Pelagic sharks: a contribution to conservation and sustainable fisheries management in the Atlantic Ocean

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Publications

A review of reported effects of pelagic longline fishing gear configurations on target, bycatch and vulnerable species

Publication . Casaca Santos, Catarina; Rosa, Daniela; Gonçalves, Jorge Manuel Santos; Coelho, Rui

1. A meta-analysis of 40 publications totalling 59 experiments was undertaken to review and assess the effects of changing the hook (circle vs. J-hooks or tuna hooks), bait (fish vs. squid) and leader (wire vs. nylon) type on retention and at haulback mortality rates of teleosts (tunas and billfishes), elasmobranchs and sea turtles caught on shallow-set and deep-set pelagic longline fisheries. 2. Circle hooks are a promising approach to mitigate the impact of pelagic longline fisheries on sea turtles, as they reduced sea turtle retention rates. The adoption of circle hooks would, however, also lead to a decrease in swordfish retention, the main target species of shallow-set pelagic longlines. 3. Using fish as bait resulted in lower retention rates of sea turtles, highlighting that option as an additional measure to further mitigate sea turtle bycatch. The bait type had non-significant effects on sharks, except for blue shark and shortfin mako, for which at-haulback mortality rates were significantly higher with fish bait. 4. The use of nylon leaders instead of wire leaders could serve as a conservation measure for sharks, as they reduced the retention of blue shark without adversely impacting the catches of swordfish. The results on the effect of the leader material types should, however, be interpreted with caution owing to the limited information available reporting on leader material effects. 5. When considering future research directions, priority should be given to experimental field work on the effects of leader material and on deep-set longlines. Evaluating the post-release survival of species should also be a priority.

2023Journal article

Open Access

Progress report for SRDCP on the Atlantic-wide study on the age and growth of shortfin mako shark

Publication . Rosa, Daniela; Mas, Federico; Mathers, Alyssa; Natanson, Lisa J.; Domingo, Andrés; Carlson, John; Coelho, Rui

The ICCAT Shark Research and Data Collection Program (SRDCP) aims to develop and coordinate science and science-related activities needed to support provision of sound scientific advice for the conservation and management of pelagic sharks in the Atlantic. This Program was developed in 2013-2014 by the Sharks Species Group, and framed within the 2015-2020 SCRS Strategic Plan. Within this Program, a specific study on the age and growth of shortfin mako in the Atlantic was developed, with the purpose of contributing to the 2017 ICCAT SMA stock assessment. In the paper, we provide an update of the project, including preliminary growth models for the North Atlantic Ocean.

2017Working paper

Open Access

Updates on habitat use and migrations patterns for shortfin mako in the Atlantic using satellite telemetry

Publication . Casaca Santos, Catarina; Domingo, Andrés; Carlson, John; Natanson, Lisa; Travassos, Paulo; Macias, David; Cortés, Enric; Miller, Philip; Hazin, Fábio H. V.; Mas, Federico; Ortiz de Urbina, Josetxu; Coelho, Rui

This paper provides an update of the study on habitat use for shortfin mako, developed within the ICCAT Shark Research and Data Collection Program (SRDCP). A total of 43 tags (29 miniPATs and 14 sPATs) have been deployed by observers on Portuguese, Uruguayan, Brazilian, Spanish and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 41 tags/specimens are available, and a total of 1656 tracking days have been recorded. Results showed shortfin mako moved in multiple directions, travelling considerable distances. Shortfin mako sharks spent most of their time above the thermocline (0-90 m), between 18 and 22 °C. The main plan for the next phase of the project is to continue the tag deployment during 2019 in several regions of the Atlantic.

2019Working paper

Open Access

Updates on post-release mortality of shortfin mako in the Atlantic using satellite telemetry

Publication . Miller, Philip; Casaca Santos, Catarina; Carlson, John; Natanson, Lisa; Cortés, Enric; Mas, Federico; Hazin, Fábio H. V.; Travassos, Paulo; Macias, David; Ortiz de Urbina, Josetxu; Coelho, Rui; Domingo, Andrés

This paper provides an update of the study on post-release mortality of the shortfin mako, Isurus oxyrinchus developed within the ICCAT Shark Research and Data Collection Program (SRDCP). Up to date, 43 tags (14 sPATs and 29 miniPATs) have been deployed by observers on Brazilian, Portuguese, Spanish, Uruguayan, and US vessels in the temperate NE and NW, Equatorial and SW Atlantic. Data from 35 out of 43 tagged specimens could be used to obtain preliminary information regarding post-release mortality, resulting in a total of 8 mortality and 27 survival events.

2019Working paper

Open Access

Leader material and bait effects on target and bycatch species caught in an Atlantic Ocean pelagic longline fishery

Publication . Casaca Santos, Catarina; Santos, Miguel N.; Rosa, Daniela; Coelho, Rui

The influence of bait type and leader material on target and bycatch species was assessed through fishing experiments in the Portuguese shallow pelagic longline fishery in the Atlantic Ocean. Wire leaders were found to decrease catch rates of commercially valuable species such as bigeye tuna and yellowfin tuna, while increasing catch rates of elasmobranchs, including the blue shark and shortfin mako. The odds ratios of capture swordfish and tunas also decrease when using wire leaders, while elasmobranchs have higher odds ratios of capture and athaulback mortality when using wire leaders. Squid bait led to higher catches of targeted tuna species, however it also resulted in higher catches of marine turtles. For most of the taxa caught at-haulback mortality risk was found to be higher on squid bait, which may be related with increased deep-hooking events. While bait type and leader material did not significantly affect size selectivity for most species, wire leaders were found to retain larger blue sharks and fish bait attracted smaller-sized swordfish. This study showed that banning wire leaders on pelagic longline fisheries is an effective measure for reducing the retention of pelagic shark species, particularly of large size blue sharks.

2024-10Journal article

Open Access