GENETIC-VARIATION IN LYSOZYME ACTIVITY AND SPONTANEOUS HEMOLYTIC-ACTIVITY IN ATLANTIC SALMON (SALMO-SALAR)

Lysozyme activity and spontaneous haemolytic activity (SH) were analys ed in three repeat blood samples of n = 960 fish from 34 full-sib grou ps within 12 paternal half-sib groups of Atlantic salmon, Salmo salar. At the first and second blood-sampling, the fish were vaccinated with a combined fish vaccine. After the third sampling, the fish were chal lenged with the pathogenic bacterium Vibrio anguillarum. A statistical ly significant effect of sire on lysozyme activity, SH activity, and s urvival after vibriosis challenge was found, providing evidence of sig nificant genetic variation in these traits. The estimated heritabiliti es were low to moderate (0.1-0.3) for the SH activity, and relatively low (< 0.1) for the lysozyme activity and survival after vibriosis cha llenge. The correlations between the three successive samplings were r elatively high for the SH activity, but low for the lysozyme activity based on both phenotypic and full-sib records. The full-sib correlatio ns between the lysozyme activity and SH activity were negative, sugges ting the existence of negative genetic correlations between these para meters. The correlations between the lytic activities and survival aft er vibriosis challenge were in general non-significant, except for a n egative phenotypic correlation between survival and lysozyme activity at second sampling.