and Growth Analysis of the Fishes of Flathead Lake -
Pygmy Whitefish. Comp. Report, Montana Fish and Game Department.
F-33-R-5, Job Ib. 10 pp. Multilith. (1972)
63
-------
26. Potter, D. S. The Zooplankton of Flathead Lake: A Historical
Review With Suggestions for Continuing Lake Resource Management.
Ph.D. thesis, Univ. of Montana (in preparation). (197*0
27. Morgan, G. R. Phytoplankton Productivity of the East-shore Area of
Flathead Lake, Montana. Unpublished M.S. thesis, Univ. Utah, Salt
Lake City. 146 pp. (1968)
28. . Phytoplankton Productivity Versus Dissolved Nutrient
Levels of Flathead Lake, Montana. Unpub. Ph.D. thesis, Univ. of
Utah. 211 pp. (1970
29. American Public Health Association. Standard Methods for the Exami-
nation of Water and Waste Water. New York. 641 pp. (1965)
30. Ivory, T. Phytoplankton Production of Poison Bay, Flathead Lake,
Montana. Unpub. Ph.D. thesis, Univ. of Utah. 213 PP- (1974)
31. Hach Chemical Company. Engineers Laboratory. Methods Manual. 6th
Ed. 66 pp. (1968)
32. Strickland, J. D. H. Measuring the Production of Marine Phyto-
plankton. Fish. Res. Bd. Can. Bull. 122. Ottawa. (I960)
33- Vollenweider, R. A. A Manual for Measuring Primary Production in
Aquatic Environments: I.B.P. Handbook No. 12. Blackwel1 Scientific
Publications, Oxford. 213 pp. (1971)
34. Steemann-Nielsen, E. The Use of Radioactive Carbon for Measuring
Organic Production in the Sea. J. Cons. Int. Explor. Mer. 43:117-140.
(1952)
35- . Production of Organic Matter in the Oceans. J. Mar. Res.
14:374-386. (1955)
36. Reid, G. K. Ecology of Inland Waters and Estuaries. Reinhold Pub-
lishing Corporation. 375 pp. (1961)
37- Clapp, C. H., M. J. Elrod, R. T. Young, C. D. Shallenberger, and J.
W. Howard. Flathead Lake - Millions of Dewdrops: The Fishes,
Zoology, Botany, Physics, Chemistry of Flathead Lake. Mimeo. 15 pp.
(1929)
38. Hutchinson, G. E. A Treatise on Limnology, Vol. II. J. Wiley, New
York. 1115 pp. (1967)
39. Pearsall, W. H. Phytoplankton in the English Lakes. J. Ecol.
20:241-262 (1932)
64
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40. El rod, M. J. Limnologlcal Investigations at Flathead Lake, Montana
and Vicinity, July, 1899- Amer. Microscop. Soc., Trans. 22:63-80.
(1901)
41. . A Biological Reconnaissance in the Vicinity of Flathead
Lake. Bulletin of the University of Montana No. 10. Biological
Series No. 3. pp. 91-182. Plates XVIM-XLVI. (1902)
42. Scheffer, V. B. and R. J. Robinson. A Limnological Study of Lake
Washington. Ecol. Monog. 9:95-143. (1939)
43. Brooks, J. L. The Systematics of North American Daphnia. Mem. Conn.
Acad. Arts Sci. 13:1-180. (1957)
44. Chambers, J. R., R. G. Burbidge, and W. A. Van Engel. The Occurrence
of Leptodora kindtii (Focke) (Cladocera) in Virginia Tributaries of
Chesapeake Bay. Chesapeake Science. 11(4):255-258. (1970)
45- Brooks, J. L. and S. I. Dodson. Predation, Body Size, and Composi-
tion of the Plankton. Science. 150:28-35- (1965)
46. Deevey, E. S. Studies on Connecticut Lake Sediments. 3. Amer. J.
Sci. 240:233-264, 313-338. (1942)
47. Evermann, Barton W. A Reconnaissance of the Streams of Western
Montana and Northwestern Wyoming. Bull. U.S. Fish Comm. 11:3~60.
(1893)
48. Eigenmann, Carl H. Leuciscus balteatus (Richardson), A Study in
Variation. Am. Naturalist. 29:10-25. (1895)
49. Gilbert, Charles H. and Barton W. Evermann. A Report Upon Investiga-
tions in the Columbia River Basin with Descriptions of Four New
Species of Fishes. Bull. U.S. Fish Comm. 14:169-208. (1895)
50. Evermann, Barton W. and Hugh M. Smith. The Whitefishes of North
America. Report U.S. Fish Comm. for 1894. 20:283-324. (1896)
51. El rod, M. J. and J. W. Howard, G. D. Shallenberger. Flathead Lake -
Millions of Dewdrops. The Fishes, Chemistry and Physics of Flathead
Lake, Montana. Montana Wildl. 2(1):5-15. (1929)
52. Weisel, George F. Fish Guide for Intermountain Montana. Univ.
Montana Press, Missoula. 88 pp. (1957)
53. Brown, C. J. D. Fishes of Montana. Big Sky Books, Montana State
Univ., Bozeman, Montana. 207 pp. (1971)
54. Stefanich, Frank A. Developing Measures to Determine Kokanee Abun-
dance in Flathead Lake. Comp. Report, Mont. Fish and Game Dept.
