&EPA
United States
Environmental Protection
Agency
Office of Marine
and Estuarine Protection
Washington DC 20460
EPA 503/3-88-001
September 1988
Water
\U/cilfcJI _^_____ • •
Linking Estuarine Water
Quality and Impacts on
Living Resources:
Shrinking Striped Bass
Habitat in Chesapeake Bay
and Albemarle Sound
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ENVIRONMENTAL SCIENCES DIVISION
LINKING ESTUARINE WATER QUALITY AND IMPACTS ON LIVING RESOURCES:
LINKING ^^^ STRIPED BASS HABITAT IN CHESAPEAKE BAY
AND ALBEMARLE SOUND
Project Title: Prioritization of Pollution Control in Estuaries
Through Analysis of Temperature and Dissolved Oxygen
Habitat Space for Biota
Charles C. Coutant
Denise L. Benson
Environmental Sciences Division
Publication No. 2972
August 1987
Prepared for
Office of Marine and Estuarine Protection
U.S. Environmental Protection Agency
401M. Street, S.W.
Washington, DC 20460
Kim Devonald, Project Officer
Interagency Agreement EPA DW 89931605-01-0
DOE 40-1629-85
Prepared by the
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831
operated by
MARTIN MARIETTA ENERGY SYSTEMS, INC
for the U.S. DEPARTMENT OF ENERGY
under contract DE-AC05-84OR21400
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DISCLAIMER
Although the research described in this report has been funded wholly or in part by the
mOP fSSSS t tf^T ^^ (EPAl thr°Ugh InteraSency Agreement No. DW89931605-01-0
t£?PL?"H ? U.S Department of Energy, it has not been subjected to EPA review and,
therefore, does not necessarily reflect the views of EPA, and no official endorsement should be inferred
11
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CONTENTS
v
LISTOFFIGURES
! vii
ABSTRACT
1
INTRODUCTION '
3
METHODS
5
RESULTS : ' '
! I. Retrospective Confirmation of Striped Bass Upper Avoidance Temperature 5
i 8
i II. Chesapeake Bay
i SummerBayResidencybySubadultandAdultStripedBass . . . . '
9
Temperatures in Chesapeake Bay •
i 18
Dissolved Oxygen in Chesapeake Bay
"70
i shrinking Habitat for Striped Bass Due to Temperature-Oxygen Squeeze
: 23
i Physiological Effects
26
Other Species
26
| Remedial Action
i 28
III. Albemarle Sound '
28
' striped Bass in Albemarle Sound-Roanoke River
A New Hypothesis for Striped Bass Decline in the Albemarle-Roanoke System 30
34
CONCLUSIONS
36
REFERENCES ' " "
111
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LIST OF FIGURES
Figure
1
Sampling locations for July data in the EPA Chesapeake Bay Program computerized
database
Stations in the Pamunkey and York rivers and in the Chesapeake Bay monitored
for temperature
May-October water temperatures at surface (broken line) and bottom (solid line)
in the York River estuary and adjacent Chesapeake Bay
Chesapeake Bay and its tributaries divided into 5 nautical mile segments and showing
features prominent for evaluating striped bass habitat
Temperature and salinity along the longitudinal axis of the Chesapeake Bay for
May-October 1968 '
10
11
15
16
7
\8
Selected depth contours for the Chesapeake Bay
Average summer temperatures along the longitudinal axis of the Chesapeake Bay 17
Contrasting summer water temperature conditions along the longitudinal, axis of
the Chesapeake Bay
Area of Chesapeake Bay bottom affected by low dissolved oxygen levels 3n the
summers of 1950 (A) and 1980 (B)
10
11
I 12
I
13
I
; 14
Dissolved oxygen concentrations with depth along the longitudinal axis of the
Chesapeake Bay
Hypothesized chronology of typical seasonal changes in distributions of temperature,
oxygen, and subadult and adult striped bass along a longitudinal axis of the
Chesapeake Bay
Hypothesized cycle of reproductive impairment of striped bass due to summer
temperature and dissolved oxygen habitat limitations
Map of Albemarle Sound and its major tributaries
Hypothesized summer striped bass distribution in Albemarle Sound . ..
19
21
24
27
29
32
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ABSTRACT
This proiect seeks to develop strategies and priorities for arresting habitat deterioration and restoring
£?££ in estuaries through identification of critical zones for maintaining hvmg resources It
uses as an example one representative and important estuarme species, the striped bass (Morone
s2tms) DatT on summe? water temperatures, dissolved oxygen concentrations, and striped bass
suitability for adults and subadults were those identified in freshwater reservoirs (<25 C and >2 mg/L
dissolved oxygen).
T^ Chesapeake Bay two key areas were identified: (1) a zone of residual cool water (<25°C) in the
River where warm surface waters (>25°C) in summer impinge on the bottom and may block egress ol
SedbSs subadults and adults from the bay. Increasing anoxia in the bay rn recent years, especially
^rStodSfiSr, has reduced the amount of suitable habitat available. Severe deoxygenation
m W summer of 1980 and 1984, which would have affected resident adults and newly maturing
subadults, is linked to record low values for the Maryland Juvenile Striped Bass Index for 1981 and U.985
in the upper bay. The Bay Bridge and sill areas are suggested as high-priority zones for pollution
monitoring and control.
A more limited analysis of Albemarle Sound suggests one key area, a zone of generally deeper water in
Ae westemSound, broadly defined at this time as lying between Pleasant Grove and River ^Neck but
also possibly including parts of the Roanoke River delta. Progressive deoxygenation of this deeper
wStern zoL sTnC, f^ mid 1970s is suspected from reported algal blooms and other signs of
SopWcation. Most aspects of the historical changes in striped bass population structure, inc^g
sever! reductions in viability of eggs spawned in the Roanoke River since 1974, are consistent with
SSioroTSorica^ important habitat in summer and resultant physiological stresses and potentially
enhanced toxicant exposure that affect reproductive competence.
vn
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INTRODUCTION
There is a need to systematically evaluate the impacts of water quality degradation on the biota of
estuaries and to develop strategies and priorities for arresting habitat deterioration and restoring lost
habitats. Estuaries throughout the United States are experiencing the pressures of increasing human
population, including domestic wastes (or the nutrients resulting from wastewater treatment); toxic
discharges; power plant cooling water use; and non-point runoff of pesticides, acid deposition, and
fertilizers. Notable improvements have been made in the quality of some systems [e.g., the Hudson
River, despite continuing PCB contamination (Smith hi press)]. Other systems, such as the Chesapeake
Bay, are exhibiting alarming trends toward progressive degradation of both water quality and living
resources (Officer et al. 1984; Seliger et al. 1985; Boreman and Austin 1985).
Two problems continually plague implementation of good intentions to clean up the nation's estuaries:
(1) an unclear relationship between water quality parameters (e.g., temperature, dissolved oxygen,
nutrients, chemical toxicants) and the viability of valued populations of the living resources inhabiting
the water, and (2) the need to place priorities on cleanup efforts because of limited financial resources.
The cost of a general cleanup of a whole estuarine system such as the Chesapeake Bay would be
immense, and thus a method for detecting and prioritizing areas of water quality degradation that are
most significant for populations of important organisms seems essential.
This project addresses and links these problems. The overall project seeks to develop a method to
prioritize pollution control in estuaries through analysis of two water quality parameters-temperature
and | dissolved oxygen-found to be especially important for one key estuarine apecies, the striped bass
(Morone saxatilis). The Chesapeake Bay, where water quality degradation and decline in populations of
striped bass are concurrent concerns, is taken as an initial example for analysis. Preliminary
considerations toward generalizing the concepts have been made through study of another estuary in
which striped bass populations are threatened, Albemarle Sound, North Carolina.
This; report presents a summary of initial results. Analyses and conclusions are tentative and subject to
revision. Nonetheless, important conclusions about linkage of water quality and critical zones for striped
bass are emerging. These tentative conclusions will be refined further in subsequent work.
