GENETIC-VARIATION IN RED-CELL MEMBRANE FRAGILITY IN ATLANTIC SALMON AND RAINBOW-TROUT

The strength and flexibility of cell membranes are of particular importance for fish which routinely experience changes in the surrounding temperature. 496 fingerlings of Atlantic salmon from 50 full- and 25 halfsib groups and 133 fingerlings of rainbow trout from 14 fullsib groups were used to study the total as well as the genetic variation in cell membrane strength, measured as red cell membrane fragility. Fragility is defined as the salinity at which 50% of the red cells are hemolyzed, and gradient as the regression coefficient of the fragility curve at the turning point. Both parameters showed significant differences between Atlantic salmon and rainbow trout. The mean fragility curve for rainbow trout was similar to the fragility curve for the family of Atlantic salmon which had the strongest cell membranes. Heritability was high for fragility and medium for gradient. There was no significant genetic correlation between red cell fragility and susceptibility to experimental infection with furunculosis.