F-7-R-1, Job IVb. 2 pp. Multilith. (1952)
65
-------
55. Stefanich, Frank A. Natural Reproduction of Kokanee in Flathead Lake
and Tributaries. Comp. Report, Mont. Fish and Game Dept. F-7-R-2,
Job MIA, 6 pp. Multilith. (1953)
56. _ , and Daniel Block. North Fork of the Flathead River Creel
Census. Comp. Report, Mont. Fish and Game Dept. F-7-R-3, 9 pp. (195*0
57. _ . Natural Reproduction of Kokanee in Flathead Lake and
Tributaries. Comp. Report, Mont. Fish and Game Dept. F-7-R-3, Job
MIA, 10 pp. Multilith. (1954)
58. _ . Developing Measures to Determine Kokanee Abundance in
Flathead Lake. Comp. Report, Mont. Fish and Game Dept. F-7-R-3, Job
IVB. 5 pp. Multilith. (1952)
59. Brunson, Royal B. , Gordon B. Castle, and Ralph Pirtle. Studies of
Sockeye Salmon, Oncorhynchus nerka, from Flathead Lake, Montana.
Proc. Mont. Acad. Sci. 12:35:I1»5T~0952)
60. _ , R. E. Pennington and R. G. Bjorklund. On a Fall Collection
of Native Trout, Salmo clarkii , from Flathead Lake, Montana. Proc.
Mont. Acad. Sci. 12:63-67. (1952)
61. Bjorklund, Richard G. The Lake Whitefish, Coregonus clupeaformis,
in Flathead Lake, Montana. Unpubl. M.S. Thesis, Univ. of Montana.
pp. (1953)
62. Brunson, Royal B. and H. William Newman. The Summer Food of
Coregonus clupeaformis from Yellow Bay, Flathead Lake, Montana. Proc.
Montana Acad. Sci. 10:5-7- (1951)
63. and Daniel G. Block. The First Report of the White
Sturgeon from Flathead Lake, Montana. Proc. Mont. Acad. Sci. 17:
61-62. (1957)
64. Block, Daniel G. Trout Migration and Spawning Studies on the North
Fork Drainage of the Flathead River. Unpubl. Thesis, Montana State
Univ., pp. 1-83. (1955)
65. Stefanich, Frank A. Survey of Cutthroat Trout Fishery in the Flat-
head River and Tributaries Above Flathead Lake. Comp. Report, Mont.
Fish and Game Dept. F-7-R-5, Job VI. 3 pp. Multilith. (1956)
66. _ . Survey of Cutthroat Trout Fishery in the Flathead River
and Tributaries Above Flathead Lake. Comp. Report, Montana Fish and
Game Dept. F-7-R-6, Job VI. 2 pp. Multilith. (1957)
67. _ . Survey of Cutthroat Trout Fishery in the Flathead River
and Tributaries Above Flathead Lake. Comp. Report, Montana Fish and
Game Department. F-7-R-7, Job IV. 3 pp. Multilith. (1958)
66
-------
68.
69.
70.
71.
72.
73-
74.
75.
Stefanich, Frank A. Survey of Cutthroat Trout Fishery in the Flat-
head River and Tributaries Above Flathead Lake. Comp. Report, Mont.
Fish and Game Dept. F-7-R-8, Job IV. 2 pp. Multilith. (1959)
Johnson, Howard E. Survey of Cutthroat Trout Fishery in the Flat-
head River and Tributaries Above Flathead Lake. Comp. Report, Mont.
Fish and Game Dept. F-7-R-9, Job III. 4 pp. Multilith. (I960)
. Observations of the Life History and Movements of Cut-
throat Trout in Flathead River Drainage, Montana. Proc. Mont. Acad.
Sci. 23:96-110. (1961)
Rahrer, Jerold F. Age and Growth of Four Species of Fish - Flathead
Lake, Montana. Proc. Mont. Acad. Sci. 23:144-156. (1967)
Robbins, Otis J. Flathead Lake (Montana) Fishery Investigation,
1961-64. Technical Paper #4, Bureau Sport Fish and Wildl. 26 pp.
(1966)
Schultz, Leonard P. Fishes of Glacier National Park Montana.
Dept. of Int. Cons. Bull. No. 22. 42 pp. (1941)
U.S.
Bailey, Reeve M. and Carl E. Bond. Four New Species of Freshwater
Sculpins, Genus Cottus from Western North America. Occ. Pap. Mus. of
Zool., Univ. Mich. No. 634:1-27- (1963)
Newell, Robert and A. G. Canaris. Parasites of the Pygmy Whitefish
and Mountain Whitefish from Western Montana. Proc. Helm. Soc. of
Wash. Vol. 36, No. 2, pp. 724-726. (1969)
67
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SECTION XV
APPENDIX — ALGAE OF FLATHEAD LAKE
I. CHLOROPHYTA
A. Volvocales
1. Volvocaceae
Eudorina elegans Ehr.
