Browsing by Author "Forselledo, Rodrigo"
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- Distribution patterns and population structure of the blue shark (Prionace glauca) in the Atlantic and Indian OceansPublication . Coelho, Rui; Mejuto, Jaime; Domingo, Andrés; Yokawa, Kotaro; Liu, Kwang-Ming; Cortés, Enric; Romanov, Evgeny V.; da Silva, Charlene; Hazin, Fábio; Arocha, Freddy; Mwilima, Aldrin Masawbi; Bach, Pascal; Ortiz de Zárate, Victoria; Roche, William; Lino, Pedro G.; García-Cortés, Blanca; Ramos-Cartelle, Ana M.; Forselledo, Rodrigo; Mas, Federico; Ohshimo, Seiji; Courtney, Dean; Sabarros, Philippe S.; Perez, Bernardo; Wogerbauer, Ciara; Tsai, Wen-Pei; Carvalho, Felipe; Santos, Miguel N.The blue shark (Prionace glauca) is the most frequently captured shark in pelagic oceanic fisheries, especially pelagic longlines targeting swordfish and/or tunas. As part of cooperative scientific efforts for fisheries and biological data collection, information from fishery observers, scientific projects and surveys, and from recreational fisheries from several nations in the Atlantic and Indian Oceans was compiled. Data sets included information on location, size and sex, in a total of 478,220 blue shark records collected between 1966 and 2014. Sizes ranged from 36 to 394 cm fork length. Considerable variability was observed in the size distribution by region and season in both oceans. Larger blue sharks tend to occur in equatorial and tropical regions, and smaller specimens in higher latitudes in temperate waters. Differences in sex ratios were also detected spatially and seasonally. Nursery areas in the Atlantic seem to occur in the temperate south‐east off South Africa and Namibia, in the south‐west off southern Brazil and Uruguay, and in the north‐east off the Iberian Peninsula and the Azores. Parturition may occur in the tropical north‐east off West Africa. In the Indian Ocean, nursery areas also seem to occur in temperate waters, especially in the south‐west Indian Ocean off South Africa, and in the south‐east off south‐western Australia. The distributional patterns presented in this study provide a better understanding of how blue sharks segregate by size and sex, spatially and temporally, and improve the scientific advice to help adopt more informed and efficient management and conservation measures for this cosmopolitan species.
- Pan-Atlantic distribution patterns and reproductive biology of the bigeye thresher, Alopias superciliosusPublication . Fernandez-Carvalho, Joana; Coelho, Rui; Mejuto, Jaime; Cortés, Enric; Domingo, Andrés; Yokawa, Kotaro; Liu, Kwang-Ming; García-Cortés, Blanca; Forselledo, Rodrigo; Ohshimo, Seiji; Ramos-Cartelle, Ana; Tsai, Wen-Pei; Santos, Miguel N.The bigeye thresher (Alopias supercilious) is occasionally caught as bycatch in pelagic longline fisheries targeting tunas and swordfish. Still, it is one of the least known and studied of all pelagic sharks, which hinders assessment of the status of its populations. As part of an ongoing cooperative program for fisheries and biological data collection, information collected by fishery observers and through scientific projects from several nations that undertake fishing activities in the Atlantic (Japan, Portugal, Spain, Taiwan, Uruguay and US) was compiled and analyzed. Datasets include information on location, size, sex and, in some cases, maturity stage. A total of 5590 bigeye thresher records collected between 1992 and 2013 were compiled, with sizes ranging from 70 to 305 cm fork length (FL). Considerable variability was observed in size, with tropical regions recording a smaller mean size compared to other regions. The distribution of juvenile and adult specimens also showed considerable variability, and the sex ratios varied between regions and size classes. Median sizes at maturity were estimated at 208.6 cm FL for females and 159.2 cm FL for males. Pregnant females were recorded in the tropical northeast and southwest Atlantic, with these regions possibly serving as nursery areas. The biological and distributional patterns presented in this study provide a better understanding of different aspects of this species in the Atlantic, which can help managers adopt more informed and efficient conservation measures.
