Статті в журналах: "Tropical tuna fisheries"

1

Nugroho, Duto, and Suherman Banon Atmaja. "KEBIJAKAN RUMPONISASI PERIKANAN PUKAT CINCIN INDONESIA YANG BEROPERASI DI PERAIRAN LAUT LEPAS." Jurnal Kebijakan Perikanan Indonesia 5, no. 2 (November 30, 2013): 97. http://dx.doi.org/10.15578/jkpi.5.2.2013.97-106.

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Penggunaan rumpon laut-dalam telah mengubah taktik dan strategi perikanan pukat cincin pelagis kecil yang beroperasi di perairan dangkal untuk bergeser pada perikanan tuna neritik tropis. Rumponisasi perikanan pukat cincin yang dirancang untuk meningkatkan produktivitas telah menjadi masalah serius pada perikanan neritik tuna. Hal ini terjadi karena tertangkapnya ikan berukuran kecil dalam jumlah yang dominan sehingga dalam jangka panjang akan berpotensi konflik dengan perikanan lainnya. Para ilmuwan yang tergabung dalam pengelolaan perikanan regional merekomendasikan bahwa pengembangan terkendali terhadap penggunaan rumpon di daerah asuhan juvenile tuna tropis. Pengendalian dalam jangka panjang dapat meminimalkan ancaman bagi kelangsungan hidup kelompok jenis tuna. Hal ini terkait dengan pentingnya memperbesar peluang masuknya sediaan kelompok jenis ini pada tingkat yang layak untuk dimanfaatkan. Di Indonesia, pilihan kebijakan perikanan tangkap baik melalui peralihan sasaran kelompok spesies maupun diversifikasi usaha penangkapan akan selalu bertumpu pada pertimbangan sosial. Bagaimanapun juga, proses mengubah pemahaman nelayan nelalui pengendalian jumlah dan teknologi kapal penangkap ikan serta penutupan sementara daerah penangkapan yang akan melalui proses panjang harus tetap dijalankan untuk mencegah runtuhnya perikanan yang saat ini sedang berjalan.The use of Fish Aggregating Devices (FADs) has radically changing the tactic and strategy shallow waters small pelagic purse seiner into high seas tropical neritics tuna fisheries. Applying FADs on purse seine fishery which initiated to increase its productivity became a serious problem to neritics tuna fishery. This indicated by the negative impact on neritics and tropical tuna populations due to large number of small size of tunas being caught and uncertain of number and of FADS position in the high seas. In the long run it will generate a potential conflict to other existing fisheries. The member scientists of regional fisheries management organization (RFMO) recommends that the development of the use of FADs, especially in the area which dominated of juvenile of tropical tuna, should be strongly regulated. FADs management through control system should be applied to minimize impact on recruitment process that associated with the importance of long term availability of its fisheries. Management option through shifting target species and diversification of the fishing activities in Indonesia would always be rely on social dimension. Nevertheles, reorientation on fishers understanding on controllable number of fishing vessels and its technological creeps should strongly be implemented to avoid collapse their existing fisheries.

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2

Kaplan, David M., Emmanuel Chassot, Justin M. Amandé, Sibylle Dueri, Hervé Demarcq, Laurent Dagorn, and Alain Fonteneau. "Spatial management of Indian Ocean tropical tuna fisheries: potential and perspectives." ICES Journal of Marine Science 71, no. 7 (February 13, 2014): 1728–49. http://dx.doi.org/10.1093/icesjms/fst233.

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Abstract Effective use of spatial management in the pelagic realm presents special challenges due to high fish and fisher mobility, limited knowledge and significant governance challenges. The tropical Indian Ocean provides an ideal case study for testing our ability to apply existing data sources to assessing impacts of spatial management on tuna fisheries because of several recent controversial spatial closures. We review the scientific underpinnings of pelagic MPA effects, spatio-temporal patterns of Indian Ocean tuna catch, bycatch and fish movements, and the consequences of these for the efficacy of spatial management for Indian Ocean tropical tuna fisheries. The tropical Indian Ocean is characterized by strong environmental fluctuations, regular seasonal variability in catch, large observed tuna displacement distances, relatively uniform catch-per-unit-effort and bycatch rates over space, and high fisher mobility, all of which suggest significant variability and movement in tropical tuna fisheries that are simply not well adapted to static spatial closures. One possible exception to this overall conclusion would be a large time/area closure east of Somalia. If closed for a significant fraction of the year it could reduce purse-seine bycatch and juvenile tuna catch. Dynamic closures following fish migratory patterns are possible, but more focused information on fish movements will be needed for effective implementation. Fortunately, several recent improvements in conventional fishery management and reporting will likely enhance our ability to evaluate spatial and non-spatial management options in the near future, particularly as pertaining to bycatch species.

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3

Jeon, Yongil, Christopher Reid, and Dale Squires. "Is There a Global Market for Tuna? Policy Implications for Tropical Tuna Fisheries." Ocean Development & International Law 39, no. 1 (February 5, 2008): 32–50. http://dx.doi.org/10.1080/00908320701641594.

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4

Danckwerts, D. K., C. D. McQuaid, A. Jaeger, G. K. McGregor, R. Dwight, M. Le Corre, and S. Jaquemet. "Biomass consumption by breeding seabirds in the western Indian Ocean: indirect interactions with fisheries and implications for management." ICES Journal of Marine Science 71, no. 9 (June 6, 2014): 2589–98. http://dx.doi.org/10.1093/icesjms/fsu093.

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Abstract Fisheries potentially affect seabirds both directly and indirectly. Well-documented direct effects have resulted in significant losses to seabird populations, but indirect effects are less well known. One way in which tropical seabirds may be indirectly affected is through overexploitation of large subsurface predators. Tropical seabirds must forage over wide areas to attain sufficient prey and have evolved various methods of increasing foraging efficiency. One strategy is their association with surface-feeding tunas. When feeding, these predators drive prey to the surface, making them available to seabirds feeding from above. Losses in predator biomass will reduce prey accessibility (but not necessarily prey abundance) for seabirds, contributing to declines in bird populations. To explore indirect fisheries effects, we compared estimates of the magnitude and spatial distributions of consumption by breeding seabirds with fisheries offtake in the western Indian Ocean (WIO). Data from the literature were compared with Indian Ocean Tuna Commission longline and purse seine landings of selected tuna and billfish species from between 2000 and 2009. Breeding seabird populations (adults and immature birds) were estimated at ∼19 million individuals, assuming 50% breeding success. Based on the literature, these birds will consume between 150 000 and 500 000 metric tonnes (t) of prey; values that are of the same magnitude as mean annual longline (904±632 t) and purse seine (349 861±61 820 t) landings for the region. Spatial overlap between fisheries and seabirds is high, especially around the Seychelles, suggesting that the indirect impacts of fisheries on seabird populations may be great. Sooty Tern (Onychoprion fuscatus) is by far the dominant seabird in the study area, accounting for over 80% of numbers and consumption estimates. Our results highlight the importance of seabirds within WIO marine trophic webs and emphasize the potential indirect effects of industrial tuna fisheries on their populations.

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5

Poisson, François, Francisco Abascal Crespo, Jim R. Ellis, Pierre Chavance, Pascal Bach, Miguel N. Santos, Bernard Séret, et al. "Technical mitigation measures for sharks and rays in fisheries for tuna and tuna-like species: turning possibility into reality." Aquatic Living Resources 29, no. 4 (October 2016): 402. http://dx.doi.org/10.1051/alr/2016030.

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Tuna 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.

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6

Escalle, Lauriane, Daniel Gaertner, Pierre Chavance, Alicia Delgado de Molina, Javier Ariz, and Bastien Mérigot. "Forecasted consequences of simulated FAD moratoria in the Atlantic and Indian Oceans on catches and bycatches." ICES Journal of Marine Science 74, no. 3 (December 13, 2016): 780–92. http://dx.doi.org/10.1093/icesjms/fsw187.

