GENETIC-ANALYSIS OF LYSOZYME ACTIVITY AND RESISTANCE TO VIBRIOSIS IN FARMED CHINOOK SALMON, ONCORHYNCHUS-TSHAWYTSCHA (WALBAUM)

Twelve full-sib families of chinook salmon, Oncorhynchus tshawytscha ( Walbaum), reared in two environments, were examined for differences in disease resistance following a natural outbreak of vibriosis on a com mercial salmon farm in British Columbia, Canada. The two replicate gro ups differed in early rearing conditions, time of introduction to sea water, and netpen environment. Family mortality data revealed a signif icant genetic component to disease resistance (sire and dam). Cumulati ve mortalities in the two replicate groups were significantly differen t, at 8.1% and 5.7%. There were no significant genotype-by-environment interactions, indicating that the genetic contribution to the disease resistance was stable across environments, Plasma lysozyme activity i n both environmental groups was found to have a significant genetic co mponent (sire), There was a significant positive correlation between p lasma lysozyme activity and vibriosis mortality.