The lipid status and feeding habits of yearlings of mykiss Parasalmo mykiss and coho salmon Oncorhynchus kisutch in autumn

Juveniles of coho salmon Oncorhynchus kisutch and mykiss Parasalmo mykiss at the age 1 + (yearlings) are differentiated by the content of different fractions of lipids (the lipid status), feeding habits, and by size-weight characteristics even eight months prior to smoltification. The juveniles of coho salmon and mykiss with high lipid status consume more calorific food items and, as a rule, have higher (on average) body length and weight. The juveniles with low lipid status consume less calorific organisms and have lower body length and weight. It is supposed that a considerable part of juveniles with high lipid status will migrate seaward the next year. The role of feeding habits in formation of this differentiation and, accordingly, in determination of timing of smoltification are discussed.