Gonium pectorale Mueller
Pandorina morum Bory
Volvox aureus Ehr.
Volvox globator
B. Tetrasporales
1. Gloeocystaceae
Asterococcus superbus (Cienk.) Scherf.
Gloeocystis ampla (Kuetz.) Lag.
Gloeocystis gigas (Kuetz.) Lag.
Gloeocystis major Gerneck
2. Tetrasporaceae
Schizochlamys compacta Presc.
Tetraspora gelatlnosa (Vauch.) Desv.
Tetraspora lacustris Lemm.
C. Chlorococcales
1. Chlorococcaceae
Characium ambiguum Hermann
Characium acuminatum A. Braun
Chlorococcum humicola (Naeg.) Rab. (?)
Planktosphaeria gelatinosa G.M. Smith
Schroederia Judayi G.M. Smith
68
-------
Chlorophyta (continued)
2. Coccomyxaceae
Elakatothrix gelatinosa Wille
Dispora crucigenioides Printz
3. Coelastraceae
Coelastrum cambricum Archer
k. Dictyosphaeriaceae
Botryococcus Braunii Kuetz.
Dictyosphaer ium pulcheUum Wood
5. Hydrodictyaceae
Euastropsis Richteri (Schm.) Lag.
Pediastrum Boryanum (Turp.) Menegh
Pediastrum duplex Meyen
Pediastrum simplex Meyen
Pediastrum sculptatum G.M. Smith
Pediastrum tetras (Ehr.) Ralfs
Sorastrum spinulosum Naeg.
6. Oocystaceae
Ankistrodesmus Braunii (Naeg.) Collins
Ankistrodesmus falcatus (Corda) Ralfs
Cerasterias staurastroides West and West
Chlorella vulgaris Beij.
Closteridium lunula Reinsch
Dactylococcus infusionum Naeg.
Kirchneriella lunaris (Kirch.) Moebius
Kirchneriella obesa (W. West) Schmidle
Mycanthococcus antarcticus Wille
Nephrocytium Agardhianum Naeg.
Nephrocytium limneticum (G.M. Smith) G.M. Smith
69
-------
Chlorophyta (continued)
Oocys taceae (cont!nued)
Oocystis Borgel Snow
Oocystis crassa Wfttr.
Oocystis elliptica W. West
Oocystis lacustris Chodat
Oocystis panduriformis var. minor G.M. Smith
Oocystis solttaria Wittr.
Oocystis submarina Lag.
Quadrigula Chodatii (Tan.-Ful.) G.M. Smith
Selenastrum gracile Reinsch
Tetraedron arthrodesmiforme (G.S. West) Wolsz.
Tetraedron regulare Kuetz.
Trochiscia reticularis (Reinsch) Hansg.
7. Palmellaceae
Sphaerocystis Schroeteri Chodat
8. Scenedesmaceae
Crucigenia rectangular is (Naeg.) Gay
Scenedesmus armatus (Chodat) G.M. Smith
Scenedesmus bijuga (Turp.) Lag.
Scenedesmus quadricauda (Turp.) Breg.
Tetrastrum heteracanthum (Nordst.) Chodat
D. Ulotrichales
!. Microsporaceae
Microspora pachyderma (Wille) Lag.
Microspora stagnorum (Kuetz.) Lag.
2. Uiotrichaceae
Binuclearia tatrana Wittrock
Geminella mutabilis (Breb.) Wille
Radiofilum conjunctivum Schmidle
Ulothrix zonata (Web. and Moh.) Kuetz.
70
-------
Chlorophyta (continued)
E. Ulvales
1. Schizogoniaceae
Schizogoniurn murale Kuetz.
F. Chaetophorales
1. Aphanochaetaceae
Aphanochaeta repens A. Braun
2. Chaetophoraceae
Chaetophora sp.
Microthamnion Kuetzingianum Naeg.
Stigeoclonium tenue (C. Ag.) Kuetz.
3. Coleochaetaceae
Coleochaete scutata de Breb.
G. Cylindrocapsales
1. Cy1i nd rocapsaceae
Cylindrocapsa geminella Wolle
H. Oedogoniales
1. Oedogon i aceae
Oedogonium spp.
Bulbochaete sp.
I. Conj uga1es
1. Desmidiaceae
Arthrodesmus incus Anderss.
Bambusina brebissonii Kuetz.
Closterium moni1iferum (Bory) Ehr
(as Cl. moni1iforme by Morgan)
71
-------
Chlorophyta (continued)
Desmidiaceae (continued)
Cosmarium protractum (Naeg.) DeBary
Cosmarium punctulatum (Nordst.) Boerges.
Desmidium Grevillii Kuetz.
Doc idiurn undulatum Bailey
Euastrum pectinatum var. inevolutum West and West
Hyalotheca dissiliens (Smith) De Breb.