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Given the increasingly extensive use of drifting fish aggregation devices (FADs) by the purse-seine fisheries targeting tropical tunas, fishing effort restrictions have been introduced to manage tropical tuna stocks. However, these measures are focused on the protection of juvenile tunas and do not take account of the potential impact on bycatch or associated megafauna (whales and whale sharks). An iterative “fishing-day” Monte Carlo simulation model was developed to investigate the consequences on tropical tunas and bycatch of introducing extensive area 6-month moratoria on FAD activities. The model allowed for variability in a range of plausible values of the parameters characterizing the fishing operations conducted by European purse-seiners in the eastern tropical Atlantic and western Indian Oceans for the period 2005–2014. Monte Carlo simulations, using probabilities based on these fishery data, were carried out for the French and Spanish fishing fleets separately to account for differences in fishing strategies. The models predicted a decrease in FAD sets and an increase in free school sets. As a consequence, the catch of small tuna (<10 kg) decreased while the catch of large tuna (≥10 kg) increased, leading to an overall increase in tuna catch of 100–200 tons/year/vessel in the Atlantic Ocean, and a decrease of 400–1500 tons/year/vessel in the Indian Ocean. The bycatch decreased in the Indian Ocean, while in the Atlantic Ocean billfishes, turtles and chondrichthyans bycatch increased slightly and other bony fishes decreased. Because fishing practices were modified, whale and whale shark associated sets increased slightly in the Indian Ocean.

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7

Bez, Nicolas, Emily Walker, Daniel Gaertner, Jacques Rivoirard, and Philippe Gaspar. "Fishing activity of tuna purse seiners estimated from vessel monitoring system (VMS) data." Canadian Journal of Fisheries and Aquatic Sciences 68, no. 11 (November 2011): 1998–2010. http://dx.doi.org/10.1139/f2011-114.

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In the lack of fishery-independent information, catch per unit of effort (CPUE) is the conventional abundance index. In the case of the tropical tuna purse seine fisheries, a critical difficulty lies in the definition of an effective fishing effort, because fishermen use two different fishing modes (free swimming schools versus schools under fish aggregating devices) alternatively during the same trip. In this study, vessel monitoring system (VMS) data were used in an operational level to study and quantify the spatial dynamic of the tropical tuna purse seine fishing activity. A Bayesian state–space model allowed classifying VMS steps into three activities (fishing, tracking, and cruising), which were characterized by a small set of complementary spatial indicators. The dominant activity (49%) was clearly the tracking of tuna schools within areas of aggregations. A hierarchical spatial organization of the three fishing activities was also evidenced. Fishing strategies described by the triplets of proportions of time devoted to each activity and interpreted as compositional data were modelled by the sum of a vessel effect and a seasonal effect.

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8

Capello, M., P. Bach, and E. Romanov. "Fine-scale catch data reveal clusters of large predators in the pelagic realm." Canadian Journal of Fisheries and Aquatic Sciences 70, no. 12 (December 2013): 1785–91. http://dx.doi.org/10.1139/cjfas-2013-0149.

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The management and conservation of large pelagic fish commonly rely on fisheries data and thus crucially depend on our understanding of the fish response to the fishing gear. Stock assessment of both tropical and temperate tuna strongly leans on the catch statistics derived from pelagic longline fisheries. However, the role of the spatial distribution of catches of tuna and bycatch species over the gear, which can affect the estimated tuna abundance, is still neglected. In this study, we analyzed data obtained from 147 instrumented pelagic longline sets equipped with hook timers and temperature depth recorders to characterize the distribution of hooking contacts and success at a fine temporal and spatial scale. Scientific surveys were carried out in the Central–South Pacific Ocean (French Polynesia), targeting tropical (Thunnus albacares, Thunnus obesus) and temperate (Thunnus alalunga) tuna. Data analysis based on spatial point processes and stochastic modeling demonstrate the presence of spatio-temporal clusters for both hooking contacts and hooking success. The comparative analysis of the observed spatio-temporal patterns for different oceanographic zones revealed the persistent structure of the clusters, suggesting that they are neither related to local environmental conditions nor to the spatial distribution of prey species.

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9

Satria, Fayakun, and Lilis Sadiyah. "THE DEVELOPMENT OF HARVEST STRATEGIES FOR TROPICAL TUNA IN INDONESIA’S ARCHIPELAGIC WATERS." Indonesian Fisheries Research Journal 24, no. 1 (August 13, 2018): 53. http://dx.doi.org/10.15578/ifrj.24.1.2018.53-63.

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Significant roles of the fishery in the Indonesia’s archipelagic waters/IAW (FMAs 713, 714 and 715), with proportion of around 60% came from the IAW, and a strong residential behavior for skipjack (SKJ) and yellowfin tuna (YFT) encourage Indonesia to develop harvest strategies for the tropical tuna in the IAW. This is a priority action of the National Tuna Management Plan (NTMP) for tropical and neritic tuna. Fisheries operating in the IAW are mainly small scale commercial vessels. A specific harvest strategy framework that appropriate with the fishery characteristics has been developed. This paper describes the process of harvest strategy (HS) development for the tropical tuna in the Indonesia’s archipelagic waters (FMAs 713, 714 and 715). The HS is developed scientific works (including data collection, analysis/modelling and series technical and consultative stakeholder workshops as well as expert consultancies. Four technical workshops and seven stakeholder workshops have been done between 2015 and 2017. An interim HS (consisted of management objective, limit reference point, monitoring, analysis, harvest control rule and management measure) has been determined and agreed. Continues collaboration and commitment from related stakeholders including Government, fishers, fishing association, NGOs by adopting co-mangement and participatory approach in implementing the agreed harvest strategy, through data collection and sustain supports.The time series of catch and effort data, and size data could be used to monitor the fishery, stok status and its performance.In addition, involvement of relevant international tuna experts through expert consultancies are integrated process with the technical and stakeholder workshops. This HS development process is still on-going and can be refined, as HS development is a cycle process.

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10

Moreno, Gala, Laurent Dagorn, Gorka Sancho, and David Itano. "Fish behaviour from fishers’ knowledge: the case study of tropical tuna around drifting fish aggregating devices (DFADs)." Canadian Journal of Fisheries and Aquatic Sciences 64, no. 11 (November 1, 2007): 1517–28. http://dx.doi.org/10.1139/f07-113.

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Purse-seining for tropical tuna is one of the most technologically advanced fisheries in the world. The purpose of this study was to apply local ecological knowledge (LEK) to assist in the planning of future in situ studies of fish behaviour around drifting fish aggregating devices (DFADs) by prioritizing research topics, thereby reducing the number of potential hypotheses to explore. Interviews of fishing masters of the purse-seine fleets working in the western Indian Ocean provided an alternate, independent, and previously unexplored source of behavioural information, specifically on the attraction, retention, and departure behaviours of tuna schools in relation to DFADs. Most fishing masters agreed that the maximum attraction distance of a DFAD is approximately 10 km and generally agreed to the following statements. Tuna form distinct schools under FADs, commonly segregated by species and size. The main reasons for the departure of tuna aggregations from FADs are changes in currents or FAD movements and location in relation to physical or oceanographic features. The number of actively monitored DFADs at sea in the western Indian Ocean was estimated at approximately 2100. Incorporating fishers into the planning and design stages of future research projects will facilitate collaborative and integrated approaches.

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Hanich, Quentin, and Yoshitaka Ota. "Moving Beyond Rights-Based Management: A Transparent Approach to Distributing the Conservation Burden and Benefit in Tuna Fisheries." International Journal of Marine and Coastal Law 28, no. 1 (2013): 135–70. http://dx.doi.org/10.1163/15718085-12341268.

