Browsing by Author "Parker, Denham"
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- 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.
- Towards mitigation of seabird bycatch: Large-scale effectiveness of night setting and Tori lines across multiple pelagic longline fleetsPublication . Jiménez, Sebastián; Domingo, Andrés; Winker, Henning; Parker, Denham; Gianuca, Dimas; Neves, Tatiana; Coelho, Rui; Kerwath, SvenBycatch in pelagic longline fleets remains a considerable source of mortality for threatened seabirds. Despite efforts to implement mitigation measures, the effectiveness of their application across multiple fleets and wide spatio-temporal scales remains poorly understood. We analyse about 15,800 sets and 36.4 million hooks observed during 583 trips aboard 132 vessels from five pelagic longline fleets (Brazil, Portugal, South Africa, Uruguay and foreign charter-vessels) operating in the south Atlantic and southwestern Indian Oceans (2002–2016) to assess the large-scale effect on bycatch rates of the implementation over time of night-setting and Tori (bird-scaring or streamer) lines. There was a highly significant decrease in standardised bycatch rate from 2002 to 2008 to 2009–2011 and a further reduction in 2012–2016, as consequence of an increased use of mitigation measures. This reduction on fleet-wide bycatch rates temporally coincides with the progressive implementation of mitigation measures in the two relevant Regional Fishery Management Organisations. Night-setting significantly reduced bycatch rates under all conditions, particularly for albatrosses. Surprisingly, bycatch rate during daylight was higher when Tori lines were deployed. Inconsistencies in Tori line deployments, entanglements with the fishing gear and the non-use of this measure with low seabird abundance may explain this pattern. At night, relative moon illumination increased bycatch rate, especially of petrels, but Tori lines significantly reduced seabird bycatch. Our results imply that a major reduction in global bycatch of threatened seabirds could be achieved, if night setting and Tori lines are correctly applied and extensively implemented by fleets operating south of 25°S.