Moore J.E.,Southwest Fisheries Science Center |
Curtis K.A.,Acadia University |
Lewison R.L.,San Diego State University |
Dillingham P.W.,Clark University |
And 8 more authors.
Environmental Conservation | Year: 2013
Fisheries bycatch threatens populations of marine megafauna such as marine mammals, turtles, seabirds, sharks and rays, but fisheries impacts on non-target populations are often difficult to assess due to factors such as data limitation, poorly defined management objectives and lack of quantitative bycatch reduction targets. Limit reference points can be used to address these issues and thereby facilitate adoption and implementation of mitigation efforts. Reference points based on catch data and life history analysis can identify sustainability limits for bycatch with respect to defined population goals even when data are quite limited. This can expedite assessments for large numbers of species and enable prioritization of management actions based on mitigation urgency and efficacy. This paper reviews limit reference point estimators for marine megafauna bycatch, with the aim of highlighting their utility in fisheries management and promoting best practices for use. Different estimators share a common basic structure that can be flexibly applied to different contexts depending on species life history and available data types. Information on demographic vital rates and abundance is required; of these, abundance is the most data-dependent and thus most limiting factor for application. There are different approaches for handling management risk stemming from uncertainty in reference point and bycatch estimates. Risk tolerance can be incorporated explicitly into the reference point estimator itself, or probability distributions may be used to describe uncertainties in bycatch and reference point estimates, and risk tolerance may guide how those are factored into the management process. Either approach requires simulation-based performance testing such as management strategy evaluation to ensure that management objectives can be achieved. Factoring potential sources of bias into such evaluations is critical. This paper reviews the technical, operational, and political challenges to widespread application of reference points for management of marine megafauna bycatch, while emphasizing the importance of developing assessment frameworks that can facilitate sustainable fishing practices. Copyright © 2013 Foundation for Environmental Conservation. Source
Dulvy N.K.,Simon Fraser University |
Davidson L.N.K.,Simon Fraser University |
Kyne P.M.,Charles Darwin University |
Simpfendorfer C.A.,James Cook University |
And 3 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2016
Sawfish are arguably the world's most imperilled marine fishes. All five species are classified as highly threatened with extinction: three are Critically Endangered (smalltooth sawfish Pristis pectinata, largetooth sawfish Pristis pristis, and green sawfish Pristis zijsron); two are Endangered (narrow sawfish Anoxypristis cuspidata, and dwarf sawfish Pristis clavata). Sawfishes are threatened primarily due to a combination of their low intrinsic rates of population increase, high catchability in fisheries, and high value. Sawfishes are among the world's largest marine fishes, and they are caught by a wide range of fishing gears owing to their tooth-studded rostra being easily entangled. Sawfish fins are some of the most valuable for shark fin soup, and their rostra have long been traded as curios. In addition, they inhabit shallow coastal waters, estuaries, and rivers of the tropics and subtropics, down to a maximum depth rarely exceeding 100 m and are associated with threatened mangrove and seagrass habitats. Historically, sawfishes were distributed in the coastal waters of 90 countries and territories. Over the past century, their geographic distribution has been greatly diminished. For example, the smalltooth sawfish is now found in <20% of its former range. Globally, sawfishes are now entirely absent from 20 countries; 43 countries have lost at least one species. Sawfishes are legally protected, to some degree, in 16 of the 90 range states. These safeguards encompass, on average, 81% of their Extant distribution; however, the quality and breadth of protection varies dramatically across countries and species. Smalltooth sawfish currently has the least amount of such coverage of only half (49%) of Extant distribution. The global conservation strategy specifies actions to protect sawfish and their habitats. Such actions are urgently warranted to avoid global extinction and to restore robust populations for the benefit of coastal ecosystem function and biodiversity. © 2014 The Authors. Aquatic Conservation: Marine and Freshwater Ecosystems published by John Wiley & Sons, Ltd. Source
Santana-Garcon J.,CRAM Foundation |
Santana-Garcon J.,University of Western Australia |
Fordham S.,Shark Advocates International |
Journal of Fish Biology | Year: 2012
This study examines the processing of fins from blue sharks Prionace glauca caught by the Spanish longline fleet and landed in Vigo, Spain, and implications of these practices for enforcing the E.U. ban on shark finning, which relies on a maximum fin-to-carcass-mass ratio. Two major sources of variability in fin-to-carcass ratios are quantified and discussed: (1) the fin set (type and number of fins retained from each shark) and (2) the cutting method used to separate fins from carcasses. The significant differences in fin-to-carcass-mass ratios between fin sets or cutting procedure demonstrates that the ratio limit is problematic and, conclusively, in order to facilitate proper enforcement, fishermen should be required to land all sharks with the fins still naturally attached to the bodies. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles. Source
Christiansen H.M.,University of Windsor |
Lin V.,Independent Researcher |
Tanaka S.,Tokai University |
Velikanov A.,Sakhalin Research Institute of Fisheries and Oceanography |
And 6 more authors.