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Abstract Determining the distribution of the conservation burden and benefit is a critical challenge to the conservation and management of trans-boundary fish stocks. Given current levels of overfishing and overcapacity in many trans-boundary fisheries, some or all participating States must necessarily reach a compromise with regard to their interests and carry some share of the conservation burden. This article proposes a new approach to distributing the conservation burden and benefit in trans-boundary fisheries, and explores this approach in the world’s largest tuna fishery: the tropical tuna fisheries of the western and central Pacific. Such an approach would enable Regional Fisheries Management Organizations (RFMOs) to transparently ensure that conservation burden and benefit distributions are consistent with international obligations. The article recommends that RFMOs consider developing decision-making frameworks that would enable existing scientific processes to determine the necessary extent of conservation measures, while a new conservation burden methodology would then determine the implementation of the measure and its impact on each member.

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Ganachaud, Alexandre, Alexander Sen Gupta, Jaclyn N. Brown, Karen Evans, Christophe Maes, Les C. Muir, and Felicity S. Graham. "Projected changes in the tropical Pacific Ocean of importance to tuna fisheries." Climatic Change 119, no. 1 (November 21, 2012): 163–79. http://dx.doi.org/10.1007/s10584-012-0631-1.

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Alcover, Maria. "United States – Measures Concerning the Importation, Marketing and Sale of Tuna and Tuna Products (US–Tuna II (Mexico) (Recourse to Article 21.5 of the DSU by the United States / Second Recourse to Article 21.5 of the DSU by Mexico), DS381." World Trade Review 19, no. 3 (July 2020): 469–71. http://dx.doi.org/10.1017/s1474745620000178.

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These compliance proceedings concern a second revised measure adopted by the United States regarding the labelling of dolphin-safe tuna products (the 2016 Tuna Measure). The 2016 Tuna Measure places three types of conditions on the use of the dolphin-safe label: (i) conditions relating to the automatic disqualification of certain tuna products (eligibility criteria); (ii) conditions relating to certifications (certification requirements); and (iii) conditions relating to record keeping and segregation of dolphin-safe and non-dolphin-safe tuna (tracking and verification requirements). Regarding the eligibility criteria, tuna harvested using large-scale driftnets on the high seas and tuna products containing tuna harvested by setting on dolphins anywhere in the world are automatically disqualified for the dolphin-safe label. Regarding the certification and tracking/verification requirements, the 2016 Tuna Measure makes a distinction between the Eastern Tropical Pacific Ocean (ETP) large purse seine fishery, on the one hand, and all other fisheries, on the other hand.

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Amandè, Monin J., Emmanuel Chassot, Pierre Chavance, Hilario Murua, Alicia Delgado de Molina, and Nicolas Bez. "Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean." ICES Journal of Marine Science 69, no. 8 (June 15, 2012): 1501–10. http://dx.doi.org/10.1093/icesjms/fss106.

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Abstract Amandè, M. J., Chassot, E., Chavance, P., Murua, H., Delgado de Molina, A., and Bez, N. 2012. Precision in bycatch estimates: the case of tuna purse-seine fisheries in the Indian Ocean. – ICES Journal of Marine Science, 69: . Estimating bycatch, i.e. the incidental catch of non-target marine animals and undersized individuals of target species, by raising observer data to the whole fishery is routine practice. The annual bycatch of the European tropical tuna purse-seine fishery over the period 2003–2009 was estimated at 11 590 t [95% confidence interval: (8165–15 818 t)], corresponding to 4.7% of the tuna landings. An analysis of the variability in the precision of this estimate, based on generalized linear models and Monte Carlo simulations, showed that the current sampling coverage of the tropical tuna fishery observer programme, which is 4.6% of the fishing trips, resulted in large uncertainties in bycatch estimates by species, i.e. none of the estimates have a relative root mean square error smaller than 50%. Although the overall magnitude of bycatch of the fishery appeared to be small, the current sampling coverage was insufficient to give any reliable estimate for low-occurring species, such as marine turtles, some oceanic pelagic sharks, and some billfishes. Increasing the sampling coverage would likely improve bycatch estimates. Simulation outputs were produced to help define (i) trade-offs between the priority species to be monitored, (ii) the estimation precision, (iii) expected accuracy, and (iv) the associated sampling costs.

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15

Dahlet, Lol I., Nicola Downey-Breedt, Gabriel Arce, Warwick H. H. Sauer, and Maria A. Gasalla. "Comparative study of skipjack tuna Katsuwonus pelamis (Scombridae) fishery stocks from the South Atlantic and western Indian oceans." Scientia Marina 83, no. 1 (March 26, 2019): 19. http://dx.doi.org/10.3989/scimar.04804.22c.

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The skipjack tuna, Katsuwonus pelamis, inhabits tropical and subtropical oceans the world over, and contributes substantially to total tuna catches. Both fishing pressure and anthropic influences affect skipjack populations, impacting on economic returns and investment. The present study analyses and compares spatial time series of catch and catch per unit effort (CPUE), of pole-and-line fishing of skipjack tuna from Brazil, South Africa and the Maldives. Both regional and inter-regional analyses were conducted for the period 1970-2014 in order to ultimately investigate potential associations between these fisheries, climatic conditions and the El Niño Southern Oscillation (ENSO). Correlation tests and spatial mapping tools were used. From 2004 to 2011, South African skipjack catches correlated positively with Brazilian ones and negatively with Maldivians. CPUEs from the Brazilian and Maldivian skipjack fisheries showed a significant positive correlation in the period 1982-1993. Yearly catches from all regions were strongly associated with the Northern Oscillation Index (p < 0.001), an ENSO index. This study reflects an effort to articulate an inter-regional appraisal of skipjack pole-and-line fisheries embedded in the context of a globally changing climate, in the face of which emerging economies are the most vulnerable. Evidence of common patterns influencing these fisheries should encourage international South-South cooperative management and understanding of the resource.

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Sardenne, Fany, N’Guessan Constance Diaha, Monin Justin Amandé, Iker Zudaire, Lydie I. E. Couturier, Luisa Metral, Fabienne Le Grand, and Nathalie Bodin. "Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean." Canadian Journal of Fisheries and Aquatic Sciences 76, no. 1 (January 2019): 69–80. http://dx.doi.org/10.1139/cjfas-2017-0368.

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In the Gulf of Guinea, bigeye tuna (Thunnus obesus; BET) and yellowfin tuna (Thunnus albacares; YFT) are an important part of commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes, we examined their trophic niche partitioning in this understudied region. Trophic niche overlap was high (>70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high δ15N values and high proportions of monounsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (δ15N values decreased by ∼0.5‰), suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatom marker 20:5(n-3) increased in the seasonal upwelling area, highlighting the influence of seasonal habitat on the diet of tuna. The relatively lipid-rich muscle (∼6% dry mass) of Atlantic tropical tuna suggests a richer diet in this region than that of Indian Ocean tropical tuna and (or) differences in energy allocation strategies.

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Dagorn, Laurent, John D. Filmalter, Fabien Forget, Monin Justin Amandè, Martin A. Hall, Peter Williams, Hilario Murua, Javier Ariz, Pierre Chavance, and Nicolas Bez. "Targeting bigger schools can reduce ecosystem impacts of fisheries." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 9 (September 2012): 1463–67. http://dx.doi.org/10.1139/f2012-089.

