Community Research and Development Information Service - CORDIS

Demonstrated interaction between growth, adiposity and response to continuous light treatments on age of puberty in salmon and rainbow trout

Monitoring growth performance and age at puberty in large groups of individually tagged salmon at different sites revealed that the bigger individuals with high condition factor around the time of winter solstice had a much higher likelihood of early maturation than their smaller and leaner siblings. This clearly suggests a link to body size, growth and adiposity for recruitment into puberty. However, restricted feeding prior to winter solstice has less effect than expected on age at puberty when studied on 3 sibling groups with individually tagged salmon in sea cages.

This may imply that other factors than growth and adiposity modulates the outcome of a certain treatment. In this particular experiment, most males and many females matured at the grilse stage (i.e. after one-sea winter), in spite of the sibling groups coming from a selected low grilsing strain (i.e. selected for high age at puberty). It may be that other environmental factors in the small sea cages (5x5x5m) applied in this experiment to some extent may have masked or overruled the effects of restricted feeding and stimulated most males to recruit into puberty.

The plasma sex steroid profiles from January to August could imply that the low fed fish recruited into puberty (i.e. commenced rapid gonadal growth and full spermatogenesis or vitellogenesis) later in the spring than the normal fed fish. This implies some flexibility in the seasonal timing of recruitment to puberty, and that fish with a lower somatic status in terms of size and/or adiposity can catch up and commence maturation when offered surplus feed after January.

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