A recent synthesis of ecological data on striped bass in both fresh and saltwater environments has
concluded that distribution and population declines of this species can be related to habitat selection
according to thermal preferences alone or in concert with dissolved oxygen (Coutant 1985). The
physiologically optimum temperature range shifts to lower temperatures as striped bass grow. The
subadult and adults of the species are limited to zones of a water body that are sufficiently cool and
well; oxygenated during critical times of the year, such as summer. The size (volume) of the thermally
suitable habitat with sufficient oxygen may be a small portion of the water body; thus the annual
carrying capacity of the whole system may be restricted.
A number of direct and secondary detrimental effects have been seen in striped bass populations in
which adults and subadults are crowded into these "thermal refuges" in summer (Coutant 1985). They
include direct mortality of those that can not find the refuge, increased disease due to crowding,
deteriorating body condition throughout the summer as food resources are exhausted, overfishing,
catch-and-release mortality, and diminished reproductive competence of females the following year
(presumably due to a bioenergetic deficit during egg development). Although evidence is not fully
conclusive that this type of habitat restriction is important for striped bass declines in estuaries such as
the Chesapeake Bay, the evidence is strongly suggestive that it may be a factor.
We emphasize summer habitat because during this season suitable habitat space can be most limiting for
marly species. Seasonal warming of surface waters, either alone or in combination with density
stratification due to salinity differences, can create thermal zones that may match the species' thermal
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niche in only limited areas or not at all. Microbial respiration diminishes oxygen resources most rapidly
in density stratified, warm temperatures of summer. Toxic materials can be most rapidly bioaccumulated
and have their most rapid effect in the active summer times of feeding and growth of organisms.
Toxicants released into the zones of fish concentration hi summer can have effects disproportionate to
those they might have if they and the fish were dispersed throughout the water body. Energy stores
accumulated in body tissues during the warm seasons are often vital for maturation of gonads in
preparation for the next year's spawning. We feel that limitations on summer habitat space can be as
critical for population survival as more commonly identified critical areas, such as spawning grounds.
The premise of this work is that identifying habitat limitations for key species in estuaries in summer,
due to temperature preferences and seasonal patterns of temperature and dissolved oxygen, will be a
productive tool for focusing attention of water quality investigations. This focus should help reduce the
cost and effort of estuary study and cleanup to more manageable levels.
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METHODS
This work consisted of careful evaluation of existing reports and data sets that may be relevant (no
original field study was included). We sought all available historical data on temperatures, dissolved
oxygen concentrations, and striped bass distributions in the Chesapeake Bay. We made use of original
reports whenever possible. The computerized water quality data base being developed by the
U.S^ Environmental Protection Agency (EPA) Chesapeake Bay Program is a resource that we attempted to
utilize for automated analyses, although coverage of the bay is not uniform in either space or time
(Fig. 1). Recent data not yet summarized in reports are not covered adequately. In the case of
Albemarle Sound, we conducted a less thorough search of the literature and are indebted to
Mr.! Anthony W. Mullis, Coastal Research Coordinator for the North Carolina Wildlife Resources
Commission, Division of Inland Fisheries, for use of his unpublished data. We consider this report to be
interim because we are not confident that our review of available data is yet comprehensive.
We [ first sought to estabh'sh water temperature patterns in the Chesapeake Bay that could direct habitat
selection by subadult and adult striped bass based on our results in reservoirs. We assumed that
juveniles would occupy shallow, warm zones (Coutant 1985), and they were not included in the purview
of this study. The fisheries literature was examined somewhat concurrently fox information on striped
bass distribution that could be correlated with the thermal regimes. We then sought to describe the
spatial and temporal patterns of dissolved oxygen in the bay. We did this, from two perspectives:
(1) characterizing the changing pattern of summer oxygen resources for the whole bay over the period
of record (since about 1950), which includes both high and declining abundances of striped bass (a task
that has been attempted by others), and (2) focusing on quantitative changes in dissolved oxygen in
specific zones we estimated from temperature analyses to be important habitats for large striped bass.
We also attempted to use the computerized water quality data base of the EPA Chesapeake Bay Program
to quantitatively graph seasonal and interannual changes in suitable striped bass habitat, as has been
done for at least one reservoir (Virginia Power 1986). Following the Chesiipeake Bay analysis, the
process was repeated in less detail for Albemarle Sound.
.
A few comments on the success of the process may be fruitful. Despite what seems to have been a
large amount of research and monitoring on Chesapeake Bay, the water quality data relevant to striped
bass populations are frustratingly spotty. Reasonable hypotheses can be developed based on current
understanding, but there are insufficient data in the critical places and times to provide rigorous tests
of them (Heinle et al. 1982 also observed this difficulty). A surprisingly large amount of time was
required to search the relevant literature and to retrieve reports (many of which were laboratory
documents with limited distribution). The laudable computerized data base at the Chesapeake Bay
Program offered another slow and sometimes frustrating learning curve to be surmounted before useful
information could be retrieved. From both hard copies and computer printouts, we realized that the
available data sets are but a sparse and discontinuous sampling of the processes believed to be relevant
and important to the dynamic striped bass populations in the bay. Perhaps tliis study will provide the
impetus to monitor selected zones in the future especially well and with unbroken time sequences.
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Fifties Chesopeake Bay Points
ORNL-DWG 87-9536
Sixties Chesopeake Boy Points
77'• Tt'u'W »'* TJ'WW 77-W» 77
Seventies Chesapeake Boy Points Eighties Chesapeake Boy Points
c t w>l) =»• -T 1
M'KTH
u-«
Fig. 1. SampUng locations for July data in the EPA Chesapeake Bay Program computerized data base, by
decade from 1950 to 1980. Numbers are the last digit of the year when samples were taken. Locations
appearing on land are for tributaries not drawn.
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RESULTS
I. Retrospective Confirmation of Striped Bass Upper Avoidance Temperature
Is 'the upper avoidance temperature of striped bass in an estuary the same as in freshwater reservoirs,
where it has been determined precisely with temperature telemetry? Although there have been no
detailed studies of temperature selection by this species in any estuary, the existing, independent
literature on water temperatures and on seasonal fish distributions can provide a reasonable retrospective
test. !
The upper avoidance temperature for adult striped bass in freshwater reservoirs in Tennessee has been
estimated to be near 25°C (Coutant 1985; Cheek et al. 1985). The temperature range in which subadult
striped bass spent 75% of their time in a small Tennessee quarry lake in summer was 20-24 C (Coutant
arid Carroll 1980) There was clear avoidance of relatively large volumes of otherwise acceptable water
ini summer when they exceeded these upper temperature ranges. The volumes of water that were avoided
included surface layers (Lambert Quarry, Cherokee Reservoir) and main reservoir reaches when cooler
tributaries were available (Watts Bar Reservoir). Several other telemetry studies of striped bass in
reservoirs have confirmed this general pattern of temperature selection in fresh water, although warmer
temperatures up to 29°C have been occupied for short periods when no cool water was available (e.g
Virginia Power 1986). The thermal niche of striped bass has been shown to change with age, with
juveniles preferring about 26°C, thus creating habitat partitioning (Coutant 1985, 1986) Earlier
research, primarily on juveniles, has misled our view of the habitat requirements of larger striped bass.
We tested the upper avoidance temperature for striped bass of the Chesapeal.ee region by examining the
York-Pamunkey River-estuary system. There, striped bass distribution was analyzed in a 1968-69 tagging
study by Grant et al. (1970) and in 1967-71 trawl catches by Grant (1974). Monthly water
temperature-depth profiles were available along the length of the system and into the main bay tor
1956-59 (Massman 1962) (Fig. 2). Additional temperature data were also indicated in Grant (1974), and
Byooks (1983a, 1983b) provided extensive data on temperature, dissolved oxygen, and salinity for 1970-80.
j
The 1956-59 data set is a useful example of the general water temperature conditions (Fig. 3). Water
temperatures at the surface and bottom were generally higher in the upper teaches in May-August and
fairly isothermal or slightly cooler upriver in September and October. Headwater temperatures were in
the 75% occupancy range of 20-24°C in May, whereas lower reaches were cooler. As seasonal warming
progressed, the upper reaches warmed above the preferred temperature range and by July, preferred
temperatures occurred only in the lower reaches or in the main bay. The August pattern was variable:
in a cool year (1957) the entire York system was in the upper part of the preferred range, whereas in a
Warm year (1959) all temperatures were above those preferred. The entire system cooled to within or
below the preferred range in September and October.