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Sustainability of living resource exploitation relies on an ecosystem management approach. Within tropical tuna purse seine fisheries using fish aggregating devices (FADs), such an approach incorporates the reduction of bycatch, in particular vulnerable species such as elasmobranchs. The levels of total bycatch (in mass) from fishing operations using FADs is known to be five times higher than when tuna are caught in free-swimming schools. We intend to find practical solutions to reduce bycatch in FAD sets through the investigation of the relationships between the ratio of bycatch to target catch across different set size classes in all oceans. Ratios were always highest when catches were small, with the smallest class of catches responsible for the highest total portion of bycatch (23%–43%) while only contributing negligibly to the total target catch (3%–10%). Reducing the number of fishing sets (a part of the total effort) while maintaining the same total yield could contribute to a substantial reduction in the impacts of human activities.

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Sardenne, Fany, Nathalie Bodin, Anaïs Médieu, Marisa Antha, Rona Arrisol, Fabienne Le Grand, Antoine Bideau, Jean-Marie Munaron, François Le Loc’h, and Emmanuel Chassot. "Benefit-risk associated with the consumption of fish bycatch from tropical tuna fisheries." Environmental Pollution 267 (December 2020): 115614. http://dx.doi.org/10.1016/j.envpol.2020.115614.

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Mannocci, Laura, Fabien Forget, Mariana Travassos Tolotti, Pascal Bach, Nicolas Bez, Hervé Demarcq, David Kaplan, et al. "Predicting bycatch hotspots in tropical tuna purse seine fisheries at the basin scale." Global Ecology and Conservation 24 (December 2020): e01393. http://dx.doi.org/10.1016/j.gecco.2020.e01393.

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Forget, Fabien G., Manuela Capello, John D. Filmalter, Rodney Govinden, Marc Soria, Paul D. Cowley, and Laurent Dagorn. "Behaviour and vulnerability of target and non-target species at drifting fish aggregating devices (FADs) in the tropical tuna purse seine fishery determined by acoustic telemetry." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 9 (September 2015): 1398–405. http://dx.doi.org/10.1139/cjfas-2014-0458.

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Characterizing the vulnerability of both target and non-target (bycatch) species to a fishing gear is a key step towards an ecosystem-based fisheries management approach. This study addresses this issue for the tropical tuna purse seine fishery that uses fish aggregating devices (FADs). We used passive acoustic telemetry to characterize, on a 24 h scale, the associative patterns and the vertical distribution of skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye tuna (Thunnus obesus) (target species), as well as silky shark (Carcharhinus falciformis), oceanic triggerfish (Canthidermis maculata), and rainbow runner (Elagatis bipinnulata) (major non-target species). Distinct diel associative patterns were observed; the tunas and the silky sharks were more closely associated with FADs during daytime, while the rainbow runner and the oceanic triggerfish were more closely associated during the night. Minor changes in bycatch to catch ratio of rainbow runner and oceanic triggerfish could possibly be achieved by fishing at FADs after sunrise. However, as silky sharks display a similar associative pattern as tunas, no specific change in fishing time could mitigate the vulnerability of this more sensitive species. For the vertical distribution, there was no particular time of the day when any species occurred beyond the depth of a typical purse seine net. While this study does not provide an immediate solution to reduce the bycatch to catch ratios of the FAD-based fishery in the western Indian Ocean, the method described here could be applied to other regions where similar fisheries exist so as to evaluate potential solutions to reducing fishing mortality of non-target species.

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Salvetat, Julie, Anne Lebourges-Dhaussy, Paulo Travassos, Sven Gastauer, Gildas Roudaut, Gary Vargas, and Arnaud Bertrand. "In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen." Marine and Freshwater Research 71, no. 9 (2020): 1118. http://dx.doi.org/10.1071/mf19153.

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Triggerfish are widely distributed in tropical waters where they play an important ecological role. The black triggerfish Melichthys niger may be the dominant species around oceanic tropical islands, whereas pelagic triggerfish, such as the ocean triggerfish Canthidermis sufflamen, can assemble around fish aggregating devices (FADs) where they are a common bycatch of tuna fisheries. In this study we combined acoustic and optical recordings to provide the first in situ target strength (TS) measurement of black and ocean triggerfish. Data were collected in the Archipelago of Fernando de Noronha off north-east Brazil. The mean TS of a 27.8-cm-long black triggerfish at 70 and 200kHz was –39.3dB re 1m2 (CV=14.0%) and –38.9dB re 1m2 (CV=14.4%) respectively. The mean TS values of ocean triggerfish (with a size range of 39–44cm) at 70 and 200kHz were –36.0dB re 1m2 (CV=15.7%) and –33.3dB re 1m2 (CV=14.0%) respectively. This work opens up the field for acoustic biomass estimates. In addition, we have shown that TS values for ocean triggerfish are within the same range as those of small tunas. Therefore, acoustic data transmitted from FADs equipped with echosounders can introduce a bias in tuna acoustic biomass estimation and lead to increased rates of bycatch.

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22

Salvetat, Julie, Anne Lebourges-Dhaussy, Paulo Travassos, Sven Gastauer, Gildas Roudaut, Gary Vargas, and Arnaud Bertrand. "Corrigendum to: In situ target strength measurement of the black triggerfish Melichthys niger and the ocean triggerfish Canthidermis sufflamen." Marine and Freshwater Research 72, no. 3 (2021): 449. http://dx.doi.org/10.1071/mf19153_co.

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Анотація:

Triggerfish are widely distributed in tropical waters where they play an important ecological role. The black triggerfish Melichthys niger may be the dominant species around oceanic tropical islands, whereas pelagic triggerfish, such as the ocean triggerfish Canthidermis sufflamen, can assemble around fish aggregating devices (FADs) where they are a common bycatch of tuna fisheries. In this study we combined acoustic and optical recordings to provide the first in situ target strength (TS) measurement of black and ocean triggerfish. Data were collected in the Archipelago of Fernando de Noronha off north-east Brazil. The mean TS of a 27.8-cm-long black triggerfish at 70 and 200kHz was –39.3dB re 1m2 (CV=14.0%) and –38.9dB re 1m2 (CV=14.4%) respectively. The mean TS values of ocean triggerfish (with a size range of 39–44cm) at 70 and 200kHz were –36.0dB re 1m2 (CV=15.7%) and –33.3dB re 1m2 (CV=14.0%) respectively. This work opens up the field for acoustic biomass estimates. In addition, we have shown that TS values for ocean triggerfish are within the same range as those of small tunas. Therefore, acoustic data transmitted from FADs equipped with echosounders can introduce a bias in tuna acoustic biomass estimation and lead to increased rates of bycatch.

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23

Chassot, Emmanuel, Nathalie Bodin, Fany Sardenne, and David Obura. "The key role of the Northern Mozambique Channel for Indian Ocean tropical tuna fisheries." Reviews in Fish Biology and Fisheries 29, no. 3 (June 13, 2019): 613–38. http://dx.doi.org/10.1007/s11160-019-09569-9.

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24

Nataniel, Anildo, Jon Lopez, and Maria Soto. "Modelling seasonal environmental preferences of tropical tuna purse seine fisheries in the Mozambique Channel." Fisheries Research 243 (November 2021): 106073. http://dx.doi.org/10.1016/j.fishres.2021.106073.

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25

Mysak, Lawrence A. "El Niño, Interannual Variability and Fisheries in the Northeast Pacific Ocean." Canadian Journal of Fisheries and Aquatic Sciences 43, no. 2 (February 1, 1986): 464–97. http://dx.doi.org/10.1139/f86-057.

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In this review I describe the oceanic and atmospheric observations, physical mechanisms, and theories associated with El Niño – Southern Oscillation (ENSO) warming episodes in the tropical Pacific, and critically examine the means by which these anomalous events are believed to produce unusual conditions in the northeast Pacific. However, not all tropical ENSO episodes have a noticeable effect at higher latitudes. Also, because of anomalous local atmospheric forcing, significant warmings, strong coastal currents, and high sea levels along the west coast of North America can occur in years during which there are no tropical ENSO episodes. The possible impacts of ENSO-induced changes and of other interannual fluctuations in the northeast Pacific on various fisheries are described. Such impacts include changes in the migration routes of the bluefin tuna (Thunnus thynuus) and Fraser River sockeye salmon (Oncorhynchus nerka), increases in the Pacific herring (Clupea pallasi) recruitment, earlier return times for the Bristol Bay sockeye salmon, and increases in the weight of mature Fraser River sockeye several years after a local warming event.

