The influence of male parental identity on growth and survival of offspring in Atlantic salmon (Salmo salar)

We found that young salmon fathered by precocious males grew faster than those fathered by anadromous males in Atlantic salmon (Salmo salar L.) during the time from hatching to yolk sac absorption, when the young are completely dependent on endogenous food resources. We first compared growth rate of artificially reared progeny of precocious and anadromous fish harvested as embryos directly on spawning grounds after reproduction. In a second experiment, we compared fish lengths and growth rate of offspring of precocious and anadromous fish that were caught before reproduction, artificially bred and reared in situ. The first experiment revealed that the progeny of precocious males had a significantly higher growth rate between hatching and yolk sac absorption, resulting in a larger body size, than anadromous offspring. In the second study, we found no significant differences in size between the two groups at any time during the experiment, which could be explained by the artificially enhanced reproductive success of potential subordinate males. Indeed, in the second experiment, the micro satellite analysis of paternal identity revealed that precocious males who fathered the most progeny had offspring with a larger mean size throughout the experiment, resulting in a marginally significant difference in length between precocious offspring and anadromous offspring. A higher but not significantly different mortality rate was also observed in anadromous than in precocious offspring throughout the second experiment. Our results indicate an inherent fitness advantage in some offspring fathered by precocious males, which may ultimately favour the development of precocious sexual maturity in Atlantic salmon.