Browsing by Author "Macías, David"
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- Challenges and opportunities in monitoring and mitigating sea turtle bycatch in tuna regional fisheries management organizationsPublication . Baéz, Jose Carlos; Domingo, Andrés; Murua, Hilario; Macías, David; Camiñas, Juan Antonio; Poisson, Francois; Jorda, María José Juan; López, Jon; Griffiths, Shane; Roman, Marlon; Hall, Martín; Gilman, Eric; Bruyn, Paul De; Swimmer, Yonat; Ceballos-Roa, Elvira; Wallace, Bryan; Coelho, Rui; Abascal, FranciscoFisheries that target tunas and tuna-like species are managed by tuna regional fisheries management organizations (t-RFMO) and are known to interact with various bycatch species, including sea turtles, with potentially negative effects. Actions and management measures implemented by t-RFMO to monitor sea turtle fisheries interactions, reduce their bycatch in fisheries, and carry out best practices for the handling and safe release of sea turtles, with the ultimate aim of improving the conservation of sea turtles are revised. Specifically, the actions and regulations for each of the following areas are revised: (i) data collection requirements, (ii) bycatch estimates and assessments, (iii) management measures, and (iv) any other conservation and management actions for sea turtle conservation. The particular case of the Mediterranean Sea also was analyzed, given that it has the highest rate of sea turtle bycatch in the world. Tuna-RFMO have a great potential for reducing fisheries bycatch impacts in marine turtle populations globally, but their actions are limited by their geographic scopes and mandates and the variety of habitats used by sea turtles during their life history. Tuna-RFMO also have a potentially significant role in leading the reduction of incidental sea turtle mortality in fisheries under their purview, both regionally and globally, by bringing together different stakeholders and initiatives.
- Differentiation of spatial units of Genus Euthynnus from the Eastern Atlantic and the Mediterranean using Otolith Shape AnalysisPublication . Muñoz-Lechuga, Rubén; Sow, Fambaye Ngom; Constance, Diaha N’Guessan; Angueko, Davy; Macías, David; Massa-Gallucci, Alexia; da Silva, Guelson Batista; Gonçalves, Jorge Manuel Santos; Lino, Pedro G.The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover possible seasonal changes and tuna size. The research encompassed both morphometric and shape analyses of left sagittal otoliths extracted of 504 fish specimens. Four shape indices (Circularity, Roundness, Rectangularity, and Form-Factor) were significantly different between two groups, showing a statistical differentiation between two clear spatial units. The degree of divergence was even more pronounced along the rostrum, postrostrum, and excisura of the generated otolith outlines between these two groups. One group corresponds to the samples from the coastal areas in the Northeast Temperate Atlantic and Mediterranean Sea (NETAM Area) and a second group from the coastal areas off the Eastern Tropical Atlantic coast of Africa (ETA Area). This study is the first to use otolith shape to differentiate tunas from separate spatial units. These results could be used to re-classify previously collected samples and to correct time series of data collected.
- Local indicators for global species: Pelagic sharks in the tropical northeast Atlantic, Cabo Verde islands regionPublication . Coelho, Rui; Macías, David; Ortiz de Urbina, Josetxu; Martins, Albertino; Monteiro, Carlos; Lino, Pedro G.; Rosa, Daniela; Casaca Santos, Catarina; Bach, Pascal; Murua, Hilario; Abaunza, Pablo; Santos, Miguel N.Pelagic sharks are an important bycatch in pelagic fisheries, especially for drifting longlines targeting swordfish. In the Cabo Verde Archipelago (tropical NE Atlantic), pelagic shark catches can reach a significant proportion of the total catches. Due to the increased concern on the status of pelagic shark species, this study was developed to enhance the current knowledge of those sharks in the Cabo Verde region in comparison to the adjacent areas, especially associated with European Union (EU) pelagic longline fishing activity. Stock status indicators for the two main species, blue shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus), were developed, based on fisheries data from logbooks and onboard scientific observers, including analysis of size frequency distributions and standardized catch-per-unit-of-effort (CPUE) indexes over time. The standardized CPUEs have been stable or increasing for both species in the past 10 years, indicating no signs of local depletion. In terms of sizes, the blue shark catch is composed mainly of adults, which can be a sign of a stable population. On the contrary, the catch of shortfin mako is composed mainly of juveniles, which in conjunction of a decrease of mean size might be a cause of concern, highlighting possible overfishing on the species in the region. Thirty satellite tags, 25 archival miniPATs and 5 SPOT GPS, were deployed in the Cabo Verde Exclusive Economic Zone (EEZ), showing that those species are highly mobile. The biomass and size distributions were modeled with spatial and seasonal models (GAMs) identifying locations where juveniles are predominantly concentrated and that should be prioritized for conservation. This work presents new information on the status of pelagic sharks in the Cabo Verde region in the context of those highly migratory species, and can now be used to promote more sustainable fisheries in the region.
- Movements, habitat use, and diving behavior of Shortfin Mako in the Atlantic OceanPublication . Casaca Santos, Catarina; Domingo, Andrés; Carlson, John; Natanson, Lisa J.; Travassos, Paulo; Macías, David; Cortés, Enric; Miller, Philip; Hazin, Fábio; Mas, Federico; Ortiz de Urbina, Josetxu; Lino, Pedro G.; Coelho, RuiThe shortfin mako is one of the most important shark species caught in Atlantic Ocean pelagic fisheries. Given increasing concerns for the stock status of the species, the present study was designed to fill gaps in the knowledge of habitat use and movement patterns of shortfin mako in the Atlantic Ocean. From 2015 to 2019, 53 shortfin makos were tagged with pop-up satellite archival tags within the North, Central, and Southwest Atlantic Ocean, with successful transmissions received from 34 tags. Generally, sharks tagged in the Northwest and Central Atlantic moved away from tagging sites showing low to no apparent residency patterns, whereas sharks tagged in the Northeast and Southwest Atlantic spent large periods of time near the Canary Archipelago and Northwest Africa, and over shelf and oceanic waters off southern Brazil and Uruguay, respectively. These areas showed evidence of site fidelity and were identified as possible key areas for shortfin mako. Sharks spent most of their time in temperate waters (18–22◦C) above 90 m; however, data indicated the depth range extended from the surface down to 979 m, in water temperatures ranging between 7.4 and 29.9◦C. Vertical behavior of sharks seemed to be influenced by oceanographic features, and ranged from marked diel vertical movements, characterized by shallower mean depths during the night, to yo-yo diving behavior with no clear diel pattern observed. These results may aid in the development of more informed and efficient management measures for this species.
- 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.