Analysis of an estuarine striped bass (Morone saxatilis) population: influence of density-dependent mortality between metamorphosis and recruitment

Compensation due to density-dependent mechanisms is essential for the maint enance of an exploited fish stock. Understanding compensation is important for understanding population regulation and responses to added mortality. W e examined possible density-dependent effects on striped bass (Morone saxat ilis) in the San Francisco Estuary. Three sets of data from sampling progra ms for young striped bass showed density-dependent mortality between 1 mont h of age and 8-12 months. The relationships between two indices of young st riped bass abundance and recruitment at age 3 fit a Beverton-Holt function, also indicating density dependence. The carrying capacity, as determined b y the asymptote of the Beverton-Holt curves, has declined over the last two to three decades. These results are consistent with a compensatory mechani sm based on food limitation occurring after metamorphosis and with the decl ine in food resources observed in the estuary over the same period. The dec line in striped bass over the last two to three decades may be partly due t o this declining carrying capacity.