lysozyme, bacterial kidney disease, necropsy, heritability, growth, Health Assessment Index
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 growthwas estimated. Signi¢cant di¡erences 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 signi¢cant 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.
Johnson, Rachel M.; Bryden, Colleen A.; and Heath, Daniel D.. (2003). Utility of genetically based health indicators for selection purposes in captive‐reared chinook salmon, Oncorhynchus tshawytscha. Aquaculture Research, 34, 1029-1036.
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