Domestic-wild hybridization to improve aquaculture performance in Chinook salmon

Salmon farming is one of Canada's fastest growing industries and contributes to Canada's economy as well as creating jobs in rural areas; however, the industry is challenged by the need to balance production economics against environmental impacts. While Atlantic salmon (Salmo salar) are the most commonly farmed species on the west coast of Canada, Chinook salmon (Oncorhynchus tshawytscha) are a valuable alternative, as they fill a niche market and generate reduced environmental concerns because they are a native species. However, Chinook salmon have not been systematically domesticated, and their performance remains highly variable. Here we report on the results of a research program designed to develop a performance-enhanced hybrid Chinook salmon stock. Growth and survival were estimated for seven domestic-wild hybrid Chinook salmon crosses at various freshwater stages and during 15 months of saltwater rearing at a British Columbia Chinook salmon farm and compared with domestic-domestic crosses (control). The project included 8640 individually (PIT) tagged offspring from the domestic stock and seven domestic-wild hybrid stocks originating from the Lower Fraser Valley, Lower Mainland Vancouver, and Vancouver Island, British Columbia, Canada. Within each stock, milt from 10 sires was used to fertilize eggs pooled from 15 highly inbred domestic females to produce 80 half-sib families. Our breeding design allows the partitioning of stock and sire effects, and minimises maternal genetic and maternal environment effects. Replicates of all families were reared under common environmental conditions in both fresh- and salt water and monitored for body size and survival. There was significant variation in survival, body size, and saltwater biomass among the Chinook salmon hybrid stocks. The performance of some of the hybrid crosses exceeded that of the fully domesticated stock, although the pattern of performance varied with rearing stage. Overall, two hybrid stocks consistently outperformed the domestic stock in terms of survival, growth, and biomass estimates. We systematically assess production performance across a wide range of wild-domestic hybrid crosses in a Pacific salmon species, and our results highlight opportunities to improve the production performance of Chinook salmon culture.