Chinook salmon impede Atlantic salmon conservation in Lake Ontario

Abstract– Non‐native species can have substantial impacts on successful restoration of native species. Here, we examined effects of chinook salmon (Oncorhychus tshawytscha), an exotic species introduced to Lake Ontario to enhance recreational angling, on reintroduced Atlantic salmon (Salmo salar) in a Lake Ontario tributary stream. Field enclosure studies revealed that adult Atlantic salmon activity rate was elevated, nest establishment delayed and mortality rates higher in the presence of chinook salmon. These results suggest that chinook salmon in Lake Ontario streams during fall spawning could impede successful re‐establishment of Atlantic salmon in the lake.