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1.
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International instruments of fisheries governance have set the core principles for the management of highly migratory fishes. We evaluated the progress of tuna Regional Fisheries Management Organizations (tRFMOs) in implementing the ecological component of ecosystem‐based fisheries management (EBFM). We first developed a best case tRFMO for EBFM implementation. Second, we developed criteria to evaluate progress in applying EBFM against this best case tRFMO. We assessed progress of the following four ecological components: target species, bycatch species, ecosystem properties and trophic relationships, and habitats. We found that many of the elements necessary for an operational EBFM are already present, yet they have been implemented in an ad hoc way, without a long‐term vision and a formalized plan. Overall, tRFMOs have made considerable progress monitoring the impacts of fisheries on target species, moderate progress for bycatch species, and little progress for ecosystem properties and trophic relationships and habitats. The tRFMOs appear to be halfway towards implementing the ecological component of EBFM, yet it is clear that the “low‐hanging fruit” has been plucked and the more difficult, but surmountable, issues remain, notably the sustainable management of bycatch. All tRFMOs share the same challenge of developing a formal mechanism to better integrate ecosystem science and advice into management decisions. We hope to further discussion across the tRFMOs to inform the development of operational EBFM plans.  相似文献   

3.
Large pelagic fishes are assessed and managed by tuna Regional Fisheries Management Organizations (tRFMOs). These organizations have been criticized for not meeting conservation objectives, which may relate to aspects of governance and management. No previous studies have systematically evaluated why management performance differs among tRFMOs and among stocks within each tRFMO. In this study, we collected data on the nature of research, management, enforcement and socioeconomics of management systems in the five principal tRFMOs of the world's oceans. We quantified influences of economic and fishery‐related factors on these management characteristics and examined how these factors vary among tRFMOs. We found that tRFMOs with a greater number of member countries, a greater economic dependency on tuna resources, a lower mean per capita gross domestic product, a greater number of fishing vessels and smaller vessels were associated with less intensive research, management and enforcement in these tuna fisheries. We also quantified the influence of specific management attributes and of biological, economic and fishery‐related factors on the trends and current status of large pelagic fish stocks in these regions. The most important factors correlated with trends and current stock status were external to the management systems, and included stock size, age at maturity, ex‐vessel price and economic dependency of countries on tuna fisheries. To improve the overall status of large pelagic fish stocks in the global high seas, more intensive data collection, research and management are needed in certain areas, especially in the Indian Ocean, and for certain stocks, especially non‐target species.  相似文献   

4.
Minimising the unintended capture of fish, marine mammals, reptiles, seabirds and other marine organisms is an important component of responsible fisheries management and for stabilising declines and rebuilding populations of threatened species. The analyses presented were designed to establish the first quantitative baseline of historical catches, catch rates and species composition for the dominant tuna fisheries operating in the western and central Pacific, the world's largest in terms of tuna catch. Using records from 612,148 fishing events collected by independent ‘at sea’ observers, estimates for finfish, billfish, elasmobranchs, marine mammals and sea turtles show that the composition and magnitude of catches varied considerably by fishery type and practice for the period 2003–2019. Simulations indicated that precision in longline estimates would be improved by monitoring a proportion of fishing sets from all fishing trips rather than full coverage from a proportion of all fishing trips. While attributing reasons for temporal trends in estimated bycatch was difficult due to the confounding impacts of changing abundances and fishing practices, the trends identified the nature of potential relationships for species that are not accurately quantified, or not covered, by fishing vessel logbooks. The trends in catch estimates, and the catch rate models, have utility in identifying species which may require targeted additional analyses and management interventions, including species of conservation interest (either due to their threatened status or vulnerability to fishing) such as elasmobranchs and sea turtles. Moreover, the estimates should support future evaluations of the impact of these industrial-scale fisheries on bycatch species.  相似文献   