Brooks (1983a 1983b) confirmed that summer temperatures are above 25°C most of the time in the York
estuary and that, on the whole, dissolved oxygen is not a problem for fish distribution. Values were
almost always above 3-4 mg/L, even in summer. Temperatures seemed to grade smoothly from the York
River mouth to the headwaters with no special anomalies.
If striped bass were to follow the preferred temperature range through the seasonally changing
temperatures (e.g., crosshatched range in Fig. 3), the fish would move up and down the estuary.
Movement would be to the upper reaches in May, and shift downstream hi summer while vacating the
upper reaches entirely. The striped bass would seek refuge in the deeper parts of the mam bay.
September or October would see the whole system in the preferred range, thus allowing widespread
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ORNL-DWG 86-9566
Chesapeake Bay
***
"*
for temperature
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ORNL-DWQ M-9SI7
1956
1957
1958
1959
SEPTEMBER
I ' . I—I 1 1
—I 1 1—I—I
OCTOBER
—i—i—i—i—i—i—
NO DATA
L_J I I 1 1 1
—i—i—i—i—i—i—
JUNE
l l I I I 1 1
I I I I I I I .1
—•' *
II _ I _ I - 1 - 1
~l.— I I - 1 — T~
— __ - — .. ------
—i—i—i—i—i—i—
AUGUST
i i ii I I—I—I
AUGUST
l I I I I 1 1
AUGUST
L_I I 1 L_l
—i—i—i—i—i—i
—i—i—i—i—i—i—
SEPTEMBER
i i II L_J 1 L
i—i—i—i—i—i—i
OCTOBER
_l_
j L
SEPTEMBER
i_J I—I 1—L
T—i—i—i—i—i—i—r
OCTOBER
16 14 12 10 8 6 4 2 16 14 12 10 8 6 4 2
STATION NUMBER
i l I .1 I 1 1 L_
16 14 12 10 8 6 4 2
SEPTEMBER
_l__l I I—I 1 L.
i—i—i—i—r~i—i—r
OCTOBER
I 1 1
16 14 12 10 8 6 4
STATION NUMBER
Fie 3 Mav-October water temperatures at surface (broken line) and bottom (solid line) in the York
1980). Station numbers are shown on Fig. 2.
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dispersal. Grant .et al. (1970) observed that the 2- and 3-year-old striped bass in his tagging study
appeared to move from the York River into Chesapeake Bay in warmer months, but return in the fall
Grant (1974) found that mature striped bass caught in the fishery rarely appeared in the river in warmer
months. There were anomalously more striped bass in the York River in the summer of 1969- this was -a
year, however, when there was rapid deoxygenation in sthe main bay (Taft et al. 1980) and the main bay
was warm in summer and had low dissolved oxygen in the deep channel (Price et al. 1985) Habitat
restriction in die bay in 1969 may have forced more fish to remain in the York River estuary in summer
Massman (1962) caught few striped bass and provided no fish sizes for catches that correspond directlv
with his temperature observations.
To the extent possible by matching sketchy fish distribution data in the York estuary to more abundant
temperature data, the general range of preferred and avoided temperatures for larger striped bass seems
confirmed Further correlations among existing data sets in the Chesapeake Bay would be desirable and
more confidence would be gained through temperature telemetry studies of Chesapeake Bay' fish
Additional confidence in the view that estuarine stocks foUow the same temperature cues that we have
'/JSSrr ", \eshwater st"Ped bass comes from the Connecticut River. There, Kynard and Warner
S^rV1? the aCtivity °f subadult striPed bass a* fi^ lifts was related to temperature and that
72% of fish passage over a 7-year period occurred from 20°C to 24°C. These results seem sufficient to
accept the published upper avoidance temperature as the basis for a working hypothesis about iabitat
suitability for subadult and adult striped bass in the Chesapeake Bay and Albemarle Sound systems.
It. Chesapeake Bay
Summer Bay Residency by Subadult and Adult Striped Bass
Much attention has been paid to the contribution of Chesapeake Bay striped bass to coastal waters
where this stock has been dominant (e.g., Kohlenstein 1981) and to seasonal migratory movements. Much
less attention has been paid to the seasonal concentrations of fish that remain in the bay Summer
records are particularly scarce because it is not the season of an intense commercial fishery. However
the literature does indicate a historical record of declining residency in the bay as striped bass age and
also significant summertime catches of large fish in certain areas, both of which may be correlated
retrospectively with water temperature and dissolved oxygen conditions.
From the early tagging and recovery studies of Vladykov and Wallace (1938) onward it has been
recognized that the younger ages of female striped bass (through about age 4) and most of the males
tend to remain in the bay throughout the year, whereas the larger females tend to leave. However
departure seems to depend on population density (Goodyear 1978; Kriete et al. 1979). This density'
dependence suggests a limitation on the amount of suitable habitat for subadults and adults. Goodyear
based his conclusion on regressions between New York landings and young-of-the-year densities in the
Maryland portion of the Chesapeake 3-6 years earlier. Kriete et al. found that when abundance is
average, an insignificant proportion of 2-year-olds (<3%) join the coastal migration; when population is
high, more do so.
Substantial numbers (perhaps half) of the females in the year before their first spawning at age 5 remain
in the bay (Kohlenstein 1981). This observation could be important for successful spawning in the next
year. Mansueti and Hollis (1963) concluded that the principal contribution to natural reproduction is
probably from the smaller females between 5 and 15 Ib (2.3-6.8 kg) because of their greater relative
abundance compared to those larger, even though larger fish produce more eggs per female (Jackson and
lul&r
Some sites of summer residence have been suggested for subadults and adults that could be important
spawners in the following year. The information from catch records and personal observations by
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authors is biased, however, by preponderance of data on smaller sizes and ailure of some studies to
Indicate clearly the sizes of fish. Vladykov and Wallace (1952) indicated "summer feedmg grounds
around Tilghman, Galesville, and Rock Hall (105, 115, and 132 nautica] mfes or 195, 213 and_245 km
from the mouth of the Chesapeake Bay, respectively), and that large fish from 6 to 15 Ib(2.7-6SI kg)
ha'd been taken by sportsmen during summer months around Rock Hall and Tilghman (Fig. 4). Mansueti
and Hollis (1%3) cited a June-September 1962 sport fishing survey in the bay bridge area near Annapolis
(120 nautical miles or 222 km from the mouth) that reported many large fish as well as smaller ones
be'ing caught. About 12% (1300 fish) were >15 Ib (6.8 kg). Personal communications from current
fisheries biologists in Maryland confirm the importance of this reach of the. bay for ™™rt™?*^
of large fish. Coker and Hollis (1950) noted the disappearance of large striped bass (33.5-106 cm) from
midday off the mouth of the Patuxent River (83 nautical miles or 154 km from the mouth) in late June
during Navy detonation testing conducted between early May and late August 1925°C) in summer and vacate them. This
generalization comes from examination of temperature-depth profiles through the summer season m the
|pA Chesapeake Bay Program computerized data base and in original reports (Brooks and Fang 1983 tor
James River; Brooks 1983c for the Mattaponi River).
toata for vertical profiles along the longitudinal axis of the main bay were profoundly revealing of
temperature patterns that would guide larger striped bass. Seitz (1971) provided what appears in
iretrospect to be a reasonably typical pattern for seasonal changes in warm-season temperatures. Heako
gave salinities that, along with temperature, strongly influence seasonal water column stratification
(Hg. 5).
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10
ORNL-DWG 87-1300
— 39*
CHESAPEAKE BAY
AND TRIBUTARIES
FIVE NAUTICAL MILE SEGMENTS
0 6 10 15 20 25
NAUTICAL MILES
mile
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11
STATIONS
ORNL-DWG 87-1304
160
140
120 100 80 60
DISTANCE FROM ENTRANCE OF BAY (Mutical mite)
STATIONS
-20
-20
160
DISTANCE FROM ENTRANCE OF BAY d
! 45 with temperatures >25°C (after Seitz 1971).
