Significance of the Timing of Initial Feeding in Hatchery Rainbow Trout, Salmo gairdneri

Abstract

The age of initial food ingestion and the influence of age at initial food presentation on alevin food intake, survival, and subsequent growth were determined for rainbow trout, Salmo gairdneri. Alevins did not show any ingestive behavior nor was any food found in their gut, before initiation of swim-up. The withholding of food from the young fish for some time after swim-up did not impair their ability to learn to feed. Further, the most satisfactory time to initiate exogenous feeding of hatchery fish is when yolk reserves have been completely absorbed, bearing in mind that a considerable quantity of yolk may yet remain in the abdominal cavity after the externally visible yolk sac has disappeared.This study contradicts the hypothesis that delayed feeding of young rainbow trout causes or enhances the likelihood of nonfeeding.