5.
6.
Estimated declines in shark and ray populations worldwide have raised major, widespread concern about the impacts of global fisheries on elasmobranchs. The mechanisms causing elasmobranch mortality during fisheries’ capture are not fully understood, but we must gain greater clarity on this topic for fisheries managers to develop effective conservation plans to mitigate further population declines. To evaluate how two important factors, respiratory mode and fishing gear type, impact elasmobranch survival, we compiled publicly available data sources on the immediate mortality percentages of 83 species and post‐release mortality percentages of 40 species. Using Bayesian models, we found that sharks and rays captured in longlines had significantly lower immediate mortality than those caught in trawls or gillnets. Our models also predicted the mean total discard mortality (combined immediate and post‐release mortality) percentages of obligate ram‐ventilating elasmobranchs caught in longline, gillnet and trawl gear types to be 49.8, 79.0 and 84.2%, respectively. In contrast, total discard mortality percentages of stationary‐respiring species were significantly lower (longline capture mean = 7.2%, gillnet capture mean = 25.3%, trawl capture mean = 41.9%). Our global meta‐analysis provides the first quantified demonstration of how mortality is affected by these two factors across a broad range of species. Our results and approach can be applied to data‐deficient elasmobranchs and fisheries to identify species that are likely to experience high rates of mortality due to respiratory mode and/or fishing methods used, so that appropriate mitigation measures can be prioritized and investigated.  相似文献   

7.
  1. Bycatch is the most significant threat to marine megafauna (sea turtles, marine mammals, elasmobranchs, seabirds) worldwide, and the leading cause of the decline of several cetacean species. The bycatch issue in the Indian Ocean is poorly understood, but high bycatch levels in gillnet fisheries have been documented for the past two decades, in both small-scale and semi-industrial fisheries. Unfortunately, methods to reduce bycatch are often unavailable, financially non-viable or socially unacceptable to fishermen.
  2. Using a network of trained boat captains in the tuna drift gillnet fishery in the Arabian Sea, targeted catch and bycatch data were collected from 2013 to 2017 off the coast of Pakistan (northern Indian Ocean). Two fishing methods using multifilament gillnets were used: surface deployment and subsurface deployment (i.e. headline of net set below 2 m depth).
  3. Predicted catch rates for targeted species did not differ significantly between the two fishing practices, although a drop in tuna (6.2%) and tuna-like (10.9%) species captures was recorded in subsurface sets. The probability of cetacean bycatch, however, was 78.5% lower in subsurface than in surface sets.
  4. Cetacean bycatch in tuna drift gillnet fisheries has the potential to be significantly reduced at a relatively low cost for fishers. However, further research with an appropriate sampling design and a large sample size is required to confirm the efficacy of the proposed mitigation method. The acceptability and adoption of subsurface setting by fishers also needs to be further investigated. Despite some limitations, this preliminary study also highlights the importance of crew-based observer data as an alternative source of data when observers cannot be deployed on fishing vessels.
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8.
With an increasing number of seabird species, particularly albatross and petrels, becoming threatened, a reduction of fishery impacts on these species is essential for their future survival. Here, mitigation methods to reduce and avoid seabird bycatch are assessed in terms of their ability to reduce bycatch rates and their economic viability for longline, trawl and gillnet fisheries worldwide. Factors influencing the appropriateness and effectiveness of a mitigation device include the fishery, vessel, location, seabird assemblage present and season of year. As yet, there is no single magic solution to reduce or eliminate seabird bycatch across all fisheries: a combination of measures is required, and even within a fishery there is likely to be refinement of techniques by individual vessels in order to maximize their effectiveness at reducing seabird bycatch. In longline demersal and pelagic fisheries, a minimum requirement of line weighting that achieves hook sink rates minimizing seabird bycatch rates should be tailored with a combination of strategic offal and discard management, bird‐scaring lines (BSLs) and night‐setting, particulary in Southern Hemisphere fisheries. Urgent investigation is needed into more effective measures at reducing seabird interactions with trawl nets and gill nets. In trawl fisheries, a combination of offal and discard management, the banning of net monitoring cables, paired BSLs, and a reduction in the time the net is on or near the surface are likely to be the most effective in reducing seabird interactions with the warp cables and net. Few seabird bycatch reduction methods have been developed for gillnet fisheries, although increasing the visibility of the net has been shown to reduce seabird bycatch. Further studies are required to determine the efficacy of this technique and its influence on target species catch rates.  相似文献   

