Ecology of Atlantic salmon (Salmo salar) in British Columbia

Commercial culture of non-native Atlantic salmon (Salmo salar ) is currently the largest legal agri-food export crop in British Columbia (BC). Atlantic salmon are now routinely encountered in coastal marine and freshwater environments. The fate of escapees and what effects their presence may have on native salmonids and the broader coastal ecosystem have become contentious issues. This work represents the first empirical examination of the invasion ecology of Atlantic salmon in BC. Objectives were to test fundamental hypotheses regarding invasion potential including reproductive capability of escapees and the competitive viability of offspring. Additionally, principal factors explaining the failure historical Atlantic salmon introductions (1905–1934) were sought. Identifying of why past introduction failed may be informative in determining the present likelihood of Atlantic salmon colonization.; Escaped Atlantic salmon production fish are capable of spawning in BC rivers and may do so during a period when interspecific competition for redd sites is at a minimum. The first documentation of naturally produced feral Atlantic salmon juveniles in the Tsitika River support these data and confirm steelhead trout (Oncorhynchus mykiss) as the principle niche equivalent competitor. Laboratory analyses of juvenile interspecific interactions suggest Atlantic salmon are capable of persisting in BC rivers if Atlantic salmon gain access to habitat and establish territories prior to steelhead. The presence of feral juvenile Atlantic salmon in the wild increased intraspecific agonism among sympatric steelhead but interspecific interactions were minimized by microhabitat partitionment. Therefore steelhead agonism is not likely to act as a biological resistance factor in Atlantic salmon invasion. The pivotal role of prior access to habitat in Atlantic salmon juvenile performance was investigated in a pilot study. Results suggest current under-representation of steelhead in BC rivers (and abundance of underutilized habitat), is likely a significant factor in explaining why historical Atlantic salmon introductions failed and the apparent success to date of current aquaculture escapees.; The fate of aquaculture escapee Atlantic salmon in BC remains a contentious issue. This work does not afford definitive impact predictions however does provide empirical evidence that runs counter to prevailing opinions that accompanied Atlantic salmon into BC. The capacity of Atlantic salmon to establish in BC is demonstrated here however the breadth and magnitude of associated effects remain in question.