Micrasterias americana (Ehr.) Ralfs
Pleurotaenium trabecula (Ehr.) Naeg.
Sphaerozosma vertebratum (Breb.) Ralfs
Spondylosium moniliforme Lund.
Spondylosium planum (Wolie) West and West
Staurastrum leptocladum Nordst.
Xanthidium subhastiferum W. West
2. Gonatozygaceae
Gonatozygon aculeata Hast.
3. Zygnemataceae
Mougeotia genuflexa (Dillw.) Ag.
Sirogonium sticticum (Engl. Bot.) Kuetz.
Spirogyra communis (Hass.) Kuetz.
Spirogyra gratiana Trans.
Zygnema pectinatum (Fritsch) Stevens
J. Charales
1. Characeae
Chara frag ills Desv.
Chara vulgaris L.
72
-------
II. CYANOPHYTA
A. Chroococcales
1. Chroococcaceae
Aphanocapsa biformis A. Braun
(A. rivularis)
Aphanocapsa elachista West 6 West
Aphanocapsa Grevillei (Mass.) Rab.
Aphanocapsa pulchra (Kuetz.) Rab.
Aphanothece nidulans P. Rlcht.
Chroococcus dispersus (v. Keussl.) Lemm.
Chroococcus giganteus W. West
Chroococcus limneticus Lemm.
Chroococcus minor (Kuetz.) Naeg.
Chroococcus Prescottii Drouet & Daily
Chroococcus turgidus (Kuetz.) Naeg.
Coelosphaerium Naegelianum Unger
Dactylococcopsis acicularis Lemm.
Eucapsis alpinum Clements & Shantz
Gloeocapsa linearis var. composita G.M. Smith
Gloeocapsa punctata Naeg.
Gomphosphaeria aponina Kuetz.
Gomphosphaeria lacustris Chodat
Merismopedia elegans A. Braun
Merismopedia glauca (Ehr.) Naeg.
B. Chamaesiphonales
1. Chamaes i phonaceae
Chamaesiphon incrustans Grunow
C. Oscillatoriales
1. Osci1latoriaceae
Oscillatoria 1imosa Ag.
Spirulina laxa G.M. Smith
73
-------
Cyanophyta (continued)
D. Nostocales
1. Nostocaceae
Anabaena circinalis Rab.
Anabaena flos-aquae (Lyngb.) Breb.
Aphanizomenon flos-aquae (L.) Ralfs
Cylindrospermum muscicola Kuetz.
Nodular!a spurnigena Hertens
Nostoc linckia (Roth) Bor. & Flah.
2. Scytonemataceae
Tolypothrix lanata Wartm.
3. Rivulariaceae
Gloeotrichia echinulata (J. E. Smith) P. Richter
Gloeotrichia pi sum Thuret
Rivularia compacta (?)
Rivularia haematites (D.C.) C. Ag.
III. CHRYSOPHYTA
A. Chrysophyceae
1. Ma 11omonadaceae
Mailomonas alpina Pascher & Ruttner
Mallomonas caudata Iwanoff
Mailomonas elliptica (Kiss.) Conrad
Mallomonas pseudocoronata Presc.
2. Ochromonadaceae
Dinobryon bavaricum Imhof.
Dinobryon divergens Bachm.
Dinobryon sertularia Ehr.
Dinobryon sociale Ehr.
Dinobryon stipitatum Stein
3- Synuraceae
Synura Adamsii G.M. Smith
74
-------
Chrysophyta (continued)
Synuraceae (continued)
Synura ulvella Ehr.
B. Xanthophyceae
1. Chiorothec i aceae
Ophiocytium parvulum (Perty) A. Braun
2. Pleurochloridaceae
Arachnochloris minor Pascher
Tetragoniella gigas Pascher
3. Rhizochrysidaceae
Rhizochrysis limnetica G.M. Smith
k. Meringosphaeraceae
Meringosphaera spinosa Presc.
C. Baci1lariophyceae
Centrales
1. Cose i nod i scaceae
Coseinodiscus bodanica Schneider
Coseinodiscus catenata Brun.
(Coseinodiscus comta (Ehr.) Kuetz.) ?
Coscinodiscus marginatus Ehr.
Cyclotella antigua W. Smith
Cyclotella bodanica En. £ Sen.
Cyclotella catenata Brun.
Cyclotella comta (Ehr.) Kuetz.
Cyclotella Kuetzingiana Thw.
Cyclotella Kuetzingiana var. planetophora Fricke
Cyclotella Kuetzingiana var. radiosa Fricke
Cyclotella Kuetzingiana var. Schumann!i Grun.
Cyclotella Meneghiniana Kuetz.
Cyclotella ocellata Pant.
Cyclotella operculata (Ag.) Kuetz.
Cyclotella stelligera Cleve & Grun.
Melosira ambigua
Melosira Binderiana Kuetz.
75
-------
Chrysophyta (continued)
Centrales - Coseinodiscaceae (continued)
Melosira crenulata (Ehr.) Kuetz.
