Management of the Gulf of Riga herring (Baltic Sea): Lessons learned and challenges ahead

Maximum sustainable yields and maintaining the intraspecific biodiversity are the aim in fish stock management. Here populations-based management would be the preferred practice. Yet available stock discrimination methods result in establishing the conventional assessment/management units as a compromise. The Baltic herring (Clupea harengus membras L.) exhibits remarkable geographical variability, forming up to12 local populations. Due to reasons mentioned above, only two distinct local populations (Gulf of Riga, (GoR) herring and Gulf of Bothnia herring), are treated as separate assessment and management units. The paper describes the annual workflow of the management process, collection of the biological information from commercial catches and from the research surveys. Management history of GoR herring has revealed a number of challenges. Acoustic estimates are the only fisheries-independent data applied in GoR herring stock assessment. The study highlights the need for methodological changes what are expected to allow enhancing the quality of stock estimates, serving as the basis for the management decisions. We show that while before climate - driven regime shift (prior - 1990s) recruitment was determined by the winter temperature, affecting survival of Young of the year, a new major productivity bottleneck is in increasing spring-summer water temperatures during hatching and larval first-feeding stage.