Feasibility and effects of spatiotemporal closures on Baltic and Eastern North Sea herring stocks

Spatiotemporal closures are a common tool in fisheries management, for preventing overfishing or rebuilding stocks, reducing bycatch, or conservation. But potential side effects of closures include effort displacement, increase of the mortality of other species or life-stages, or alteration of different parameters of stock status through different mechanisms. Setting testable objectives and an appropriate evaluation framework including both ecological and socio-economic indicators are necessary when implementing closure areas.

In the Baltic Sea, spatiotemporal closures have been applied or simulated mostly in relation to cod and coastal species (e.g. pike, perch), but much less is known about the feasibility and potential effects of spatiotemporal closures on small pelagic fish like herring. The status of several herring stocks in the Baltic Sea and Eastern North Sea is currently raising concerns, and in 2023 DG MARE issued a special request to ICES on Central Baltic herring and Gulf of Bothnia herring, requiring advice on different possible measures to contribute to improve the SSB and age-structure of the populations. In particular, a roadmap was requested on six potential evidence needs, of which three concerning spatial and/or temporal closures.

The objectives of this project are to:

Objectives

- Specify the expected effects of spatiotemporal closures of the herring fisheries in the Baltic and Eastern North Sea in terms of stock size, age-structure, population structure, habitat changes, socio-economic costs and benefits

- Identify the corresponding time-area combinations to close, and assess how precisely they can be defined

- Based on genetic tools, identify the different stocks/populations that can co-occur in potential closed areas

- Assess the presence of ecological stock structuring despite a lack of genetic stock structuring of herring in the Baltic Sea

- Evaluate the quantitative intended effects and side-effects of these closures, in terms of stock size, age-structure, applicability to mixed fisheries, displaced effort, habitat, fuel consumption

- Evaluate the corresponding socio-economic short- and long-term impacts of these closure scenarios

- Considering the costs, benefits and pending uncertainties of the different possible spatiotemporal closures, in their different dimensions, provide recommendations on the use of spatiotemporal closures as a tool to improve the management of herring fisheries in the Baltic and Eastern North Sea