Page 16

when combined with adequate chemical analyses of environ-
mental and tissue samples.

The appearance of new reports of sublethal effects of
contaminants on marine animals has been aptly described (Lewis
1980) as of “avalanche” proportions. In a thought-provoking
discussion of options in environmental management and the
deployment of future research efforts concerned with popula-
tion effects of pollution, he made the point that “The more subtle
threats of chronic pollution well away from the hot-spots, and
which because of their subtlety have always been seen as
potentially the most dangerous, do not appear to have developed
and produced effects on the scale that was feared a decade ago.”
Lewis then asked difficult questions: “If after all the recent,
intensive effort there is still difficulty in finding chronic effects
upon communities does this not suggest that such effects are
negligible? That while the initial concern over chronic effects
was justified is it not now time to acknowledge that it is only
acute pollution that matters?” Most of us in pollution research
would detect a faint odor of heresy in this superficially logical
line of thought, probably rejecting it out-of-hand, since it tends
to overestimate human ability to sort out effects of natural versus
man-induced population changes, and it tends toward too easy
acceptance of the significance of acute pollution events in
reducing overall abundance of marine populations. However,
we would have to admit that our arguments would not have a
strong base in adequately demonstrated population impacts. We
might also admit that, just as with certain terrestrial species, a
point may be reached where contaminants in the marine
environment could reach a level, or operate over sufficient time,
to greatly affect population abundance.

Assessment of quantitative effects of pollution and other
human-induced environmental perturbations on fish popula-
tions depends on an understanding of the stock-recruitment
relationships of fish populations of concern, and on knowledge
of the density-dependent and density-independent factors influ-
encing those relationships (Leggett 1977). Of particular concern
is mortality imposed by toxic levels of pollutants on eggs, larvae,
and juveniles of economically important fish species. However,
models predicting effects of human intrusions (other than
fishing) must be used conservatively, especially when impacts on
early life stages are included. Leggett (1977) has voiced the
concern with precision: “the potential for error in numerical
predictions of the effect of proposed levels of increased mortality
on pre-recruit stages is large, while the biologically acceptable
range of error is small,” and further that “Until a better
understanding is achieved of the interacting roles of density-
dependent and density-independent factors in regulating popu-
lation size and stability, and until a much better data base is
available for the majority of the stocks subject to mortality from
industrial activity, precise numerical predictions of the impact of
this incremental mortality on adult stocks should be interpreted
with great caution.”

By assuming the correctness of the generally held principle
that recruitment variability is a consequence of events that occur
in egg, larval, and postlarval stages, it is logical to focus pollution
studies more directly on reproductive success of populations at
tisk. This has been done in a number of studies, but one

disturbing conclusion that can be reached after examining some
of the accumulated literature is that investigators rarely if
ever carry their findings to the point of actually estimating
quantitative effects on fish populations and species. Let’s
consider a few examples. Von Westernhagen et al. (1981), von
Westernhagen, Sperling, et al. (1987), and von Westernhagen,
Dethlefsen, et al. (1987) examined contaminant content of
ovaries of Baltic flounder, and established a threshold level of
0.12 ppm PCB beyond which reproductive impairment would
occur. These authors found that 8.5 percent of the sample
exceeded that level (with a range of 0.05-3.17 ppm), and they
reported that viable hatch was lower than 15 percent if gonad
PCB levels exceeded 0.25 ppm. They did not take the final
quantitative steps. The Baltic flounder catches are known; the
extent of PCB contamination in the Baltic is known - why not
make a rough estimate from these data of the possible impact of
PCB contamination on recruitment of Baltic flounder? As
another example, Cross and Hose (1988) found reproductive
impairment and high levels of ovarian DDT and PCB in white
croaker froma contaminated site near Los Angeles. Again, white
croaker catch statistics are available, and environmental levels of
chlorinated hydrocarbons on the California coast have been
examined extensively - why not take another step, armed with
the data, and provide a rough estimate of possible impact on
recruitment?

Only once, to my knowledge, has even the penultimate step
~- of estimating effects of pollution on recruitment -- been taken.
This was the report by von Westernhagen et al. (1988) on
developmental defects in pelagic fish embryos from the western
Baltic. Plankton net catches of cod, plaice, and flounder eggs and
larvae were examined for mortality and abnormalities. Prevalences
of defective embryos and abnormal larvae in various locations in
the western Baltic were determined, and effects on survival of
larvae of two year classes (1983 and 1984) were estimated.
Decreases (18-44 percent) were considered too small in terms of
biological significance to cause a detectable impact on recruit-
ment, although the authors pointed out that even a small impact
on larval production could, in the case of overexploited Baltic
stocks, lead eventually to reduced recruitment. It is puzzling,
considering the availability of excellent fishery statistics and
environmental information for the Baltic, some of it extending
back for more than a century, why the ultimate step - of
estimating total possible population effects of existing pollution
levels - was not taken, since it is only at this stage that pollution
information would become meaningful to resource managers.

Part of the problem may be that professionals interested in
problems created by coastal /estuarine pollution do not commu-
nicate effectively with population dynamics specialists, so full
exploitation of available data does not happen. Only rarely, such
as in the Mid-Atlantic striped bass program discussed earlier,
when simulations based on good resource and environmental
data sets are attempted, is some measure of integration achieved.
The assessment scientist is often. loath to use the minimalist
approach necessary with the environmental scientist's data.

To do an effective job of quantifying pollution effects on
fish stocks, a large interdisciplinary research and monitoring
program is required. The principal ingredients are shown in


Page 10

lating well with the pollution gradient. Analysis of PCBs in eggs
did not indicate a correlation between contaminant levels and
the cytogenetic data. A previous preliminary study by Longwell
etal. (1983) had also disclosed high percentages of chromosomal
anomalies in winter flounder from the western end of Long
Island Sound.

Another pollution gradient, this one a composite of stations
in Narragansett Bay, Rhode Island, and Buzzards Bay, Massa-
chusetts, was exploited in a study of effects of inherited
contaminants on eggs and larvae of resident winter flounder
(Black et al. 1988). Progeny from flounders captured in
Buzzards Bay, an area noted for PCB contamination, contained
significantly higher levels of PCBs (averaging 39.6 ug/g dry
weight), and hatched larvae were smaller in length and weight
than progeny from reference site adults. No information was
given on percent viable hatch, but as larvae grew to metamorpho-
sis the length/weight differences disappeared; the compensa-
tory growth of larvae from contaminated parents but grown in
clean water was attributed by the authors to biotransformation
and detoxification of contaminants via mixed-function oxidase
systems of the embryos and larvae.

Petroleum contamination can affect survival of winter
flounder larvae. Experimental exposures of mature female
winter flounder and their developing eggs and larvae to low
concentrations of No. 2 fuel oil (Kuhnhold et al. 1978) produced
results that would be useful in population analyses. Exposure to
100 ppb throughout gonad maturation of parents, and during
fertilization and embryogenesis, resulted in a 3- to 9-day delay in
hatching, a 19-percent reduction in viable hatch, and a four-
percent prevalence of spinal defects in hatched larvae. Larvae
produced from gametes contaminated during parental gonadal
maturation, but then reared in clean water, had a mortality
coefficient of 0.130, considered by the authors to be much higher
than the calculated mortality coefficient for untreated labora-
tory-reared winter flounder larvae of 0.036-0.059 (Laurence
1975, 1977). Growth of larvae hatched from gametes from oil-
exposed spawners was also slower (growth coefficient of 0.220-
0.284 compared to the controls of 0.334). [It might be noted that
the topic of acute and chronic oil pollution in the sea was
examined in detail from a fishery perspective by McIntyre
(1982). He concluded a detailed review by stating that “no long-
term adverse effects on fish stocks can be attributed to oil, but
local impacts can be extremely damaging in the short term....”]

The NMFS’s Northeast Fisheries Science Center, and
especially its Milford (Connecticut) Laboratory, is carrying on an
extensive interdisciplinary examination of the effects of pollu-
tion on winter flounder populations of the Northeast. A recent
3-year (1986-88) study of winter flounder from selected stations
in Long Island Sound and Boston Harbor (Nelson et al. 1991)
disclosed a low-percent viable hatch, small larvae, and delayed
embryogenesis in offspring from fish taken at the most polluted
sites (New Haven Harbor and Boston Harbor). Such findings
indicate low larval survival and reproductive impairment at the
most severely degraded sites. A related study found greatest
prevalences of chromosomal abnormalities and mitotic disrup-
tions in developing embryos from spawning adults taken at the
most polluted sites (Perry et al. 1991).

Attempts to quantify total pollution impacts on flounder
populations of Long Island Sound - the ultimate objective of this
intensive NMFS study -- must employ complex multivariate
analytical methods. Variables of greatest significance are extent
of reproductive suppression in spawning females, annual larval
and YOY mortality, areal extent of toxic levels of pollutants, and
annual variations in natural mortality exclusive of that caused
by pollution,

Results from earlier studies with other estuarine-dependent
species have provided additional evidence that high tissue
concentration of chlorinated hydrocarbons in spawning adults
can result in mortalities in developing eggs and larvae. Repro-
ductive failure of a spotted seatrout population in Texas was
attributed to this phenomenon (Butleretal. 1972). The seatrout
population inhabited an estuary that was contaminated heavily
with DDT, where DDT concentration in ovaries reached a peak
of 8 ppm prior to spawning, compared to less than 0.5 ppm in
seatrout from other less contaminated estuaries. Spawning
seemed normal, but eggs failed to develop.

Spies et al. (1985) compared the reproductive success of
starry flounders (Platichthys stellatus) from polluted San Fran-
cisco Bay with that of a reference population from an unpolluted
site. Total PCB content of eggs correlated inversely with
embryological success and hatching success -- supporting the
stated hypothesis that chronic contamination of reproductive
tissues by relatively low PCB concentrations (less than 200 ig/
kg) has a pervasive deleterious effect on reproductive success of
starry flounder in San Francisco Bay.

Baltic flounder (P. flesus) with elevated levels of PCBs in
their ovarian tissues had a significant reduction in viable hatch
of larvae (von Westernhagen et al. 1981). A threshold level of
120 ng/g (0.12 ppm) PCB (wet weight) in eggs and ovarian
tissue was considered to be a contamination point above which
reduced survival of developing eggs and larvae of
that species could be expected. Levels of other chlorinated
hydrocarbons or heavy metals could not be correlated with
reductions in viable hatch. In a subsequent study of whiting
(Merlangius merlangus) in the North Sea, von Westernhagen et
al. (1989) selected 0.2 ppm PCB in ovarian tissue as a threshold
above which impaired reproductive success could be expected.

Effects of PCB and DDE on reproductive success of herring
(Clupea harengus membras) in the Baltic Sea were investigated
by Hansen et al. (1985). Findings included: (1) viable hatch
being significantly reduced by ovarian PCB concentrations of
more than 120 ng/g, and by DDE concentrations of more than
18 ng/g (wet weight); (2) a positive correlation between ovarian
residues of PCBs and DDE; (3) a linear relationship between
ovarian residue levels of PCBs and DDE and viable hatch; and
(4) effects of PCBs and DDE on reproductive success probably
being additive. Levels of contaminants that reduced reproduc:
tive success in this study were low; the authors suggested that
other contaminants, not analyzed, may also be involved.