Melosira distans (Ehr.) Ralfs
Melosira granulata (Ehr.) Ralfs
Melosira italica Kuetz.
Melosira italica var. valida Grun...
Melosira italica var. subarctica Mull.
Melosira varians Ag.
Stephanodiscus astraea (Ehr.) Grun.
Stephanodiscus astraea var. minutula (Kuetz.) Grun.
Stephanodiscus Hantzschii Grun.
Stephanodiscus niagarae Ehr.
Pennales
1. Achnanthaceae
Achnanthes affinis Grun.
Achnanthes brevipes Cleve
Achnanthes calcar Cleve
Achnanthes chilensis var. subaequalis Reim.
Achnanthes Clevei Grun.
Achnanthes Clevei var. rostrata Hust.
Achnanthes deflexa Reim.
Achnanthes exiguua Grun.
Achnanthes exiguua var. constricta (Grun.) Hust.
Achnanthes exiguua var. heterovalva Krass.
Achnanthes flexella (Kuetz.) Grun.
Achnanthes inflata (Kuetz,.) Grun.
Achnanthes lanceolata (Breb.) Grun.
Achnanthes lanceolata var. dubia Grun.
Achnanthes lanceolata var. elliptica Cleve
Achnanthes lanceolata var. rhomboides A. Mayer
Achnanthes lapponica var. ninckei (Grun.) Mang.
Achnanthes Lemmermannii Hust.
Achnanthes Levanderi Hust.
Achnanthes linearis f. curta H.L. Smith
Achnanthes macrocephala (Kuetz.) Grun.
Achnanthes minutissima Kuetz.
Achnanthes pergal1i Brun. 6 Herib.
Achnanthes saxonica Krass.
Achnanthes Stewart!i Ptr.
Achnanthes sublaevis var. crass Reim.
Cocconeis diminuta Pant.
Cocconeis placentula Ehr.
Cocconeis placentula var. euglypta (Ehr.) Cleve
Cocconeis placentula var. lineata (Ehr.) V.H.
76
-------
Chrysophyta (continued)
Pennales - Achnanthaceae (continued)
Cocconeis scutellum Ehr.
Cocconeis scutellum f. parva Grun.
Rhoicosphenia curvata (Kuetz.) Grun.
2. Cymbellaceae
Amphora bullatoides Hohn & Heller.
Amphora coffeaeformis (Ag.) Kuetz.
Amphora 1ineolata (Ehr.) Ehr.
Amphora oval is (Kuetz.) Kuetz.
Amphora oval is var. pediculus (Kuetz.) V.H.
Amphora veneta Kuetz.
Cymbella affine Kuetz.
Cymbella aphicephala Naeg.
Cymbella angustata (W. Smith) Cleve
Cymbella aspera (Ehr.) Herib.
Cymbella Brehmii Hust.
Cymbella Cesatii Grun.
Cymbella cistula Grun.
Cymbella cuspidata Kuetz.
Cymbella delicatula Kuetz.
Cymbella delicatula var. intermedia McCall.
Cymbella fluminea Patr.
Cymbella gracilis (Rab.) Cleve
Cymbella heteropleura (Ehr.) Kuetz.
Cymbella Hustedtii Krass.
Cymbella hybrida Grun.
Cymbella laevis Naeg.
Cymbella lata Grun.
Cymbella mexicana (Ehr.) A.S.
Cymbella microcephala Grun.
Cymbella Mulleri var. javanica (Hust.) Hust.
Cymbella naviculiformis (Auer. & Rab.) Kirch.
Cymbella parva (W. Sm.) Cleve
Cymbella perpusilla Cleve
Cymbella pus ilia Grun.
Cymbella Reinhatdtii Grun.
Cymbella rhomboidea Boyer
Cymbella similis Patr.
Cymbella sinuata Greg.
Cymbella triangulum^(Ehr.) Cleve
Cymbella tumida (Breb.) V.H.
Cymbella tumidula Grun.
Cymbella turgida Greg.
Cymbella turgidula Grun.
Cymbella ventricosa Ag.
77
-------
Chrysophyta (continued)
Pennales - Cymbellaceae (continued)
Cymbella ventricosa var. Girodil (Her.) H. Kob.
Cymbella ventricosa var. ovata f. minor Cleve
Cymbella ventricosa var. silesiaca (Bleish) Cleve
Epithemia argus (Ehr.) Kuetz.
Epithernia Reichelti Fricke
Epithemia sorex Kuetz.
Epithemia turgida (Ehr.) Kuetz.
Epithemia turgida var. granulata (Ehr.) Brun.
Epithemia zebra (Ehr.) Kuetz.
Rhopalodia gibba (Ehr.) Hull.
Rhopalodia parallela (Grun.) Mull.
3. Diatomaceae
Diatoma anceps (Ehr.) Kirch.
Diatoma hiemale var. mesadon (Ehr.) Grun.
Diatoma tenue Agardh.
Diatoma tenue var. elongatum Lynbg.
Diatoma vulgare«var. pachycephala Grun.