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12
ORNL-DWO 87-1305
160 140
120 100
60 40
DISTANCE FROM ENTRANCE OF BAY (n«Jttail mite,)
1UU 80 60 40
DISTANCE FROM ENTRANCE OF BAY (nautical mil,,)
Fig. 5. (continued).
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TO
8
I
CD
DEPTH (It)
g S S S
DEPTH (m)
DEPTH (m)
DEPTH (m)
DEPTH (m)
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Hall. This cool water
adults throughout the
Pooles Island, 140
14
^^^r^T^^r^'^T^^^
the
' °f
b""8 SUbadultS
that is seasonally
bass hav, pted
U a
off fc Mouttfepao* ^5 ° f ^^ "• *' " ta &°»
would appear to provide an effective closure of tS ,, k T- ? ™™uig m many summers
of large striped bL, which we Sd ™tt°o »oM tf y f • °Ca"°° *" 'he Sea^d "iSratio»
there are similarly shallow sills father S?,£ h te-»P«ratures m excess of about 25°C. Although
of the aorthernmost sill I± sZed hT^h "* T/ ™ nf'5 C°°ler *" ^C- UP««™
°
vacated (warm) sul and °
Rappahinock Rivers
from the Virginia tributaries (especially dJ
stocks noted throughout the striped bas li
confirmation, but theyldicate that
\movement by upper bay fish to repopulate the
SST "* ^ "" 'r660 the P°t0mac and
JamesTand' ^ ??!! t13^ °f Striped bass
for ^th ^ ° POt°maC and UpPer
r
25°C with the sill (in terms of how hkh the tlnTf J cuonv;ergence of temperatures above
These differences are due pardy toTamofmJ »t ^ S ^ *"* ^ lonSitudinal ^stance covered).
true interannual differences due" t^ °4S£ Winter S f ^ ^ °f ^ ^ but 3re most ^
solar heating, air temperatures ocJaTt^S^T^^^^' i**™*™* freshwater flows,
described some of these ^c^c^rTS^ ^^T" ^r^' SeUger et d' W
discharge of the Susquehanna R™ve r for st a ificadon ?n Th %> ' 'T^^ °f Variati°ns ^
Pritchard (1986). The^hermal pattern oTl%8 KS 5Tis not a " 7" T^*™* by Schubd and
Lt^^^^^
<«*•-< conditions with respect to probable
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15
ORNL-DWG 87-1302
A
CHESAPEAKE BAY
30 ft CONTOUR
(9.1 m)
Fig 6 Selected depth contours (A, 30 ft or 9.1 m; B, 40 ft or 12.2 m) for the Chesapeake Bay showing
the horizontal extent of deep water in the Pooles Island-Rock Hall-bay bridge vicinity (upper circles on
A and B) and the relatively shallow sill that cuts off the deep bay channel near the mouth of the
Rappahannock River where maximum water temperatures occur (lower circle on B) (after Hires et al.
1963).
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16
ORNL-DWG 87 1301
CHESAPEAKE BAY
40 ft CONTOUR
(12.2 m)
Hg. 6. (continued).
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QRNL-DWG 87-1307
924QQ 918T 908 848E
STATION
818P
927SS
20 -
120
7070 657W
I I
39°20'
I I
39°00' 38°40
38°20' 38°00'
LATITUDE
37°40' 37°20' 37°00' N
Fig. 7. Average summer
Stroup and Lynn 1963).
temperatures along the longitudinal axis of the Chesapeake Bay, 1949-61 (after
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18
filled with water of 21-24°C (Fig. 8B) (Stroup and Lynn 1963). In 1958 (Fig. 8A), the 25°C isotherm
does not appear to have reached the bottom at the sill, thus maintaining a migration access.
Interannual variability in temperature patterns, therefore, encompasses conditions that could either
stimulate or prevent migration out of the bay to coastal waters and conditions that could cause severe
or little crowding in the residual cool water (based on temperature alone). It appears that strong
density stratification, as seen in 1961 (Fig. 8B), produces both especially high temperatures at the siU
(and thus strong blockage) and preserves cool temperatures in the refuge. Historically, the two thermal
effects may have compensated for each other somewhat in maintaining suitable striped bass habitat
Year-to-year differences in temperature distributions and thus striped bass distributions may have
iunctional significance for widely varying year-class success of this species.
There is only sketchy evidence to suggest a change in thermal patterns in the bay that correlates with
drastic population declines of striped bass since the early 1970s. The EPA Chesapeake Bay Program data
set suggests that surface waters in the uppermost reaches of the bay may have been more consistently
above 25 C since 1969. Thermal power stations such as the Calvert Cliffs station or those on the
Potomac River might be adding sufficient heat to affect large areas of the bay in marginal years
(although we have not examined their influence rigorously). Priority zones to consider when examining
long-term temperature records to establish if there has been a general temperature change important to
striped bass would be the cool refuge below 15 m in the bay bridge-Pooles Island reach and the bottom
water over the sill just north of the mouth of the Rappahannock River. The sill area near nautical mile
45 would appear to be an especially sensitive area for future anthropogenic heating, such as from
thermal electric power plants.
Dissolved Oxygen hi Chesapeake Bay
As suitable as the deep, cool water zone near the bay bridge seems for summer habitat of subadult and
adult striped bass blocked upstream of the sill, its suitability is compromised by depleted concentrations
of dissolved oxygen. Telemetry studies in reservoirs have shown that water masses at acceptable
SCrai"r.eS but wth dissolved oxygen values less than about 2 mg/L will be actively avoided (Coutant
1985). This response, coupled with temperature selection, produces a summer habitat "squeeze" in which
surface warming and deep-water deoxygenation by microbial respiration shrink the volume of suitable
habitat, often to relatively tiny "thermal refuges." One can assume from the evidence gathered in
Ireshwater reservoirs that striped bass occupying the central basin of the Chesapeake and, in particular
the cool water mass near the bay bridge in summer will be subjected to such a habitat "squeeze-
Avoidance of unsuitably warm water at the surface (or horizontally, both laterally and along the
longitudinal axis of the bay) and unsuitably low dissolved oxygen concentrations in the deeper water
shrinks the habitable water volume.
Oxygen depletion is a major feature resulting from water pollution that regulatory agencies seek to
control. Microbial activity, largely in the sediment, reduces dissolved oxygen in the overlying water
mass by decomposmg (oxidizing) organic wastes and the accumulated remains of phytoplankton
Phytoplankton in the water is stimulated to grow in large numbers by discharge and runoff of nutrients'
Although water temperatures may not have changed markedly in recent decades, the degree of
deep-water deoxygenation certainly has, both in lakes and reservoirs undergoing eutrophication and in
estuaries (e.g., Officer et al. 1984; Price et al. 1985). The central basin of the Chesapeake Bay
experiences some summer oxygen reduction naturally (Newcombe and Home 1938- Taft et al 1980)
However trends that suggest increasingly depleted oxygen resources, mostly in summer, have aroused
considerable concern among scientists and water quality regulators alike (Heinle et al. 1982; EPA 1983-
Officer etal. 1984; Price etal. 1985; Seligeretal. 1985).
-------
924QQ 918T 908
848E
19
STATION
818P
813D 804C
ORNL-DWG 87-1309
744B 724R 707O 657W
39-20- 39=00' 38-40- 38=20- 38°00" 37'40" 37°:>0- 37>00' N
924QQ 918T 908 848E
914S I904N 850DI 834G I 813D 804C 744B 724R 707O 657W
100 —
39°20' 39°00' 38°40'
38°20- 38°00'
LATITUDE
37°40" 37°20" 37°00' N
i
Fig. 8. Contrasting summer water temperature conditions along the longitudinal axis of the Chesapeake
Bay (after Stroup and Lynn 1963). In a cool year (A) the 25°C isotherm does not reach the sill at
nautical mile 45; in a warm year (B) temperatures there exceed 27°C. Strong density stratification seems
to produce both especially high temperatures at the sill and cool temperatures in the residual pocket.
