Size-Selective Mortality in Young-of-the-Year Yellow Perch (Perca flavescens): Evidence from Otolith Microstructure

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Abstract
Large body size and high growth rates can strongly influence the survival of larval and juvenile fish during periods of intense predation pressure. Experimental evidence suggests that piscivorous fish often feed size selectively, but direct field evidence of size-selective mortality and of the effect of rapid growth on the intensity of size-selective mortality is limited. We used the growth record from otolith microstructure to test the hypothesis that young-of-the-year yellow perch (Perca flavescens) that survived their first growing season were the larger and faster growing members of their cohort. Strong size-selective mortality was identified within the first growing season for a slowly growing population. During the same year, a faster growing population showed minimal size-selective mortality. In contrasting the two populations, differences in predator species composition confounded the growth rate size-selectivity relationship, but it was clear that size-selective predation could be intense, favouring the survival of the faster growing individuals within a population.

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