Endurance of simulated winter conditions by age-0 walleye pollock: effectsof body size, water temperature and energy stores

Survival of age-0 walleye pollock Theragra chalcogramma in the absence of f ood followed simple bioenergetic models, with large body size, high initial condition, and cold temperatures all increasing survival rates. High survi val after >200 days at cold temperatures (<3.0 degrees C) indicated extende d tolerance of extreme cold, as long as sufficient body size and condition are attained during the summer growth period. Analysis of body constituents demonstrated a substantial increase in tissue water and depletion of lipid during starvation. Survivors had significantly higher lipid stores than mo rtalities, and larger fish had higher levels of lipid than smaller fish amo ng experimental survivors, laboratory fish that were never starved, and wil d fish. Fish returned to warm temperatures and high rations following 205 d ays of food deprivation displayed nearly complete recovery, with rapid incr eases in length, weight, and condition and minimal mortality (6.8%) during the subsequent 3 months. Age-0 walleye pollock collected in September in th e Bering Sea were substantially smaller and generally had lower lipid level s than fish used in laboratory starvation experiments, suggesting they are susceptible to size- and condition-dependent mortality during the winter. T he results are interpreted with respect to field distributions of age-0 wal leye pollock, overwinter survival, and synergistic effects of food and temp erature under varying models of climate change. (C) 2000 The Fisheries Soci ety of the British Isles.