-------
20
It is clear from the analyses by Officer et al. (1984) and Seliger et al. (1985) that two of the areas
where dissolved oxygen in summer has been degraded most severely between 1950 and the present lie
(1) in the thermal refuge" near Baltimore and the bay bridge and (2) in the reach near the mouth of
the Potomac River upstream of the sill (Fig. 9). Historically, the reach just upstream of the bay bridge
seems to have maintained high dissolved oxygen values in spite of oxygen depletion elsewhere, although
the data are sparse (Hires et al. 1963) (Fig. 10). Heinle et al. (1982) included the refuge area in the
zone called "heavily enriched" with nutrients, and the sill area in the zone where oxygen has shown
marked change. Much of the deep-water zone between these two areas has also shown expansion of
both the bottom area and the water column thickness affected by low dissolved oxygen.
Shrinking Habitat for Striped Bass Due to Temperature-Oxygen Squeeze
Progressive restriction of habitat for subadult and adult striped bass in Chesapeake Bay by the combined
effects of high temperature and low dissolved oxygen can be seen over the decade and a half (1965-80}
for which most data were filed on the EPA Chesapeake Bay Program computerized data set when we
conducted these analyses. For our analysis we illustrated the suitability of habitat during Julv on
schematic water columns for the standard EPA bay zones (these drawings are too numerous to be
reproduced here) The cool thermal refuge is generally represented by data from zone CB-3 in which
most data were taken from the deep channel area. Zone CB-4 generally represents the upper part of
the central basin, and CB-5 the lower part terminating about at the sill.
Although the data are sparse and discontinuous, the pattern for zone CB-3 shows suitable habitat
through a large segment of the water column. Habitat limitation is mostly by high temperature at the
surface. In zone CB-4, however, a pronounced squeeze is noticeable in most years, intensifying with
tuneover the years examined. In CB-5, there are so few data from deep water that a pattern cannot be
A dynamic picture of the generally concurrent seasonal warming and deoxygenation processes as thev
appear to us to generate a habitat squeeze for large striped bass has been outlined for the Chesapeake
Bay by Schubel and Pritchard (1986). The exact pattern will vary from year to year as numerous
climatic and other environmental factors (mentioned in the temperature section) vary.
The onset of deoxygenation in the lower layers of the bay is ascribed by Schubel and Pritchard (1986) to
(1) a sharp increase in stratification following the spring freshet, (2) a change in the thermal structure
from near vertical homogeneity to a condition of warmer surface and cooler depths, which adds to the
density differences due to vertical differences in salinity, and (3) a decrease in the intensity and
frequency of high winds that accompanies the transition from spring to summer.
Timing and duration of high Susquehanna River flow in spring have major impacts on initiation of
oxygen conditions Early freshets (winter) are dissipated in the bay by strong winds, and oxygen
deplehon is delayed until thermal input causes stratification in summer. Late freshets (April and May)
cause strong salinity stratification which, augmented by rising surface temperatures, isolates bottom
waters and speeds the onset of low dissolved oxygen conditions. Intensity of the low-oxygen condition
(i.e. longttudmal extent and vertical thickness of layers with low dissolved oxygen) depends to a
considerable extent on the accumulated freshwater discharge in May through July.
The duration of hypoxia in the upper bay is also affected by the Susquehanna River discharge The end
ot the hypoac period is associated with a weakening of vertical stratification and a downward mixing of
higher-oxygen surface waters in the face of autumn winds and cooling temperatures, a process that
normal y occurs in September but can occur in late August or early October. Citing Goodrich (1985)
Schubel and Pntchard described how the influx of fresh water in this period can strengthen vertical
Stratification in opposrtion to the forces that would otherwise weaken it. Overturn of the water column
is delayed and hypoxic conditions persist until some time in October.
-------
21
ORNL-DWG 87-1657
Fig. 9. Area of Chesapeake Bay bottom affected by low dissolved oxygen levels in the summers of 1950
(Ai) and 1980 (B) (after Officer et al. 1984). Two areas showing marked decrease in summer oxygen
resources are off Baltimore (upper circle on B) and between the Rappahannock and Potomac rivers (lower
circle on B) that correspond to the bay bridge thermal refuge and upstream of the sill, respectively.
-------
STATION
924QQ 918T 908 848E 818P
927SS 922Y 914S 904N 850D 834G 813D 804C
ORNL-DWG 87-1308
744B
120
724R 7070 657W
J I L
1 JULY-3 AUGUST 1949 ,
39°20' 39°00' 38°40'
38°20'
LATITUDE
38°00' 37°40' 37°20' 37°00'N
Fig. 10. Dissolved oxygen concentrations with depth along the longitudinal axis of the Chesapeake Bay
Wm§ * ™*& °* ^ ^^ C°ntent extendin§ to the bottom m the *&** <* the
-------
f
We have translated these processes into influences on striped bass adults and subadults (Fig. 11). In
spring high freshwater flows from the Susquehanna River establish a strong demsity stratification. The
greater the freshwater flow, the more intense is the stratification. Striped bass overwinter in the deep
basin oxygenated by vertical mixing in fall and winter and by a densuy underflow from the coast.
Especially cold, windy winters will probably have the coolest and most well oxygenated deep water.
Vertical stratification is intensified in spring by warm riverine flows (that attract spawning striped bass)
and solar heating of the bay surface. Oxygen depletion begins in the deep basins. By late spring or
early summer, riverine inflows including tributaries exceed 25 C and are avoided by large striped bass
whilib the bay surface is near 25°C. The warmest surface waters lie above the lower main basin Low
dissolved oxygen values occur in progressively shallower depths, and the density return flow is largely
anSc fron?decomposition in the downstream end of the central basin. Stnped bass subadults and
adults begin to be squeezed vertically, and some escape the main basin over the sill. Others move
northward toward the residual cool water.
By a typical midsummer, warm (>25°C) water at the surface has impinged on the bottom at the sill,
closing the upper and middle bay to emigration. Low dissolved oxygen has overlapped warm surface
water in all but the uppermost reach of the basin, excluding large striped bass. Subadults and adults
trapped upstream of the sill crowd in the refuge near the bay bridge, while those downstream of the siU
car? still follow the thermal gradient toward cooler coastal waters. Declining temperatures and
wind-induced destratification in autumn replenish striped bass habitat in the mam basin and tributaries,
and the fish respond by spreading out, particularly southward. As the bay becomes colder than the
coast, some fish continue past the sill, toward the warmer ocean temperatures that are now closer to
preferred.
In this hypothesized sequence of habitat changes, two areas are critical zones for striped bass survival:
the! thermal refuge near the bay bridge and the sill. These areas most warrant special attention in
monitoring and remedial action.
Models of the deoxygenation process (Taft et al. 1980; Officer et al. l^Seliger et al 1985) could be
combined with temperature and circulation models (e.g., Elliot 1976; Goodrich 1985) to more
quantitatively estimate the timing and extent of habitat exclusion. Such models have been developed for
freshwater reservoirs (Brown 1983; Brown et al. 1985). The models could illustrate the annual variability
in habitat suitability and in fish movements and concentrations caused by variable climatic factors In
addition to the generalized features averaged over several weeks, one should also consider the effects ot
the prominent tilting of density dines by winds, and thus shifting of temperature and oxygen regimes
(Carter et al. 1978). The models could also include the weather-related mechanisms of induction and
destruction of density stratification that affect striped bass habitat (Goodrich 1985).
Physiological Effects
The long-term trend of progressively greater deoxygenation in the cool refuge- must increasingly require
subadult and adult striped bass to occupy waters with warmer temperatures and/or lower concentrations
of dissolved oxygen than normal, with resulting physiological stress. Physiological stress of this type in
freshwater reservoirs has led to reduced reproductive capability (Coutant 1987). This reduced capability
took two main forms: (1) reduced percentage of adult females capable of spawning and (2) reduced
survivorship of eggs and larvae after successful spawning. These effects were demonstrated by 6 years
of controlled hatchery spawning of stocks derived from reservoirs with differing water quality. Reduced
survivorship in the early life stages has been characteristic of reproduction in the Chesapeake Bay in
recent years.