Diatoma vulgare Bory
Diatoma vulgare var. breve Grun.
Diatoma vulgare var. linearis V.H.
Opephora americana M. Perag.
Opephora ansata Hohn & Heller
Opephora Marty! Herib.
Opephora Schwartzii (Grun.) Petit
4. Eunotiaceae
Ceratoneis arcus (Ehr.) Kuetz.
(Eunotia arcus Ehr.)
Eunotia arcus Ehr.
Eunotia arcus var. bidens Grun.
Eunotia curvata Kuetz.
Eunotia pectinalis (Kuetz.) Rab.
«=» E. pectinalis (O.F. Mull.) Rab.
Eunotia pectinalis var. stricta (Rab.) V.H.
Eunotia praerupta Ehr.
Eunotia Vanheurckii Patr.
5. Fragilariaceae
Asterionella formosa Hass.
Asterionella gracillima (Hantzsch) Heib.
78
-------
Chrysophyta (continued)
Pennales - Fragilarlaceae (continued)
Ceratoneis arcus (Ehr.) Kuetz.
(Fragilaria arcus)
Fragilaria brevistriata Grun.
Fragilaria capuctna Desmar.
Fragilaria capuclna Desmar. var. mesolepta Rab.
Fragilaria construens (Ehr.) Grun.
Fragilaria construens var. binodis (Ehr.) Grun.
Fragilaria construens var. venter (Ehr.) Grun.
Fragilaria crotonensis Kitton
Fragilaria crotonensis var. oregona Sov.
Fragilaria inflata
Fragilaria intermedia Grun.
(Fragilaria tenutcollis Heib. var. intermedia Grun.)
Fragilaria ieptostauron (Ehr.) Hust.
Fragilaria mutabilis var. intercedens Grun.
Fragilaria pinnata Ehr.
Fragilaria pinnata var. intercedens W. Smith
Fragilaria pinnata var. lancettula (Schm.) Hust.
Fragilaria vaucheriae (Kuetz.) Peter.
Fragilaria vaucheriae var. cap!tellata (Rab.) Patri.
Hannaea arcus (Ehr.) Patr.
Hannaea arcus var. amphioxys (Rab.) Patr.
Synedra actinastroides Learn.
Synedra acus Kuetz.
Synedra amphicephala var. austrica (Grun.) Hust.
Synedra cyclopum Brutschy
Synedra cyclopum var. gibbosa Mag.
Synedra cyclopum var. robustum Schulze
Synedra delicatissima W. Sm.
Synedra delicatissima var. angustissima Grun.
Synedra Demerarae Grun.
Synedra familica Kuetz.
Synedra fascTculata Kuetz.
Synedra fasciculata var. truncata (Grev.) Patr.
Synedra incisa Boyer
Synedra mazamaenses Sov.
Synedra-parasltica (W. Smith) Hust.
Synedra parasitica var. subconstricta (Grun.) Hust.
Synedra puichella Ralfs ex Kuetz.
Synedra radians (Kuetz.) Grun.
Synedra rumpens var. fragilarioides Grun.
Synedra rumpens var. scotica Grun.
Synedra ulna (Nitzsch) Ehr.
Synedra ulna var. amphirhynchus (Ehr.) Grun.
Synedra ulna var. danica (Kuetz.) V.H.
Synedra ulna var. spathulifera (Grun.) V.H.
79
-------
Chrysophyta (continued)
Pennales (continued)
6. Gomphonemataceae
Didymosphenia geminata (Lyngb.) M. Schmidt
Gomphoneis acumfnata var. Brebissonii
(Gomphonema acuminata var. Brebissonii (Kuetz.) Grun.)
Gomphonema acuminata var. coronata (Ehr.) Rab.
Gomphonema acuminatum var. Brebissonii (Kuetz.) Grun.
Gomphonema angustatum var. obesa Lauby
Gomphonema constrictum var. capitatum (Ehr.) V.H.
Gomphonema geminatum (Lyngb.) Kuetz.
Gomphonema gracile var. aurita (A.Br.) Cleve
Gomphonema intricatum Kuetz.
Gomphonema intricatum var. bohemicum (Rech. 6 Tr.)
Gomphonema intricatum var. dichotomum (Kuetz.) Grun.
Gomphonema intricatum var. pumila Grun.
Gomphonema longicepsf. gracilis Hust.
Gomphonema olivaceioides Hust.
Gomphonema o1ivaceum (Lynbg.) Kuetz.
Gomphonema parvulum (Kuetz.) Kuetz.
Gomphonema parvulum var. micropus (Kuetz.) Cleve
Gomphonema septata Magh.
7. Meridionaceae
Her id ion circulare (Grev.) Ag.
Herid ion circulare var. constrictum (Ralfs) V.H.
8. Naviculaceae
Amphipleura Lindheimeri Grun.
Amphipleura pellucida Kuetz.
Amphiprora ornata Bailey
Anomoeoneis sphaerophora (Kuetz) Pfitzer
Anomoeoneis sphaerophora var. sculpta 0. Mull.
