Estimation of heritabilities of growth traits, and phenotypic and genetic correlations in juvenile masu salmon Oncorhynchus masou

Heritabilities, and genetic and phenotypic correlations were estimated for total length, body weight, body depth, and head length of masu salmon Oncor hynchus masou. During 4 month period after first starting to feed in juveni les, 20 full-sib and 10 half-sib families were reared separately and each f amily was given environmental conditions as equal as possible. Data were co llected at 4 months and 8 months of age by individual tagging with fin cut 1994. The same experiments using colored fluorescent elastomer tags as fami ly markers were repeated in 1995. Overall survivals in the study varied amo ng each family. The heritabilities of growth related traits estimated for s ire components (in 1994 and 1995) at 4 months age were found to be quite hi gh: 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. Si milar 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 w ere found to be remarkably high, about three times as high as that in the t otal length of the masu salmon. Phenotypic correlations between 4 and 8 mon th ages were 0.45-0.63. Selective breeding in growth related traits would b e effective in masu salmon culture.