Thus far in this section, effects of pollution on early life
history stages have been emphasized, but effects on adults must
not be ignored. Detailed studies of pollution effects on winter
flounder began decades ago, with one of the first experimental
studies of tissue lesions resulting from exposure to copper (Baker


Page20

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. ABSTRACT

\

"Pollution of estuarine /coastal waters has been viewed as a concomitant of increasing population density and
industrialization of the coastal zone. One primary concern has been possible impacts of present and future contaminant
loading on abundance of resource species. Information accumulated during the past three decades, especially from
experimental studies, indicates a range of lethal and sublethal effects on coastal fish, but has not demonstrated a clear cause-
and-effect relationship with population abundance. What has emerged clearly is the extreme difficulty of separating effects
of one contaminant or group of contaminants from those of overfishing, or from those of a host of other environmental

~ stresses:

By using a case history approach, the literature on three species of East Coast coastal fish - Atlantic menhaden (Brevoortia
tyrannus), striped bass (Morone saxatilus), and winter flounder (Pleuronectes americanus) -- has been examined for
evidence of quantitative effects on populations. General findings with menhaden were that because of extreme variability
in recruitment, detection of reductions in abundance because of pollution would be feasible only in the case of catastrophic
events; @reater. than 50-percent year<lass-reduction).” With striped bass, a dominant role of high fishing mortality was
proposed, possibly augniented ‘by severe’ larval mortality in some estuaries if stressful environmental conditions existed
concurrently with toxic levels of contaminants..In studies of winter flounder, reduced reproductive success as a consequence
of pollution was indicated in several studies, with a range of genetic and cytological abnormalities in developing eggs, and
teratogenic effects in larvae. ‘

Studies of fish in other parts of the world suggest that, for species which are subjected to moderate exploitation or which
are unexploited, decreases in survival rates due to pollution effects would be too small to detect, whereas in overexploited
populations with severely reduced spawning stocks, the added impact of pollution may result in reduced recruitment.
However, studies of long-term trends in such heavily fished areas as the-North Sea have found no consistent decline of
commercial species that could be attributed to deteriorating habitat conditions. ~

2. Significant negative impacts of pollution on commer-
INTRODUCTION cial fish stocks have not been demonstrated, even for

areas suchas the North Sea, where statistical information

This paper is best introduced by, listing a series of hypotheses is teasonably. adequate: (Cole 1975, 1983; Hempel: 1978;
about effects of pollution on fish and shellfish populations ~ Lee 1978; Cushing 1979; McIntyre 1982). Lee, for ex-
hypotheses that have variable data support and may eventually ample, stated “There is no evidence either way as to whether
be proved incorrect. They are as follows: or not contamination of North Sea waters by metals,

pesticide/ residues, etc. has affected the well being of the

1. Habitat destruction in estuaries and contaminant fish stocks.” This pronouncement is an oversimplification;
disposal in the ocean have had localized adverse a more rational viewpoint can be found in other published
effects on resource organisms, but the broad regional reports, especially that of Dethlefsen and Tiews (1985): “at
effects at the species level have not been determined. present it is impossible to define the role of pollution on fish

Lack of any early success in assessing effects of pollution on stocks of the North Sea as a whole. This is largely due to

population abundance may be because “the scale of impact the fact that only drastic changes in marine ecosystems

lemphasis mine] usually is much smaller than the geo- would be detectable and could be interpreted as manmade.
graphical range of the species” (Cross et al. 1985). Normally chronic and sublethal changes are taking place

Two decades ago, Cole (1972) pointed out a critical very slowly and it will be impossible to separate natural
guideline for evaluating conclusions reached about marine fluctuations from anthropogenically caused. Long-term
pollution -- that we must be careful to differentiate large- ” research over decades might be necessary to clearly distin-
scale changes due to pollution from purely local, almost guish between man-made and natural fluctuations espe-
parochial, situations, usually in a few square kilometers of cially in offshore waters.” Cushing (1979) also stated the
estuarine /coastal waters. issue clearly: “The major problem of population/commu-

Cross et al. (1985) provided cogent additional admo- nity monitoring, bearing in mind the non-specific nature of
nitions: “Improvement in our capacity to predict the effects the response to pollutants, is to distinguish pollution
of pollution on fisheries requires an understanding of the induced changes from those due to other causes.”

+ environmental factors that control variability in fish popu-

- lations and the effect of multiple ‘stresses on these stocks | 3. Marine resource populations are subject to large natu-
over their entire geographical range. Increased predictive ral fluctuations whose causes are incompletely under-
capability can be gained most cost-effectively through closer stood. Turning again to the North Sea, where resource and
integration of the disciplines of population dynamics and environmental data are probably better than anywhere else

toxicology.” in the world, Hempel’s 1978 detailed report on recent


Page17

PRINCIPAL REQUIREMENTS FOR ASSESSING
POLLUTION EFFECTS ON FISH POPULATIONS.

Y

ENVIRONMENTAL ASSESSMENTS

Surveys and monitoring of environmental fectors-

physical, chemical, biologieal, natural and man-induced, that

may atfect fish stocks, Sample network must permit mapping
of Intensity variables, geogrephically and seasonally

FISH POPULATION ASSESSMENTS

Data trom the fishery and from resource surveys-
principal species at risk

Analysis: annual year claas and stock assessments

Dynamics: growth, fecundity, survival, recruitment

7

ee

EXPERIMENTAL STUDIES

Levele of pollutants that produce lethal and eublethal
‘effects on growth, reproduction, larval survival and
recruitment in the presence of natural variables
(safinity, temperature, oxygen.ete.)
Examined on a species by species basis

population responses to varying pollution loads

[Fowriaeo wowToRING oF sTOOKS AND ENVIRONMENT |

VERIFICATION ANO MODIFICATION OF MODEL.

Figure 11.

Figure 11. A triumvirate of population assessments, environ-
mental assessments, and experimental studies constitutes the
basic information source for the required modeling effort. Such
a program must be long-term as well as geographically broad.
Until now, only the Mid-Atlantic striped bass program has
approached the level of research commitment required, and
even this major effort must face an annual struggle for adequate
funding, in spite of its considerable importance and high levels
of lobbying for the program.

CONCLUSIONS

More than a decade ago, in a major symposium titled
“Protection of Life in the Sea,” held at the Biologische Anstalt
Helgoland, a series of conclusions was proposed about pollution
effects on fisheries -- conclusions that seem still relevant today:

Pollution effects on fisheries have received some scrutiny in
recent decades, and information is accumulating, but is still
insufficient to be very useful in resource management decisions
~- except as they involve local areas. Evidence exists for localized
effects of pollutant stress on fisheries, but as yet there is little
specific evidence for widespread damage to major fisheries
resource populations resulting from coastal/estuarine
pollution. This may well be because we are unable to separate
clearly the effects of pollutant stress from effects of the many
other forms of environmental stresses to which marine popula-
tions are subject. Other factors, such as shifts in geographic
distribution of fish populations, changes in productive ecosys-
tems, or overfishing, may cause pronounced changes in fisheries
~ changes which could obscure any effects of localized habitat
degradation. It seems, with the evidence presently avail-
able, that factors other than pollution are overriding in
determining fish abundance, but we lack sufficient quan-
titative data to make positive statements about cause and
effect relationships of abundance and pollution.

Principal requirements for assessing the effects of pollution on fish stocks.

It may be, of course, that estuarine/coastal pollution is
exerting some overall influence on certain resource species, but
that this influence may be masked by increased fishing effort, or
by favorable changes in other environmental factors which create
a positive effect on abundance, outweighing any negative effects
of pollutants. Many experimental studies, particularly more
recent ones concerned with long-term exposure of fish and
shellfish to low levels of contaminants, suggest that some long-
term effects on abundance should be felt, but our statistics, our
monitoring, and our population assessments are not yet adequate
to detect them.

Effective long-term monitoring of stocks and environment
must be the basis of any attempt to isolate and identify pollution
effects. A continuous integrated effort in stock assessment,
environmental assessment, and experimental studies will
be required to understand the role of all environmental
stresses -- natural and man-induced -- in determining
abundance of resource populations. However, we do not yet
have the principal pieces of the puzzle in place, so in the absence
of full understanding of the phenomena involved, management
decisions affecting estuarine /coastal pollution must be made on
the basis of “best available scientific information,” just as deci-
sions about allowable resource exploitation are made. In both
types of decision processes, a conservative action provides a lower
risk of damage and loss than does a more extreme action.
Conservatism can be especially significant when decisions are
made that might permit pollution to continue or increase, since
long-term effects of existing levels on abundance of resource
populations are largely undetermined. In addition to advocating
conservatism, we must persist in attempts to quantify the effects
of pollution, and to determine the precise pathways through
which fishery resources are affected (Sindermann 1980).

Freely admitting to a conservative mind-set (and a mild
infatuation with my own prose), there is little about these
conclusions that I would change today -- more than a decade after
their original publication. Research in the intervening years has


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striped bass: recruitment declining below replacement. Trans.
Am. Fish. Soc. 114: 146-151.

Haedrich, R.L; Haedrich, $.0. 1974, A seasonal survey of the
fishes of the Mystic River, a polluted estuary in downtown
Boston, Massachusetts. Estuarine Coastal Mar. Sci. 2: 59-73.

Hall, L.W., Jr; Horseman, L.O.; Zeger, S. 1984. Effects of organic
and inorganic chemical contaminants on fertilization, hatch-
ing success, and prolarval survival of striped bass. Arch.
Environ. Contam. Toxicol. 13: 723-729.

Hall, LW., Jr; Pinkney, A-E.; Herman, R.L; Finger, S.E. 1987.
Survival of striped bass larvae and yearlings in relation to
contaminants and water quality in the upper Chesapeake Bay.
Arch. Environ. Contam. Toxicol. 16: 391-400.

Hall, LW., Jr; Pinkney, A-E; Horseman, L.O,; Finger, SE. 1985.
Mortality of striped bass larvae in relation to contaminants
and water quality conditions in a Chesapeake Bay tributary.
Trans. Am. Fish. Soc. 114: 861-868.

Hansen, P-D.; von Westernhagen, H.; Rosenthal, H. 1985.
Chlorinated hydrocarbons and hatching success in Baltic
herring spring spawners. Mar. Environ. Res. 15: 59-76.

Hempel, G. 1978. North Sea fisheries and fish stocks~a review
of recent changes. Rapp. PV. Reun. Cons. Int. Explor. Mer
173: 145-167.

Hughes, J.B.; Nelson, D.A. Perry, DM, Miller, J.B; Sennefelder,
GR; Periera, JJ. 1986. Reproductive success of the winter
flounder (Pseudopleuronectes americanus) in Long Island
Sound. Int. Counc. Explor. Sea C.M. 1986/E:10; 11 p.

Hunt, E; Linn, J. 1969. Fish kills by pesticides. In: Gillette, J.W.,
ed. Proceedings of the Symposium on the Biological Impact
of Pesticides in the Environment. Corvallis, OR: Oregon State
University; p. 44-59.

Johnson, C.C.; Casillas, E.; Misinato, D.; McCain, B.B.; Myers,
MS; Rhodes, L.D.; Olson, O.P.; Gronlund, W.D. 1988.

