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SEAwise Report on the first identification of limiting species of fishing activity using management evaluation models

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posted on 2024-01-05, 08:42 authored by Anna RindorfAnna Rindorf, Isabella Bitetto, Marga Andrés, Sonia Sánchez-Maroño, Dorleta Garcia, Leire Ibaibarriaga, Maria-Teresa Spedicato, Giovanni Romagnoni, M. Giannoulaki, Vasiliki Sgardeli, Stavroula Tsoukali, Angelos Liontakis, Celia Vassilopoulou, Klaas Sys, J. (Jochen) Depestele, Bernhard Kühn, Marc Taylor, Alexander Kempf

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 (EBFM) in their fisheries. This report describes the evaluation of fisheries management strategies integrating different aspects of the system in multispecies-multifleet predictive models. In particular, the integration of the socio-economic effects of fisheries management demonstrates whether management strategies are likely to be consistent in terms of economic and society key priority objectives. This is important to predict the relationship between management measures and policy targets and to provide the input to the revision of the Common Fisheries Policy (CFP) and the 2024 Marine Strategy Framework Directive (MSFD) assessment.

The management measures currently used in the EU include modification of the fishing gear, temporal closures, spatial closures, landing obligation, TAC and catch limits. These measures may result in a variety of consequences including “choke” species issues, under- or overutilization of stocks depending on their status relative to agreed biomass levels, change in species composition, change in fish size composition and change in the proportion of unwanted catches/landings. From a socio-economic perspective, the identification of limiting ("choke”) species and under- or overutilized fishing opportunities represents a useful source of information for the design of measures aimed at sustainable exploitation of the target stocks, economic efficient fishing fleets and welfare of fishing communities.

In this report, a suite of bio-economic models were applied in their current configuration as used in ICES, GFCM or other arenas for a variety of case studies to identify stocks limiting the catch of other stocks or the attainment of social objectives. A set of scenarios were agreed in coordination with task 6.4 and the main conclusions across the various case studies were:

In the Bay of Biscay, demersal fishery (Western Waters), the exploitation of some stocks was below FMSY in the first year of the simulation. The effort in the min scenario was limited in most of the cases by pollack that was modelled using a constant catch per unit of effort approach. The trends in effort were smooth and fairly constant in all the scenarios except the min scenario where large annual changes were observed, related to changes in the limiting stock. In the multistock HCR ( scenario) (García et al., 2019) the effort was higher than in the min scenario. In the scenario, fishing mortality ranges were used in an attempt to overcome the choking effect: Anglerfish (ANK) becomes a choking stock and the choking impact of Seabass and Sole increased as the overall pattern of fishing mortality was driven by the the fishing mortality outside the Bay of Biscay area.

In the Bay of Biscay, Basque inshore pelagic fishery (Western Waters), the report explores the use of FLBEIA for a sequential fishery. If a given fleet segment in this fishery exhausts the quota of a given species, this does not necessarily limit the effort devoted to the rest of the stocks. In fact, the opposite may be the case, since when one fishery is closed (as was the case of anchovy from 2005-2010), the effort allocated to the other consecutive fisheries could be even increased (Andrés & Prellezo, 2012). Maximum profit increased for almost all fleets under the landing obligation (min) scenario albeit at a much lower effort.

In the Celtic Sea (Western Waters), there was no single choke species that chokes all the fleets under the “min” scenario. Fleets with a higher share of cod in the species composition of the catch, performed better economically under the status quo effort scenario as the catches of the target species were not affected by the low status of the cod stock (e.g. sole for the Belgian beam trawl fleets). Fisheries which often catch cod performed better under the “min” scenario as the cod stock increased. In the absence of environmental effects on recruitment in the model, the cod stock was rebuilt to unprecedented levels in the model of the min scenario. It should be noted that the exploitation of other demersal stocks isalso impacted by fishing in the Bays of Biscay. Merging the Celtic Sea and Bay of Biscay models could solve the problem but would highly increase the complexity.

In the North Sea, harvesting with the current effort (Status Quo effort) is unsustainable for stock biomass and further economically suboptimal compared to scenarios with a landing obligation. Although the income of the Status Quo effort scenario was higher than all landing obligation scenarios in the first two years of the simulation, the risk of suffering a 20% income loss or larger severely increased after these initial years. Under the landing obligation, fleets must pass this initial income loss in the first years, before they profit from increased stock levels. Measures to relax the choking situation, like allowing harvesting in the upper FMSY-range if stocks are within save limits could buffer against income losses of the fishermen.

In the Eastern Mediterranean study of Greek demersal fisheries catching more than 80 commercial stocks, technical interactions among fleets are strong and MSY related targets could not be achieved simultaneously for all stocks. The deep water rose shrimp stock was underutilized in the scenario but an increase in harvest of the stock could lead to the depletion of hake. To achieve sustainable fishing of the hake stock (i.e. the scenarios F01, Fup and FLw), an effort reduction was required. Here, this was accomplished by an equal reduction of both fleets. However, there are multiple other effort re-allocations that can achieve the given target and may result in a better trade-off between ecological, economic, social or other objectives.

In the Central Mediterranean case study, a reduction of effort of 69% did not produce greater benefits to the system than a 58% reduction. This was due to the fact that some stocks would be underutilized with the larger effort reduction, while the negative economic-social system impact would be high, especially for trawlers in the short term. The economic indicators of the vessels using polyvalent passive gears only (PGP) and the vessels using hooks (HOK) improved over time. This was due to the advantage for the two fleets to not be impacted by the reduction of effort opportunities, according to the Management Plan. The scenarios with a less severe effort reduction (40%), driven by setting the fishing mortality of the stock with the second highest F/FMSY to FMSY and applied to all fleet segments, would reduce the underutilization of the stocks in good status and mitigate the negative economic impact on the fleet. Other possible options, to be explored in the next steps, are an improvement of the fleet selectivity or the closure of key areas.

A general caveat of these results is that the simulations have not implemented a suite of specific sub-models, e.g. environmental changes in productivity, fishers’ behavior, fuel consumption, differentiated fish price, or impact on the employment that remain constant given that a reduction of vessels was not considered. Enhanced sub-models on social aspects developed in task 2.2 and 2.3 will be integrated in the next steps, enhanced submodels of environmental impacts will be integrated in task 6.2 and both will be considered in the deliverable 6.5.


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