9.
1. Of the myriad of anthropogenic and natural threats to seabirds, one of the most critical global problems is incidental mortality in longline fisheries. Hesitance or failure by fishery managers and longline industries to adequately address this acute problem could result in the extinction of several albatross and petrel species within our lifetimes. 2. An integrated management approach is needed to comprehensively manage longline fisheries to address seabird bycatch. A review of relevant multilateral accords, declarations and actions by regional and international organizations reveals the need to augment international collaboration, especially to address pirate longline fishing. Management authorities and stakeholders need to collaborate to: promote adoption and compliance with effective legally binding accords that cover the ranges of all affected seabirds; ensure that all Range States and relevant distant water fishing nations become contracting parties to these accords; coordinate national implementation of the Food and Agriculture Organization's International Plan of Action on seabirds; set management goals; establish and implement policies to employ seabird deterrent measures; disseminate information on new deterrent measures; locally tailor seabird deterrent measures; standardize data reporting and establish a centralized data repository; coordinate research and monitoring; develop regional surveillance and enforcement systems; and augment less developed countries' capacity and resources to mitigate seabird and longline fishery interactions. 3. Establishing protected areas containing seabird colonies and adjacent waters within a nation's Exclusive Economic Zone (EEZ) is potentially an expedient method to reduce interactions between seabirds and longline fisheries. However, establishing high seas marine protected areas to restrict longline fishing in seabird foraging areas, which would require extensive and dynamic boundaries and large buffer zones, may not be a viable short‐term solution due to the long time it is anticipated it could take to resolve legal complications with international treaties, to achieve international consensus and political will, and to acquire requisite extensive resources for surveillance and enforcement. High seas marine protected areas may eventually become a feasible mechanism to address seabird bycatch if nations develop the will to close ocean areas to commercial fisheries to attempt to rehabilitate depleted pelagic fish stocks. 4. Direct involvement of longline industries, through partnerships with national governments and regional organizations, to develop seabird mitigation measures and policies prescribing the use of these measures, is critical. Direct involvement of stakeholders to find solutions to resource management problems leads to stakeholder groups taking ownership of and supporting rules. Bottom‐up approaches are successful in changing interest groups' attitudes and behaviour, to maximize voluntary compliance and minimize conflict and resources required for enforcement. 5. Data gaps must be filled and scientific uncertainty addressed through multilateral collaboration. Research to develop and improve practicable mitigation measures is most urgently needed. Information on the status and trends of albatross populations, where albatrosses forage, the causes of population declines, seabird mortality rates and levels in each longline fishery, and the type of impacts from longlining on seabird populations is also needed. It is well documented that several seabird species are at risk of extinction, incidental bycatch in longline fisheries significantly contributes to many species' decline, and proven mitigation measures are available. Thus, while additional research is critically needed, we should not delay taking precautionary action to wait for additional information, but should immediately act to protect seabirds from the known acute threat of mortality in longline fisheries. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

10.
Bycatch in fisheries has been recognized as a threat to many endangered populations of sea turtles, sea birds and marine mammals. Interactions between pelagic longline fisheries and critically endangered populations of leatherback sea turtles (Dermochelys coriacea) have led to temporary closures of the Hawaiian pelagic longline swordfish fishery and severe bycatch quotas. The negative impact of these events on both the populations of certain endangered species and the economic livelihood of the fishermen has resulted in a strong push from all sides to better understand bycatch events. Typically, analyses of longline catch and bycatch have examined fishing effort summarized over large areas (≥1°). Although aggregation of effort to this level may be necessary to account for uncertainty, confidentiality concerns, or to make comparisons across regions, it specifically limits the researcher's ability to characterize the local oceanographic factors that may drive individual bycatch events. Higher resolution analyses must be undertaken to identify such features. However, for these higher resolution analyses, the methods currently used to spatially represent pelagic longline fishing effort may significantly affect researcher's results. Here, we look at different methods to represent this fishing effort (i.e., points, centroids, polylines and polygons) at various resolutions (2 km to 5°) to better understand which method and spatial resolution are most appropriate. Our results validate the use of point features to represent fishing effort in previous low resolution studies of the Hawaiian pelagic longline fishery by showing that the set point method is suitable for studies with resolutions lower than 15 km. However, at higher resolutions (≤15 km) and in areas with more sparsely distributed fishing, aggregated effort values differed significantly between spatial representation methods. We demonstrate that the use of polygons to describe pelagic longline fishing effort is more representative and necessary for such high resolution analyses.  相似文献   

