Comparing competitive ability and associated metabolic traits between a resident and migratory population of bull trout against a non-native species

Abstract

Juvenile bull trout Salvelinus confluentus from two geographically and ecologically distinct popu- lations were compared with regard to their ability to compete with non-native brook troutSalvelinus fontinalis in an artificial stream, and with respect to their rates of oxygen consumption. Bull trout collected from a migra- tory population foraged more successfully against brook trout competitors than those from a resident population, capturing more of a limited amount of food items presented. The migratory population was also more ag- gressive (measured by the number of nips, chases and lateral threat displays) against brook trout competitors than the resident population. Bull trout from the migra- tory population had a higher oxygen consumption rate (203 mg O2 kg · hr -1 ) in the field than similar sized fish from the resident population (183 mg O2kg · hr -1 ). These results suggest native bull trout have population-level variation in competitive ability against a non-native spe- cies and such competitive ability is positively associated with metabolism and migratory life history.