Page 19

Effects of toxicant exposure on reproductive success of female
English sole (Parophrys vetulus) from Puget Sound, Washing-
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Johnson, H.E.; Pecor,C. 1969. Cohosalmon mortality and DDT
in Lake Michigan. Trans. N. Am. Wildl. Nat. Resour. Conf.
34: 159-166.

Jones, R. 1982. Population fluctuations and recruitment in
marine populations. Philos. Trans. R. Soc. Lond. B Biol. Sci.
297; 353.368.

Kanciruk, P.; Breck, J.E.; Vaughan, D.S, 1982. Population-level
effects of multiple stresses on fish and shellfish. Oak Ridge
Nat. Lab. Tech. Memo. 8317. Available from: Oak Ridge
National Laboratory, Oak Ridge, TN.

Khan, R.A. 1987. Effects of chronic exposure to petroleum
hydrocarbons on two species of marine fish infected with a
hemoprotozoan, Trypanosoma murmanensis. Can. J. Zool. 65:
2703-2709.

Kinne, O.; Rosenthal, H. 1967. Effects of sulfuric water
pollutants on fertilization, embryonic development and larvae
of the herring, Clupea harengus. Mar. Biol. (Berl.) 1: 65-83.

Kooijman, S.A.LM.; Metz, J.AJ. 1984. On the dynamics of
chemically stressed populations: the deduction of population
consequences from effects on individuals. Ecotoxicol. Environ.
Saf. 8: 254-274.

Kihnhold, W.W,; Everich, D.; Stegeman, J.J; Lake, J; Wolke,
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Lee, A. 1978. Effects of man on the fish resources of the North
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Leslie, PH. 1948. Some further notes on the use of matrices in
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466.


Page14

herring, striped bass, and whiting in the North Sea) can result
in low (less than 50 percent) viable hatch of eggs, due to
abnormal development and high embryo mortality (von
Westernhagen et al. 1981, 1988; Hansen et al. 1985; Westin et
al. 1985; Cameron et al. 1986). On the California coast, white
croaker (Genyonemus lineatus) inhabiting contaminated waters
near Los Angeles had high body burdens of chlorinated hydro-
carbons, greater early oocyte degeneration, lower fecundity, and
lower fertilization rates than fish from reference areas (Cross
and Hose 1988). Other effects of environmental pollutants on
fecundity have been reported. Asan example, a study of ovarian
development in plaice captured on the French coast in 1979 and
1980, near the site of the Amoco Cadiz oil spill in 1978, revealed
reduced concentrations of developing follicles, and no mature
follicles in any season (Stott et al. 1983).

Effects of contaminants also include hormonal imbalances,
which may affect ovulation or spawning (Struhsaker 1977;
Wedemeyer et al. 1984). Additionally, hatchability of eggs and
viability of larvae may be impaired, either by high tissue
contaminant levels in the parent females, or by toxic levels of
contaminants in the spawning environment (Ernst and Neff
1977; Smith and Cameron 1979; Hansen et al. 1985; Johnson
et al. 1988).

Of course, the basic question that must be asked is “Can
defective embryonic development and high embryo mor-
tality due to pollution affect recruitment?” Some observa-
tions relative to this question have been proposed by von
Westernhagen et al. (1988). According to their reasoning, total
mortality during the embryonic stage of development of marine
fish has been estimated tobe high - 95-99 percent for species such
as cod and plaice in the Baltic Sea, for example. At this mortality
level, decreases in survival rates due to embryo abnormalities, at
observed levels from 22 to 33 percent, would be too small to
detect in unexploited populations, but inoverexploited popu-
lations in which spawning stocks have been reduced severely,
the added impact of abnormal embryonic development and high
embryo mortality could result in reduced recruitment. The
authors also pointed out that, for the North Sea, the highest
prevalences of embryonic malformations occurred in highly
polluted areas (off the mouths of the Rhine and Elbe Rivers, and
in the vicinity of the dumping zone for titanium dioxide wastes).

From the perspectives of the research scientist and the
resource manager, three rather clear responsibilities exist when
considering pollution effects on fisheries: one is to demonstrate
that estuarine/coastal pollution is really affecting fish and
shellfish stocks, the second is to define the local or regional
stocks (especially shellfish) that are affected, and the third is to
propose management measures to mitigate damage if it exists.

These responsibilities can be satisfied in four stages which
are easy to state but difficult to accomplish: (1) isolate and
quantify pollution effects on resource species -- as distinct from
effects of natural environmental variations; (2) conduct critical
examinations of pollution effects at levels of the individual, the
local population, and the species; (3) encourage the identifica-
tion and quantification of sensitive early-warning indicators of
environmental degradation; and (4) attempt to reduce pollutant
inputs where damage to living resources has been or can be

demonstrated. Item 4 is particularly difficult to achieve; it points
out the need for aquatic scientists to interact with those
responsible for managing and regulating terrestrial sources of
pollution.

Case histories of quantitative effects of pollution on popu-
lations of Atlantic menhaden, striped bass, and winter flounder,
as presented in this paper, illustrate a series of generalizations
useful in stock management:

1. In assessing pollution impacts, the entire range of the
species should be considered, and precise information about
levels of all contaminants throughout that range should be
available. Furthermore, migratory characteristics must be
considered, since some species may move rapidly into or out
of areas of severe pollution.

2. Particular attention must be paid to controlling pollution
levels in spawning/ nursery areas, since most pollution.
associated mortality will occur during the first year of life.
It is generally accepted by fish population biologists that
survival during the first 60 days of life determines the size
of the year class of many estuarinedependent species,
including striped bass (Westin and Rogers 1978); factors
affecting early survival (such as pollution) should be of
concern and be subjects of management action.

3. “Very little impact [from pollution] should be tolerated at
low stock size, because it would prevent recovery to
a..maximum sustained yield” (Cushing 1979).

4, Simulation models can supply meaningful information, but
the degree of reliability of such models depends on the
extent of the data base employed, and very few have
worked at all.

we

Marine /anadromous fish populations are characterized by
aperiodic dominant year classes which may form the basis
for a fishery for many years. (An example would be the
1970 striped bass year class in Chesapeake Bay.) Existence
of these dominant year classes, and examination of factors
responsible for their production, can lead to important
insights about environmental influences on abundance.

Previous sections of this paper examined case histories that
indicated points in the life cycles of fish and shellfish where
pollutant stresses can exert lethal and sublethal influences. From
experimental studies, it seems obvious that with all these
potential impact points throughout life cycles, populations in
contaminated waters should dwindle and disappear; yet from
experience on the North American East Coast, this has not
happened (at least not yet). Only in severely degraded local
waters, which are a small part of the total range of most fish and
shellfish species, have there been localized disappearances; even
in those areas, other species which might be expected to be
affected are still present and are in some instances abundant.
This is true particularly of a number of coastal/estuarine-
dependent fish species, many of which spend much of their life


Page6

other species: spotted seatrout (Cynoscion nebulosus), weakfish
(C regalis), Atlantic croaker (Micropogonias undulatus), striped
bass, summer flounder (Paralichthys dentatus), bluefish
(Pomatomus saltatrix), and king mackerel (Scomberomorus
cavalla). The study, using Leslie matrix modeling, was designed
not only to examine population effects, but also to compare the
relative vulnerability of several marine fish stocks to pollution.
Findings of Schaaf et al. included these:

1. “The modeled stocks responded to a simulated catastrophic
event (a one-time 50-percent reduction in first year sur-
vival) by taking, on average, 10 years to equilibrate at 88
percent of preimpact abundance.

2. Severe problems in the simulations were in estimating the
inherent compensatory capacity of the stock, and in random
density-independent variability in first-year survival.

3. Species that are impacted the most by coastal/estuarine
pollution seem to stabilize most rapidly following acute
stress.

4. Stocks most susceptible to acute stress are even more
susceptible to chronic stress for at least up to 20 yr.

5. _ Estimates of first-year survival are critical to any attempts at
simulation modeling.

6. Estimates of a species’ susceptibility to pollution stress (in
terms of stabilization time after impact) can be made from
life history data, including age-specific survival and fecun-
dity rates.”

As Schaaf et al. pointed out, simulations of this kind can
provide estimates of the magnitude and duration of pollution
impacts that will be useful to resource managers.

Exploring the possible effect of a single human-induced
catastrophic event (such as an oil spill) on stock abundance in
future years, Vaughan er al. (1986) examined the effect of mass
mortalities of young menhaden that occurred in 1984, to test the
ability to detect reductions in populations following acute
pollution events, because of variability in young-of-the-year
(YOY) survival. They concluded that: “a catastrophic loss to the
Atlantic menhaden 1984 year class (eg., greater than a 50-
percent loss in abundance of the 1984 menhaden year class from
the entire Atlantic coast) would have to occur to be detectable
at reasonable levels of statistical power (eg., greater than 70-
percent chance of detection), but more subtle-reductions (eg.,
less than a 25-percent loss to the Atlantic menhaden 1984 year
class from the entire Atlantic coast) would undoubtedly go
undetected (e.g., chance of detection less than 12 percent). Such
difficulties in detecting reductions are typical of most fish
stocks having comparable or larger inherent variability in
recruitment or landings [emphasis mine].” They stated also
that “The occurrence of any confounding source of mortality
will make it more difficult to detect a reduction due specifically
to the cause of mortality under investigation.”

These studies with menhaden by Vaughan et al. (1986)
were preceded by similar attempts to analyze the ability to detect
reduction in year-class strength of white perch (Morone
americana) in the Hudson River (Van Winkle 1977; Van
Winkle et al. 1981, Vaughan and Van Winkle 1982). Their
general conclusions with the white perch analysis were that at
least 20 yr of data collection would be required to detect an actual
50-percent reduction in mean year-class strength; and that
annual fluctuations can mask major reductions in mean year-
class strength.

The simulation models developed for predicting impacts of
pollution and other human-induced habitat changes can be
designed to do two things: (1) simulate the annual effect on
recruitment of YOY fish into the adult population (YOY
model), and (2) simulate the long-term effect of reduced
recruitment on population size (life cycle model). The YOY
models predict either the number of YOY surviving to age 1, or
the percent reduction in the YOY. These outputs from YOY
models are then used in conjunction with a Leslie matrix model
(life cycle model) to predict long-term yields or adult population
reduction (Swartzman et al, 1977).

An important consideration in any modeling is the determi-
nation of density-dependent and density-independent sources of
mortality. If the probability of death of an individual decreases
as the density of individuals in the population decreases,
mortality is termed density dependent or compensatory. The
extent of compensatory mortality incorporated in the model can
account for large variations in predicted population reductions.
The manner in which compensatory mortality acts was hypoth-
esized by Swartzman et al. (1977) as follows: “For densities of
[YOY] fish below an age-specific, critical density, survival is
density independent; above this critical density, survival is
density dependent in that it decreases as density increases.”

Development and application of simulation models to
predict effects of pollution on fish stocks are of course only one
approach in the battery of approaches that can be and are being
applied to sorting out the causes of mortality in resource species.
Other sources of information are data from: (1) fisheries
landings and fisheries-independent surveys, useful in estimating
stock size, recruitment, and mortality; (2) measurements of
physical /chemical changes in the oceans; (3) chemical analyses
of contaminant levels in habitats and fish tissues, (4) measure:
ments of physiological responses and biochemical transforma-
tions of contaminants by marine organisms; (5) experimental
exposures to single or multiple contaminants; and (6) field
exposures of resource species in polluted zones.

