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Chaboud, C., & Vendeville, P. (2011). Evaluation of selectivity and bycatch mitigation measures using bioeconomic modelling. The cases of Madagascar and French Guiana shrimp fisheries. Aquatic Living Resources, 24(2), 137–148.
Résumé: Tropical shrimp fisheries are characterized by various interactions with their natural environment and with other fisheries. These latter interactions can be explained by the high quantity of bycatch taken by industrial trawler fleets, which has a significant impact on fish populations associated with shrimps and thus also on finfish fisheries. Bycatch also includes emblematic species, which are subject to strict conservation measures decided by the international community. It seems important to identify and assess the biological and economic consequences of different mitigation measures (increase of mesh size, turtle excluder devices and bycatch reducing devices). This communication is based on case studies undertaken on the Indian white prawn (Fenneropenaeus indicus) and speckled shrimp (Metapenaeus monoceros) fisheries in Madagascar and on the brown shrimp (Farfantepenaeus subtilis) and pink spotted shrimp (Farfantepenaeus brasiliensis) fishery in French Guiana. A review of the impacts of these fisheries on resources and ecosystems is made and some results of experiments on mitigation devices given. Finally, the results of simulations obtained using a multi-species, multi-fleet, age-structured bioeconomic model, including modifications of catchability and costs related to the adoption of these devices, is presented and discussed.
Mots-Clés: Bioeconomics; Bycatch; mitigation; modelling; selectivity; Shrimp fisheries
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Gilman, E., Chaloupka, M., Bach, P., Fennell, H., Hall, M., Musyl, M., et al. (2020). Effect of pelagic longline bait type on species selectivity: a global synthesis of evidence. Rev. Fish. Biol. Fish., 30(3), 535–551.
Résumé: Fisheries can profoundly affect bycatch species with 'slow' life history traits. Managing bait type offers one tool to control species selectivity. Different species and sizes of marine predators have different prey, and hence bait, preferences. This preference is a function of a bait's chemical, visual, acoustic and textural characteristics and size, and for seabirds the effect on hook sink rate is also important. We conducted a global meta-analysis of existing estimates of the relative risk of capture on different pelagic longline baits. We applied a Bayesian random effects meta-analytic regression modelling approach to estimate overall expected bait-specific catch rates. For blue shark and marine turtles, there were 34% (95% HDI: 4-59%) and 60% (95% HDI: 44-76%) significantly lower relative risks of capture on forage fish bait than squid bait, respectively. Overall estimates of bait-specific relative risk were not significantly different for seven other assessed taxa. The lack of a significant overall estimate of relative capture risk for pelagic shark species combined but significant effect for blue sharks suggests there is species-specific variability in bait-specific catch risk within this group. A qualitative literature review suggests that tunas and istiophorid billfishes may have higher catch rates on squid than fish bait, which conflicts with reducing marine turtle and blue shark catch rates. The findings from this synthesis of quantitative and qualitative evidence support identifying economically viable bycatch management measures with acceptable tradeoffs when multispecies conflicts are unavoidable, and highlight research priorities for global pelagic longline fisheries.
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Lemahieu, A., Blaison, A., Crochelet, E., Bertrand, G., Pennober, G., & Soria, M. (2017). Human-shark interactions: The case study of Reunion island in the south-west Indian Ocean. Ocean & Coastal Management, 136, 73–82.
Résumé: An uncommon series of shark attacks, mostly involving surfers, occurred on the West coast of Reunion Island between 2011 and 2013, causing eight deaths. Following these events, which resulted in social, economic and political upheaval, and referred to as the “shark crisis”, a scientific program with the aim of understanding shark behavior and ecology in Reunion Island was launched in 2012. It integrated spatial and temporal monitoring protocol of coastal uses allowing for the study of shark attack repercussions on the dynamics of 15 types of uses. In this paper, we bring shark and users observations together in order to assess human-shark interactions. Firstly, we assess the impacts that shark attacks have triggered in terms of users spatiotemporal distribution between 2011 and 2013. Secondly, we explore human-shark interactions in 2013 using cross-mapping techniques. Results show that three areas (Saint-Gilles, Trois-Bassins, Etang-Salé) have high levels of potential interaction and should be of high interest for the local authorities and stakeholders for further mitigation policies. Although further studies are needed to better understand the link between shark presence and shark attack, this study provides a first insight into human-shark interactions in Reunion Island.
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Poisson, F., Abascal Crespo, F., Ellis, J. R., Chavance, P., Pascal, B., Santos, M. N., et al. (2016). Technical mitigation measures for sharks and rays in fisheries for tuna and tuna-like species: turning possibility into reality. Aquat. Living Resour., 29(4), 402.
Résumé: 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.
Mots-Clés: at-vessel mortality; Bycatch; california recreational fishery; circle hooks; eastern pacific-ocean; Elasmobranch; great-barrier-reef; j-hook performance; Mitigation; mortality; pelagic; pelagic longline fishery; postrelease survival; Purse seine fishery; rare-earth-metal; tuna regional fishery management organizations
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Rabearisoa, N., Bach, P., & Marsac, F. (2015). Assessing interactions between dolphins and small pelagic fish on branchline to design a depredation mitigation device in pelagic longline fisheries. ICES J. Mar. Sci., 72(5), 1682–1690.
Résumé: Depredation by false killer whales (Pseudorca crassidens) and short-finned pilot whales (Globicephala macrorhynchus) in pelagic longlining is an issue leading to negative impacts on the economics of the fishery and on odontocetes themselves. We investigated the efficacy of a new depredation mitigation device called “DEPRED” in the interaction between bottlenose dolphins (Tursiops aduncus), spinner dolphins (Stenella longirostris), and small pelagic fish (SPF) attached to branchlines to simulate caught fish. We suggest implications for DEPRED efficacy with larger toothed whales interacting with pelagic longline capture in the open ocean. The design of the device uses streamers to both deter cetaceans and protect fish from predation. In controlled experiments, we tested its efficacy by observing changes in the dolphin's behaviour brought on by the presence or absence of the device on branchlines. First, dolphin–SPF interactions were observed at the small scale using video footage recorded with an underwater camcorder. Second, the efficacy of the device was quantified from interactions between dolphins and 80 branchlines deployed on a longline 500 m long baited with SPF. One half of the SPF on successive branchlines was protected by DEPRED and the other half was not. A total of 707 branchlines were set when dolphins interacted with SPF, and among them, 355 were equipped with DEPRED. Encouraging results were obtained: over the short term, the number of damaged unprotected SPF was on average more than twice the number of protected ones. Nevertheless, habituation behaviour was observed for a resident group of T. aduncus in the experimental area. The relation between the deterrent effect of the device and constraints related to the design of such a device to be used at a commercial operational level are discussed.
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