- Sea turtles in the Atlantic and Indian Oceans, a step towards understanding bycatch and management of these species in tuna fisheriesPublication . Domingo, Andrés; Baéz, José Carlos; Miller, Philip; Parker, Denham; Ramos, María Lourdes; Sabarros, Philippe S.; Brown, Craig; Camiñas, Juan Antonio; Coelho, Rui; Forselledo, Rodrigo; Fiedler, Fernando Niemeyer; Giffoni, Bruno; Macías, David; Hanke, Alex; Kerwath, Sven; Lauretta, Matthew V.; Poisson, Francois; Rueda, Lucía; Ruiz, Jon; Sales, Gilberto; Leite, Nilamon de Oliveira; Salmerón, Francisca; Santiago, Josu; Taylor, Nathan; Jiménez, SebastiánKnowledge of the spatiotemporal behavior and interactions with fishing gear of bycatch species is essential to improve conservation and fisheries management strategies. We analyze fine-scale data from onboard observers, covering 25 fishing fleets from 2002 through 2018, to assess temporal trends and spatial variation in sea turtle bycatch in longline and purse seine tuna fisheries in the Atlantic and Indian oceans. For the spatial analysis, we used the latest Regional Management Units for Sea Turtles (RMUs). In 117,381 fishing sets (51,431 in longlines and 65,950 in purse seine), a total of 26,050 sea turtles were incidentally caught. Bycatch was significantly higher in the Atlantic than in the Indian Ocean. Some bycatch trends were observed in longline fisheries but should be interpreted with caution due to low observer coverage and uneven sampling. In purse seine fisheries, where observer coverage was higher, an increasing trend over time was found in the bycatch rate of the three most caught species during the study period. This could be related to an increase in population size as suggested in other regional-scale analyses. We identified RMUs that should receive further attention from the perspective of increased capture rates over time. Our large-scale analysis confirms that surface longline sets capture significantly more turtles than deep longline sets. Purse seine sets on fish aggregating objects (FOB) captured more turtles than sets made on free schools of fish. These results are of relevance for the management and protection of these threatened species and the development of management measures.
- Spatial and temporal size distribution of swordfish in the Atlantic Ocean: implications for conservation and managementPublication . Rosa, Daniela; Schirripa, Michael; Gillespie, Kyle; Macías, David; Forselledo, Rodrigo; Mourato, Bruno; Kai, Mikihiko; Arocha, Freddy; Su, Nan-Jay; Kerwath, Sven; Bahou, Laurent; Pappalardo, Luigi; Diaz, Guillermo A.; Lino, Pedro G.; Salmeron, Francisca; Urbina, Josetxu Ortiz de; Cardoso, Luis Gustavo; Sant’Ana, Rodrigo; Travassos, Paulo; Santos, Miguel N.; Erzini, Karim; Domingo, Andrés; Báez, Jose Carlos; Hanke, Alex; Brown, Craig; Coelho, RuiSwordfish (Xiphias gladius) is a common target species of surface pelagic longline fisheries. In the Atlantic Ocean and Mediterranean Sea, swordfish is managed as three separate stocks, all having management measures in place to rebuild or conserve the stocks, including minimum landing sizes. The objective of this study was to review size data for swordfish in the Atlantic Ocean, model the sex-specific size distribution and determine areas where there is higher likelihood of capturing undersized fish. The size distribution differed between males and females and varied by quarter, indicating movements of large fish between temperate and tropical waters. Undersized fish seems to occur in association with coastal waters, with higher proportions in the Northwest Atlantic and tropical areas. This study provides a better understanding of the temporal and spatial size and sex distribution of swordfish and presents insights into the distribution of undersized swordfish that is subject to management measures.