-------
24
ORNL-DWG 87-1311
LATE WINTER - EARLY SPRING OCEAN
HIGH FRESHWATER FLOW
COLD ^srS7fi\nrsTT*ATff7c^T/gjrp
FLOWS
COLD, OXYGENATED WATER
SPRING
WINTERING STRIPED BASS
.*. '. " '
OCEAN
HEAT WARMING SURFACE <25°C
ty ^— FLOW
DEOXYGENATION
BEGINNING
gs-Vi
T^&c<^>;#i*$y* >
£J^^^x4^;'
3 ^ ^ LATE^SPRING - EARLY SUMMER OCEAN
WARM^T25"C WJf^NARMM^^
>£>* -^ANOXIC
SQUEEZE ,_ '\^==-x*S' \FLOW-3f
BEGINS ^ ;:•'A?7 - •«' ,>^^/ , ., ,
' , " '*">•. ,^a. '*"'' ,' i , J"' » ' , •,'*,''
s?7t\,^ v! ,/!.,' ;' ' "' Vl ^ '''//'
«"*'it'1]?1'f%''% * '/% f ^ ^ "*
-J- _ . * ^ " X' % \^ Sl' / ' ^ *,
r "•'«""., ^ i ' ; v s , • '
FLOW
.. SOME STRIPED BASS
LEAVE BAY OVER SILLS
-------
25
SUMMER
ORML-DWG 87-1310
OCEAN
WARM
HEAT >25»C
FLOW,
*<25°C
LOW OXYGEN
SMALL TO "
NON-EXISTEN
ZONE OF <25 C
AND >2 mg/L OXYGEN " „< vV~*
- "-. - ,' NO STRIPED BASS
,\- \ „"•-•• ; HABITAT IN CENTRAL BASIN
I i, - . .- { >25;<2mg/LO2)
^<
"\:,^j ~ .. ^'^
~\,- ? -•-
EGRESS BY STRIPED BASS
BLOCKED BY TEMPERATURES
>25°C.VIRGINIA FISH CAN
FALL
OCEAN
STRiPEb BASS SPREAD
SOUTHWARD IN COOLED AND
REOXYGENATED BAY (INCREASING
ATTRACTION TO WARMER
COASTAL WATER)
«"«•
6
CRITICAL HABITAT ZONES
Fig. 11. (continued).
-------
26
= BE
S
(speculated to be from the York James £ H,T • mJL984Jtnd ^mxgrahon of a different stock
Other Species
-
herrings" in the bay, displayed upger afoidante ^n thl SS T ? *? "^
important for other species as weU.' important for striped bass are likely to be
Remedial Action
s „, «
could be b&W ,o
years
rOUtl! of
-------
ORNL-DWQ 87-9516
Cycle of Reproductive Impairment Due to Summer Habitat Limitations
Low Spawning
(R, H)
Poor Egg Fertilization
(R,H)
Stressed Subadults and Adults
Crowding (.25C, .2 mg/L oxygen)
Disease
Overharvest
Energetic Inefficiency
Poor Gonad Maturation
Poor Hatch
(R, H, A)
Evidence Key:
R reservoirs
H hatchery
C Chesapeake Bay
A Albermarle Sound
> \
"i_-;| Normal Juvenile Survival?
' ~ ' (24-26C preferred)
(R)
Poor Larval Survival?
(C?, A?)
Poor Juvenile Index
(C,A)
Fig. 12. Hypothesized cycle of reproductive impairment of striped bass due to summer temperature and
dissolved oxygen habitat limitations.
-------
28
Citizen Report, Spring 1987) A shnrf SnoTT f (HydroQual, Inc., as reported in Chesapeake
HI. Albemarle Sound
Striped Bass in Albemarle Sound-Roanoke River
at the
":r^^^^^
spo« Gsl,emen (M* and Guier % and
recovered m coastal ™tel, The nigra^ co,stal stocks a. ' ""
-------
ORNL-DWG87-1389
WELDON *
(RIVER MILE 130)
HALIFAX •
(RIVER MILE 120)
EGG SAMPLING
STATION
(RIVER MILE 105)
WILLIAMSTON _
(RIVER MILE 375)
OREGON
INLET
NORTH CAROLINA
SHOWING LOCATION
ALBEMAHLt Suun'D
OF
Fig. 13. Map of Albemarle Sound and its major tributaries.
-------
30
Once hatched, larval striped bass
found abnormally large numbers ™ aui-vivmg larvae with emnrv where
in ^othesized avoidance of warm
thejeastern sound is supported by resource maps
S°Und m March-May and October-December, bu
-------
31
It is SUSpected that striped bass vacating * —
an4 cooler zones (Fig. 14). The deepesparts of
Pleasant Grove and River Neck. S
tagging studies suggest not. Resource maps
Rrfer Neck in July-October and the deeper
32Ybridge year-round. ArmuaUepor s
Hassler (summarized in Hassler et al ^
Carolina Division of Marine Fisheries) show the genend
mouth of the Roanoke
historically occupying the deeper water off
between Pleasant Grove and the Highway
y 2- to 4-lb striped bass by W. W.
data submitted to the North
June-September to be the
<* ^ ^ 1985
^ western found (although stiU above
els dropped
The suspected historic refuge of relatively
increasingly less suitable by ^*
than it was formerly (Mulhs and Guier 1981
nutrient levels in the Chowan River
fertilizer plant near Tunis (that
5
are
communication). This trend is due to high
^ ^ ^^ from a
^ began appearing in the Chowan
ofpOor striped bass reproduction. Elevated
adecompose i deeper reaches, where
s
restricted by salinity stratification.
EvidMc. d- stressW
comes from evaluations of bony
o &*> Betted in 1980 showed many take
otolith5' to oldeiTlsl1 ta partic"lar'
an increased occurrence of false annuh.
Reduced reproductive competence may be the
reside through the summer m J^« .T
mortalities, or deteriorating ^ ^
reduction in egg viability recorded in detail for the
they may still occur). The
spawners since the mid
eutrophic Cherokee
reinforces the ^ of
Reproductive impairment we have proposed (Fig. 12).
of subadu,, and a«
| summer
and receiving and retaining effluent materials
maximum
developing eggs (as suggested by Guier and Mullis 1982).
The impact of a reduction in egg viability could
in the Roanoke River ^^^^^
first symptoms reported (Hassler et al. 1981 ,^ Hode 1 and
quantities ol :eggs by a normal Dumber
viability) (Hassler et al. 1981)
production of normal
^ ^ rf ^
but ander stressed conditions.
female ^ though
-------
ROANOKE RIVER
EDENTON, HWY
PLEASANT 32
GROVE BRIDGE RIVER NECK
ORNL-DWG 87-1388
ROANOKEAND
CROAT AN SOUNDS
EFFLUENTS^ =
DISCHARGING
INTO RESTRICTED
HABITATS?
J-OWO
SSS^SS'NCREASINGLY
^P!^B^?! - - HAL°CL,Ng
STRIPED BASS
FORCED TO OCCUPY > 25° r
OREGON INLET
to
-------
! 33
population Mullis and Guier (1981) reported an increase in the average size of striped bass caught by
Semite' Sound sport fishermen from 1977 to 1980, attributed to fewer smaller fish bemg recnuted to
the population.
With increased population pressure from reduced habitat size for subadults sod adults in the western
"reL^more fish could be expected to remain in the previously less suitable eastern zone. These fish
it^eSsqueezed by low oxygen to the marginal temperature conditions there Those >***£?
mc/st able to tolerate this shift would be the younger subadults There has m fact bee, ^jbfl M«
distribution of the "nursery area" to the east in recent years (Hodel and Baklnge 1985). Mulhs and
£Scr0981) reported a shift in both fishing effort and harvest to more eastern portions of the
Sbemarie Sound'area. Also, the catch has been dominated by younger fish (1+ and 2+ ages contributog
an average of 69% of the annual sport harvest). The necessity for occupymg water at temperatures
SoJTSLd for growth would explain the numerous false annuli reported by Humphreys and Kornegay
(1985).
