Pink Salmon Competition Reduces Chinook Survival
Young chinook salmon fair poorly when competing with large numbers of pink salmon. Between 1984 and 1997, survival of juvenile chinook salmon released during even-numbered years from Chilliwack, Chehalis and Capilano hatcheries in southern British Columbia was 51 percent lower than for odd-numbered year releases.
This pattern corresponds with the dynamics of pink salmon populations that also inhabit southeastern Georgia Strait. During even-numbered years, hundreds of millions of juvenile pink salmon emerge from the Fraser River, while during odd-numbered years, almost no young pink salmon migrate.
In contrast, chinook salmon originating from hatcheries at Qualicum, Chemainus, Cowichan and Robertson rivers on southern Vancouver Island had uniform survival rates, regardless of the year released. These salmon face considerably less competition from pinks. Vancouver Island supports relatively small pink salmon runs of similar size each year.
Gregory T. Ruggerone and Frederick A. Goetz. 2004. Survival of Puget Sound chinook salmon (Oncorhynchus tshawytscha) in response to climate-induced competition with pink salmon (Oncorhynchus gorbuscha). Canadian Journal of Fisheries and Aquatic Sciences. 61(9): 1756-1770.