Compensatory growth following winter food deprivation in hatchery produced coho and chinook salmon smolts

Abstract

This study investigated whether coho and Chinook smolts that experienced food deprivation during the winter would increase growth rates in the spring and attain the same physiological attributes as smolts fed to satiation twice per week during the winter. The treatment groups were deprived of food for 10 and 16 weeks, centered on the winter solstice. All groups were returned to daily satiation feeding at the end of the respective food reduction periods. Treatment fish were smaller than control fish after food deprivation but had higher growth rates after feeding resumed and the 10 week fish were not significantly different in size from the control fish at the end of the study. Protein and lipid content decreased during deprivation, while moisture and ash content increased, but all groups were not different by the end of the study. Gill ATPase activity was unaffected by deprivation. Hematocrit levels declined in response to deprivation but a consistent response was not observed after feeding resumed. Coho and Chinook smolts subjected to winter food deprivation grew faster in the spring, restored body composition, and did not lose osmoregulation ability but the long-term effects on body size are unknown.