11.
Elasmobranch mortality in pelagic longline fisheries poses a risk to some populations, alters the distribution of abundance between sympatric competitors, changing ecosystem structure, processes and stability. Individual and synergistic effects on elasmobranch catch and survival from pelagic longline gear factors, including methods prescribed to mitigate bycatch of other vulnerable taxa, were determined. Overall relative risk of higher circle vs. J‐shaped hook shark catch rates conditioned on potentially informative moderators, from 30 studies, was estimated using an inverse‐precision weighted mixed‐effects meta‐regression modelling approach. Sharks had a 1.20 times (95% CI: 1.03–1.39) significantly higher pooled relative risk of capture on circle hooks, with two significant moderators. The pooled relative risk estimate of ray circle hook catch from 15 studies was not significant (RR = 1.22, 95% CI: 0.89–1.66) with no significant moderators. From a literature review, wire leaders had higher shark catch and haulback mortality than monofilament. Interacting effects of hook, bait and leader affect shark catch rates: hook shape and width and bait type determine hooking position and ability to sever monofilament leaders. Circle hooks increased elasmobranch catch, but reduced haulback mortality and deep hooking relative to J‐shaped hooks of the same or narrower width. Using fish vs. squid for bait increased shark catch and deep hooking. Pelagic stingray (Pteroplatytrygon violacea) catch and mortality were lower on wider hooks. Using circle instead of J‐shaped hooks and fish instead of squid for bait, while benefitting sea turtles, odontocetes and possibly seabirds, exacerbates elasmobranch catch and injury, therefore warranting fishery‐specific assessments to determine relative risks.  相似文献   

12.
Fishery management measures to reduce interactions between fisheries and endangered or threatened species have typically relied on static time‐area closures. While these efforts have reduced interactions, they can be costly and inefficient for managing highly migratory species such as sea turtles. The NOAA TurtleWatch product was created in 2006 as a tool to reduce the rates of interactions of loggerhead sea turtles with shallow‐set longline gear deployed by the Hawaii‐based pelagic longline fishery targeting swordfish. TurtleWatch provides information on loggerhead habitat and can be used by managers and industry to make dynamic management decisions to potentially reduce incidentally capturing turtles during fishing operations. TurtleWatch is expanded here to include information on endangered leatherback turtles to help reduce incidental capture rates in the central North Pacific. Fishery‐dependent data were combined with fishing effort, bycatch and satellite tracking data of leatherbacks to characterize sea surface temperature (SST) relationships that identify habitat or interaction ‘hotspots’. Analysis of SST identified two zones, centered at 17.2° and 22.9°C, occupied by leatherbacks on fishing grounds of the Hawaii‐based swordfish fishery. This new information was used to expand the TurtleWatch product to provide managers and industry near real‐time habitat information for both loggerheads and leatherbacks. The updated TurtleWatch product provides a tool for dynamic management of the Hawaii‐based shallow‐set fishery to aid in the bycatch reduction of both species. Updating the management strategy to dynamically adapt to shifts in multi‐species habitat use through time is a step towards an ecosystem‐based approach to fisheries management in pelagic ecosystems.  相似文献   