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26

Snouck-Hurgronje, Julia E., David M. Kaplan, Emmanuel Chassot, Alexandra Maufroy, and Daniel Gaertner. "Fishing on floating objects (FOBs): how French tropical tuna purse seiners split fishing effort between GPS-monitored and unmonitored FOBs." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 11 (November 2018): 1849–58. http://dx.doi.org/10.1139/cjfas-2017-0152.

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Fishing on floating objects (FOBs) dominates catch in tropical tuna purse seine fisheries. One frequently cited advantage of deploying GPS-monitored FOBs is that the position information can be used for directed fishing to reduce search time for tuna. However, purse seiners also fish on foreign objects for which position information is not available. It is critical to quantify the prevalence of fishing on GPS-monitored versus unmonitored FOBs to understand how they impact fishing effort and catch per unit effort. We analyzed French commercial, observer, and FOB trajectory data in the Atlantic and Indian oceans to determine how often purse seine vessels fish on GPS-monitored FOBs. Only 2.7%–20.4% of French FOB fishing sets over 2007–2013 in both oceans were made on GPS-monitored FOBs. Though increasing over time, the low percentage suggests that French vessels do not primarily use GPS-monitored FOBs to reduce search time for tuna. We hypothesize that fishery-wide FOB deployments have important collective consequences for overall fishing effort and recommend that future effort metrics should be based on fishery-wide FOB activities.

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Griffiths, Shane P., Gary C. Fry, Fiona J. Manson, and Dong C. Lou. "Age and growth of longtail tuna (Thunnus tonggol) in tropical and temperate waters of the central Indo-Pacific." ICES Journal of Marine Science 67, no. 1 (August 30, 2009): 125–34. http://dx.doi.org/10.1093/icesjms/fsp223.

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Abstract Griffiths, S. P., Fry, G. C., Manson, F. J., and Lou, D. C. 2010. Age and growth of longtail tuna (Thunnus tonggol) in tropical and temperate waters of the central Indo-Pacific. – ICES Journal of Marine Science, 67: 125–134. Age and growth of longtail tuna (Thunnus tonggol) were assessed by examination of annual growth increments in sectioned sagittal otoliths from 461 fish (238–1250 mm fork length, LF) sampled from tropical and temperate waters in the central Indo-Pacific between February 2003 and April 2005. Edge and microincrement analyses (presumed daily increments) suggest that longtail tuna deposit a single annual growth increment mainly between August and October. Age was, therefore, estimated for all fish by counting assumed annual growth increments. Ages ranged from 154 d to 18.7 years, with most fish being 3–9 years. Five growth models were fitted to length-at-age data, all of which indicated that the species is relatively slow-growing and long-lived. Recaptures of two tagged fish at liberty for 6.2 and 10.5 years support this notion. A bias-corrected form of Akaike's Information Criterion determined that the Schnute–Richards model provided the best fit to length-at-age data, with model parameter estimates (sexes combined) of L∞ = 135.4 cm LF, K = 22.3 year−1, t0 = 0.120 years, δ = 150.0, v = 0.019, and γ = 2.7 × 10−8. There was no significant difference in growth between sexes. The results suggest that longtail tuna grow more slowly and live longer than other tuna species of similar size. Coupled with their restricted neritic distribution, longtail tuna may be vulnerable to overexploitation by fisheries, and caution needs to be exercised in managing the species until more reliable biological and catch data are collected to assess the status of the population.

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Rubio, Iratxe, Unai Ganzedo, Alistair J. Hobday, and Elena Ojea. "Southward re‐distribution of tropical tuna fisheries activity can be explained by technological and management change." Fish and Fisheries 21, no. 3 (January 28, 2020): 511–21. http://dx.doi.org/10.1111/faf.12443.

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29

Castro, C., K. Van Waerebeek, D. Cárdenas, and JJ Alava. "Marine mammals used as bait for improvised fish aggregating devices in marine waters of Ecuador, eastern tropical Pacific." Endangered Species Research 41 (March 12, 2020): 289–302. http://dx.doi.org/10.3354/esr01015.

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Fish aggregating devices (FADs) are floating objects typically used to attract and capture pelagic fish in industrial tuna fisheries. This study documents 9 cases, involving 31 marine mammals, of incidentally captured, killed or otherwise retrieved cetaceans and pinnipeds which were used, or presumably used, as bait for improvised fish aggregation devices (IFAD) by artisanal fishers in coastal Ecuador. At least 3 species of small cetaceans were affected, including pantropical spotted dolphin Stenella attenuata, short-finned pilot whale Globicephala macrorhynchus, pygmy killer whale Feresa attenuata and an unidentified small delphinid, as well as South American sea lions Otaria byronia which were reportedly killed on purpose for this fishing practice. A sperm whale Physeter macrocephalus and a humpback whale Megaptera novaeangliae were presumably found floating at sea and opportunistically exploited as FADs. The South American sea lion represented 80.6% of marine mammals used as bait associated with FADs (25 sea lions out of 31 marine mammals), while the remaining 5 (possibly 6) cetacean species represented 19.4%. This is the first report of baited FADs in Ecuador, the extent of which is still unknown. This fishing technique has not been documented in other nations along the west coast of South America, although baiting of gillnets with marine mammal parts is common in Peru. Without fisheries management and regulation, this illegal fishing practice could rapidly expand and lead to further direct kills and conservation problems for targeted marine mammal populations in the eastern tropical Pacific. A bottom-up fisheries policy in concert with community-based conservation to ban the use of marine mammals as FAD bait is recommended.

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Kleiber, Pierre, Michael G. Hinton, and Yuji Uozumi. "Stock assessment of blue marlin (Makaira nigricans) in the Pacific using MULTIFAN-CL." Marine and Freshwater Research 54, no. 4 (2003): 349. http://dx.doi.org/10.1071/mf01246.

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In the Pacific, blue marlin are an incidental catch of longline fisheries and an important resource for big game recreational fishing. Over the past two decades, blue marlin assessments by different techniques have yielded results ranging from an indication of declining stock to a state of sustained yield at approximately the maximum average level. Longline fishing practices have changed over the years since the 1950s in response to changes in principal target species and to gear developments. Despite increasingly sophisticated attempts to standardize fishing effort with changing fishing practices, the stock assessments to date are likely confounded to a greater or lesser degree by changes in catchability for blue marlin. Yet, only data from commercial longline fisheries targeting tuna provide sufficient spatial and temporal coverage to allow assessment of this resource. To re-assess the blue marlin stocks in the Pacific and also to assess the efficacy of a habitat-based standardization of longline effort, a collaborative analysis was conducted involving scientists at the National Research Institute of Far Seas Fisheries, Shimizu, Japan, the Inter-American Tropical Tuna Commission, La Jolla, California, and the NOAA Fisheries Honolulu Laboratory, Honolulu, Hawaii. Using MULTIFAN-CL as an assessment tool, there was considerable uncertainty in quantifying the fishing effort levels that would produce a maximum sustainable yield. However, it was found that, at worst, blue marlin in the Pacific are close to a fully exploited state, that is the population and the fishery are somewhere near the top of the yield curve. Furthermore, it was found that effort standardization using a habitat-based model allowed estimation of parameters within reasonable bounds and with reduced confidence intervals about those values.

