Abstract
Three health indicators, plasma lysozyme activity, PCR-based detection of Renibacterium salmoninarum (a causative agent of bacterial kidney disease), and a necropsy-based Health Assessment Index (HAI), were used to examined genetically based variation in a captive population of chinook salmon (Oncorhynchus tshawytscha W.). The study group consisted of four distinct genetic cross-types: two purebred cross-types originating from mating wild parents (Big Qualicum River, BC, Canada) and domestic parents (Yellow Island Aquaculture, Ltd, Quadra Island, BC, Canada) and two reciprocal hybrid cross-types from the mating of wild and domestic parents. Narrow-sense heritability estimates for plasma lysozyme activity and the incidence of R. salmoninarum were calculated, and the genetic correlation of health indicator response with survival and growth was estimated. Significant differences among cross-types were found for plasma lysozyme activity, HAI, survival after a natural outbreak of vibriosis (but not after a vibriosis disease challenge), relative growth rate, size-at-age (420 and 615 days post fertilization), and R. salmoninarum presence. Despite a significant sire component of heritability for plasma lysozyme activity, the lack of significant heritability estimates for R. salmoninarum presence, and non-significant genetic correlations with performance variables indicates that selection to improve the health status of fish stock using the three health indicators examined here would likely not result in a measurable correlated response in survival or growth.
Published Version
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