Abstract
Yellow perch ( Perca flavescens ) occur in lakes varying widely in trophic status and zooplankton abundance. We initially hypothesized that the selection of zooplankton by larval yellow perch would vary among lake trophic classes based on optimal foraging theory suggesting that niche breadth would be narrow in lakes with more zooplankton prey. We also hypothesized that selection would show ontogenetic shifts as larval yellow perch grew and gape size and swimming ability increased. We explored patterns in zooplankton prey selection in larval yellow perch across 14 Michigan lakes ranging widely in size and trophic status. Zooplankton samples and larval yellow perch diet samples were collected concurrently in each lake, allowing evaluation of selection at a fine temporal scale. We used Chesson’s Rescaled Index of Selection as a measure of selection. We found that selection for prey type and size varied in relation to fish size but showed no significant difference across lake trophic status. The general ontogenetic pattern of selection starts with copepod nauplii being preferred by the smallest yellow perch, progressing to cyclopoid copepods, small cladocerans such as Bosmina and calanoid copepods, and culminating with large cladocerans such as Daphnia. These ontogenetic shifts occur quite rapidly as young yellow perch grow, highlighting the importance of timing and species composition of zooplankton blooms in the spring.