Lipid Status and Feeding Habits of Salmonid Juveniles
in the Year Preceding Seaward Migration as Factors Controlling
Their Future Smoltification

D. S. Pavlov^a, N. N. Nemova^b, P. I. Kirillov^a, E. A. Kirillova^a, Z. A. Nefedova^b, and O. B. Vasil’eva^b

^a Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskii prospekt 33, Moscow, 119071 Russia

^b Institute of Biology, Karelian Research Center, Russian Academy of Sciences, Petrozavodsk, Russia

e-mail: pavlov@sevin.ru

Received December 12, 2006

Abstract—Juveniles of coho salmon Oncorhynchus kisutch (Walb.) and mykiss Parasalmo mykiss (Walbaum)
of the same age (1+) become differentiated as early as eight months before smoltification and seaward migra-
tion by their lipid level, feeding habits, and size and weight parameters. It is found that juveniles of coho salmon
and mykiss with a high lipid status have a greater (on average) length and weight and consume more calorific
food items. The juveniles with a lower lipid status have a lower length and weight and consume less calorific
organisms. It is presumed that a considerable part of juveniles with a high lipid status will migrate seaward next
year. The role of the trophic factor in development of this differentiation and, accordingly, in determination of
smoltification dates is discussed.

DOI: 10.1134/S003294520703006X

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