Abstract
Juvenile rainbow trout (Salmo gairdneri) were fed six diets containing different percentages of soybean meal as a replacement for herring meal for a 168-day period. Fish fed a diet with 65% soybean meal and no herring meal grew at an acceptable rate and remained in good health. Weight gain offish fed a diet with 5% herring meal and 56% soybean meal was not significantly different from that of fish fed a diet with 20% herring meal and 31% soybean meal. Protein retention, energy retention, percentage mortality, and whole-body composition (crude fat excepted) did not vary significantly among fish fed the various diets.