A spatio-temporal framework for evaluating and minimizing economic and stock impacts of fishing closures - insights from the western Baltic cod fishery

Abstract

Fishing closures and marine protected areas are essential measures in fisheries management. This study applied a statistical species distribution model (LGNB-SDM) to design various types of fishing closures based on the concept of essential fish habitats. The potential effect of these closures were subsequently evaluated with the spatial-explicit management strategy evaluation tool DISPLACE to identify the optimal balance between socio-economic and biological impacts and sustainability demands within an ecosystem approach. The application focused on the management of the western Baltic (WB) cod, for which we used a recent 15-year time-series (2005-2019) to unravel persistent nursery and spawning grounds. Three potential nursery and one spawning closures were identified, with most of the spawning closure overlapping one of the nursery closures. These closures were further compared against a standard seasonal spawning closure that was enforced until 2019. Overall, our simulations indicated that all fishing closures were beneficial to both supporting fisheries and the WB cod recovery. Fishing effort was nevertheless largely displaced towards other fishing grounds with redirection of catches to other fish stocks. We argue that the higher economic return was due to the increased catches of other stocks, rather than a direct consequence of the WB cod recovery in mid-term perspective. Results regarding specifically the protection of nursery and spawning grounds remained inconclusive as no substantial differences were found among them; however, both led to higher spawning stock biomass and economic return, despite at a lower level than the standard spawning closure. We conclude that the standard spawning closure was the most beneficial in terms of socio-economic and biological returns, and that it is paramount to account for the socio-economic components when evaluating the effectiveness of fisheries closures.