Policy Brief: Improved herring stock assessment aids sustainable management

Policy brief of the EMFAF project Improving the science basis of the fisheries management of the Gulf of Bothnia herring (ImproFish). Herring is a central species in the northern Baltic Sea fishery both in terms of landing weight and economic value. Herring is also a key species in the ecosystem, and an important food item to seals, birds, and predatory fish. During the last decades, the Gulf of Bothnia herring stock has undergone major changes in biomass, as well as in individual growth, weight-at-age, and maturity-at-age, but the causes of these changes are poorly understood. Consequently, the herring fisheries management can not properly account for these changes, their causes and consequences. To ensure good management of this important resource, improvements in the knowledge base are needed. ImproFish proposes three changes to the stock assessment. These changes could significantly improve the herring stock assessment, and hence support sustainable fisheries management. 1. Improve abundance indices 2. Consider fish size and growth 3. Identify sub-stocks