RESUMORio Grande do Norte (RN) was the main Brazilian exporter of tunas and other species of fish during the period from 2006 to 2016, generating food, employment and income, due to its proximity to the migratory routes these fishes. In the attempt to better understand the dynamic and the composition of the fleet's captures, that operates with pelagic longline in the Southwestern Equatorial Atlantic and based in RN, their landings data, were analyzed between 2006 and 2014. Nearly 80% of the catch by weight was composed of only four species, being 34,1% Thunnus albacares, 30,8% Xiphias gladius, 8,8% Prionace glauca and 6,8% Thunnus obesus. The expenses with crew, fuel, bait and fishing gear represented 65% of the total. Of the total exported by Brazil, the RN was responsible for exporting approximately 77% fresh and 26% frozen of T. albacares, 92% fresh and 90% frozen of T. obesus, and 55% fresh and 95% frozen of X. gladius. This study provided information that should be taken into account for the sustainability of tuna fishing caught by the Potiguar fleet.Key words: fishing; tunas; CPUE; export; costs. RESUMOO Rio Grande do Norte (RN) foi o principal exportador brasileiro de atuns e afins durante o período de 2006 a 2016, gerando alimento, emprego e renda, haja vista a sua proximidade com as rotas migratórias desses peixes. Visando a um melhor entendimento da dinâmica e composição das capturas da frota sediada no RN e que opera com espinhel pelágico no Atlântico Sudoeste Equatorial, também foram analisados dados de desembarques entre 2006 e 2014. Cerca de 80% das capturas em peso foram apenas de quatro espécies, sendo 34,1% Thunnus albacares; 30,8% Xiphias gladius; 8,8% Prionace glauca e 6,8% Thunnus obesus. A remuneração da tripulação, combustível, isca e material de pesca representaram 65% dos custos de produção. Do total exportado pelo Brasil, em peso, o RN foi responsável por aproximadamente 77% de T. albacares fresco e 26% congelado, 92% de T. obesus fresco e 90% congelado e 55% de X. gladius fresco e 95% congelado. Este estudo produziu informações que devem ser levadas em consideração para a sustentabilidade da atividade de pesca de atuns e afins pela frota Potiguar.

Pelagic fish species, such as tunas, represent important resources for the fishing fleets of several countries. Identifying spatiotemporal distributions of abundance, structure of sizes, weights and influences of environmental variables is extremely important to promote sustainable catches and efficient management plans for fisheries stocks. This present study aimed to analyse the spatiotemporal distribution of Thunnus albacares, their relationships with oceanographic variables, as well as size and weight structure, and the proportions of life stages/phases in catches, mainly within the Brazilian Exclusive Economic Zone. Data were obtained on longline fleet catches; the sea surface temperature (SST) and chlorophyll‐a (Chla) were measured in an area ranging from 42.2° to 24.8° W and 5.9° S to 8.8° N; the lunar cycle was also studied. Generalised Additive Models and spatial statistics techniques were used to model the effect of the variables on catch per unit effort (CPUE) and on length structure. The results indicate that the distribution, abundance and length structure of T. albacares are strongly associated with environmental (SST and Chla), temporal (year, months, seasons and moon phases) and spatial (latitude, longitude and hemisphere) variables. The comparison of catch sizes with the first length at maturity (L50) indicated that approximately half of the catches are on young specimens, showing great variation over the years, reaching 74.8% in 2012. These results show that providences should be taken focusing on mitigating young specimens' capture and the sustainable exploitation of tuna in the Atlantic. The patterns of CPUE and length strongly support the feeding and spawning migration hypotheses.

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