Competition among juvenile Atlantic salmon (Salmo salar) and steelhead (Oncorhynchus mykiss): relevance to invasion potential in British Columbia

Atlantic salmon (Salmo salar) are routinely captured in both freshwater and marine environments of coastal British Columbia (Canada). Recent evidence suggests that this species is now naturally reproducing in Vancouver Island rivers. Our objective was to quantify the performance of each species in i ntra- and inter-specific competition by assessing the competitive ability o f Atlantic salmon sympatric with native niche equivalent steelhead - rainbo w trout (Oncorhynchus mykiss). Significant behavioural differences, particu larly with respect to agonism, were observed between species; however, the status of an individual as resident or challenger was the best predictor of performance. Resident fish always outperformed challengers, regardless of species. Thus, we suggest that Atlantic salmon may be capable of colonizing and persisting in coastal British Columbia river systems that are underuti lized by native species, such as the steelhead.