Body Size and the Ontogeny of the Functional Response in Fishes

Abstract

The development of foraging abilities is crucial to the survival and subsequent recruitment of young fishes. We examined experimentally the notion that the foraging abilities of species are so different that useful generalizations across taxa are impossible. We investigated the ontogeny of feeding, reflected in their functional responses, in three Great Lakes' fishes, alewife (Alosa pseudoharengus), yellow perch (Perca flavescens), and bloater (Coregonus hoyi). No strong evidence of species-specific differences in the ontogeny of feeding ability was found. A single size-based relationship explained 52–88% of the variation in the parameters of the functional response equation. We conclude that interspecific differences in feeding abilities of larval fishes may have been overemphasized, and we suggest that interspecific differences should only be addressed within a size-based framework. This approach appears to provide an acceptable basis for first-order predictions of foraging abilities across taxa, for the identification of exceptional abilities which may lead to advances in the understanding of foraging ability, and for estimating foraging rates for important species for which data are now lacking.