The effort required for an integrated long-term program
that includes all these elements would appear to be overwhelm-
ing, but problems of the complexity described can be addressed
with modern computer power and a major commitment of
research resources.

STRIPED BASS

The striped bass has had a long history of extensive
fluctuations in catches (and presumably abundance); its center


ADULTS WITH ABNORMALITIES
AND HIGH BODY BURDENS
OF CONTAMINANTS

JUVENILES WITH
SKELETAL AND @
OTHER ABNORMALITIES

LARVAL DEVELOPMENTAL
DEFORMITIES MAY
RESULT IN MORTALITIESG

Vi ZIM

os
QF

HATCHING--ANOTHER
CRITICAL MORTALITY (3525
PERIOD

Figure 2.

population concerns the compensatory response -- espe-
cially the amount of compensatory reserve that is left in an
exploited population.

The point about effects of exploitation was made forcefully
by Cushing (1979). Defining the term “impact” as “the loss of
eggs, larvae, or juveniles to the recruitment of fish stocks,” he
stated that: “Variability of recruitment in marine and anadro-
mous fish stocks is high - one to two orders of magnitude - and
an impact due to pollution would be difficult to detect. How-
ever, the effect of an impact depends on the degree of exploita-
tion, so if stocks are low and heavily exploited, no impact can be
tolerated until the stock has been returned to the desired
objective, the maximum sustainable yield or any lesser quantity
that might be optimal.”

This point is consistent with a related statement about
environmental effects by Jones (1982): “in general, recruitment
[annual addition toa fishable stock] is not directly dependent on
the size of the spawning stock, but appears to be dependent on
other factors, frequently environmental in origin [empha-
sis mine], that affect the fish during the early larval and juvenile
stages. Fluctuations in stock size are therefore very largely due

Page3

ye UNFERTILIZED EGGS SPAWNED

WITH_ CONTAMINANT.
, ALREADY PRESENT
SECOND MEIOTIC DIVISION
OF EGG IS ESPECIALLY

ESP!
SENSITIVE TO CONTAMINANTS

LOAD

FERTILIZED EGG x

N\ SPERM_ SENSITIVE
Xe TO CONTAMINANTS

IN WATER COLUMN

BLASTODISC STAGE WITH
CYTOLOGIC AND CHROMOSOMAL
ANOMALIES

GASTRULA STAGES MAY BE
SPECIALLY SENSITIVE
‘O CONTAMINANTS

EMBRYO WITH DEVELOPMENTAL
ANOMALIES {MORPHOLOGICAL
AND PHYSIOLOGICAL |

Points in the life cycle when fish are especially sensitive to pollutants.

to events that occur during the early life stages and are generally
less dependent on events that influence the size of the adult
stock.”

Coastal / estuarine pollution can affect any life stage of fish
(Figure 2), but it is during their first year of life - and more
specifically during their first few months of life -- that fish can
be particularly sensitive to toxic contaminants (Rosenthal and
Alderdice 1976). Factors affecting pre-recruit mortality are
therefore of great significance in determining long-term popula-
tion stability. Death may occur at any point in the life cycle; when
translated into population terms, mortality may be chronic or
catastrophic, as shown in Figure 3. Pollution impacts may occur
at several points in this process.

Life history patterns of fish are important in determining
the extent of pollution effects. Potential critical aspects include:
(1) location of spawning (freshwater, estuarine, coastal); (2)
location of egg deposition (pelagic, demersal); (3) depth prefer-
ence of hatched larvae in water column -- surface film to bottom;
(4) location of nursery area for postlarvae and juveniles; (5)
feeding behavior and diets of all life stages; and (6) extent of
migration into and out of polluted zones, and duration of
occupation of those zones.


Page2

lepende' rocesse:

Decreased natural mortality

pi-compensation [Pr increased growth rate

Increased numbers of eggs produced

Added stress from pollutants

Lackot |
. Compensation mel

Figure 1. Population responses to pollution stress. Note, in addition, that the gains from compensation are added (in an algebraic sense) to the
losses from the added pollution stress. The net result could indeed be decreased M, but it could instead be constantM (if compensation

Increased natural mortality and
decreased abundance

precisely offsets the contaminant stress) or reduced M (if compensation is incomplete).

changes in fisheries and fish stocks concluded with this
remarkably nebulous conclusion: “It seems that direct and
indirect effects of changes in the fisheries as well as climatic
changes in their consequences for the biotic environment
caused the recent changes in the fish stocks of the North
Sea. It is not possible to quantify the effects of man-made
and natural factors separately because of the complexity of
interactions between the various fish stocks and the stages
of their early life history.”

There are really two important points tobe made about
this and the preceding hypothesis: (1) fish populations are
subject to great variability, and partitioning this variability
into its components (one of which is pollution induced) is
difficult; and (2) population levels (or for that matter
recruitment levels) are themselves estimated only impre-
cisely, so that our ability to detect secular changes in
population size or recruitment is quite poor (Peterman and
Bradford 1987; Peterman 1990). This imprecision is a
major reason for difficulty in detecting contaminant effects
on populations. So the problem, then, is not only to
partition the causes of variability, but also tomeasure the
variability itself with any precision.

Because of the inability to distinguish population
changes due to pollution, such changes might become
catastrophic before they are noted. Effects of pollutants
on reproduction, recruitment, behavior, and survival may
be particularly critical. Survival can be reduced by parental
(inherited) and dietary contaminants, such as polychlori-
nated biphenyls (PCBs) (Westin et al 1985). Sperm
viability and egg fertilizability might be reduced. Larval
behavior can be affected, reducing food capture and preda-
tor avoidance. Pollution may result in immunosuppression
and increased susceptibility to disease in early life stages.
The reproductive rate -- usually considered in the literature

on environmental toxicology to be a more sensitive param-

eter than survival (Kooijman and Metz 1984) - can be
severely affected. According to those authors, toxic chemi-
cals may reduce reproductive rates by: (1) causing diversion
of maintenance energy to metabolic deactivation or tissue
repair; (2) directly impairing protein synthesis, hence
growth; (3) ‘affecting digestion and assimilation; or (4)
interfering with gonad maturation and gamete production.

These physiological responses of individuals under
chemical stress can contribute to reproductive failure of the
population as a whole -- although other factors may be
involved, as described by Waldichuk (1979): “(1) the fish
may be unable to reach its spawning grounds because of
unfavourable ecological conditions, or its own weak physi-
cal state, and goes unspawned; (2) the eggs may never be
released by the female owing to some unsuitable physiologi-
cal condition; (3) the eggs and larvae may die because of
their unhealthy state or poor conditions on the spawning
grounds; (4) the eggs and larvae may be poisoned by a
substance bioaccumulated in the gonads of the parent, e.g.
DDT; or (5) the eggs and larvae may be poisoned by toxic
substances in the environment.”

Offshore fish stocks are not immune to damage from
pollutants, since year-class abundance is determined early
in the life history, which for many marine species is spent
in coastal/estuarine waters. The reality of this statement
is demonstrated in the next section on pollution effects on
menhaden stocks.

Many major fish stocks are already overexploited and
may be more vulnerable to additional stresses (such as
pollution) than unexploited populations. A fish popu-
lation that is heavily fished may have limited compensatory
reserve and thus may be particularly sensitive to pollution-
induced mortality (Cross et al, 1985; von Westernhagen et
al, 1988) (Figure 1). A critical question for each stressed


cycles in waters that are to some extent contaminated. It may also
be true for migratory species that can move into or through
degraded zones, although any possible impacts of transient
exposures to contaminants are more difficult to recognize, and
much more difficult to quantify.

A statistical analysis of the fishery resources of the United
States (Wise 1974) discussed catches of all important marine
fish and shellfish, on a species by species basis, for the preceding
20 yr (1950-70). Included were the major Atlantic species
usually considered estuarine-dependent or estuarine and
nearshore inhabitants, species which might be expected to
demonstrate some effects of estuarine and coastal pollution.
With few exceptions, according to that publication, catches of
those species were relatively steady or showed some increases in
the 20-year period. One of the summarizing statements in the
report is of particular note: “In general there are no good fishing
effort data available for those estuarine species whose catches
have remained constant, so it is possible that maintenance of
catch levels is due to constantly increasing fishing effort.
Nonetheless, the evidence from catch records of a substan-
tial number of exploited estuarine species in United States
waters indicates that pollution and damage to estuaries
have not yet shown any measurable overall effect on the
part of the marine resource which might be expected to
show the first effects [emphasis mine].” Admittedly, Wise’s
report covered only 1950-70, but for at least some of the species
considered, the situation has not changed dramatically since that
time (with the possible exception of striped bass -- but even here,
overfishing seems to have been the principal cause of the recent
(1973-86) decline in abundance).

Two major recent attempts have been made to assess
pollution impacts on fish stocks off portions of the U.S. coasts
-- one by Prager and MacCall (1993) examining data from the
Southern California Bight, and the other by Summers et al.
(1986) using historical data for a number of fish species from five
estuaries of the northeastern states. Using two modeling
methods -- a biomass-based model and a recruitment model --
Prager and MacCall looked for significant effects of climatic
conditions and contaminant loadings on spawning success of
three Pacific species - northern anchovy (Engraulis mordax),
Pacific sardine (Sardinops sagax), and chub mackerel (Scomber
japonicus). By using the models, no climate or contaminant
influences on spawning success of northern anchovies were
detected, but spawning success of chub mackerel seemed to be
strongly influenced by climatic variability, and (with the recruit-
ment model) spawning success of Pacific sardines was strongly
negatively correlated with contaminant loadings -- being consis-
tent with the hypothesis that the stock, which had been
overfished and had collapsed in the 1950s, was stressed beyond
its limits by poor larval survival due to ambient contaminant
concentrations. The study of fish populations of five Atlantic
Coast estuaries by Summers et al. (1986), using a biostatistical
modeling approach based on catch statistics, disclosed consistent
patterns of pollution effects among similar species across differ-
ent estuaries.

Another analysis -- this one of recent changes in abundance
of North Sea fish stocks ~ failed to find an effect of pollution.

Page15

Tiews (1989) examined abundance trends of 25 species for 35
yr (1954-88) from trawl catches on the German North Sea coast.
He found that some species had declined, some had increased,
and others had fluctuated irregularly, but that no consistent
long-term decline of commercial species could be attributed to
deteriorating habitat conditions. Tiews (1983) had earlier
expressed suspicion that, at least for some species, declines might
be due to pollution effects, but his latest analysis concluded with
the comment that “this study shows that the majority of species
studied seems to be able to tolerate the present status of
environmental deterioration of the ecosystem. Furthermore, the
study does not indicate any fundamental impairment of the
fishery biological situation of the area during the last 7 years in
comparison to the preceding period from 1954 to 1981. Six
species have even substantially increased in abundance.” Tiews
cautioned, however, that 35 yr may be too short a period to reveal
natural population fluctuations, so that a very conservative
interpretation of the data is necessary.

