**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**



Experimental and spatial modeling of environmental factors affecting foraging success of age-0 yellow perch

Christine Mayer2, Jonathon Bossenbroek2, Thomas Bridgeman2, Stuart Ludsin3, Jeff Tyson4, Nathan Manning2



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



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.