NOTE Age-0 and Age-1 Yellow Perch Diet in Southeastern Lake Michigan

Age-0 yellow perch (Perca flavescens) were collected during October 1998 and age-1 yellow perch were collected during June 1999 from southeastern Lake Michigan off St. Joseph and Muskegon, Michigan, to evaluate diets relative to recent ecosystem changes. Size range of yellow perch examined was 72 to 118 mm. In October at a 15-m site off Muskegon, both Gammarus spp. and Isopoda were found in nearly 71% of age-0 yellow perch stomachs, and accounted for 71 and 26% of the diet by weight respectively. The following spring at the 15-m site (June 1999), Gammarus spp. and Isopoda were only a small part of age-1 yellow perch diet, and Chironomidae and Mysis relicta dominated the diet. In October at depths of 25 to 35 m, M. relicta, was found in 100 and 80% of the age-0 yellow perch containing food off Muskegon and St. Joseph, respectively, and comprised over 96% of the diet by weight. Gammarus spp., Isopoda, and M. relicta were eaten in higher numbers than would be expected based on their low abundance in the environment. The high occurrence of Gammarus spp. and Isopoda in yellow perch diet may indicate ongoing changes in the nearshore benthic community. INDEX WORDS: Yellow perch, fish diets, Lake Michigan. 235 *Corresponding author. E-mail: [email protected] INTRODUCTION The ecology of the nearshore regions of southeast Lake Michigan has undergone widespread changes over the past two decades. Recent changes include possible disruption of the pelagic food web by zebra mussels (Dreissena polymorpha) (Marsden et al. 1993), major declines in the amphipod Diporeia (Nalepa et al. 1998), and invasion by Bythotrephes cederstroemi (Evans 1988). These changes could affect the diet and competitive interactions of fishes in Lake Michigan, including yellow perch (Perca flavescens), which feed on both zooplankton and zoobenthos (Crowder et al. 1981). Although yellow perch abundance in Lake Michigan has fluctuated widely among years (Wells 1977, Jude and Tesar 1985), a relatively large yearclass occurred in 1998 following nearly 10 years of poor recruitment (D. Jude, Ann Arbor, Michigan, Center for Great Lakes and Aquatic Sciences, University of Michigan, personal communication). The high relative abundance of age-0 yellow perch provided an opportunity to evaluate diet relative to the environmental changes which have occurred in the southeastern portion of the lake.