Goodyear (1984b) has described the dimensions of the
problem of interpreting population responses to direct (lethal)
and indirect (sublethal) levels of contaminants very succinctly:

1. For cases where contaminants are directly lethal, two types
of information are required: (a) “the timing and extent of
the excess mortality,” and (b) “the nature, timing, and
intensity of the density-dependent processes that regulate
the size of the population.” This, as Goodyear pointed out,
is “a key, largely unsolved problem in fishery research and
management in general.”

2. For cases where indirect (sublethal) levels of contaminants
exist, “The interpretation of the population response to the
indirect effects of the contaminants on the species of
interest requires quantification of the response in terms of
a change in survival probability or a change in reproductive
rates, and knowledge of the density-dependent processes
that control population size.” Goodyear then pointed out
that “none of the required information is particularly
amenable to measurement”!

Experimental demonstrations of the negative effects of
chemical contaminants on survival and well-being of marine fish
and shellfish are abundant, but the variability that results from
the influences of natural factors is so great and so incompletely
understood that experimental findings cannot usually be applied
directly to assessments of exploited populations ~ despite re-
peated attempts to do so. Some extrapolations from single-
contaminant experimental studies can be useful, however. Féyn
and Serigstad (1989) described calculations of year-class reduc-
tions in cod, herring, and saithe populations of the Norwegian
coast that might result from a major oil spill. Detailed field
studies of seasonal larval herring distribution and concurrent
laboratory studies of effects of oil on larvae, when presented in
a worst-case scenario, enabled calculation of what turned out to
be a low percentage of potential reduction in recruitment. Field
experimental studies, in which fish were exposed in situ to
contaminated waters, have also produced meaningful results



population size

Pages

'
& a eS
2 '
a :
it
a o&
time
Figure 4a. Simplified response in which a population stabilized at Figure 4b. Simplified response of a population subject to long-term
cyclical variation and short-term random variation (AB)
that is perturbed from time, to time,, The result of the
perturbation causes a change in population size (CD) to
be different than had the perturbation not occurred (EE).
(From Jones 1982, Figure 4. Copyright The Royal
Society. Reprinted with permission.)

NATURAL MORTALITY. { [ J
FISHING MORTALITY

POLLUTION MORTALITY | [

Figure 5.

level AB is perturbed from time, to time, and becomes
stabilized at a new level CD. Responses are shown with
and without random fluctuations in population size
superimposed on average levels. (From Jones 1982,
Figure 3. Copyright The Royal Society, Reprinted with
permission.)

tL

c
[
.

Schematic diagram of Leslie matrix model adapted for menhaden. (From Cross et al. 1985. Copyright ASTM. Reprinted with

permission.)


Schaaf, W.E. 1979. An analysis of the dynamic population
response of Atlantic menhaden, Brevoortia tyrannus, to an
intensive fishery. Rapp. P..V. Reun. Cons. Int. Explor. Mer
177; 243-251.

Schaaf, W.E,; Peters, D.S.; Vaughan, D.S.; Coston-Clements, L;
Krouse,C.W. 1987. Fish population responses to chronic and
acute pollution: the influence of life history strategies. Estu-
aries 10: 267-275. 7

Segar, D.A.; Stamman, E. 1986. Monitoring in support of
estuaries pollution management needs. In: Oceans '86 confer-
ence proceedings. Washington, DC: Marine Technology
Society; p. 874-877.

Sindermann, CJ. 1980. Pollution effects on fisheries - potential
management activities. Helgol. Meeresunters, 33: 674-686.

Smith, R.L; Cameron, J.A. 1979. Effect of water soluble fraction
of Prudhoe Bay crude oil on embryonic development of
Pacific herring. Trans. Am. Fish. Soc. 108: 70-75.

Smith, R.M. 1973. Pesticide residues asa possible factor in larval
winter flounder mortality. In: Pacheco, A.L, ed. Egg, larval
and juvenile stages of fish in Atlantic Coast estuaries. Mid.
Atl. Coastal Fish. Cent. Tech. Publ. 1. Available from:
National Marine Fisheries Service, Highlands, NJ.

Smith, R.M,; Cole, C.F. 1970. Chlorinated hydrocarbon
insecticide residues in winter flounder, Pseudopleuronectes
americanus, from the Weweantic River estuary, Massachu-
setts. J. Fish. Res. Board Can. 27: 2374-2380.

Smith, R.M.; Cole, C.F. 1973. Effects of egg concentrations of
DDT and dieldrin on development in winter flounder
(Pseudopleuronectes americanus). J. Fish. Res. Board Can. 30;
1894-1898.

Spies, R.B.; Rice, D.W., Jr; Montagna, P.A.; Ireland, RR. 1985.
Reproductive success, xenobiotic contaminants and hepatic
mixed-function oxidase (MFO) activity in Platichthys stellatus
populations from San Francisco Bay. Mar. Environ. Res. 17:
117-121.

Stott, G.G.; Haensly, W.E; Neff, J.M; Sharp, JR. 1983.
Histopathologic survey of ovaries of plaice, Pleuronectes
platessa L., from Aber Wrac’h and Aber Benoit, Brittany,
France: long-term effects of the Amoco Cadiz crude oil spill.
J. Fish Dis. 6: 429-437.

Struhsaker, J.W. 1977. Effects of benzene (a toxic component
of petroleum) on spawning Pacific herring, Clupea harengeus
pallasi. U.S. Nat. Mar. Fish. Serv. Fish. Bull. 75: 43-49.

Summers, J.K.; Polgar, T.T.; Rose, K.A.; Cummins, R.A.; Ross,
RN, Heimbuch, D.G. 1986. Assessment of the relationships
among hydrographic conditions, macropollution histories,
and fish and shellfish stocks in major northeastern estuaries.
NOAA Contract Rep. NA83-AA-D-00059. Available from:
Martin Marietta Environmental Systems, Bethesda, MD.

Swartzman, G.; Deriso, R; Cowan, C. 1977. Comparison of
simulation models used in assessing the effects of power-plant-
induced mortality on fish populations. In: Van Winkle, W.,
ed. Proceedings of the Conference on Assessing the Effects of
Power-Plant-Induced Mortality on Fish Populations. New
York, NY: Pergamon Press; p. 333-361.

Tiews, K. 1983. On the changes of fish and crustacean stocks
in the German North Sea coast during the years 1954-1981

Page21

and the hypothetical role of pollution asa causative factor. Int.
Counc. Explor. Sea C.M. 1983/E:16; 18 p.

Tiews, K. 1989. 35 years’ abundance trends (1954-1988) of 25
fish and crustacean stocks on the German North Sea coast.
Int. Counc. Explor. Sea C.M. 1989/E:28; 11 p.

Topp, R.W. 1967. Biometry and related aspects of young winter
flounder, Pseudopleuronectes americanus (Walbaum), in the
Weweantic River estuary. (Thesis). Amherst, MA: Univer-
sity of Massachusetts; 65 p.

Van Winkle, W., editor. 1977. Proceedings of the Conference
on Assessing the Effects of Power-Plant-Induced Mortality on
Fish Populations. New York, NY: Pergamon Press; 380 p.

Van Winkle, W.; Vaughan, D.S.; Barnthouse, L.W,; Kirk, B.L.
1981, An analysis of the ability to detect reduction in year-
class strength of the Hudson River white perch (Morone
americana) population. Can. J. Fish. Aquat. Sci. 38: 627-632.

Vaughan, DS.; Kanciruk, P.; Breck, J.E. 1982. Research needs
to assess population-level effects of multiple stresses on fish
and shellfish. Oak Ridge Nat. Lab. Tech. Memo. 8375.
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Vaughan, D.S.; Merriner, J.V.; Schaaf, W.E. 1986. Detectability
of a reduction in a single year class of a fish population. J.
Elisha Mitchell Sci. Soc. 102: 122-128.

Vaughan, D.S.; Van Winkle, W. 1982. Corrected analysis of the
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Available from: Oak Ridge National Laboratory, Oak Ridge,
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von Westernhagen, H.; Cameron, P.; Dethlefsen, V.; Janssen, D.
1989. Chlorinated hydrocarbons in North Sea whiting
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von Westernhagen, H.; Dethlefsen, V.; Cameron, P; Berg, J;
Farstenberg, G. 1988. Developmental defects in pelagic fish
embryos from the western Baltic. Helgol. Meeresunters. 42:
13-36.

von Westernhagen, H.; Dethlefsen, V.; Cameron, P.; Janssen, D.
1987. Chlorinated hydrocarbon residues in gonads of marine
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von Westernhagen, H.; Rosenthal, H.; Dethlefsen, V.; Ernst, W;
Harms, U.; Hansen, PD. 1981. Bioaccumulating substances
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von Westernhagen, H.; Sperling, K.R.; Janssen, D,; Dethlefsen,
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Kremling, K. 1987. Anthropogenic contaminants and
reproduction in marine fish. Ber. Biol. Anst. Helgol. 3: 1-70.



oll rina ifn - |

Suen )
> NOAA Technical Memorandum ‘NMFS-F/NEC-104

This TM series is used for documentation and timely communication of preliminary results,
interim reports, or special purpose information, and has not undergone external scientific
review,

g

i ;
A IS
aN Si

,
aR MENT OF on

Quantitative Effects of Pollution
on Marine and Anadromous
Fish Populations

Carl J. Sindermann

Oxford Cooperative Lab., National Marine Fisheries Serv., Oxford, MD 21654

U. S. DEPARTMENT OF COMMERCE
Ronald H. Brown, Secretary
National Oceanic and Atmospheric Administration
D. James Baker, Administrator
National Marine Fisheries Service
Rolland A. Schmitten, Assistant Administrator for Fisheries
Northeast Region
Northeast Fisheries Science Center
Woods Hole, Massachusetts

June 1994


“> Pages .

mixtures) of selected contaminants resulted in increased mortal-
ity (Hall et al. 1984, 1987). Yolk-sac larvae exposed in in situ
chambers to Nanticoke River water (a tributary of Chesapeake
Bay) also died differentially; the authors (Hall et al. 1985)
suspected that high aluminum and low pH levels could be
implicated. However, a later experimental study of yolk-sac
larvae by Hall et al, (1987), also using in situ chambers placed
in their natural habitat in the upper Chesapeake Bay (Chesa-
peake and Delaware Canal), did not indicate acute harmful
effects although sublethal gill abnormalities were seen in year-
lings.

In addition to possible effects of toxic chemicals on larvae,
effects on reproduction were also investigated as a possible cause
of the population decline. Concentrations of PCBs up to 26 ppm
were reported in adult striped bass from the Hudson River, and
elevated concentrations of PCBs, DDT, and dieldrin were found
in striped bass eggs (Mehrle et al. 1982). The organochlorine
tesidues were associated with failure of cleavage in fertilized
eggs, but correlations were not significant, according to the
authors. In an earlier study of striped bass in California, eggs
were found to contain 5-10 ppm DDT, but reproductive
depression was not demonstrated (Hunt and Linn 1969).

