Overwinter Mortality and Energy Depletion in Juvenile Pacific Salmon Off the West Coast of British Columbia and Alaska

摘要

Winter is generally considered a critical period in the early life of fish. As prey productivity and water temperature are typically lower during this season, it is commonly believed that food consumption rates of juvenile fish are greatly reduced over winter and insufficient to meet their energy demands. As a consequence, fish are expected to rely on the energy reserves accumulated during the growing season to fuel their metabolic functions during the winter months. Thus, fish with low energy reserves at the end of the growing season may be expected to experience higher mortality over winter. Smaller and slow growing fish are believed to be particularly vulnerable to winter conditions due to their lower lipid reserves. In addition, because laboratory experiments have consistently showed that mass specific metabolic rates decreased with size, we may expect that energy depletion over the winter months would be higher in smaller fish. The objectives of this study were to examine the winter ecology of juvenile salmon, and to test the hypotheses that overwinter mortality and energy depletion are higher in smaller salmon (Beamish and Mahnken 2001).