Yellow Perch Population Assessment in Southwestern Lake Michigan, Including Evaluation of Sampling Techniques and Identification of the Factors that Determine Yellow Perch Year-Class Strength April 1, 2007 – March 31, 2008

The objectives of this study are to expand the Illinois Department of Natural Resources (IDNR) annual yellow perch (Percaflavescens) stock assessment data, monitor densities of age-0yellow perch cohort, and identify some of the factors likely to have limited yellow perch recruitment since 1989. We sampled adult yellow perch during the spring to assess the reproductive potential and age and size structure of the spawning population. Anal spines were collected from yellow perch at two known angling sites and analyzed to determine the angler-caught age distribution in 2007. Age-0 yellow perch were sampled at multiple depths and distances from shore with neuston nets, a mid-water Tucker trawl, gill nets, and a bottom trawl. We compared the use of gill nets and bottom trawling for sampling demersal age-0 yellow perch. We also monitored yellow perch egg skein densities, post-larval yellow perch abundance, age-0 yellow perch diets, and continued to evaluate factors that might regulate yellow perch year-class strength. The results of this project will enable fish managers to develop effective management strategies for this important native sport fish. Larval yellow perch sampling will expand our understanding of the early life history of yellow perch in terms of larval fish movements, feeding behavior, and survival. Early life history data will eventually lead to an understanding of factors that affect juvenile survival and future year-class strength. We highlight below some of the important results from 2007 sampling associated with our study objectives.