Influence of Prey Abundance on Species and Size Selection by Young Yellow Perch (Perca flavescens)

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Abstract
Prey selection by young yellow perch (Perca flavescens) (22-62 mm TL) was measured during 11 experiments over two summers, 1982-83. For each experiment fish were offered different densities of the same mixture of zooplankton from Oneida Lake, NY. As density of prey increased, several measures of selectivity for Daphnia either remained unchanged or declined, while all measures of selectivity for calanoids and cyclopoids increased. At all densities small to mid-sized Daphnia were preferred to large Daphnia. Reanalyses of other studies suggests this may be the general pattern for young planktivores, despite the contrary predictions of several models of prey selection. For young planktivores, differences in the nutritional quality of zooplankton prey, including resultant growth efficiency and speed of digestion, can account for these results.