Effect of paternal life-history form and egg size on offspring life-history traits in masu salmon Oncorhynchus masou

To clarify the effect of paternal life-history form and egg size on offspring life-history traits (e.g., growth and maturation) in masu salmon (Oncorhynchus masou), we studied an artificially fertilized population for 3 years using mark-recapture methods. The body size of offspring in early life was associated with egg size, but not paternal life-history form. By contrast, the growth rate of individuals during summer and winter seasons was not influenced by egg size or paternal life-history form. Movement within the tributary differed between males and females, with more females moving downstream during early life stages compared to males. However, the effects of egg size and paternal life-history form on the movement of offspring were not detected. Out of 192 males that remained in the tributary, 77 had relatively large body sizes and reached sexual maturity at one year old. The probability of maturation was associated with the body size in September, but not with paternal life-history form and egg size. We concluded that offspring life-history traits are profoundly influenced by environmental conditions, whereas they are slightly influenced by parental genetic effects.