In establishing harvest levels, resource management requires tradeoffs among conservation, economic and political concerns. The Precautionary Approach brings scientists, resource managers and stakeholders together to identify clear management objectives and to agree on population benchmarks that would initiate certain management actions when these benchmarks are crossed. A conceptual framework for applying the precautionary approach to marine mammal harvests is outlined. For a data-rich species, precautionary and conservation reference levels are proposed. When a population falls below the precautionary reference level, increasingly risk-adverse conservation measures are applied. A more conservative, risk-adverse approach is required for managing data-poor species. The framework has been implemented for the management of commercial seal harvests in Atlantic Canada.