13.
  1. Many shark and ray (elasmobranch) species are threatened with extinction, due to overfishing and commercial trade
  2. Sarawak is situated in Malaysian Borneo in the Coral Triangle: a global priority region for elasmobranch conservation. Malaysia is the world’s eighth largest elasmobranch fishing nation, and Sarawak is one of Malaysia’s largest fishing states, yet there are limited species-specific data on catch and trade of elasmobranchs to support conservation and fisheries management decisions.
  3. This study presents landing site and market survey data, collected in Sarawak from January 2017 to December 2019. Geographical, temporal and operational trends in volumes of catch and trade are explored; the total volume, value and species composition of Sarawak's local elasmobranch markets is estimated; and simple size-based indicators are used to assess the sustainability of elasmobranch utilization for several conservation-priority and frequently traded species, including Critically Endangered and CITES-listed scalloped hammerhead sharks (Sphyrna lewini) and bottlenose wedgefish (Rhynchobatus australiae).
  4. The results conservatively estimate that >26,500 elasmobranchs (~90,000 kg) are locally traded in Sarawak annually, worth ~US$125,000 per year at the market level.
  5. Trade is dominated by small to medium-sized coastal requiem sharks (Carcharhinidae) and stingrays (Dasyatidae), with endangered and CITES-listed species making up 26% and 32% of total landings and trade, respectively.
  6. High proportions of immature individuals were recorded, with evidence of overfishing for several species, based on simple size-based indicators.
  7. Several options are outlined for improving management of elasmobranch fishing and trade in the future, including spatio-temporal closures and live release protocols, which could help to reduce the mortality of critically endangered species and implement CITES. Such measures could have large conservation impacts with limited socio-economic cost, since these species make up <5% of the total value of the elasmobranch market. However, management plans need to be co-designed with full participation of affected coastal communities in order to be ethical and effective.
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14.
  • 1. Fishing spans all oceans and the impact on ocean predators such as sharks and rays is largely unknown. A lack of data and complicated jurisdictional issues present particular challenges for assessing and conserving high seas biodiversity. It is clear, however, that pelagic sharks and rays of the open ocean are subject to high and often unrestricted levels of mortality from bycatch and targeted fisheries for their meat and valuable fins.
  • 2. These species exhibit a wide range of life‐history characteristics, but many have relatively low productivity and consequently relatively high intrinsic vulnerability to over‐exploitation. The IUCN — World Conservation Union Red List criteria were used to assess the global status of 21 oceanic pelagic shark and ray species.
  • 3. Three‐quarters (16) of these species are classified as Threatened or Near Threatened. Eleven species are globally threatened with higher risk of extinction: the giant devilray is Endangered, ten sharks are Vulnerable and a further five species are Near Threatened. Threat status depends on the interaction between the demographic resilience of the species and intensity of fisheries exploitation.
  • 4. 4. Most threatened species, like the shortfin mako shark, have low population increase rates and suffer high fishing mortality throughout their range. Species with a lower risk of extinction have either fast, resilient life histories (e.g. pelagic stingray) or are species with slow, less resilient life histories but subject to fisheries management (e.g. salmon shark).
  • 5. 5. Recommendations, including implementing and enforcing finning bans and catch limits, are made to guide effective conservation and management of these sharks and rays.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

15.
Intertidal habitats (i.e. marine habitats that are (partially) exposed during low tide) have traditionally been studied from a shorebird-centred perspective. We show that these habitats are accessible and important to marine predators such as elasmobranchs (i.e. sharks and rays). Our synthesis shows that at least 43 shark and 45 ray species, of which 54.5% are currently threatened, use intertidal habitats. Elasmobranchs use intertidal habitats mostly for feeding and as refugia, but also for parturition and thermoregulation. However, the motivation of intertidal habitat use remains unclear due to limitations to observe elasmobranch behaviour in these dynamic habitats. We argue that elasmobranch predators can play an important role in intertidal food webs by feeding on shared resources during high tide (i.e. ‘high-tide predators’), which are accessible and also consumed by terrestrial or avian predators during low tide (i.e. ‘low-tide predators’). In addition, elasmobranchs are able to change the bio-geomorphology of intertidal habitats by increasing habitat heterogeneity due to feeding activities and may also alter resource availability for other consumers. We discuss how the ecological role of elasmobranchs in intertidal habitats is being affected by the continued overexploitation of these species, and conversely, how the global loss of intertidal areas poses an additional threat to an already vulnerable taxonomic group. We conclude that studies on intertidal ecology should include both low-tide (e.g. shorebirds) and high-tide (e.g. elasmobranchs) predatory guilds and their ecological interactions. The global loss of elasmobranch predatory species and intertidal habitat provides additional compelling arguments for the conservation of these areas.  相似文献   

