WINTER MORTALITY OF YOUNG-OF-THE-YEAR HUDSON RIVER STRIPED BASS (MORONE-SAXATILIS) - SIZE-DEPENDENT PATTERNS AND EFFECTS ON RECRUITMENT

Winter mortality plays a significant role in the dynamics of some temp erate fish populations and has been shown to be size-dependent for som e species, but not for others. Our objective was to determine how wint er mortality affects the recruitment dynamics of Hudson River striped bass (Morone saxatilis). We used catch-per-unit-effort data from three separate surveys targeting young-of-the-year (YOY), overwintering, an d age 1 striped bass. Age 1 abundance was negatively correlated with t he severity of winter. In contrast, the abundance of age 0 fish was no t correlated with age 1 abundance, suggesting that winter mortality gr eatly modifies year-class strength. A progressive increase in the mean length of YOY fish, coupled with a decrease in the coefficient of var iation in length, occurred during some winters. Laboratory experiments showed that growth in length requires temperatures in excess of 10 de grees C; hence, these changes likely result from selective mortality o f smaller fish. Direct evidence of size-dependent mortality was obtain ed from a laboratory experiment that exposed fish to ambient condition s throughout the winter. Accounting for interannual differences in the severity and size dependency of winter mortality may improve our abil ity to evaluate striped bass year-class strength in the Hudson River.