Investigating effects of behavioural flexibility and neuroplasticity on acclimation success of outcrossed Chinook salmon (Oncorhynchus tshawytscha): applications in aquaculture

After generations of artificial selection and domestication of animals for consumption, unintended consequences such as inbreeding depression have impacted production via impacts on growth and survival. Outcrossing is a common method used to negate these effects and introduce variation to the broodstock. This thesis aims to assess how animals respond to novel environments both behaviourally and transcriptionally to captivity. Seven wild-domestic hybrid stocks of Chinook salmon (Oncorhynchus tshawytscha) and a highly inbred domesticated stock population included as control were used in this study to determine what, if any, effects outbreeding has on the variation of behavioural and neural transcriptional phenotypes produced. Two behavioural assays were completed on the same set of individuals as juveniles and as adults to test for the occurrence of traits involved in the acclimation to new environments via traits such as sociality, exploration, activity, predator responsiveness and neophilia. These behaviours were then contrasted against performance at each time point and across life-history stage. We found inter-population variation in four distinct behavioural types and changes across ontogeny. In each life stage we demonstrated certain behaviours are linked to performance. Whole brain samples were collected from juvenile and adult fish to assess via qRT-PCR mRNA expression of genes associated with a variety of neural traits purportedly involved in acclimation: stress responses, synaptoplasticity and neurogenesis. A subset of transcriptional profiles and candidate genes related to neural stress responses and neuroplasticity were able to predict performance, however, there were no stock differences in their expression. As more animals are brought into captivity for consumption or conservation it is important to consider how behavioural and neural responses integrate to affect animal survival and develop efficient screening processes

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 \u3c 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

Domestic-wild hybridization to improve aquaculture performance in Chinook salmon

Salmon farming is one of Canada\u27s fastest growing industries and contributes to Canada\u27s 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