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Advanced Models for Fisheries Stock Assessment of Large Pelagics

Final Report Summary - AMFISALS (Advanced Models for Fisheries Stock Assessment of Large Pelagics)

The main aim of the project AMFISALS was the training of the fellow in advanced stock assessment techniques, hosted by the Oceanic Fisheries Program of the Secretariat of the Pacific Community (SPC-OFP), and the further development of the models. The SPC-OFP is the Scientific Services Provider of the Western and Central Pacific Fisheries Commission (WCPFC), and regularly carries out state-of-the-art stock assessments of the highly migratory species covered by this Regional Fisheries Management Organization (RFMO). The assessments carried out by this institution continually evolve, in response to the need of reducing the uncertainties in the determination of the stock status of the species, some of which are already overexploited. The fulfilment of a full assessment involves expertise in many tasks, many of which are specific to the methodology used. In this regard, the fellow has received exhaustive training in (i) the management of databases of the WCPFC (catch and effort, VMS, biological sampling data...); (ii) use of specific software developed by the host institution (Tagdagger, Mufdagger, CES...); (iii) management of the data by means of R programming; and (iv) the use of the stock assessment software MULTIFAN-CL, which is continuously under development by SPC-OFP.
The main deliverable that summarizes this work is the participation of the fellow in a Pacific-wide assessment of bigeye tuna (McKechnie et al., 2015). This work has been performed in response to one of the recommendations of the peer-review (Ianelli et al., 2012) of the latest stock assessment of bigeye in the Western and Central Pacific, which ignored the dynamics of the species in the Eastern Pacific (area managed by other Regional Fisheries Management Organization). Due to recent tagging data showing considerable movement of bigeye tuna between the central and eastern Pacific Ocean, the peer-review considered the re-evaluation of the spatial domain of the models as a priority.

The study was presented at the 11th Regular Session of the Scientific Committee of the Western and Central Pacific Fisheries Commission. It concluded that the dynamics of bigeye tuna in the WCPO estimated using the Pacific-wide model are not substantially different from those estimated using the WCPO-only model, especially with respect to the main indicators used by that RFMOs.
The researcher has developed actively some of the tasks involved in this assessment: (i) correction of tag releases to account for mortality, tag shedding... estimation of reporting rates based on tag seeding trials (tags seeded aboard the vessels without the knowledge of the crew); (ii) Correction of purse seine size data (use of port sampling data reweighted by the catch spatial distribution); (iii) generation of input files to run the MFCL-CL software; (iv) running sensitivity scenarios to improve the models (selectivity of the gears, use of weight for longline catch instead of size, use of the number of purse seine sets as effort metrics, instead of fishing days....).
The fellow has been for several years in charge of the data provision of the EU fleet in the Western and Central Pacific Commission, and has also advised the Spanish and EU fisheries administration in issues related to the fishing fleets in this area. The expertise gained during this time will certainly improve this line of work as the researcher takes back his position in January 2016.
Other remarkable line of work during the period of the fellowship is the work on electronic tagging. The fellow has leaded two publications on pop-up satellite tagging of swordfish (published in Fisheries Research) and bluefin tuna (currently under revision in Fisheries Oceanography), respectively. He is also leading a Pacific-wide study on the vertical behaviour of bigeye tuna, in collaboration with researchers from the host institution, the Inter-American Tropical Tuna Commission and the University of Hawaii. The bycatch of bigeye juveniles in purse seine sets on FADs has been identified as one of the major sources of overfishing and reduces significantly the performance of the fisheries (not only the maximum sustainable yield of bigeye, but also of skipjack, which accounts for c. 60% of the global tuna catch). Tuna resources are of utmost important for the Small Island Developing States. This work will show important differences in fish behavior at a basin scale, and will help identifying potential bigeye bycatch mitigation measures.
Other activities worth of mentioning during the fellowship include (i) three communications to the WCPFC Scientific Committee (on fish aggregating devices data holdings, purse seine size data and conventional tagging information used in the tropical tuna assessments, respectively); (ii) work on shark bycatch mitigation with other EU colleagues (ongoing); (iii) participation in a consortium which has recently submitted a proposal for an H2020 project (call identifier: H2020-BG-2015-2; topic: BG-02-2015). This proposal, aimed at providing decision makers with the best science for addressing the impact of climate change over fish production, has passed the first cut and is currently under evaluation; (iv) two communications two the last CLIOTOP symposium. One of them, in collaboration with scientists from AZTI (Spain) and CSIRO (Australia), studies the habitat shifts of tropical tunas across the globe, and is expected to be published in the near future. The other one studies the spatial distribution of Atlantic swordfish and has been made in collaboration with scientists from the NOAA (United States), Fisheries and Oceans (Canada), The Spanish Institute of Oceanography (Spain) and the International Commission for the Conservation of Atlantic Tunas; and (v) a collaboration with scientists from the Spanish Institute of Oceanography on the effect of global oceanographic variables on the physiological condition of different fish species.