BODY SIZE AND THE ONTOGENY OF THE FUNCTIONAL-RESPONSE IN FISHES

The development of foraging abilities is crucial to the survival and s ubsequent recruitment of young fishes. We examined experimentally the notion that the foraging abilities of species are so different that us eful generalizations across taxa are impossible. We investigated the o ntogeny of feeding, reflected in their functional responses, in three Great Lakes' fishes, alewife (Alosa pseudoharengus), yellow perch (Per ca flavescens), and bloater (Coregonus hoyi). No strong evidence of sp ecies-specific differences in the ontogeny of feeding ability was foun d. A single size-based relationship explained 52-88% of the variation in the parameters of the functional response equation. We conclude tha t interspecific differences in feeding abilities of larval fishes may have been over-emphasized, and we suggest that interspecific differenc es should only be addressed within a size-based framework. This approa ch appears to provide an acceptable basis for first-order predictions of foraging abilities across taxa, for the identification of exception al abilities which may lead to advances in the understanding of foragi ng ability, and for estimating foraging rates for important species fo r which data are now lacking.