The effects of variation in acclimation- and growth-maximizing behavioural types of outcrossed Chinook salmon (Oncorhynchus tshawytscha) on growth and survival in captivity

While outbreeding is a common method used to introduce variation to a broodstock in aquaculture to maintain healthy genetic stocks, little consideration is given to identifying stocks that can experience easy acclimation to captivity. Because the ability of individuals to behaviourally adjust to novel captive conditions influences who will reach broodstock age, behaviours can be used to screen for potential source stocks for outbreeding. To determine the effects outbreeding has on the variation of behavioural phenotypes produced, and whether these phenotypes can be predictive of growth and survival to captive conditions, an experimental design was created consisting of seven wild-domestic hybrid stocks of Chinook salmon (Oncorhynchus tshawytscha) and domesticated control stock. Behavioural assays were conducted on the same captive individuals as juveniles in fresh water and sub-adults in salt water to test for the occurrence of acclimation / growth-maximizing behavioural phenotypes such as flexibility: exploration, neophilia, and predator responsiveness; and growth-promotion: sociality, activity, and food-motivation. These behaviours were then contrasted against performance (growth and survival) within and across life-history stages. We found inter-population variation in four distinct behavioural types at each life-history stage. Still, we found individuals that were less shy (LMM: β = -0.14, P < 0.001), or inactive (β = -0.32, P = 0.004), or more social (β = 0.018, P = 0.01) as juveniles; or were risk-averse (β = 0.022, P = 0.056) as sub-adults experienced greater short and/or long-term performance. While not one behavioural type emerged in predictive power of performance, better performing stocks possessed more of these desired behavioural traits. By identifying which behavioural attributes contribute most to first-generation acclimation, screening tools can be developed to recommend natural populations for outcrossing, balancing both production and animal welfare.