Competitor Density and Size Effects on Aggression and Feeding in Cutthroat Trout: Implications for Aquaculture

ABSTRACT

Competitor density and aggressive behavior influences the ability of fish to use food resources during aquaculture production. Using cutthroat trout Oncorhynchus clarkii (Richardson) from the same filial generation, this study investigated the effects of both body size and rearing density on aggression and feeding behavior. Four experiments were conducted using different numbers of both small and large trout obtained after grading. In each experiment, regardless of the number of each size of fish, small fish made significantly fewer attempts to forage in comparison to large fish. However, the number of aggressive interactions increased as small fish densities increased. These results suggest that grading and rearing differently-sized fish separately during rearing will likely maximize growth and rearing efficiencies in wild-strain cutthroat trout during hatchery rearing.