In other studies, Westin et al. (1985) reported that survival

___ .of larvae from eggs spawned by contamiinated female striped bass
was inversely related.to concentrations of chlorinated hydrocar-
bons (hexachlorobenzene, DDT, PCBs, and chlordane) in the
eggs, and that parental sources of these contaminants had greater
effects on survival than did dietary sources. However, in an
earlier study (Westin et al. 1983), eggs with PCB content from
1.1 to 8.1 pg/g (ppm) wet weight did not differ from controls
in survival and growth after yolk absorption.

In still other studies, tissue contaminants were found to
produce abnormalities that might affect stock abundance. Mehrle
et al. (1982) found that YOY striped bass from the Hudson
River had high tissue PCB levels and vertebrae that were fragile
and ruptured under minimal force. The authors referred to
laboratory studies indicating that contaminants such as PCBs,
cadmium, and lead could weaken vertebral structure and
contribute to mortality.

Goodyear (1985b) attempted, with simulation models, to
examine the relative influence of two factors -- increased fishing
mortality and contaminant toxicity - in producing the observed
decline. His principal findings were these:

1. “At low levels of density-dependent mortality, an increase

in fishing mortality, or an equivalent decrease in early life-
stage survival caused by the toxic effect of a contaminant|,}
would cause similar declines in the stock.”

2. “At high levels of density-dependent mortality, the effects
on the yield are similar if the contaminant-induced mortal-
ity precedes the density-dependent mortality. However, if.

the contaminant-induced mortality occurs after the period -

of density-dependent mortality, the decline in yield will be
more severe than that caused by an equivalent increase in
fishing mortality.”

However, despite the impressive amount of data and
analyses available from Goodyear’s and other studies, he con-
cluded that “the actual level of any excess mortality that is
imposed on the striped bass population from toxic substances is
unknown, and it will probably remain so for some time.” But he
then went on in a more optimistic vein, stating that reduced
fishing mortality could result in a 20- to 30-fold increase in
population fecundity which could “offset even rather severe
losses due to contaminant toxicity, and could halt or reverse the
decline in stock.”

Itis very interesting, and no doubt significant, that Goodyear’s
(1985b) conclusions were supported by the behavior of the
fishery and the population in the late 1980s. Beginning in 1985,
the states of Maryland and Virginia imposed a moratorium on
striped bass fishing that remained in effect until 1990. A
dramatic increase in spawning stocks occurred (an estimated
fivefold increase in spawning females in 1989 as compared to
1984), as well as a high average YOY index. Based on available
evidence for the resurgence of striped bass stocks, the Atlantic
States Marine Fisheries Commission adopted a conservative
management plan for limited harvest and a quota system
beginning in 1990.

What can be concluded from results of this research on
“Chesapeake ‘Bay striped ‘bass, followed by implementation of
management measures, and the resurgence of the population in
the late 1980s? It begins now (1994) to appear that high fishing
mortality was the principal culprit in the decline in stocks since
1973. (It might be noted that to some quantitative biologists it
has appeared that way all along, especially because fishing
mortality rates on immature striped bass were very high.) It also
appears that high larval mortality in some spawning tributaries
may have been contributory, if stressful environmental condi-
tions (pH, hardness) occurred coincident with toxic levels of
specific contaminants (as, for example, aluminum did in the
studies of Hall et al. (1985) in the Nanticoke River). These
conclusions support the concept that a heavily exploited popu-
lation may have limited compensatory reserve and may be
particularly sensitive to pollution (Cross et a/. 1985). In the
present case, drastic reduction in fishing mortality during 1985-
90 because of the moratorium allowed population expansion,
even if other factors such as low larval survival due to pollution
had contributed to the previous decline.

WINTER FLOUNDER

Over the past two decades, the winter flounder has been the
subject of many studies that have emphasized pollution effects
on early life history stages (Figure 8). The average female
produces about 600,000 eggs, of which an estimated 10-16
percent hatch. Only an estimated 18 individuals per 100,000

. hatched larvae survive to age 1 (Saila 1962; Berry et al. 1965).

The species is estuarine dependent, both for nursery areas and
for overwintering sites for adults. Many estuaries are’polluted, *
especially the sediments, and much of the life history of the
winter flounder is spent in close association with the contami-


LARVAE VULNERABLE TO LETHAL
OR SUBLETHAL CONTAMINANT

LEVELS iN WATER COLUMN

EARLY EMBRYO SENSITIVE “1
TO WATERBORNE
CHEMICAL MUTAGENS,

UPPER TRIBUTARIES

RIVERS AND BAYS

Figure 6.

of abundance is Chesapeake Bay, with lesser centers in the
Hudson and Delaware estuaries (Mansueti 1962; Saila and
Lorda 1977).

During their life cycle, striped bass occupy a variety of
aquatic habitats, from the lower freshwater zones of spawning
rivers to the open sea (Figure 6). For most of their lives, but
especially during the first year, they are in habitats exposed to an
array of chemical contaminants, as well as to the highly variable
estuarine and riverine environments. It is generally accepted
that survival during the first 60 days of life determines the size
ofa year class (Figure 7). It is also well accepted that certain early
life stages are particularly vulnerable to environmental toxicants.

Two aspects of human interference with the natural order
of things (other than overfishing) have been responsible for
extensive quantitative studies of striped bass on the Atlantic
coast of United States: (1) possible population impacts of power
plant siting and operation on the Hudson River, and (2) the
possible role of toxic contaminants in reducing abundance of
Chesapeake Bay stocks, The Hudson River studies peaked in the
mid-1970s; the Chesapeake Bay studies culminated in extensive
documentation in the late 1970s and early 1980s. Investigators
were particularly interested in quantitative information linking
human activities with effects on striped bass survival. Popula-
tion aspects of the Hudson River studies were well summarized
ina conference volume (Van Winkle 1977) that includes papers
by Saila and Lorda, Leggett, Horst, and others. An excellent
series of papers by Goodyear (1978-85), Goodyear et al, (1985),
Boreman and Austin (1985), and others provide analyses based
on information from the Chesapeake Bay investigations.

The recent decline in striped bass stocks in the Chesapeake
Bay, beginning in 1973 and continuing to 1985, was attributed
to various causes, especially overfishing and reduced survival of
larvae because of chemical pollution. A major research effort in
the late 1970s and early 1980s confirmed that fishing effort had
increased since the mid-1960s, and might have affected recruit-

Page?

JUVENILES IN| CONTAMINATED
ESTUARINE NURSURY AREAS

Life cycle of the striped bass, Morone saxatilis, with potential pollutant impact points.

Period
12 13

+

Log of No. of Surviving Fish

|-—-+-+_______

Time (Years)

Hypothetical survival curve of one year class of fish. The
division of the survival curve into three periods is
discussed in the text in relation to the prospect of
epidemic diseases contributing to mortality in cach period:
period 1, eggsand larval fish; period 2, pre-recruit fish; and
period 3, fished stocks. (From Munro et al, 1983.
Copyright ICES. Reprinted with permission.)

Figure ?,

ment (Merriner 1976; Goodyear 1978, 1980, 1984a,b; Levin
and Goodyear 1980; Florence 1980; Mehrleet al. 1984; Boreman
and Austin 1985; Goodyear et al. 1985). Evidence was also
found of elevated levels of PCBs and other contaminants in
tissues of YOY and in their habitats (Mehrle et al. 1982; Pizza
and O’Connor 1983), and experimental exposure of yolk-sac
larvae in the laboratory to environmental levels (but artificial


-Pagea”

Chronic (background) mortalities

el

Caused by man-made
mused by natural catastrophic events, nee nces of Consequences of
Including oil spills from environmental lethal genetic defects
contaminante in developing embryos
l |
Epizootics of || Algal blooms | [Environmental Direct chemical Low-level chronic Morphological,
facultative and toxin changes beyond| injury to animals disease caused by physiological,
pathogens in production physiological facultative pathogens and biochemical
stresssed accompanied ||limits (salinity, abnormalities
Populations by anoxia temperature,
lstorms,etc.)
Figure 3. Causes of mortality in marine fish.

These life history factors are, of course, modulated by the
nature, extent, and intensity of pollution in every part of the
habitat occupied by the species at any developmental stage, from
embryo to adult.

CASE HISTORIES OF
POLLUTION IMPACT STUDIES

Probably the most critical problem in assessing pollution
effects on fish stocks is that of separating natural and fishing
mortality from pollution-induced mortality. The nature of
the problem was explored thoroughly by Jones (1982), whose
illustration of the complexity of population responses is pre-
sented as Figures 4a and 4b.

The extent of continuing frustration about inability to
distinguish causation can be detected in extreme statements such
as those of Segar and Stamman (1986): “Biological monitoring
programs that cannot separate pollution-induced change from
natural change should be terminated and those regulatory
requirements which require such programs changed.” A reason.
able rebuttal to such subjective conclusions might be that “We
should intensify research leading to better delimitation of
pollution-induced from natural changes in marine populations,
and in the interim should adopt a ‘precautionary principle’
developed recently by Germany (Dethlefsen and Tiews 1985;
Dethlefsen 1986). and accepted at the Second International
Conference on the Protection of the North Sea in 1987.” The
principle “requires action to reduce pollution even in the
absence of soundly established scientific proof for cause
and effect relationships [emphasis mine].”

Cause-and-effect relationships -- demonstrations of popula-
tion impacts of pollutants -- have been subjects of searches by
many ‘investigators, especially during the past two decades.
Quantitative studies have focused on species of economic
importance that may be at risk from coastal/ estuarine pollution.
Three of these species - Atlantic menhaden (Brevoortia tyrannus),
striped bass (Morone saxatilus), and winter flounder (Pleuronectes
americanus) ~ will be examined as case histories in the following
sections.

ATLANTIC MENHADEN

Estimations of mortality rates in fish stocks from fishing
and from natural causes can be made through use of a variety of
models developed for assessment and management purposes.
Subject to some degree of imprecision, such models may be
adapted to assessing effects of pollution by integrating pollution
mortality terms into them (Ricker 1954; Schaaf 1979; Cross et
al. 1985). The modified models can provide estimates of varying
pollution mortality on fish stocks at various levels of exploitation
(Vaughan, Kanciruk, and Breck 1982; Vaughan, Yoshiyama,
Breck, and DeAngelis 1982; Kanciruk et al. 1982). Cross et al.
-independent variation of a Leslie
matrix model (Leslie 1945, 1948; O’Neill ec al. 1981) that was
used to demonstrate population responses of Atlantic menha-
den, a relatively shortlived species, to simulated pollution
events. They pointed out that all sources of mortality - natural,
fishing, and pollution ~ at all life stages of a species throughout
its range, must be quantified for effective prediction of pollution
effects. A diagram of their model is shown as Figure 5. By using
the extensive menhaden data base of the National Marine
Fisheries Service’s (NMFS's) Beaufort (North Carolina) Labora-
tory, and imposing both one-time pollution-related catastrophic
mortalities and chronic mortalities on one age class, the response
of the entire population for the next 30 yr was simulated.

