ESTIMATES OF GENETIC AND PHENOTYPIC PARAMETERS FOR BODY-WEIGHT, GROWTH-RATE AND SEXUAL MATURITY IN ATLANTIC SALMON

Body weights were recorded at tagging on 1704 one year old presmolts ( offspring of 26 males and 115 females) and again after 4, 12, 16, 24 a nd 27 months in seawater. After 16 months in seawater the fish were cl assified, based on secondary sex characters, into early maturing fish and early immatures and after 27 months into normal maturing fish and non-matures. Sexually maturing fish were significantly heavier than ea rly immatures and non-matures several months before secondary sex char acters reduced their market quality. Estimated heritabilities were 0. 10 to 0.32 for the six weight traits; 0.04 to 0.26 for specific growth rate (% day-1) in the periods between each weight recording and 0.09 and 0. 1 5 for early and normal sexual maturity when estimated on the observed binary scale (0.34 and 0.24, respectively, transformed to the underlying liability scale). Genetic correlations between the weights were medium to high (0.48 to 0.98), while the results indicated a neg ative genetic as well as phenotypic correlation between specific growt h rate in adjacent periods. Genetic correlations of early sexual matur ity with weights until 16 months in seawater were all positive (0.11 t o 0.49).