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Imzilen, Taha, Christophe Lett, Emmanuel Chassot, and David M. Kaplan. "Spatial management can significantly reduce dFAD beachings in Indian and Atlantic Ocean tropical tuna purse seine fisheries." Biological Conservation 254 (February 2021): 108939. http://dx.doi.org/10.1016/j.biocon.2020.108939.

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Yuliantiningsih, Aryuni. "The Participation of Indonesia in Regional Fisheries Management Organizations (RFMOs): The Legal and Globalization Perspectives." UNIFIKASI : Jurnal Ilmu Hukum 6, no. 2 (December 21, 2019): 137. http://dx.doi.org/10.25134/unifikasi.v6i2.1943.

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Abstract : The purpose of this research is to find out and analyse the participation of Indonesia in Regional Fisheries Management Organizations (RFMOs) viewed from the legal and globalization perspectives. The method used in this research was a normative juridical by employing secondary data sources which were analysed qualitatively. The results showed that there are 4 (four) RFMOs bordering Indonesian waters, namely IOCT, CCSBT, WPPC, and Inter-American Tropical Tuna Commission (IATTC). Currently, Indonesia has participated as a member of RFMOs with the reasons, firstly, to participate in conserving fish resources and secondly, if Indonesia is not a member of RFMOs, the fishery products can be embargoed and categorized as IUU fishing. In relation to law and globalization, developed countries have implemented their hegemony to dominate the high seas through legal instruments, namely international treaties and organizations. On the other hand, the participation of Indonesia in RFMO is merely to facilitate the citizens to be able to access fish resources in the high seas.Keywords: Indonesia, RFMOs, law, globalization.�Keikutsertaan Indonesia dalam Regional Fisheries Management Organizations (RFMOs): Perspektif Hukum dan Globalisasi�Tujuan penelitian ini untuk mengetahui dan menganalisis keikutsertaan Indonesia dalam Regional Fisheries Management Organizatios (RFMOs) ditinjau dari perspektif hukum dan globalisasi. Metode penelitian yang digunakan adalah yuridis normatif, menggunakan sumber data sekunder dan analisis dilakukan secara kualitatif. Hasil penelitian yaitu terdapat 4 (empat) RFMOs yang berbatasan dengan perairan Indonesia yaitu, IOCT, CCSBT, WPPC, Inter-American Tropical Tuna Commission (IATTC). Saat ini Indonesia telah ikut serta menjadi anggota RFMOs dengan alasan, pertama, ikut melakukan konservasi sumber daya ikan dan kedua,� jika tidak menjadi anggota RFMOs maka hasil tangkapan dapat� diembargo dan dikategorikan sebagai IUU fishing.� Dikaitkan dengan hukum dan globalisasi, negara maju telah menerapkan hegemoninya untuk menguasai laut lepas melalui instrumen hukum yaitu perjanjian internasional dan organisasi internasional. Di sisi lain keikutsertaan Indonesia dalam RFMO� untuk memfasilitasi warga negaranya agar dapat mengakses sumberdaya ikan di laut lepas.Kata Kunci: Indonesia, RFMOs, hukum, globalisasi.

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Wibawa, Teja A., Patrick Lehodey, and Inna Senina. "Standardization of a geo-referenced fishing data set for the Indian Ocean bigeye tuna, Thunnus obesus (1952–2014)." Earth System Science Data 9, no. 1 (February 28, 2017): 163–79. http://dx.doi.org/10.5194/essd-9-163-2017.

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Abstract. Geo-referenced catch and fishing effort data of the bigeye tuna fisheries in the Indian Ocean over 1952–2014 were analyzed and standardized to facilitate population dynamics modeling studies. During this 62-year historical period of exploitation, many changes occurred both in the fishing techniques and the monitoring of activity. This study includes a series of processing steps used for standardization of spatial resolution, conversion and standardization of catch and effort units, raising of geo-referenced catch into nominal catch level, screening and correction of outliers, and detection of major catchability changes over long time series of fishing data, i.e., the Japanese longline fleet operating in the tropical Indian Ocean. A total of 30 fisheries were finally determined from longline, purse seine and other-gears data sets, from which 10 longline and 4 purse seine fisheries represented 96 % of the whole historical geo-referenced catch. Nevertheless, one-third of total nominal catch is still not included due to a total lack of geo-referenced information and would need to be processed separately, accordingly to the requirements of the study. The geo-referenced records of catch, fishing effort and associated length frequency samples of all fisheries are available at doi:10.1594/PANGAEA.864154.

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Jatmiko, Irwan, Fathur Rochman, and Maya Agustina. "VARIASI GENETIK MADIDIHANG (Thunnus albacares; Bonnaterre, 1788) DENGAN ANALISIS MIKROSATELIT DI PERAIRAN INDONESIA." Jurnal Penelitian Perikanan Indonesia 24, no. 3 (October 8, 2018): 157. http://dx.doi.org/10.15578/jppi.24.3.2018.157-164.

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Madidihang (Thunnus albacares) merupakan spesies yang bermigrasi jauh yang distribusinya di perairan tropis hingga perairan subtropis. Spesies ini ditemukan di Samudra Atlantik, Hindia dan Pasifik. Informasi genetik ikan dengan migrasi jauh seperti tuna penting diketahui untuk kepentingan pemanfaatan secara lestari. Penelitian ini bertujuan untuk memperoleh informasi keragaman genetik dan struktur populasi yang dieksploitasi dan kekerabatan populasi madidihang di perairan Indonesia. Pengumpulan sampel genetik dilakukan di tiga lokasi yaitu di Barat Sumatra, Selatan Bali dan perairan Sulawesi Utara. Metode yang digunakan adalah analisis mikrosatelit yang terdiri dari ekstraksi, purifikasi, amplifikasi polymerase chain reaction (PCR) dan elektroforesis. Hasil analisis terhadap 3 loci DNA mikrosatelit menunjukkan bahwa tingkat kekerabatan ketiga kelompok sampel relatif dekat yaitu berkisar antara 0,132-0,206. Hal ini menunjukkan bahwa Populasi madidihang di perairan Indonesia merupakan stok tunggal dan terjadi perkawinan acak. Meskipun demikian, sebagai spesies yang bermigrasi jauh lintas negara, pengelolaan madidihang juga memerlukan kerjasama yang baik antar negara yang tergabung dalam organisasi pengelolaan perikanan tuna regional.Yellowfin tuna (Thunnus albacares) is a highly migratory species that distribute from tropical to subtropical waters. This species can be found in the Atlantic, Indian and Pacific Oceans. Genetic information in fish with long distance migration such as tuna is very important for sustainable use. This study aims to obtain information on genetic diversity and population structure exploited and kinship of yellowfin tuna populations in Indonesian waters. Genetic sampling of yellowfin tuna was conducted in three locations in Indonesian waters in western Sumatra, southern Bali and North Sulawesi waters. The methods used was microsatellite analysis which consist of extraction, purification, polymerase chain reaction (PCR) amplification and electrophoresis. The result of 3 microsatellite DNA locus analysis showed that the level of kinship between the three sample groups in Indonesian waters was relatively close, ranging from 0.132 to 0.206. This shows that yellowfin tuna population in Indonesian waters is a single stock and random copulation. However, as a highly migratory species that migrate across the nations, yellowfin tuna management also requires good cooperation among countries incorporated in regional tuna fisheries management organizations.

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Kanaji, Yu, Toshiyuki Tanabe, Hikaru Watanabe, Tatsuki Oshima, and Makoto Okazaki. "Variability in reproductive investment of skipjack tuna (Katsuwonus pelamis) in relation to the ocean - climate dynamics in the tropical eastern Indian Ocean." Marine and Freshwater Research 63, no. 8 (2012): 695. http://dx.doi.org/10.1071/mf11146.