For a simulated catastrophic event (an oil well blowout in
coastal waters), and assuming a one-time, 50-percent reduction
in survival of Oagegroup menhaden, Cross et al. (1985)
estimated that the total biomass would be reduced by about 12
percent over 30 yr. Because stocks are heavily exploited and thus
may have little compensatory reserve, the simulation indicated
a permanent reduction in stock size of nine percent as a
consequence of the event. For a simulation of chronic effects,
Cross et al. assumed slow but continuous decline in estuarine
water quality and substantial increase in ocean dumping. The
‘simulation predicted a.40-percent decrease in total population
biomass in 30 yr: :

In a subsequent paper (Schaaf et al. 1987), estimates of
acute and chronic pollution effects derived from simulation
modeling were made for Atlantic menhaden as well as seven



Page 18

added substantially but only incrementally and not concep-
tually, to our understanding of pollution effects on resource
species; some of that information has been summarized in the
case histories just presented. The major problem -- being able to
distinguish adequately the effects of pollution from all the other
influences on marine fish population abundance - still confronts
us, even though the boundaries of our knowledge have ex-
panded. Recent advances include the creation and implementa-

tion of new pollution monitoring and assessment programs,
developments in simulation modeling, annual lengthening of
critical resource and environmental data sets, and findings from
field and laboratory experimental studies.

Some pessimists feel that we will never have adequate data
to distinguish clearly the quantitative effects of pollution on fish
stocks; I think the accumulation of analyses and insights relevant
to the problem forecasts a brighter future than that.

REFERENCES CITED

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chronic effects of DDT on cutthroat trout. U.S. Fish Wildl.
Serv. Res. Rep. 64; 30 p.

Baker, J.T.P. 1969. Histological and electron microscopical
observations on copper poisoning in the winter flounder
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2785-2793.

Berry, RJJ.; Saila, S.B.; Horton, D.B. 1965. Growth studies of
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Bigelow, H.B; Schroeder, W.C. 1953. Fishes of the Gulf of
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Black, D.E; Phelps, D.K; Lapan, R.L. 1988. The effect of
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Boreman, J.; Austin, H.M. 1985. Production and harvest of
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Burdick, GE; Harris, EJ; Dean, H.J.; Walker, T.M.; Skea, J;
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Butler, PA; Childress, R.; Wilson, AJ. 1972. The association
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Calabrese, A; Thurberg, F.P; Dawson, M.A; Wenzloff, D.R.
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Cameron, P.; von Westernhagen, H.; Dethlefsen, V,; Janssen, D.
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Cole,H.A. 1972. North Sea pollution. In: Ruivo, M.,ed. Marine
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Cole, H.A. 1983. Effects of pollution on fish stocks. Mar. Pollut.
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Cross, F.A.; Peters, D.S.; Schaaf, W.E. 1985. Implications of
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Dethlefsen, V.; Cameron, P.; von Westernhagen, H.; Janssen, D.
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‘SMALLER
FORAGE
SPECIES

JUVENILE
FORAGE FISH

Figure 9. Food chains of winter flounder life history stages.

1969). Principal effects were hemolytic anemia, fatty degenera-
tion of the liver, and renal necrosis -- all potentially lethal.
Sublethal physiological effects of two other heavy metals,
cadmium and mercury, were reported by Calabreseet al. (1975),
and the distribution, metabolism, and excretion of DDT and
Mirex were examined by Pritchard et al. (1973), with the
interesting observation that the winter flounder stores its
pesticide burden primarily in body muscle.

A recent study of contaminants in winter flounder froma
number of polluted sites on the northeast coast of United States
(Zdanowicz et al. 1986) disclosed that levels of polycyclic
aromatic and chlorinated hydrocarbons in stomach contents
were higher than those in bottom sediments ~ indicating that the
compounds were being accumulated by prey organisms (Figure
9). Relating these findings to biological effects, the authors
described several kinds of necrotic and degenerative liver and
kidney lesions that were relatively more prevalent in fish from
severely polluted sites. Zdanowicz et al. (1986) did not make
inferences about possible pollution-induced mortality, but the
correlation of certain sublethal pathological conditions with
contaminated habitats and elevated contaminant levels in tissues
seemed evident.

An experimental study, exposing adult winter flounders to
oil-contaminated sediments for 4-5 mo, resulted in mortalities in
summer months, possibly because the oil was acting as a
nonspecific stress at a time when temperatures approached an
incipient lethal level (Fletcher et al. 1981).

The association of progressively severe liver pathology and
several types of hepatic neoplasms with badly degraded estua-
rine /coastal waters is becoming evermore apparent from recent
reports. Among them, winter flounder from several degraded
areas on the U.S. East Coast (New Haven Harbor, upper
Narragansett Bay, Boston Harbor) had prevalences of 3.4-7.5
percent for tumors classified as hepatocarcinomas or

Page 11

cholangiocarcinomas (Murchelano and Wolke 1985) (Figure
10). What seems to be emerging from these studies of tumors
in winter flounder and other species in different polluted
estuaries, is a sequence of histopathological changes in livers,
beginning with fatty deposits and pre-neoplastic changes in liver
parenchyma cells, The progression of pathological changes also
seems roughly correlated with the extent of estuarine degrada-
tion and the length of residence of fish in the estuary. In studies
of West Coast flatfish species, positive correlations were ob-
tained between neoplasm prevalence in bottom-dwelling fish
and levels of “certain individual groups of sediment-associated
chemicals” (aromatic hydrocarbons, chlorinated hydrocarbons,
and heavy metals) (Malins et al, 1984, 1988). Other studies of
East Coast winter flounder have identified an oncogene, derived
from tumorous liver and possibly indicating a specific interaction
of flounder DNA with polycyclic aromatic hydrocarbons (PAHs)
(McMahon et al. 1988).

A persistent question, still unresolved fully, is whether the
liver tumors kill the fish, or if they regress when the fish moves
from the heavily polluted habitat. If the tumors do not regress,
the survival of individual fish, as described by Murchelano
(1988), “depends on many factors, including the extent of liver
damage, the degree of toxicity resulting from decreased hepatic
function, the impairment of other essential organs, whether
metastasis occurs, and the degree of behavioral modification (the
ability to capture prey and avoid predators may be compro-
mised). Population effects are possible if large numbers of fish
with hepatic carcinoma die...”

Limited recent information is available about possible
reduction in immune responses and hence reduced survival
potential of winter flounder as a consequence of exposure to
pollutants. In one study, a 4-mo exposure to oiled sediments
resulted in statistically significant reduction in liver macrophage
aggregates, believed to be important components of the cellular


effects on winter flounder population abundance in Long Island
Sound (Thurberg, personal communication)!. The sheer mass
of relevant information available -- biological and environmental
-- should enhance the likelihood of success for such a project.

In advance of the availability of any model, it might be
instructive to discuss the kinds of information that would be
most useful as a data base in developing it. Some elements are:
(1) annual landings by geographic subdivisions, with short- and
long-term trends and fluctuations; (2) population estimates from
trawling surveys, including age structure, age-specific fecundity,
and average annual age-specific survival; (3) annual larval
abundance and distribution estimates from plankton surveys;
(4) data from routine long-term monitoring of physical/chemi-
cal variables over the entire range of the species, but emphasizing
spawning/ nursery areas; (5) descriptions and detailed maps of
the levels of principal pollutants (PAHs, PCBs, heavy metals) in
sediments and the water column in important estuarine / coastal
habitats of winter flounder; (6) a history of the nature and
degree of pollution in each major estuary important in the life
history of winter flounder; (7) additional descriptions of the
effects of pollutants on developing eggs and larvae, with
projections of population impacts at various pollutant levels, and
(8) additional descriptions of the effects of pollutants on juvenile
and adult fish, with estimates of population impacts at various
pollutant levels.

Needed, then, is information on: (1)population size, age
structure, and age-specific fecundity; (2) natural mortality rates;
(3) fishing mortality rates; and (4) pollution-induced mortality,
especially in early life history stages. Simulation models can then
be constructed to predict population effects of: (1) a one-time
acute pollution event (oil spill, other); (2) long-term increasing
levels of pollution; and (3) longterm decreasing levels of
pollution.

DISCUSSION

The case histories of quantitative pollution effects on
populations of Atlantic menhaden, striped bass, and winter
flounder presented here are, of course, only examples. Some
information is available for certain other species. If this paper
were to be written from a European perspective, the long-term
research of German workers (Rosenthal, Dethlefsen, von
Westernhagen, and their colleagues), examining pollutant ef-
fects on larval survival and development, would certainly be
emphasized. This series of studies began in 1967 (Kinne and
Rosenthal 1967) and continues to the present time (Rosenthal
et al. 1986; Dethlefsen et al. 1987; Dethlefsen 1988; von
Westernhagen 1988). Among the many significant findings
reported in this series of papers are these:

1. -,Exposure of maturirig females to low concentrations of
contaminants « especially those which are bioaccumulated
~-can affect gonad tissue, with effects expressed in the next
generation.

' Dr. EP. Thurberg, NMFS, 212 Rogers Ave., Milford, CT 06460.

Page 13

2. Life cycle stages most vulnerable to contaminants are
maturing females, early embryos, early-hatched larvae, and
larvae at transition from yolk-sac to feeding.

3. Awide range of morphological, behavioral, and physiologi-
cal abnormalities in larvae result from exposure to contami-
nants, in rough proportion to the environmental level of the
particular contaminant.

4, Common morphological abnormalities include malformed
lower jaw, eye deformities, anomalies in the vertebral
column, and reduced size at hatching.

5. Common physiological abnormalities include reduced heart
rate, reduced swimming ability, disturbance in equilibrium,
and reduced feeding.

6. Early developmental stages showed the highest malforma-
tion rates.

Inarecent study of pelagic fish embryos from the North Sea,
malformations were found with high frequency in several
species - dab (Limanda limanda), Baltic flounder, whiting,
Atlantic cod (Gadus morhua), and plaice (Pleuronectes platessa)
~ taken in regions with known high contamination levels
(Dethlefsen et al. 1986).

Inother studies, malformations of embryos of Baltic herring
(Clupea harengus membras) were found to be abundant and in
great variety following exposure to crude oil and chemical
dispersants (Linden 1976).

Abnormalities induced by pollutants are, of course, only
part of the spectrum of pollution effects; it is also important to
examine thosemortalities that may result from exposure of pre-
spawning females to contaminated habitats. Some evidence
exists. Chlorinated hydrocarbons can contribute substantially to
larval mortality by accumulation in tissues and by transfer to eggs
from the parent females. One specific example of larval
mortality which seems related to increased environmental
contamination -- mortalities of larval winter flounder in a
Massachusetts estuary related to pesticide pollution (Smith
1973) -- was discussed in this paper’s case history section. Adult
females concentrated DDT, DDE, and heptachlor epoxide in
their ovaries as spawning approached, and mortality of post-yolk-
sac larvae approached 100 percent.

Another earlier study, referred to previously, provided
evidence that high tissue concentrations of chlorinated hydro-
carbons in spawning adults can cause mortalities of developing
eggs. Reproductive failure of a spotted seatrout population in
Texas was attributed to this phenomenon (Butler et al. 1972).
The seatrout population inhabited an estuary that was contami-
nated heavily with DDT, and DDT concentration in the ovaries
reached a peak of 8 ppm prior to spawning, compared to less than
0.5 ppm in seatrout from other less contaminated estuaries.
Spawning seemed normal, but the eggs failed to develop.

Several more recent studies have indicated that high levels
of PCBs in the gonads of spawning fish (Baltic flounder, Baltic


Page ii

CONTENTS

Abstract
Introduction

Case Histories of Pollution Impact Studies
Atlantic Menhaden
Striped Bass
Winter Flounder

Discussion...

