Abstract
Heritabilities, and genetic and phenotypic correlations were estimated for total length, body weight, body depth, and head length of masu salmon Oncorhynchus masou. During 4 month period after first starting to feed in juveniles, 20 full-sib and 10 half-sib families were reared separately and each family was given environmental conditions as equal as possible. Data were collected at 4 months and 8 months of age by individual tagging with fin cut 1994. The same experiments using colored fluorescent elastomer tags as family markers were repeated in 1995. Overall survivals in the study varied among each family. The heritabilities of growth related traits estimated for sire components (in 1994 and 1995) at 4 months age were found to be quite high: ranging between 0.35 and 0.47 in total length. Estimated heritabilities at 8 months age in each year ranged from 0.18 and 0.42 in total length. Similar values were obtained in the other three related areas of body weight, body depth and head length. Genetic and phenotypic correlations among the growth traits were all positively high. Genetic variations in body weight were found to be remarkably high, about three times as high as that in the total length of the masu salmon. Phenotypic correlations between 4 and 8 month ages were 0.45-0.63. Selective breeding in growth related traits would be effective in masu salmon culture.