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The Indian Ocean is characterised by significant climatic and oceanographic variability such as the seasonal monsoon and the decadal and inter-annual oscillation of the Indian Ocean Dipole (IOD). Understanding the effects of ocean–climate variability on marine top predators is important for both fisheries and ecosystem management. To test the hypothesis that variability in surface and subsurface temperature affects the annual reproductive cycles of skipjack tuna (Katsuwonus pelamis) in the tropical eastern Indian Ocean, we examined the seasonal and inter-annual variations of the gonadosomatic index (GSI) and determined hatch date by using otolith microstructure analysis. The GSI tended to be higher in January–February during the north-eastern monsoon when seawater cooling at the subsurface layer is induced by the seasonal inflow of the South Equatorial Countercurrent (SECC). The mode of the hatch-month distribution was also detected in that season. The generalised linear model (GLM) resulted in a dome-shaped quadratic relationship, with a peak GSI between 24°C and 26°C occurring at a depth of 50 m during austral summer. These findings indicate that seasonal monsoons and associated changes in oceanographic conditions strongly affect the energy-allocation pattern of skipjack tunas.

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Shiao, Jen-Chieh, Han-Bo Lu, Jhen Hsu, Hui-Yu Wang, Shui-Kai Chang, Min-Yu Huang, and Taiki Ishihara. "Changes in size, age, and sex ratio composition of Pacific bluefin tuna (Thunnus orientalis) on the northwestern Pacific Ocean spawning grounds." ICES Journal of Marine Science 74, no. 1 (August 5, 2016): 204–14. http://dx.doi.org/10.1093/icesjms/fsw142.

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The Pacific bluefin tuna (Thunnus orientalis, PBF), an iconic fisheries species, is heavily exploited and its biomass is at a historically low level. To enhance effectiveness of management and conservation, a study was initiated to examine the demographic changes of the PBF between 2002 and 2015. Annual tuna age compositions were estimated by applying an empirical age-length key, based on the ages and lengths of 892 fish, to the length frequencies observed among annual catches in the northwestern Pacific spawning grounds located near Taiwan. Ages of the spawners concentrated in 7–20-years old (range = 4–28 years), corresponding to fork lengths between 200 and 240 cm. The size and age compositions were influenced by the strong 1994 and 1996 year-cohorts, which showed a relatively high abundance in most years except 2007–2009. Between 2013 and 2015, recruits of 2005–2009 year-cohorts (age 6–10) increased in relative abundance while the strong 1994 and 1996 year-cohorts decreased as they neared the end of their lifespan. PBF smaller than 200 cm were rarely found in the tropical areas and the mean sizes of the PBF caught south of 24°N were significantly larger than those caught north of 24°N. These results suggested that the choice of spawning latitudes of the PBF was influenced by the size of spawning adults. The sex ratio of smaller (<200 cm) and intermediate size classes (200–230 cm) was female biased (50–75%) while that of larger fish (>240 cm) were male biased (62–100%). The size and age composition of the PBF was mainly influenced by the recruitment of young spawners and was less sensitive to the catch of longline fisheries. However the impact of longline fisheries on the reproductive potential of this species warrants further investigation.

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Farley, Jessica H., Naomi P. Clear, Bruno Leroy, Tim L. O. Davis, and Geoff McPherson. "Age, growth and preliminary estimates of maturity of bigeye tuna, Thunnus obesus, in the Australian region." Marine and Freshwater Research 57, no. 7 (2006): 713. http://dx.doi.org/10.1071/mf05255.

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Biological parameters such as age, growth and age (or size) at maturity are vital for accurate stock assessments and management plans to ensure that fisheries develop sustainably. Despite this, very few validated age studies have been conducted for large tropical pelagic species within the Australian region. Age and growth parameters were estimated for bigeye tuna, Thunnus obesus (Lowe, 1839), sampled from longline fisheries in the Australian region using validated techniques based on counts of annual increments. Poor increment clarity reduced the number of otoliths included in the final analysis to only 50% of the 3200 selected for reading (39–178-cm fork length). Microincrement analysis confirmed the position of the first two annual increments in these otoliths. A maximum age of 16 years was obtained, but over 80% of fish in the Australian catch were <5 years old. Growth is most rapid in the first few years of life and asymptotic length is reached at about age 9 to 10 years. The von Bertalanffy growth parameters were estimated at L∞ = 169.09, k = 0.238, and to = –1.706 for the south-west Pacific Ocean and L∞ = 178.41, k = 0.176, and to = –2.500 for the eastern Indian Ocean. These parameters were significantly different, suggesting that there is little mixing between populations in the Pacific and Indian Oceans. Length at 50% maturity for females sampled in northern Queensland was estimated to be 102.4-cm fork length.

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38

Juan-Jordá, M. J., I. Mosqueira, J. Freire, and N. K. Dulvy. "Population declines of tuna and relatives depend on their speed of life." Proceedings of the Royal Society B: Biological Sciences 282, no. 1811 (July 22, 2015): 20150322. http://dx.doi.org/10.1098/rspb.2015.0322.

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Larger-bodied species in a wide range of taxonomic groups including mammals, fishes and birds tend to decline more steeply and are at greater risk of extinction. Yet, the diversity in life histories is governed not only by body size, but also by time-related traits. A key question is whether this size-dependency of vulnerability also holds, not just locally, but globally across a wider range of environments. We test the relative importance of size- and time-related life-history traits and fishing mortality in determining population declines and current exploitation status in tunas and their relatives. We use high-quality datasets of half a century of population trajectories combined with population-level fishing mortalities and life-history traits. Time-related traits (e.g. growth rate), rather than size-related traits (e.g. maximum size), better explain the extent and rate of declines and current exploitation status across tuna assemblages, after controlling for fishing mortality. Consequently, there is strong geographical patterning in population declines, such that populations with slower life histories (found at higher cooler latitudes) have declined most and more steeply and have a higher probability of being overfished than populations with faster life histories (found at tropical latitudes). Hence, the strong, temperature-driven, latitudinal gradients in life-history traits may underlie the global patterning of population declines, fisheries collapses and local extinctions.

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Gaertner, Daniel, and Jean-Pierre Hallier. "Combining Bayesian and simulation approaches to compare the efficiency of two types of tags used in tropical tuna fisheries." Aquatic Living Resources 17, no. 2 (April 2004): 175–83. http://dx.doi.org/10.1051/alr:2004016.

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40

Poisson, François, Bernard Séret, Anne-Lise Vernet, Michel Goujon, and Laurent Dagorn. "Collaborative research: Development of a manual on elasmobranch handling and release best practices in tropical tuna purse-seine fisheries." Marine Policy 44 (February 2014): 312–20. http://dx.doi.org/10.1016/j.marpol.2013.09.025.

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41

Matear, R. J., M. A. Chamberlain, C. Sun, and M. Feng. "Climate change projection for the western tropical Pacific Ocean using a high-resolution ocean model: Implications for tuna fisheries." Deep Sea Research Part II: Topical Studies in Oceanography 113 (March 2015): 22–46. http://dx.doi.org/10.1016/j.dsr2.2014.07.003.

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42

C. Fielder, Paul, and Cleridy E. Lennert-Cody. "Seasonal and interannual variations in the distributions of tuna-associated dolphins in the eastern tropical Pacific Ocean." IWC Journal of Cetacean Research and Management 20, no. 1 (January 1, 2019): 67–79. http://dx.doi.org/10.47536/jcrm.v20i1.240.