Anomoeoneis vitrea (Grun.) Ross
Anomoeoneis vitrea f. lanceolata (A. Mayer) Mogh.
Anomoeoneis vitrea var. gomphonemacea (Grun.) Mogh.
Calone is amphisbaena (Bory) Cleve
Caloneis bad Hum (Grun.) Cleve
Caloneis lewisii var. inflata (Schultz) Patr.
Caloneis silicula f. Foged.
Caloneis ventricosa (Ehr.) Meist.
Calonets zachariasii Reich.
80
-------
Chrysophyta (continued)
Pennales - Naviculaceae (continued)
Diploneis elliptica (Kuetz.) Cleve
Diploneis oculata (Breb.) Cleve
Diploneis oculata var. linearis Gallik.
Diploneis ostracodarum (Pant.) Jur.
Frustulia rhomboides var. amphipleuroides (Grun.) Cleve
Frustulia vulgaris (Thw.) DeToni
Frustulia vulgaris var. capitata Krass.
Gyrosigma acuminatum (Kuetz.) Cleve
Gyrosigma attenuatum var. hippocampus (W.Sm.) Brock
Gyrosigma exilis (Grun.) Reimer
Gyrosigma eximium (Thw.) Boyer
Gyrosigma Kuetzingi? (Grun.) Cleve
Gyrosigma obtusatum (Sulliv. & Worm.) Cleve
Gyrosigma sciotense (Sulliv. & Worm.) Cleve
Gyrosigma Spenceri (Quek.) G. & H.
Mastogloia Braunii Grun.
Mastogloia Grevillei W. Sm.
Mastogloia Smithii Thw.
Mastogloia Smithii var. amphicephala Grun.
Mastogloia Smithii var. lacustris Grun.
Navicula absolute Must.
Navicula amphibela Cleve
Navicula anglica var. subsalsa (Grun.) Cleve
Navicula arenaria Donk.
Navicula aurora Sov.
Navicula bacillum Ehr.
Navicula bicapitellata Hust.
Navicula capitata var. hungarica (Grun.) Ross
Navicula capitata var. luneburgensis (Grun.) Patr.
Navicula cocconeiformis Greg.
Navicula costulata Grun.
Navicula cryptocephala Kuetz.
Navicula decussin Ostr.
Navicula disjuncta Hust.
Navicula eligensis (Greg.) Ralfs
Navicula flavasinus Mogh.
Navicula gastrum (Ehr.) Kuetz.
Navicula Gaufinii Mogh.
Navicula graciloides A. Mayer
Navicula gregaria Donk
Navicula Harder! Hust.
Navicula Heufleri var. leptocephala Breb.
Navicula ingrata Krass.
Navicula Jaernefeltii Hust.
81
-------
Chrysophyta (continued)
Pennales - Naviculaceae (continued)
Navicula laevissima Kuetz.
Navicula lanceolata (Ag.) Kuetz.
Navicula latens Krass.
Navicula laterostrate Hust.
Navicula Lundstromii Cleve
Navicula menisculus var. upsaliensis (Grun.) Grun.
Navicula minima Grun.
Navicula minuscula Grun.
Navicula montana Mogh.
Navicula mural is Grun.
Navicula peregrina (Ehr.) Kuetz.
Navicula peticolasii M. Perag.
Navicula pseudoreinhardtii Patr.
Navicula pseudoscutiformis Hust.
Navicula pupula Kuetz.
Navicula pupula var. capttata Shv. & Mey.
Navicula pupula var. elliptica Hust.
Navicula pupula var. rectangularis (Greg.) Grun.
Navicula pusio Cleve
Navicula pygmea Kuetz.
Navicula radiosa Kuetz.
Navicula radiosa var. parva Wallace
Navicula radiosa var. tenella Breb.
Navicula rhyncocephala var. amphiceros (Kuetz.) Grun.
Navicula rotunda Hust.
Navicula salinarum Grun.
Navicula scutelloides W. Smith
Navicula secura Patr.
Navicula seminulum Grun.
Navicula Simula Patr.
Navicula subhamulata Grun.
Navicula subocculata Hust.
Navicula subscutelloides
Navicula subtillisima Cleve
Navicula Swaniana Mogh.
Navicula tantula Hust.
Navicula tripunctata var. senizonemoides (V.H.) Patr.
Navicula tuscula Ehr.
Navicula tuscula f. minor
Navicula UtermohleiJ Hust.
Navicula variostriata Krass.
Navicula viridula (Kuetz.) Kuetz.
Navicula viridula var. avenacea (Breb.) V.H.
Navicula viridula var. linearis Hust.
Navicula vitabunda var. montana Mogh.
Navicula vulpina Kuetz.
Neidium affine (Ehr.) Pfitz.
82
-------
Chrysophyta (continued)
Pennales - Naviculaceae (continued)
Neidium affine var. amphirhynchus (Ehr.) Cleve
Neidium affine var. ceylonicum (Skv.) Cleve
Neidium binodis Hust.