Conclusions...

References Cite

LIST OF FIGURES

Figure 1. Population responses to pollution stress
Figure 2. Points in the life cycle when fish are especially sensitive to pollutants
Figure 3. Causes of mortality in marine fish..
Figure 4a. Simplified response in which a population stabilized at level AB is perturbed from time, to time,

and becomes stabilized at a new level CD ..
Figure 4b. Simplified response of a population subject to long-term cyclical variation and short-term random

variation (AB) that is perturbed from time, to time, —
Figure 5. Schematic diagram of Leslie matrix model adapted for menhaden ..
Figure 6. Life-cycle of the striped bass, Morone saxatilis, with potential pollutant impact p<
Figure 7. . Hypothetical-survival curve of one year class of fish....
Figure 8. _ Lifé history stages-of demersal fish that are vulnerable to pollution.
Figure 9. Food chains of winter flounder life history stages...
Figure 10. Gross lesions in liver of winter flounder, Pleuronectes americanus...
Figure 11. Principal requirements for assessing the effects of pollution on fish stocks



Page22

Waldichuk, M. 1979. Review of the problems. In: Cole, HA.,
ed. The assessment of sublethal effects of pollutants in the sea.
Philos. Trans. R. Soc. Lond. B Biol. Sci. 286: 399-424,

Wedemeyer, G.A.; McLeay, DJ; Goodyear, CP. 1984. Assess-
ing the tolerance of fishand fish populations to environmental
stress: the problems and methods of monitoring. In: Cairns,
V.W,; Hodson, P.V; Nriagu, }.D.,eds. Contaminant effects on
fisheries. New York, NY: John Wiley & Sons; p. 163-195.

Westin, D.T.; Olney, CE; Rogers, B.A. 1983. Effects of parental
and dietary PCBs on survival, growth, and body burdens of
larval striped bass. Bull. Environ. Contam. Toxicol. 30: 50-57.

Westin, D:T; Olney, CE; Rogers, B.A. 1985. Effects of parental
and dietary organochlorines on survival and body burdens of
striped bass larvae. Trans. Am. Fish Soc. 114: 125-136.

Westin, DT; Rogers, B.A. 1978. Synopsis of biological data on
the striped bass, Morone saxatilis (Walbaum). Univ. Rhode
Island Mar. Tech. Rep. 67.

Wise, J.P., editor. 1974. The United States marine fishery
resource. Nat. Mar. Fish. Serv. MARMAP Contrib. 1; 379 p.

Wolke, RE; George, CJ; Blazer, V.S. 1985. Pigmented
macrophage accumulations (MMC; PMB): possible monitors
of fish health. In: Hargis, WJ, Jr, ed. Parasitology and
pathology of marine organisms of the world ocean. NOAA
Tech. Rep. NMFS 25: 93-97.

Wolke, R-E; Murchelano, R.A; Dickstein, C.D.; George, CJ.
1985. Preliminary evaluation of the use of macrophage
aggregates (MA) as fish health monitors. Bull, Environ.
Contam. Toxicol. 35: 222-227.

Zdanowicz, V.S.; Gadbois, D.F.; Newman, M.W. 1986. Levels
of organic and inorganic contaminants in sediments and fish
tissues and prevalences of pathological disorders in winter
flounder from estuaries of the northeast United States, 1984.
In: Oceans ‘86 conference proceedings. Washington, DC:
Marine Technology Society; p. 578-585.

Ziskowski, JJ.; Murchelano, R.A. 1975. Fin erosion in winter
flounder. Mar. Pollut. Bull. 6: 26-29.


Page il

NOTE ON SPECIES NAMES

The NMFS Northeast Region’s policy on the use of species names in technical publications and reports is to follow the American
Fisheries Society's (AFS) lists of scientific and common names for fishes (Robins et al. 1991)*, mollusks (Turgeon et al, 1988)*,
and decapod crustaceans (Williams er al. 1989)‘, and to follow the American Society of Mammalogists’ list of scientific and
common names for marine mammals (Wilson and Reeder 1993)4. This policy applies to all issues of the NOAA Technical
Memorandum NMFS-F/NEC and -E/NER series.

Robins, C.R. (chair); Bailey, R.M.; Bond, C.E.; Brooker, J.R.; Lachner, E.A.; Lea, R.N.; Scott, W.B. 1991. Common and scientific
names of fishes from the United States and Canada. Sth ed. Amer. Fish. Soc. Spec. Publ. 20; 183 p.

Turgeon, D.D. (chair); Bogan, A.E.; Coan, E.V.; Emerson, W.K.; Lyons, W.G.; Pratt, W.L.; Roper, C.FE.; Scheltema, A.;
Thompson, F.G.; Williams, J.D. 1988. Common and scientific names of aquatic invertebrates from the United States and Canada:
mollusks. Amer. Fish. Soc. Spec. Publ. 16; 277 p.

Williams, A.B. (chair); Abele, L.G.; Felder, D.L.; Hobbs, H-H., Jr., Manning, R.B.; McLaughlin; P.A.; Pérez Farfante, I. 1989.
Common and scientific names of aquatic invertebrates from the United States and Canada: decapod crustaceans, Amer. Fish. Soc.
. Spec. Publ. 17; 77 p.

Wilson, D.E.; Reeder, D.M. 1993, Mammal species of the world: a'taxonoimic and geographic reference. Washington, DC:
Smithsonian Institution Press; 1206 p.



H& tucshos EXPOSED

TO CONTAMINANTS

LARVAE VULNERABLE TO
LETHAL AND SUBLETHAL
CONTAMINANT LEVELS IN
WATER COLUMN

Figure 8.

nated bottom sediments in those estuaries. Adults lie partially
buried in bottom sediments; spawning occurs near the bottom;
eggs sink to the bottom, where they aggregate in clusters; and
larvae, after hatching, alternately swim upward and then sink to
the bottom (Bigelow and Schroeder 1953; Hughes et al. 1986).
Fin erosion (a good pollution indicator) is a commonly seen
condition in adults from polluted habitats (Ziskowski and
Murchelano 1975; O'Connor et al. 1987), and tissue levels of
pollutants in juveniles and adults can be significantly elevated.

Accumulation of chlorinated hydrocarbons in the tissues of
adults and transfer to eggs by females have been found in several
studies to contribute substantially to larval mortality. Evidence
was found that high mortalities of larval winter flounder in a
Massachusetts estuary (a tributary of Buzzards Bay) could be
related to pesticide pollution (Topp 1967; Smith and Cole
1970). Adult females concentrated DDT, DDE, and heptachlor
epoxide in their ovaries as spawning approached, and mortality
of post-yolk-sac larvae was estimated to approximate 100 per-
cent, The authors pointed out the similarity of this pattern of

reduced hatchability and larval mortality to that reported for »

several salmonid species, and considered to be the result of DDT
contamination (Burdick et al. 1964; Allison et al. 1964; Johnson
and Pecor 1969). The explanation offered by Burdick et al. was
that DDT was translocated to the maturing eggs, where, bound
to yolk fats, it remained inactive biologically until such fats were

JUVENILES IN INTIMATE
CONTACT WITH CONTAMINATED
SEDIMENTS

OFTEN CONTAIN HIGH :
CONTAMINANT LEVELS

Page

OVERWINTERING ADULTS
IN ALMOST CONTINUOUS
CONTACT WITH
CONTAMINATED
SEDIMENTS

Life history stages of demersal fish that are vulnerable to pollution.

metabolized by the developing fry; DDT at this time was then
released with lethal results.

In addition to mortality of winter flounder larvae, Smith
(1973) also reported that juveniles of age 2 and younger, year-
round residents of the polluted Massachusetts estuary, con-
tained higher tissue levels of pesticide residues than did the
migratory adults, but mortalities were not observed.

Ina related experimental study of DDT effects on develop-
ing eggs (Smith and Cole 1973), adult female winter flounder
were exposed to sublethal concentrations of DDT and dieldrin.
Dieldrin exposure did not affect survival to hatching, but DDT
exposure of females resulted in abnormal gastrulation and
mortality after fertilization, and in severe vertebral deformities
in 39 percent of the larvae at hatching. Experimentally induced
levels of the insecticides in gonads of spawning females dupli-
cated levels found in feral fish in an earlier study (Smith and
Cole 1970).

A more recent study of the effects of polluted habitats on
reproductive success of winter flounder was reported by Hughes
et al. (1986), Examining samples collected along a composite
pollution gradient in Long Island Sound, the authors found no
significant differences in percent viable hatch from eggs taken
from females at each site. In cytogenetic studies, however,
increased percentage of mitotic anomalies and reduced mitotic
rates characterized embryos from the more polluted sites, corre-


Page 12

Figure 10. Gross lesions in liver of winter flounder, Pleuronectes americanus. (Photograph courtesy of Dr. R. A. Murchelano.)

immune system of fish, and possibly primitive analogues of the
mammalian lymph nodes (Payne and Fancey 1989). However,
in an earlier study (Wolke, George, et al. 1985; Wolke,
Murchelano, et al. 1985), the numbers of aggregates in fish from
polluted areas were not greater than those from reference sites,
although their size was. In still other studies with different fish
species, aggregates were found to be more numerous and larger
in samples from polluted areas than in those from unpolluted
sites (Peters et al. 1987). It seems plausible, as Payne and Fancey
pointed out, that at low chronic levels of pollution, the cellular
defense system may function effectively, whereas at higher, more
toxic levels of pollution, phagocytosis may be impaired, leading
to a decrease in melanomacrophage aggregates.

One final study of pollution effects on adult winter
flounder - this one demonstrating synergism between chronic oil
pollution and protozoan (trypanosome) parasitization -- was
reported by Khan (1987). Infected fish exposed for 6 wk to oil-
contaminated sediments had higher mortality rates than
uninfected fish; intensity of infection was higher in oil-exposed
fish than in untreated controls; and retardation of gonad
development was more pronounced in the oil-treated, parasit-
ized fish than in the other experimental fish.

So here then, with winter flounder, we have a species that
has been examined extensively, from pathological, immunologi-

cal, physiological, and biochemical perspectives, in an effort to
understand pollution effects. Probably the most significant
findings, from a population point of view, are the demonstrated
negative impacts on larval survival due to exposure to chlori-
nated hydrocarbons - acting either on prespawning females or
on eggs and larvae, Next in order of significance might be the
severe morphological changes ~ liver tumors and fin erosion in
particular -- that have been seen in samples from badly degraded
habitats such as the New York Bight apex, western Long Island
Sound, and Boston Harbor. Not to be ignored, however, is the
observation by Haedrich and Haedrich (1974) that chronically
polluted environments seem to have little influence on winter
flounder populations.

The one missing ingredient in this scrutiny of pollution
effects on the species is a serious attempt to quantify the
observations made, and to provide numerical estimates of
the extent of population reduction that may result from
exposure to pollutants. Some narrowly focused efforts have
been made, such as Smith and Cole’s (1973) study of DDT.
effects on larval mortality, but we are left with little published
information that can be extrapolated to the entire population of
winter flounder on the northeast coast of United States.

At present, an initial effort is being made by staff members
of the NEFSC to develop and test a model to assess pollution