Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar

Olhão, Portugal

Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar

Olhão, Portugal

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Rooker J.R.,Texas A&M University | Arrizabalaga H.,Tecnalia | Fraile I.,Tecnalia | Secor D.H.,University of Maryland Center for Environmental Science | And 9 more authors.
Marine Ecology Progress Series | Year: 2014

Assessment and management of Atlantic bluefin tuna Thunnus thynnus populations is hindered by our lack of knowledge regarding trans-Atlantic movement and connectivity of eastern and western populations. Here, we evaluated migratory and homing behaviors of bluefin tuna in several regions of the North Atlantic Ocean and Mediterranean Sea using chemical tags (δ13C and δ18O) in otoliths. Significant emigration of bluefin tuna from their place of origin was inferred from otolith δ13C and δ18O, with both eastern and western bluefin tuna commonly 'crossing the line' (45° W management boundary) in the Central North Atlantic Ocean and mixing with the other population. Several western migrants were also detected in Moroccan traps off the coast of Africa, indicating that trans-Atlantic movement occurs for members of the western population; however, the degree of mixing declined with proximity to the eastern spawning area (Mediterranean Sea). The origin of bluefin tuna collected at the entrance to the Strait of Gibraltar and from several regions within the Mediterranean Sea (Balearic Islands, Malta, and Sardinia) was essentially 100% eastern fish, demonstrating that natal homing is well developed by the eastern population, with western migrants rarely entering the Mediterranean Sea. © Inter-Research 2014.


Santos M.N.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar | Coelho R.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar | Coelho R.,University of Algarve | Fernandez-Carvalho J.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar | Amorim S.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar
Bulletin of Marine Science | Year: 2012

Here we report a component of the results of the SELECT -PAL project, namely marine turtle bycatch composition and rates, hooking location, and status at haulback and at release for several hook-bait combinations in a Portuguese commercial longline fishery targeting swordfish in the Atlantic equatorial region. In total, 221 longline sets were deployed during the fishing season (February-October) by the Portuguese fleet operating in the area. Three different hook types were tested, traditional J-hook (9/0) and two 17/0 circle hooks (non-offset and 10° offset), but only one bait type was used in each set (Scomber spp. or Illex spp.). Four species of sea turtle were caught, most consisting of the olive ridley, Lepidochelys olivacea (Eschscholtz, 1829), and leatherback, Dermochelys coriacea (Vandelli, 1761). The highest mean bycatch per unit effort (BPU E) values for both species combined and for the individual species occurred with the J-hook. The 10° offset circle hook baited with mackerel provided a reduction of 88% and 85% on the bycatch rates, for all turtles combined and olive ridleys, respectively. Although hook location was species-specific and only bait appeared to be driving bycatch rate differences, most sea turtles were caught in the mouth, except for leatherbacks. Only hook type contributed significantly to haulback mortality, with J-hooks associated with slightly higher mortality rates. © 2012 Rosenstiel School of Marine & Atmospheric Science of the University of Miami.


Coelho R.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar | Coelho R.,University of Algarve | Santos M.N.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar | Amorim S.,Instituto Nacional Dos Recursos Biologicos Inrb Ip Ipimar
Bulletin of Marine Science | Year: 2012

We examined the effects of different hook style and bait type combinations on the catches of targeted, bycatch, and discarded fishes in equatorial Atlantic waters. In total, 221 longline sets (>305,000 hooks) were deployed from Portuguese pelagic longline vessels (SELECT -PAL Project) during the February-October fishing season. Three different hook styles and two bait types were tested: the traditional J-hook was compared to two circle hooks (one non-offset and one with 10° offset), and squid bait was compared to mackerel. Catch per unit effort (CPU Es) were calculated and compared between the different hook style and bait type combinations, which indicated that the effects of hook style and bait on the CPU Es were species-specific. For example, swordfish CPU Es were higher with J-hooks baited with squid, while for targeted tunas and blue shark only the bait effect was significant, but with opposite effect (i.e., higher catches of tuna with squid bait and higher catches of blue shark with mackerel bait). For the discarded species, at-haulback mortality was also species-specific. Proportions of alive vs dead specimens at time of fishing gear retrieval did not vary significantly by hook style or bait type combinations. The total retained catch was analyzed in value per unit effort (VPU E), and indicated losses in fishery revenue when mackerel was used instead of squid, but not when circle hooks were used instead of J-hooks. © 2012 Rosenstiel School of Marine & Atmospheric Science of the University of Miami.

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