SEAwise report on effects of spatial management measures suggested in SEAwise to safeguard species, habitats and choke species on fisheries selectivity and fuel cost

The SEAwise project works to deliver a fully operational tool that will allow fishers, managers, and policy makers to easily apply Ecosystem Based Fisheries Management. This SEAwise report investigated the available tools for predicting the impact of various spatial management options on fisheries distribution, yield, profitability, and selectivity. Such spatial plans may affect the remaining ‘fishable’ areas by displacing and concentrating the fishing pressure, and so may alter stock abundances, distributions, size- and species catch composition and fuel expenditure and cost. The report provides insights into how spatial plans that exclude certain fishing activities may affect these outcomes. Spatially explicit approaches are used, along with scenarios of underlying stock productivities and distributions, to assess the performance of spatial management measures. Scenario-based testing is conducted to examine the interrelated effects of management options and stock productivity.

The evaluations were conducted with dynamic spatial bioeconomic models that considered changes in environmental drivers and spatial restrictions to assess potential changes in fishing effort facing, for example, new regulatory or ecological conditions. A suite of bioeconomic models was deployed to provide preliminary findings about the effect of spatial restrictions on fish, fisheries, benthos and bycatch:

• In the eastern Ionian Sea, the DISPLACE model showed that the most effective management measures would be closing nursery grounds for hake while simultaneously reducing overall fishing effort. Alternatively, closing the nursery grounds can be a way to achieve some protection of hake while reducing short-term socioeconomic effects. ECOSPACE demonstrated that excluding bottom trawling from MPAs would lead to an increase in fishing effort throughout the open part of the study area, rather than just around the MPAs. Decreasing fishing pressure from small-scale fisheries might have a broader impact on stock recovery, but incorporating climate warming into fishing management simulations substantially influenced the outcomes. Both models agreed that fisheries closures will lead to fisheries redistribution and that future climate change can potentially alter the expected effects of the closures. Further, the DISPLACE model points to the need to reduce fishing pressure to attain full stock recovery.
• In the Adriatic and Western Ionian Sea (GSAs17-18-19), ECOSPACE showed a moderate increase in the biomass of juveniles when protecting Essential Fish Habitats (especially red shrimps) with a closed area. Combining closed areas with effort reduction to FMSY resulted in increased biomass for many species and decreased bycatch of juveniles. Combining the closed area with the PGY scenario, a catch reduction of juveniles also occurred. The spatial BEMTOOL component showed that the closures would increase fuel consumption of the >18 m fleets in South GSA 17 by 12% but decreased the fuel consumption of the >18m fleets in the center of GSA 19 by 18%. Under the FMSY scenario, the fuel consumption for all the fleets decreased significantly due to the decrease in fishing effort. In conclusion, both models agreed that fisheries closures will lead to changes in fleet distribution and hence fuel consumption. The ECOSPACE model demonstrated that the closure areas led to decreased pressure on juveniles and that reductions of fishing pressure are needed to attain full stock recovery.
• In the North Sea, the DISPLACE model showed that relative benthos status improved in areas where bottom fishing was excluded from previously fished areas and decreased in newly fished areas. When testing the preservation of 30% of the highest RBS area, the main outcome was a gain for long-lived benthic groups. Protecting current high RBS areas may lead to a net gain in RBS with a large potential for recovery at a low cost of fisheries catch. ECOSPACE estimated an increase in biomass in the southern part of the North Sea inside closed areas but the losses of catches inside the MPAs were not outweighed by increased catches outside the closed areas. Larger coherent protection zones were more efficient than small scattered protection zones for reducing the bycatch risk and the effect on sensitive benthic habitats. The FISHCODE model of the southern North Sea and the German fisheries found closing existing MPAs led to ecological benefits and short-term profit losses for both bottom and beam trawl fleets. The spatial fishing effort increased in remaining fishable areas across all scenarios, with possible devastating ecological consequences. The OSMOSE model showed that climate change resulting in a decrease in future ecosystem productivity has a more pronounced effect on biological and catch indicators than area closure in 2060. Approximately a 10% reduction in the overall catch was anticipated under the RCP8.5 2060 climate scenario. Implementing spatial restrictions (MPAs and OWFs) did not strongly affect fish biomass when combined with the climate scenario. Together, the models point to closed areas potentially being an efficient tool to protect sensitive benthic habitats, preferably in the shape of larger areas. Depending on the location of these areas, they may lead to substantial losses in profit and unintended negative consequences for areas which are not currently fished. Further, the negative impacts of climate change on the ecosystem may override any potential benefits of area closure, leading to future losses of catch and profit.
• In the French area of the Bay of Biscay the ISIS-Fish model shows effects on the economy of larger vessels by restricting their offshore fishing grounds on the continental slope. On the contrary, more coastal fleets practicing both active and passive gears may benefit and potentially improve their economic return.

In summary, if specific fishing techniques are prohibited not only in all currently designated MPAs but also in fit-to-purpose areas to limit juvenile catches, the risk of incidental bycatch and the degradation of the benthos status, this will have pronounced impacts on the overall fisheries economy and fish populations in the short term. The protection and displacement from new regional scale closures will more effective than restrictions in the currently designated MPAs only. These areas would be specifically designed to protect vulnerable stages for exploited stock, bycatch risk of unwanted species, and sensitive benthic habitats while improving spatial and gear selectivity. Such conservation measures had effects on the socioeconomic objectives, such as decreased short-term catches and increased operating costs like e.g., fuel expenses. This may result from a displacement of effort to surrounding areas, with some potentially harmful counterproductive effects on biodiversity in some cases. In the long term, a changing climate could overwhelmingly affect fish and fisheries' productivity and the marine ecosystems at large, thereby greatly changing the predicted benefits and costs of closed areas.

Read more about the SEAwise project at https://seawiseproject.org/