1 i ,
vvEPA
United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
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Research and Development
EPA-600/S3-82-072 Oct. 1982
Project Summary
Impact of a Once Through
Cooling System on the
Yellow Perch Stock in the
Western Basin of Lake Erie
A. L. Jensen and T. A. Hamilton
Conventional stock assessment
models have been applied to determine
the impact of entrainment and im-
pingement at the Monroe Power Plant
on the yellow perch stock of the
western basin of Lake Erie. First the
surplus production model was applied.
Biological parameters of the model
were estimated from commercial
catch and effort data, and entrainment
and impingement coefficients were
estimated from power plant data. The
model was used to estimate stock
biomass, egg production, and larvae
production; the proportions entrained
and impinged were then estimated.
The impact of water withdrawal on the
equilibrium standing stock and maxi-
mum sustainable yield from the
fishery were estimated and the impacts
of increased water withdrawal were
simulated.
An analytical model was also applied.
Parameters of the analytical model
were estimated using power plant
data, biological data available in the
literature, and commercial catch data.
The model was used to estimate the
age structure and biomass of the
perch stock and to estimate the
impact of the power plant on abun-
dance of the impingeable stock and
biomass of the exploited stock. The
level of impact was examined under a
range of mortality conditions. The two
models are much different in terms of
mathematical structure and in terms
of the data applied for estimation of
parameters but give similar estimates
of impact of about a 1% to 3%
reduction in the size of the exploited
stock.
This Project Summary was devel-
oped by EPA's Environmental Research
Laboratory, Duluth, MN, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
The Monroe Power Plant isa four-unit
3150 megawatt, coal-fired plant located
on the western shore of Lake Erie. The
plant uses once through cooling, and
has a pumping capacity of 0.29 x 1010
mVyr. Its maximum requirement is
about 85 mVsec. The yellow perch
(Perca flavesences), a highly valued
sport and commercial fish, is one of the
most frequently entrained and impinged
fish at the power plant.
For assessment of the impact of
entrainment and impingement on the
yellow perch stock of western Lake Erie,
at the Monroe Plant, two conventional
fishery assessment models were applied.
The surplus production model, which
uses commercial catch and effort data
to estimate model parameters, was
applied. The fitted model was used to
estimate stock size and the number of
eggs and larvae produced. It was also
used to determine the proportion of the
US GOVERNMENTPRINTINCIOFFICE 1982-559-017/0855
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standing stock impinged and the propor-
tion of larvae entrained andtodetermine
the impact of entrainment and impinge-
ment on the standing stock. The
maximum sustainable yield was then
determined. The impact of increased
water withdrawals on the biomass of
the stock and maximum sustainable
yield was estimated.
An analytical or dynamic pool model
was also applied. Biological data from
the literature and power plant data were
used to estimate parameters. The
impact on total population size and
fishable biomass were assessed under
a range of natural and fishing mortality
conditions.
Over the twelve-month period an
estimated total of 861,000 fish were
impinged, of which 14.2% were yellow
perch. During this period, 21,392,301
larvae were entrained, of which approx-
imately 23% were yellow perch. During
the same period, 13,083,131 eggs were
entrained at Monroe. Only 0.7% of the
eggs were yellow perch, but 77% of the
eggs were not identified. Assuming that
the same relative amount (0.7%) of the
unidentified eggs were yellow perch,
the total percent of yellow perch eggs
entrained was 2.9%.
The impact which an additional
mortality source, such as a power plant,
exerts on the fishable biomass and the
population size is a function of natural
and fishing mortality. Four cases were
examined that represented different
possible combinations of natural and
fishing mortality rates. This provided an
assessment of a wide range of impacts
on the yellow perch population size and
biomass. These cases ranged from an
adult population experiencing low
levels of both fishing and natural mortal-
ity to one experiencing high levels of
both variables.
Conclusions and
Recommendations
The Monroe Power Plant has a
relatively small impact on the yellow
perch population in the western basin of
Lake Erie. The maximum reduction in
fishable biomass of 1.75% occurs with a
low natural mortality and a high fishing
mortality, the conditions' which might be
most representative of the actual
conditions in the lake.
The two assessment models, though
based on entirely different data for
parameter estimation, yielded similar
predicted impact. The surplus production
model gave the reduction in biomass at
full pumping capacity as 3.08% while
the dynamic pool gave 1% to 3.5%.
Since the two models gave similar
predicted impacts, the criterion used to
select between them would be the ease
of application. All of the surplus
production model parameters except
eggs per unit biomass and egg and
larvae mortality can be estimated
objectively from catch and effort data. If
a large amount of such data are
available, the surplus production model
is most easily applied.
Application of the two models together
gives nearly independent estimates of
impact, and enables assessment of
impacts with some confidence.
A. L Jensen and T. A. Hamilton are with the School of Natural Resources,
University of Michigan, Ann Arbor, Ml 48109.
Nelson Thomas is the EPA Project Officer (see below).
The complete report, entitled "Impact of a Once Through Cooling System on the
Yellow Perch Stock in the Western Basin of Lake Erie," (Order No. PB 82-240
284; Cost: $10.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Large Lakes Research Station
Environmental Research Laboratory—Duluth
U.S. Envirpruriental Protection Agency
Grosselle*MI48138
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
*
AGENCY
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