SEAwise Report on Carbon footprint, economic and social impacts of revised management strategies in a changing climate based on information from full MSEs

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 explored the impact of alternative future socio-economic scenarios (Global Sustainability, National Enterprise, Local Stewardship, World Markets), integrating climate change and incorporating enhanced economic (Bitetto et al., 2023) and productivity (Melià et al., 2023) sub-models. Deliverable 2.4 is aimed at exploring the full MSEs conducted in WP6, focusing on the management strategies other than F_MSY and PGY. In particular, the socio-economic and carbon emission impacts of management measures based on change in selectivity and on the new spatial closures from task 5.5 (Bastardie et al., 2024) are investigated.

The socioeconomic scenarios examined differ in climate change impact, fuel and fish price following the categorisation developed in the CERES project (Peck et al., 2020). These scenarios were combined with management scenarios and with a specific focus on small scale (SSF) and large-scale (LSF) fleets in the North Sea, Celtic Sea, Bay of Biscay and Central Mediterranean Sea. In addition to indicators related to socioeconomic aspects such as GVA and wages, carbon emissions were estimated as kg CO₂ per kg of fish landed for all cases. Moreover, a specific focus was made in this Deliverable on the organic carbon pool in the stocks, in terms of biomass left in the sea and extracted by the sea (landings) to provide some insights on the carbon cycle.

The Bay of Biscay case study reveals that under the Landing Obligation, the Gross Value Added (GVA) increased over time across all scenarios. Although the one-month spatial closure aimed at reducing the bycatch of common dolphins could have negative effects on GVA, these are mitigated by the positive impacts of the socio-economic scenarios. The first sale price under these socio-economic scenarios is higher than in the status quo or baseline scenario, compensating for the increase in fuel prices. The CO₂ emissions per kg fish show an increasing trend over the projected period for the Large-Scale Fisheries (LSF), indicating that a dedicated effort is needed to reduce carbon emissions from these fleets. In contrast, the CO₂ emissions from the Small-Scale Fisheries (SSF) decreased from the first period (2025 – 2030) to the second period (2035 – 2040) and then remained relatively stable. Regarding organic carbon in the Spawning Stock Biomass (SSB), the simulations show differences between scenarios only in species whose biomass dynamics have been modelled considering climate change (anchovy and northern hake). For anchovy, organic carbon is higher without climate change, while for northern hake, organic carbon is higher in the RCP8.5 scenarios.

In the Celtic Sea case study, the effect of an alternative fleet structure was explored. The effort of bottom trawl fleets was reduced with 50%, and the effort of static fleets was increased with a factor of 2, 5 and 10. This explorative analysis showed that such fleet modification would increase catches of several demersal stocks without compromising the biomass. A reduction of bottom trawling combined with a doubling of the static fishing effort is currently identified as the best scenario. It would result in a better uptake of catches of the different stocks, allow rebuilding of the cod stock, and reduce direct CO₂ emissions per kg of landed fish below current levels. However, CO₂ emissions per kg landed fish still exceeded emissions in the strict implementation of the Landing Obligation (FMSY-min).

In the North Sea, applied gear modifications led to lower catches of young roundfish, while utilising higher quotas of flatfish, thus delaying choking for the fleets under the landing obligation scenarios. The effect in the bioeconomic submodel explicitly accounting for price differences with age was stronger, as a larger portion of older age classes of roundfish were targeted. Even though the gear modifications resulted in an effort increase for fleets to fish out their quota, with higher fuel utilisation and costs, the impact of the positive fish price developments under the CERES projections still exceeded higher fuel price effects, resulting in a general positive economic performance of both the large and small scale fleets under the landing obligation. However, due to the decrease in CPUE under the gear modification scenarios, the CO₂ emissions per kg fish generally increased over the level of the Status-quo scenario.

In the Central Mediterranean case study (Adriatic and Western Ionian) the scenarios on gear modification to improve selectivity led to economic improvement in the medium to long term, with the best scenario for social and economic sustainability (Local Stewardship) emerging from 2035. In general, CO₂ emissions per kg of fish decreases over time for large-scale fisheries (LSF), but the most negative climate scenarios (related to RCP8.5, NE and WM) are less efficient and yield lower catches. For small-scale fisheries (SSF), emissions remain stable and lower than those of LSF. Organic carbon stored in fish stocks increases over time due to management measures, especially under moderate climate scenarios. In general, the organic carbon stored in hake and red mullet stocks increase until 2040, followed by a decline, in line with the SSB corresponding trends.

The additional management scenarios analysed in this deliverable provided further insights on how the gear modification to improve selectivity, effort reallocation among gears and spatial closures, can impact on carbon emissions and fleet performances under the four socio-economic scenarios across the four case study areas. Finally, further insights on the carbon cycle were provided (e.g. organic carbon in SSB).