BJcause both temperatures and estuary mixing will vary from year to year (low mixing creating
oStions for enhanced deoxygenation), there will undoubtedly be considerabb mterannud ^bihty ni
habitat space available for subadult and adult striped bass. This variability wdl be reflected ui the
v£be effects on egg viability in the Roanoke River the following springs. Egg viabihly has ; been
shown to vary amonfyears (Kornegay and Mullis 1984) although there has been no attempt to test
statistical correlations with climatic conditions.
If 'the population problems with striped bass in Albemarle Sound are due to a
squeeze abated by increasing deoxygenation and possible toxicants m the refuges, the, , i J»
that this would be the only species affected. Many estuarine and freshwater species have temperature
eleTin the same range as those of subadult and adult striped bass. They could be expected to
Som "he same shrinking habitat. On the other hand, some other species prefer much warmer
and they would likely be less affected. In fact, all species harvested from Albemarle
exephe waJ-water largemouth bass and white catfish were declining in 1980 (Mulhs and G^x
) Stocks of the anadromous alosid stocks of the Atlantic coast have been in decline over the same
period as the general decline in striped bass stocks (Richkus and DiNardo 1984).
In summary, current information suggests that a critical zone of especially cool and °x^enated
necessary in summer for maintaining a healthy population of striped bass in the A bemar e Sound ^
That zone appears to be a reach of deeper water in the western sound, now still poorly defined. It is
beSmTng mcreasingly eutrophic, and its suitability as the critical summer habitat for striped bass (as
deS by thermal preferences) has been reduced because of progressively greater deoxygenation during
the period of striped bass decline. The restricted zone of suitable habitat m summer may also be the
site of heightened toxicant exposures.
-------
34
CONCLUSIONS
What guidance has this study provided for the general problem of prioritizing pollution monitoring and
control in estuaries? Our evaluation of habitat space for striped bass in Chesapeake Bay and Albemarle
bound as defined by temperature and dissolved oxygen concentration might be viewed as simply a
parochial effort with the environmental biology of one fish species that happens to interest the authors.
First, the notion that critical zones in an estuary have a predominant influence on the "health" of the
system seems supported, if not confirmed. These are not necessarily the places with greatest effluent
discharge (as water quality engineers might suspect) or the places where organisms spawn (as biologists
usually proffer). ^
The next lesson is that the zones will be recognized by interaction among spheres of investigation that
are all too often separated. The health of an estuary is displayed in many ways, including declines in
fishery productivity, changes in distribution patterns of important aquatic organisms, algal blooms
hypoxia and anoxia, numbers and kinds of pollutant discharges, and effluent toxicity. Specialization has'
led to creation of discrete disciplines that follow each of these topics with little reference to others
The relevance of other disciplines such as hydrography and sedimentary geology goes unexplored The
result is perpetuation of mystery rather than elucidation. Yet understanding the suitability of an estuary
for continued population success of one representative fish species is shown here to depend on a
blending of data gathered by all of the disciplines-water quality (temperature, oxygen), hydrography
(seasonal water flow), sedimentary geology (coastal sediment import and sill development), fish physiology
(temperature preferences), fisheries biology (seasonal behavior of the fish in the field) and so forth It
is not sufficient for pollution control agencies to concentrate on the traditional physical and chemical
tools of the water quality trade.
Third, water quality measurements can be used to define the changing extent of suitable habitat in an
estuary, not simply to show values on a tolerance scale. The volume of water having suitable qualities
and its spatial and temporal distribution (and the reasons for changes in volume) constitute especially
important information for resource management.
Fourth, many old data sets can be very useful for establishing patterns when there is a hypothesis
against which to compare them. Elaborate computerized data management systems may not be the most
useful for recognizing habitat trends, especially when their organization is not, or only poorly
consistent with natural estuary subdivisions.
Fifth, prioritization implies having a management objective. "Cleaning up the bay is not a sufficiently
clear objective to guide meaningful monitoring or control efforts when financial and human resources to
accomplish it are necessarily limited. Priority areas can be defined when the analysis becomes specific
enough to specify the requirements of the most valued components of the estuarine system, usually the
Irving resources. *
Sixth, the importance of temperature or, more correctly, the seasonal thermal structure of an estuary for
controlling important biological responses is emphasized as a feature worthy of general attention The
seasonal distribution of organisms in relation to thermal structure appears to set the background against
which maintenance of other habitat requirements (e.g., needs for dissolved oxygen, toxicity tolerance)
-------
i 35 ;
i
Last,' this analysis has tentatively identified critical zones in two major estuaries and offers promise that
m the critical zones in Chesapeake Bay and Albemarle Sound may be further refined for benefit of all
cool^ater Secies and (2) a similar evaluation in other estuaries using the temperature and oxygen
requirements of indigenous species and broad knowledge of the estuary's geography and hydrography may
be similarly productive.
-------
36
REFERENCES
Boreman J and H. M. Austin. 1985. Production and harvest of anadromous striped bass stocks along
the Atlantic coast. Trans. Am. Fish. Soc. 114:3-7. &
197lo«n pM. data rep0rt' TemPerature> ^™*y, dissolved oxygen.
1971-1980. Data Report No. 19. Virginia Institute of Marine Science, Gloucester Point, Virginia 38
pp + appendices. &
+a endes
Water data rep°rt TemP^ure, salinity, dissolved oxygen.
^^ °f ^^ Sden°e' Gloucester Pomt> Virginia 40
Brooks, T. J. 1983c. Mattaponi River slack water data report. Temperature, salinity, and dissolved
oxygen. £70-1980. Data Report No. 21. Virginia Institute of Marine Science, Sou^Ler Point,
Virginia. 36 pp + appendices. '
Brooks, T J and C. S Fang 1983. James River slack water data report. Temperature, salinity, and
dissolved oxygen 1971-1980. Data Report No. 12, Virginia Institute of Marine Science, Gloucelr
roint, Virginia. 38 pp + appendices.
Brown, R T 3383 Modeling the effects of aquatic weed loads on Cherokee Reservoir dissolved oxygen
Rept. No. WR28-1-12-102, Tennessee Valley Authority, Knoxville, Tennessee.
Brown, R T., G. E. Mauser, M. K. McKinnon, and M. C. Shiao. 1985. Two dimensional water quality
modeling of Fort Loudoun Reservoir. Rept. No. WR28-1-10-100, Tennessee Valley Authority
JfcnoxviUe, Tennessee. •"
Carter, H H., R. J Regier, E. W. Schiemer, and J. A. Michael. 1978. The summertime vertical
SS2S1 ^ ^f M "STn ^ ?1V6rt CMS GeneratinS Stati°": A physical interpretation.
A? t ?nc ' ' °' 1&'^ ChesaPeake Bay In^itute, The Johns Hopkins University, Baltimore
Maryland. 95 pp + appendix. '
Chapman, R. W 1987. Changes in the population structure of male striped bass, Morone saxatilis
spawning in the three areas of the Chesapeake Bay from 1984 to 1986. Fish. Bull. U.S. 85:167-170 '
rih,5" Mf J/'V^De° A?e' 3nd C> C' COUtanL 1985' Influences of water quality on
distribution of striped bass in a Tennessee River impoundment. Trans. Am. Fish. Soc. 114:67-76.
dissolved
Coutant,C.C. 1986. Thermal niches of striped bass. Sci. Am. 254:98-104.
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I • 37 :
Coutknt, C. C. 1987. Poor reproductive success of striped bass from a reservoir with reduced summer
! habitat. Trans. Am. Fish. Soc. 116:154-160.
Couiant, C. C., and D. S. Carroll. 1980. Temperatures occupied by ten ultrasonic-tagged striped bass in
; freshwater lakes. Trans. Am. Fish. Soc. 109:195-202.
Cronin W B 1971 Volumetric, areal, and tidal statistics of the Chesapeake Bay estuary and its
'; tributaries. Spec. Rept. 20, Ref. No. 71-2, Chesapeake Bay Institute, The Johns Hopkins University,
Baltimore, Maryland. 135 pp.
