Fish size and prey availability affect growth, survival, prey selection, and foraging behavior of larval yellow perch

Zooplankton availability is strongly linked with the growth, survival, and ultimately recruitment of fish during their early life history. We examined how different types of zooplankton affected the growth. survival, and prey selection of larval yellow perch Perca flavescens in a series of laboratory experiments. The growth and survival of newly hatched (5-7-mm) to 12-mm yellow perch larvae was greatest when feeding on adult copepods and copepod nauplii. The growth and survival of yellow perch larvae longer than 12 mm was greatest when feeding on adult copepods and small cladocerans. Prey selection patterns closely followed trends in growth and survival; smaller larvae positively selected adult and naupliar copepods, whereas larger larvae selected adult copepods and small cladocerans. Foraging behavior experiments conducted with larvae longer than 12 mm revealed that these fish derived similar energetic gains when feeding solely on adult copepods and small cladocerans. The pathway to this energetic benefit differed substantially between prey types. Adult copepods yielded substantial energy to larval yellow perch because of the minimal handling time involved, despite the lower capture efficiency than with cladocerans. Conversely, yellow perch larvae realized high energetic gain from small cladocerans because of high capture efficiency, despite the higher handling times than with adult copepods. These results illustrate the importance of experimentally quantifying the feeding behavior of fish larvae to gain insight into how larval fish behavior and food type interact to shape larval fish growth patterns.