Variability in First-Year Growth of Yellow Perch (Perca flavescens): Predictions from a Simple Model, Observations, and an Experiment

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Abstract
First-year growth of yellow perch, Perca flavescens, varies by greater than an order of magnitude among populations and among cohorts within populations. The variability in growth rates of natural and enclosure-reared young-of-the-year yellow perch could be explained by the availability of benthic and/or plank-tonic prey (R2 = 0.093–0.098). Mean annual water temperature and cumulative degree-days did not add to the explanatory power of the relationships. The faster growing natural cohorts included more benthos in their diet; however, benthos is not necessary to sustain the highest growth rates because the fastest growth rates were observed in enclosure cohorts that lacked benthic invertebrates. Cohorts in lakes and enclosures that had a high proportion of Daphnia in the zooplankton community also supported higher first-year growth rates. The results of the enclosure experiment suggest that the dominant mechanism creating growth variability is density-dependent intra-age-class competition. Our empirical results, when coupled with a simple model, suggest that the assumption of a negative relationship between energetic costs of foraging and prey abundance, on a daily time scale, is the most appropriate because it acts to amplify growth variability across ranges of prey abundance.

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