SEAwise Report on the impacts of fisheries on stocks and landings under existing management plans
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 investigates the impact of existing management plans and alternative management strategies on the ecosystem. The simulations used in this deliverable built on those used in deliverables 6.5 and 6.8 in Task 6.3 and Task 6.4, respectively. Additionally, case specific management strategies have been tested related to the main concerns in corresponding areas. Moreover, further improvements have been made to the biological and fleet operating models in some cases. A wide range of models has been applied to various case study areas across the Northeast Atlantic and Mediterranean.
This deliverable is the second deliverable of Task 6.6 “Positioning fisheries in the Social Ecological System”. Previous deliverable focused on the impact of management strategies in stocks and landings. This new deliverable goes beyond that, including new management strategies and considering the impact on the broader ecosystem.
The work provides important information on likely impact of different management scenarios on the ecosystem at different time horizons. The scenarios investigated were grouped in five groups:
1. Main management scenarios that include: the full implementation of MSY (Maximum Sustainable Yield) approach and landing obligation, a Pretty Good Yield (PGY) approach and landing obligation, current effort level and a case specific scenario that tried to describe the fleet dynamics more realistically.
2. Climate change scenarios that combined the scenarios in 1 with two climate change scenarios RCP4.5 and RCP8.5.
3. Technical change scenarios where changes were made in the gear to change the selection pattern or adjustments in the effort quotas.
4. Trawl Ban scenarios where the effort of bottom trawlers was reduced by a 50% and different options were analysed for the static gears
5. Spatio-temporal closures scenarios in the Bay of Biscay where on the one hand a spatio-temporal closure of one month to protect Dolphins was simulated and on the other different MPA-s with different extension to protect benthic communities were tested.
Management measures and the impacts of climate change varied significantly across regions, fleets, and stocks, underscoring the need for region-specific customization. While status quo scenarios provided stability, they were the least sustainable option. In contrast, MSY (Maximum Sustainable Yield) scenarios resulted in improved ecological outcomes but at the expense of reduced landings and economic performance in some regions. Flexible approaches, such as PGY (Pretty Good Yield) and tailored strategies from case studies, showed promise in achieving a balance between socio-economic and ecological objectives.
Climate change effects were region-specific, predominantly negative, though localized positive impacts were observed in certain areas. Technical measures produced diverse outcomes across regions, highlighting the critical importance of targeted implementation. The trawl ban revealed that losses in landings could only be offset by significantly increasing efforts in static gears. However, this compensation primarily stemmed from higher catches of two main target species, while losses among other species remained uncompensated. Spatio-temporal closures generally had minimal impact but were highly significant for certain fleets.
Multi-Criteria Decision Analysis (MCDA) demonstrated to be a useful tool to summarize information from a wide range of scenarios, identify trade-offs and rank scenarios based on the preference of the stakeholders. In the Bay of Biscay, the North Sea and Central Mediterranean, the MCDA revealed that stakeholder priorities, whether environmental or economic, significantly influenced the choice of management options. In the Bay of Biscay, status quo scenarios favoured balanced or economy-first preferences, while MSY and PGY rules aligned better with environmental priorities. In the North Sea, the status quo was deemed the least effective option, with climate change proving more impactful than management strategies. MSY reflected environmental preferences, while PGY addressed socio-economic goals, though gear modifications were generally ineffective in meeting objectives. In Central Mediterranean Sea the effort quotas adjusted following FMSY of crustaceans scenario performed best when prioritizing the environment, while the "economy first" approach favoured FMSY and FMSY with spatial closures. The Status Quo and gear modification yielded the lowest and similar utility scores.
The comparison of mixed-fisheries and ecosystem models highlights the challenges of integrating structurally different models. Mixed fisheries models focus on detailed single-stock assessments and fleet responses, while the ecosystem model used here models nutrient fluxes. The ecosystem model generally showed less optimistic outcomes under climate change, with significant decreases in biomass and catches in both the Celtic and North Seas. In order to advance in Ecosystem Based Fisheries management it is essential to leverage the strengths of each modelling approach to provide actionable management advice that integrates ecosystem considerations, ensuring practical solutions in the short term.
The illustrations in this report are designed to serve as readily accessible inputs for the web interface, summarizing the impacts of various management scenarios.
