Diurnal Feeding Rhythm of Plankton-Eating Salmon Juveniles in the Kamchatkan Waters of the Bering and Okhotsk Seas

摘要

For estimation of food requirements of salmon juveniles was provided with regular 24-hour stations during coastal surveys to carry out from 1970s, and also with surveys in the offshore of the Bering and Okhotsk Seas from 1990s (Karpenko 1982, 1998). For the period mentioned there were accomplished more than 30 diurnal (24 hour) stations; the results more of half of this number have been used in this work (Fig. 1). The surveys were accomplished in the estuary-coastal zone (12 stations) and in the coastal-offshore waters (7 stations). Diurnal feeding by three Pacific salmon species (pink, chum and sockeye salmon) and the basis of food spectrum of these species, consisting of plankton organisms, was studied. To provide a comparison of feeding dynamics we also used results of studying food composition of the species mentioned, obtained in the course of standard juvenile trawl surveys. Stomachs of several thousand fishes of each species and also the composition of plankton in several 24-hour stations of some surveys were examined. We also used the data on the diurnal feeding rhythm of salmon juveniles in the other regions of Far East.