16.
The U.S. Atlantic coastal pelagic longline fishery that targets tunas and swordfish also interacts with a wide range of non-target species including billfishes and sea turtles. Preliminary studies indicate that a change in terminal gear from J-style hooks to circle hooks may reduce bycatch mortality, but the effects of this change on catch rates of target species are unclear. To evaluate this, we monitored catch composition, catch rates, hooking location, and number of fish alive at haulback during 85 sets in the fall and spring seasonal fisheries from a commercial vessel operating in the western North Atlantic. Circle (size 16/0, 0° offset) and J-style (size 9/0, 10° offset) hooks were deployed in an alternating fashion. Hook–time recorders were used to assess time at hooking and temperature–depth recorders to measure gear behavior. Catch rates for most species categories were not significantly different between hook types (P < 0.05), although circle hooks generally had higher tuna catch rates in the fall and lower swordfish catch rates in the spring. In the fall, both total catches and catches of pelagic rays were significantly higher on J-style hooks. Yellowfin tuna in the fall and dolphinfish in the spring caught on circle hooks were significantly larger than those caught on J-style hooks. In both seasonal fisheries, circle hooks caught fishes in the mouth more frequently than J-style hooks, which hooked more often in the throat or gut, although these differences between hook types were not statistically significant. Yellowfin tuna in the fall fishery were over four times more likely to be hooked in the mouth with circle hooks than with J-style hooks. Several target and bycatch species showed higher rates of survival at haulback with circle hooks, although only for dolphinfish in the fall fishery was this difference statistically significant. Our results suggest that the use of 0° offset circle hooks in the coastal pelagic longline fishery will increase the survival of bycatch species at haulback with minimal effects on the catches of target species.  相似文献   

17.
18.
  • 1. Several species of marine mammals are at risk of extinction from being captured as bycatch in commercial fisheries. Various approaches have been developed and implemented to address this bycatch problem, including devices and gear changes, time and area closures and fisheries moratoria. Most of these solutions are difficult to implement effectively, especially for artisanal fisheries in developing countries and remote regions.
  • 2. Re‐zoning of the Great Barrier Reef World Heritage Area (GBRWHA) in 2004 closed 33% of the region to extractive activities, including commercial fishing. However, the impact of re‐zoning and the associated industry restructuring on a threatened marine mammal, the dugong (Dugong dugon), is difficult to quantify. Accurate information on dugong bycatch in commercial nets is unavailable because of the large geographic extent of the GBRWHA, the remoteness of the region adjacent to the Cape York Peninsula where most dugongs occur and the artisanal nature of the fishery.
  • 3. In the face of this uncertainty, a spatial risk‐assessment approach was used to evaluate the re‐zoning and associated industry restructuring for their ability to reduce the risk of dugong bycatch from commercial fisheries netting.
  • 4. The new zoning arrangements appreciably reduced the risk of dugong bycatch by reducing the total area where commercial netting is permitted. Netting is currently not permitted in 67% of dugong habitats of high conservation value, a 56% improvement over the former arrangements. Re‐zoning and industry restructuring also contributed to a 22% decline in the spatial extent of conducted netting.
  • 5. Spatial risk assessment approaches that evaluate the risk of mobile marine mammals from bycatch are applicable to other situations where there is limited information on the location and intensity of bycatch, including remote regions and developing countries where resources are limited.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

19.
20.
Failure to understand the potential responses of fishers to management measures creates a significant risk of revisiting the familiar scenario of perverse and unintended consequences of those measures. This paper reports on a choice experiment survey to evaluate fisher's preferences for various management measures proposed under the EU Common Fisheries Policy (CFP) reform process, but the conclusions have wider relevance as similar measures are used by comparable fleets in fisheries globally. The survey was conducted with fishers involved in mixed pelagic and demersal fisheries in Ireland, pelagic fisheries in Denmark and demersal fisheries in Greece. Fisheries management policies were characterized by five attributes designed both to cover the principal CFP reform proposals and to integrate ecological, social, economic and institutional factors affecting fisher's decisions. The study uses a random utility modelling framework to reveal the preferences of the fishers across the alternative policy attributes. Results show that while there are generally preferences both for healthy stocks and for maintaining the importance of fishing to the local community, strong interfishery preference differences exist. These differences are most notable in relation to a discard ban and to the use of individual transferable fishing rights, favoured in Denmark, but not in Ireland for instance. The strength of these interfishery differences supports the assertion that there are no panaceas in fisheries management and that solutions should be tailored within the context of specific fisheries. Not doing so could create a significant risk of inappropriately managed fisheries that may lead to unsustainable outcomes.  相似文献   

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