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Seasonal and interannual (El Niño–La Niña) variations in dolphin distributions in the eastern tropical Pacific Ocean have not been quantified, inspite of an extensive research vessel database. Fisheries observer data from the yellowfin tuna purse-seine fishery, collected year-round from 1986through 2015, were used to construct a binned spatiotemporal dataset of the presence/absence of spotted, spinner and common dolphin schools bymonth and 1° area. Distribution patterns were predicted from generalised additive logistic regression models applied to the binned data, with dynamicpredictors of surface temperature and salinity, thermocline depth and a stratification index. The dolphin taxa, especially common dolphins, showsome niche separation in relation to these variables. Predicted distributions for each taxon showed seasonal and interannual differences. Spottedand spinner dolphins responded to changes in the position and size of the eastern Pacific warm pool and avoided the equatorial cold tongue inSeptember–October and during La Niña. Common dolphins responded to seasonal and interannual changes in the Costa Rica Dome, the cold tongue,and the coastal upwelling habitat along Baja California, Peru and Ecuador. These predicted temporal variations are consistent with changes inpreferred habitat driven by environmental variability.

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Maufroy, Alexandra, David M. Kaplan, Nicolas Bez, Alicia Delgado De Molina, Hilario Murua, Laurent Floch, and Emmanuel Chassot. "Massive increase in the use of drifting Fish Aggregating Devices (dFADs) by tropical tuna purse seine fisheries in the Atlantic and Indian oceans." ICES Journal of Marine Science 74, no. 1 (October 26, 2016): 215–25. http://dx.doi.org/10.1093/icesjms/fsw175.

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Since the mid-1990s, drifting Fish Aggregating Devices (dFADs), artificial floating objects designed to aggregate fish, have become an important mean by which purse seine fleets catch tropical tunas. Mass deployment of dFADs, as well as the massive use of GPS buoys to track dFADs and natural floating objects, has raised serious concerns for the state of tropical tuna stocks and ecosystem functioning. Here, we combine tracks from a large proportion of the French GPS buoys from the Indian and Atlantic oceans with data from observers aboard French and Spanish purse seiners and French logbook data to estimate the total number of dFADs and GPS buoys used within the main fishing grounds of these two oceans over the period 2007–2013. In the Atlantic Ocean, the total number of dFADs increased from 1175 dFADs active in January 2007 to 8575 dFADs in August 2013. In the Indian Ocean, this number increased from 2250 dFADs in October 2007 to 10 300 dFADs in September 2013. In both oceans, at least a fourfold increase in the number of dFADs was observed over the 7-year study period. Though the relative proportion of natural to artificial floating objects varied over space, with some areas such as the Mozambique Channel and areas adjacent to the mouths of the Niger and Congo rivers being characterized by a relatively high percentage of natural objects, in no region do dFADs represent <50% of the floating objects and the proportion of natural objects has dropped over time as dFAD deployments have increased. Globally, this increased dFAD use represents a major change to the pelagic ecosystem that needs to be closely followed in order to assess its impacts and avoid negative ecosystem consequences.

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Lezama-Ochoa, Nerea, Hilario Murua, Jon Ruiz, Pierre Chavance, Alicia Delgado de Molina, Ainhoa Caballero, and Igor Sancristobal. "Biodiversity and environmental characteristics of the bycatch assemblages from the tropical tuna purse seine fisheries in the eastern Atlantic Ocean." Marine Ecology 39, no. 3 (June 2018): e12504. http://dx.doi.org/10.1111/maec.12504.

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Gaertner, Daniel, Jean-Pierre Hallier, and Mark N. Maunder. "A tag-attrition model as a means to estimate the efficiency of two types of tags used in tropical tuna fisheries." Fisheries Research 69, no. 2 (September 2004): 171–80. http://dx.doi.org/10.1016/j.fishres.2004.05.006.

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46

Mannocci, Laura, Fabien Forget, Mariana Travassos Tolotti, Pascal Bach, Nicolas Bez, Hervé Demarcq, David Kaplan, et al. "Corrigendum to “Predicting bycatch hotspots in tropical tuna purse seine fisheries at the basin scale” [Global Ecol. Conserv. 24 (2020) e01393]." Global Ecology and Conservation 25 (January 2021): e01427. http://dx.doi.org/10.1016/j.gecco.2020.e01427.

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47

Maufroy, Alexandra, Emmanuel Chassot, Rocío Joo, and David Michael Kaplan. "Large-Scale Examination of Spatio-Temporal Patterns of Drifting Fish Aggregating Devices (dFADs) from Tropical Tuna Fisheries of the Indian and Atlantic Oceans." PLOS ONE 10, no. 5 (May 26, 2015): e0128023. http://dx.doi.org/10.1371/journal.pone.0128023.

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Ladino, Felipe, Sandra Martínez, María Duarte, Natalia Vélez, and Sandra Bessudo. "Monitoring of the status of eleven bony and cartilaginous fish populations in the Malpelo Sanctuary of Fauna and Flora, Colombian Pacific." Boletín de Investigaciones Marinas y Costeras 50, no. 1 (June 30, 2021): 105–20. http://dx.doi.org/10.25268/bimc.invemar.2021.50.1.1084.

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To determine trends over time in the relative abundance of species prioritized in the Malpelo Fauna and Flroa Sanctuary Management Plan, underwater visual censuses were done from April 2009 to August 2019. Data were collected for five species of bonefish: bluefin trevally (Caranx melampygus), longfin yellowtail (Seriola rivoliana), yellowfin tuna (Thunnus albacares), leather bass (Dermatolepis dermatolepis) and sailfin grouper (Mycteroperca olfax), and six cartilaginous fish: spotted eagle ray (Aetobatus laticeps), silky shark (Carcharhinus falciformis), Galapagos shark (Carcharhinus galapagensis), whitetip reef shark (Triaenodon obesus), whale shark (Rhincodon typus) and scalloped hammerhead shark (Sphyrna lewini). A negative non-significant trend in abundance through time was observed for most of the evaluated species, except A. laticeps and T. obesus, which showed positive non-significant trends. The hammerhead shark (S. lewini) was the only species that showed a statistically significant decrease in abundance over time. The results of this study highlight the urgent need to establish more effective fisheries management and regulation measures that promote the conservation of important fish species, not just inside the sanctuary but also within the Tropical Eastern Pacific.

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Fonteneau, Alain, Emmanuel Chassot, and Nathalie Bodin. "Global spatio-temporal patterns in tropical tuna purse seine fisheries on drifting fish aggregating devices (DFADs): Taking a historical perspective to inform current challenges." Aquatic Living Resources 26, no. 1 (January 2013): 37–48. http://dx.doi.org/10.1051/alr/2013046.

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Su, Nan-Jay, Chia-Hao Chang, Ya-Ting Hu, Wei-Chuan Chiang, and Chen-Te Tseng. "Modeling the Spatial Distribution of Swordfish (Xiphias gladius) Using Fishery and Remote Sensing Data: Approach and Resolution." Remote Sensing 12, no. 6 (March 15, 2020): 947. http://dx.doi.org/10.3390/rs12060947.

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Swordfish, Xiphias gladius (Linnaeus, 1758), is a commercially important species that is widely distributed throughout three oceans. This species inhabits oceanic waters with preferred environmental ranges and migrates vertically to the surface layer for feeding. However, the spatial distribution pattern and habitat preferences of swordfish have been rarely studied in the Pacific Ocean due to the wide geographic range of this species. This study examined the spatial distribution and preferred ranges of environmental variables for swordfish using two approaches, generalized additive models and habitat suitability index methods, with different spatio-temporal data resolution scales. Results indicated that sea surface temperature is the most important factor determining swordfish spatial distribution. Habitat spatial pattern and preferred environmental ranges, estimated using various modeling approaches, were robust relative to the spatio-temporal data resolution scales. The models were validated by examining the consistency between predictions and untrained actual observations, which all predicted a high relative density of swordfish in the tropical waters of the central Pacific Ocean, with no obvious seasonal movement. Results from this study, based on fishery and remote sensing data with wide spatial coverage, could benefit the conservation and management of fisheries for highly migratory species such as swordfish and tuna.

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