Browsing by Author "Murua, Hilario"
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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.
- 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.
- Technical mitigation measures for sharks and rays in fisheries for tuna and tuna-like species: turning possibility into realityPublication . Poisson, François; Crespo, Francisco Abascal; Ellis, Jim R.; Chavance, Pierre; Bach, Pascal; Santos, Miguel. N.; Séret, Bernard; Korta, Maria; Coelho, Rui; Ariz, Javier; Murua, HilarioTuna fisheries have been identified as one of the major threats to populations of other marine vertebrates, including sea turtles, sharks, seabirds and marine mammals. The development of technical mitigation measures (MM) in fisheries is part of the code of conduct for responsible fisheries. An in-depth analysis of the available literature regarding bycatch mitigation in tuna fisheries with special reference to elasmobranchs was undertaken. Studies highlighting promising MMs were reviewed for four tuna fisheries (longline, purse seine, driftnets and gillnet, and rod and line – including recreational fisheries). The advantages and disadvantages of different MMs are discussed and assessed based on current scientific knowledge. Current management measures for sharks and rays in tuna Regional Fishery Management Organizations (t-RFMOs) are presented. A review of relevant studies examining at-vessel and postrelease mortality of elasmobranch bycatch is provided. This review aims to help fisheries managers identify pragmatic solutions to reduce mortality on pelagic elasmobranchs (and other higher vertebrates) whilst minimizing impacts on catches of target tuna species. Recent research efforts have identified several effective MMs that, if endorsed by t-RFMOs, could reduce elasmobranchs mortality rate in international tropical purse seine tuna fisheries. In the case of longline fisheries, the number of operational effective MMs is very limited. Fisheries deploying driftnets in pelagic ecosystems are suspected to have a high elasmobranchs bycatch and their discard survival is uncertain, but no effective MMs have been field validated for these fisheries. The precautionary bans of such gear by the EU and by some t-RFMOs seem therefore appropriate. Recreational tuna fisheries should be accompanied by science-based support to reduce potential negative impacts on shark populations. Priorities for research and management are identified and discussed.