**The title, authors, and abstract for this completion
report are provided below. For a copy of
the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**
2University of Toledo
Lake Erie
Center
6200 Bayshore
Rd.
Oregon, OH
43618
3The Ohio State University
Aquatic
Ecology Laboratory
1314 Kinnear
Rd.
Columbus, OH
43212
4Ohio Department
of Natural Resources
Division of
Wildlife
305 E.
Shoreline Dr.
Sandusky, OH
44870
December 2010
ABSTRACT:
The
goal of this project was to describe how the foraging of age-0 yellow perch
responds to turbidity and to model how this response will affect growth and
abundance of fish in a turbid ecosystem.
Understanding the effect of turbidity on fish populations is important
because cultural eutrophication and land-based sedimentation are concerns
across the Great Lakes. There were two
specific objectives for this project: 1) Quantify the interactive effects of
zooplankton density and turbidity type (sediment and phytoplankton) and level
on foraging rates of age-0 yellow perch using laboratory experiments; and 2)
Build a spatially explicit foraging and growth model for age-0 yellow perch in
the western basin of Lake Erie by combining laboratory foraging data with existing
and supplemental field data on habitat variables and yellow perch size. For the
first objective, laboratory experiments completed in 2007 showed that prey
consumption usually increases with prey density, but fish foraging in highly
turbid areas may have a modified functional response and therefore do not
forage at the expected rate. Across prey densities, consumption by yellow perch
was less in phytoplankton turbidity compared to sediment turbidity. For larvae,
this effect was dependent on turbidity level (larger difference at higher
turbidity), while for juveniles the difference with turbidity type was equal
across turbidity levels. Our results suggest that phytoplankton blooms are
detrimental to the ability of late season age-0 yellow perch to forage and
support the need to control factors leading to excessive phytoplankton growth
in lakes. Results from these experiments are described in a manuscript entitled
“Wellington C. Mayer C.M., and Bossenbroek J. 2010. Effects of turbidity and
prey density on the foraging success of age-0 yellow perch (Perca flavescens). Journal of Fish Biology
76: 1729–1741. In the second objective,
a modeling exercises completed in 2010, we show that turbidity has a
significant effect on the August length and abundance of age-0 yellow perch in
the Western Basin of Lake Erie. The results of this model are described in a
manuscript entitled “Effects of Turbidity on the Length and Abundance in August
of Age-0 Yellow Perch in the Western Basin of Lake Erie”, which will be submitted
to the Transactions of the American Fisheries Society. Generalized Additive
Models (GAMs) were used to analyze the relationship between environmental
variables and abundance and size of yellow perch across a suite of
environmental variables drawn from the ODNR and OMNR 1984-2008 interagency data
trawls. The best-fit model for abundance revealed that August abundance
decreased dramatically as turbidity decreased from 0.25 to 1 m of Secchi depth,
indicating that the higher turbidity observed in the southeast area of the
basin provided some advantage to survivability for age-0 yellow perch. The
best-fit model for length in August showed a steady increase in length of
individuals as turbidity decreased up to about 3m of visibility, where the
relationship levels off. These relationships indicated that there is an
increasing ability to feed, and thus increased growth, as turbidity levels
decrease. Together, results from these
two objectives highlight the need to know the quality and timing of turbidity
events in order to predict how conditions will affect yellow perch
populations. Although higher turbidity
may be associated with higher age-0 yellow perch abundance, late season
turbidity, especially algal blooms, may reduce foraging and growth.