| Summary: | Genetic parameters and genotype by environment interactions were estimated for early sexual maturity in Atlantic salmon. About 23984 (24999) individuals from 115 (118) full-sib families were tested in six sea-cages at five different locations in Norway. After 15 to 16 months in the sea, all individuals were classified for indications of maturation. Large variation in percentage of maturing were observed at different farms for two year-classes . The heritabilities estimated for early sexual maturity ranged from 0.02 to 0.11 on observed scales, and varied from 0.04 to 0.21 on liability scale. Besides, the heritability estimates on observed scale were roughly two times higher than those on the linear scale. The effects common to full-sibs other than additive genetic effects accounted for less than 5% of the total phenotypic variance on observed scale and less than 7% on liability scale . Gentic correlation were estimated between pairs of test environments, for 0.67 to 0.99 in year-class 1983, and 0.36 to 0.99 in year-class 1987. Most estimates of genetic correlation were significantly different from unity which indicated the presence of genotype by environment interaction. The low and significant correlations of effects common to full-sibs were estimated which indicates the effects common to full-sibs became smaller after separating into production environments. The genetic gain was calculated based on estimated breeding values of full-sib families, and unfavorable genetic gains were observed in present study both for expect gain and and realized gain. M-AA
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