Neidium dubium (Ehr.) Cleve
Neidium hercynicum f. subrostratum Wallace
Neidium iridis var. amphigomphus (Ehr.) A. Mayer
Neidium iridis var. ampliatum (Ehr.) Cleve
Neidium koslowi Meresch.
Neidium mage 11 anicum Cleve
Neidium temper! Reimer
Pinnularia abaujensis var. linearis (Hust.) Patr.
Pinnularia abaujensis var. subundulata A. Mayer
Pinnularia biceps Greg.
Pinnularia biceps f. Petersenii Ross
Pinnularia boreal is Ehr.
Pinnularia boreal is var. rectangularis Caris.
Pinnularia Brebissonii (Kuetz.) Rab.
Pinnularia gibba (Ehr.) Hust.
Pinnularia Hilseana Jan.
Pinnularia major (Kuetz.) Rab.
Pinnularia Martyi (?)
Pinnularia mesogonglya Ehr.
Pinnularia mesolepta (Ehr.) Sm.
Pinnularia microstauron (Ehr.) Cleve
Pleurosigma delicatulum W. Sm.
9. Nitzschiaceae
Bacillaria paradoxa Gmel.
Hantzschia amphioxys (Ehr.) Grun.
Nitzschia acicularis (Kuetz.) W. Sm.
Nitzschia acuta Hantz.
Nitzschia amphibia Grun.
Nitzschia angustata (W.Sm.) Grun.
Nitzschia angustata var. acuta Grun.
Nitzschia bacata Hust.
Nitzschia bremensis Hust.
Nitzschia capitellata Hust.
Nitzschia congolens is Hust.
Nitzschia denticula Grun.
Nitzschia dissipata (Kuetz.) Grun.
Nitzschia filiformis (W.Sm.) Schutt
Nitzschia fonticola Grun.
Nitzschia frustulum var. subsalina Hust.
83
-------
Chrysophyta (continued)
Pennales - Nitzschiaceae (continued)
Nitzschia Hantzschiana Rab.
Nitzschia Kuetzingianum Hilse
Nitzschia linear is (W.Sm.) W. Smith
Nitzschia microcephala Grun.
Nitzschia parvula Lewis
Nitzschia pa lea (Kuetz.) W. Sm.
Nitzschia recta Hantz.
Nitzschia sinuata (W. Sm.) Grun. var. tabellaria V.H.
Nitzschia vermicularis (Kuetz.) Hantz.
10. Rhizosoleniaceae
Rhizosolenia eriensis H. L. Smith
Rhizosolenia eriensis var. morsa West & West
Rhizosolenia stagnalis
]]. Surirellaceae
Campylodiscus hibernicus Ehr.
Cymatopleura solea (Breb.) W. Smith
Cymatopleura solea var. apiculata (W.Smith) Ralfs
Surirella angustata Kuetz.
Surirella biseriata var. bifron (Ehr.) Hust.
Surirella capronii Breb.
Surirella didyma Kuetz.
Surirella linearis W. Smith
Surirella linearis var. helvetica (Brun.) Meister
Surirella oblonga Ehr.
Surirella oval is Breb.
Surirella ovata Kuetz.
Surirella robusta Ehr.
Surirella tenera Greg.
12. labellariaceae
Tabellaria fenestrata Kuetz.
Tabellaria flocculosa (Roth) Kuetz.
Tabellaria quadrisepta Knuds.
Tetracyclus lacustris Ralfs
84
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-76-039
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Llmnologlcal Studies of Flathead Lake Won.ta.na.:
A Status Report
5. REPORT DATE
April 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
A. R. Gaufin, G. W. Prescott and J. F. T1bbs
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
University of Montana
Mlssoula, Montana
11. CONTRACT/GRANT NO.
1-F1-WP-26, 212-1-4
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Corvallis Environmental Research Laboratory
200 S. 35th Street
Corvallis, Oregon 97330
13. TYPE OF REPORT AND PERIOD COVERED
1971 - 1973 Final
14. SPONSORING AGENCY CODE
EPA/ORD
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Flathead Lake, a dimictic oligotrophic lake located in western Montana, has been
the subject of several investigations beginning with Forbes' study of aquatic
invertebrates in the lake in 1893. Young in 1935 presented the results of four
years of data collecting on the chemistry and biology of the lake. During the
last ten years (1964-1974) a number of limnological studies have been conducted
dealing with the physical, chemical, and biological characteristics of the lake.
The objectives of these studies have been to determine the standing crop of
phytoplankton and zooplankton during all seasons of the year, to observe the
succession, distribution and diversity of planktonic forms, to determine the role
of chemical nutrients 1n relationship to phytoplankton productivity, and to
study fish population trends, life histories and seasonal fish distribution
of the Flathead Lake system.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Limnology, aquatic productivity,
phytoplankton, zooplankton, fish,
nitrates, phosphates
Flathead Lake, Montana
06-F
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
91
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
85
ft U.S. GOVERNMENT PRINTING OFFICE: 1976-697.055/79 REGION 10
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