GENETIC-VARIATION IN RESISTANCE TO BACTERIAL KIDNEY-DISEASE WITHIN AND BETWEEN 2 STRAINS OF COHO SALMON FROM BRITISH-COLUMBIA

Genetic variation in resistance to bacterial kidney disease (BKD) was investigated between and within the Robertson Creek and Kitimat River strains of coho salmon Oncorhynchus kisutch from British Columbia. For each strain, juvenile fish from 20 pairs of paternal half-sib families were inoculated with Renibacterium salmoninarum, the causative agent of BKD. Mortality due to BKD began 26 d after inoculation, and had reached a level of 68% when the experiment was terminated on day 113. Survival was greater (P = 0.08) and time to death (in days) was longer (P < 0.05) among juvenile coho salmon from the Kitimat River strain than among those from the Robertson Creek strain. The estimated sire component of survival heritability, based on binomial data, was 0.53 +/- 0.16 (mean +/- SE), which became 0.90 +/- 0.26 when survial was considered to be a threshold trait. The sire component estimate of heritability of time to death was 0.26 +/- 0.10. There was no consistent genetic correlation between fish weight and survival time after inoculation. The results that increased BKD resistance could be achieved in domesticated coho salmon brood stocks both by judicious choice of the wild progenitor strain and by subsequent selective breeding.