Elliot A J 1976 A numerical model of the internal circulation in a branching tidal estuary. Spec.
Rept. 54, Ref. No. 76-7, Chesapeake Bay Institute, The Johns Hopkins University, Baltimore,
Maryland. 85 pp + appendices.
Environmental Protection Agency (EPA). 1983. Chesapeake Bay: A profile of environmental change.
EPA Region 5, Philadelphia, Pennsylvania.
Fast A W 1974. Restoration of eutrophic lakes by artificial hypolimnetic oxygenation. pp 21-34 in
;' Proc. Human-Accelerated Eutrophication of Fresh-Water Lakes. Brooklyn Botanical Garden, Ossming,
New York.
Fast, A. W., W. J. Overholtz, and R. A. Tubb. 1975. Hypolimnetic oxygenation using liquid oxygen.
' Water Resour. Res. 11:294-299.
Goodrich, D. M. 1985. On stratification and wind-induced mixing in the Chesapeake Bay. Ph.D. Diss.,
i Marine Sciences Research Center, State University of New York at Stony Brook. 134 pp.
Goodyear, C. P. 1978. Management problems of migratory stocks of striped bass, pp 75-84 in
H. Clepper (ed.), Marine Recreational Fisheries 3. Sport Fishing Institute, Washington, D. C.
Grant, G. C. 1974. The age composition of striped bass catches in Virginia waters, 1967-1971, and a
description of the fishery. Fish. Bull. 72:193-199.
Grant G. C., V. C. Burrell, Jr., C. E. Richards, and E. B. Joseph. 1970. Preliminary results from striped
bass tagging in Virginia, 1968-1969. Proc. Annu. Conf. Southeast Assoc. Game Fish Comm.
23:558-570.
Guier, C. R., and A. W. Mullis. 1982. Investigations of egg and larval mortalities in Roanoke River
striped bass. Final Report on Federal Aid in Fish Restoration Project F-22, Study VII. N.C.
i Wildlife Resources Commission, Raleigh, North Carolina. 38 pp.
Hassler W. W., N. L. Hill, and J. T. Brown. 1981. The status and abundance of striped bass hi the
Roanoke River and Albemarle Sound, North Carolina, 1956-1980. Spec. Sci. Rep. No. 38, N.C.
Department of Natural Resources and Community Development, Division of Marine Fisheries,
i Moorehead, North Carolina. 156 pp.
Heinle, D. R., and six coauthors. 1982. Historical review of water quality and climatic data from
I Chesapeake Bay with emphasis on effects of enrichment. Rept. No. EPA 600/3-82-083,
Environmental Protection Agency, Chesapeake Bay Program, Annapolis, Maryland. 238 pp.
-------
38
Hires, R L, E. D Stroup and R. C. Seitz. 1963. Atlas of the distribution of dissolved oxygen and PH
" Ref'63-4' Ch- Bay institute, The Johns Hop^Univerlty,
to the
°f the Use of bony structures for aging
bass.^lone saxatilis). Federal Aid in Fish Restoratio!
-22, N.C. Wildhfe Resources Commission, Raleigh, North Carolina. 16 pp.
HydroQual, Inc., 1 Lethbridge Plaza, Mahwah, New Jersey. Unpublished.
Bay stock of striped
Kornegay, J W. and AW. MuUis. 1984. Investigations into the decline in egg viability and juvenile
survival of Afoemarle Sound striped bass (Morone ^riii.). Final Report on FedeTal^Id Slfsh
Restoration Project F-22. N.C. Wildlife Resources Commission, Raleigh, North Carolina 13 pp
Kornegay, P. 1985. Stripers at the crossroads. Wildl. N.C. 49(4): 11-14.
' H ''
H> M" AUStin" 1979' Movement of 1970 year class striped bass
' ^ England PrOC" ^^ C°nf " Fish
Kynard, B and J. P Warner. 1987. Spring and summer movements of subadult striped bass Moron
.saxatilis, in the Connecticut River. Fish. Bull. U.S. 85:143-147.
' Natural
-
Education Series No. 61. 28 pp.
Massman, W H 1962 Water temperatures, salinities, and fishes collected during trawl surveys of
Chesapeake Bay and York and Pamunkey Rivers, 1956-1959. Spec. Sci. Rept No. 27, vSnia
Institute of Marine Science, Gloucester Point, Virginia. 3 pp + appendices.
«*
Mullis, A.W., N.C. Wildlife Resources Commission, personal communication to C. C. Coutant, 1985.
emso H ,, Determination of Albemarie Sound sport fishery harvest with
emphasis on striped bass harvest rates and growth. Final Report on Federal Aid in Fish
Restoration Project F-22, Study V. N.C. Wildlife Resources Commission, Raleigh, North Ca'oUna
P°°r
°f the Ch^apeake Bay. Science
-------
39
Offiier, C. B., R. B. Biggs, J. L. Taft, L. E. Cronin, M. A. Tyler, and W. R. Boyaton. 1984. Chesapeake
•' Bay anoxia: origin, development, and significance. Science 223:22-27.
Price K S and seven coauthors. 1985. Nutrient enrichment of Chesapeake Bay and its impact on the
: habitat of striped bass: a speculative hypothesis. Trans Am. Fish. Soc. 114:97-106.
I
Reutter J M., and C. E. Henderdorf. 1974. Laboratory estimates of the seasonal final preferdum of
; some Lake Erie fish. Proc. 17th Conf. Great Lakes Res. 1974:59-67.
Richkus W A and G. DiNardo. 1984. Current status and biological characteristics of the anadromous
losid stocks of the eastern United States: American shad, hickory shad alewife, and blueback
! herring. Atlantic States Marine Fisheries Commission, Fisheries Management Rept. 4,
Washington, D.C.
Rulifson R A 1984. Food and feeding of larval striped bass in western Albemarle Sound North
Carolina. N.C. Department of Natural Resources and Community Development, Division of Marine
Fisheries. Completion Rept. for Contract No. C-1366. 48 pp.
Scnubel, J. R., and D. W. Pritchard. 1986. Responses of upper Chesapeake Bay to variations in
discharge of the Susquehanna River. Estuaries 9:236-249.
Seitz. R C 1971 Temperature and salinity distributions in vertical sections along the longitudinal axis
^ and across the entrance of the Chesapeake Bay (April 1968 - March 1969). Graphical Summary
No. 5, Ref. 71-7. Chesapeake Bay Institute, The Johns Hopkins University, Baltimore, Maryland.
99 pp.
Seiiger, H. H., J. A. Boggs, and W. H. Biggley. 1985. Catastrophic anoxia in the Chesapeake Bay in
1 1984. Science 228:70-73.
Smith, C. L. (in press). Fisheries Research in the Hudson River. State University of New York Press,
! Albany.
Stroup ED and R. J. Lynn. 1963. Atlas of salinity and temperature distributions in Chesapeake Bay
?952-1961 and seasonalaverages 1949-1961. Graphical Summary Rept. No. 2, Ref. 63-3. Chesapeake
Bay Institute, The Johns Hopkins University, Baltimore, Maryland. 409 pp.
Taft, J. L., W. R. Taylor, E. O Hartwig, and R. Loftus. 1980. Seasonal oxygen depletion in Chesapeake
' Bay.' Estuaries 3:242-247.
Virginia Power. 1986. Environmental study of Lake Anna and the lower North Anna River. 316(a).
Demonstration to the Virginia Water Control Board, Richmond Virginia.
Vladykov, V. D., and D. H. Wallace. 1938. Is the striped bass (Roccus hneatus) of Chesapeake Bay a
migratory fish? Trans. Am. Fish. Soc. 67:67-86.
Vladvkov V D and D. H. Wallace. 1952. Studies of the striped bass, Roccus. saxatilis (Walbaum) with
special'reference to the Chesapeake Bay region during 1936-1938. Bull. Bingham Oceanogr. Collect.
14:132-177.
Wells, L. 1968. Seasonal depth distribution of fish in southeastern Lake Michigan. U.S. Fish. Wild.
Serv. Fish. Bull. 67:1-15.
*U.S. Government Printing Office : 1988 - 516-002/80235
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