PLoS ONE | Year: 2014
White sharks are highly migratory apex predators, globally distributed in temperate, sub-tropical, and tropical waters. Knowledge of white shark biology and ecology has increased recently based on research at known aggregation sites in the Indian, Atlantic, and Northeast Pacific Oceans; however, few data are available for the Northwest Pacific Ocean. This study provides a meta-analysis of 240 observations of white sharks from the Northwest Pacific Ocean between 1951 and 2012. Records comprise reports of bycatch in commercial fisheries, media accounts, personal communications, and documentation of shark-human interactions from Russia (n = 8), Republic of Korea (22), Japan (129), China (32), Taiwan (45), Philippines (1) and Vietnam (3). Observations occurred in all months, excluding October-January in the north (Russia and Republic of Korea) and July-August in the south (China, Taiwan, Philippines, and Vietnam). Population trend analysis indicated that the relative abundance of white sharks in the region has remained relatively stable, but parameterization of a 75% increase in observer effort found evidence of a minor decline since 2002. Reliably measured sharks ranged from 126- 602 cm total length (TL) and 16-2530 kg total weight. The largest shark in this study (602 cm TL) represents the largest measured shark on record worldwide. For all countries combined the sex ratio was non-significantly biased towards females (1:1.1; n = 113). Of 60 females examined, 11 were confirmed pregnant ranging from the beginning stages of pregnancy (egg cases) to near term (140 cm TL embryos). On average, 6.062.2 embryos were found per litter (maximum of 10) and gestation period was estimated to be 20 months. These observations confirm that white sharks are present in the Northwest Pacific Ocean year-round. While acknowledging the difficulties of studying little known populations of a naturally low abundance species, these results highlight the need for dedicated research to inform regional conservation and management planning.©2014 Christiansen et al. Source
The next ten years could be critical for sharks. At least a quarter of the world’s sharks and related species are already endangered, many of them dangerously so. With the pressures on these ancient species increasing, many sharks and rays may not have much time left before they reach the point of no return. But that fate can be avoided according to a new report, “Global Priorities for Conserving Sharks and Rays,” which lays out a ten-year strategy to prevent shark extinctions and ensure that shark fishing becomes sustainable and responsible. The strategy—the result of 18 months of hard work by eight conservation organizations and a long list of experts—makes it clear that saving sharks won’t be easy. “We’re admitting that it’s complicated,” says how Sonja Fordham, president of Shark Advocates International and one of the strategy’s authors. “But at the same time, we’re asserting that it’s possible and that the need is really urgent.” Fordham calls the strategy the result of “unprecedented support and partnership” of people from many fields and from around the world. She says this broad collaboration indicates that this is the right time to take every effort to save not just sharks but their often overlooked relatives, including skates, stingrays, sawfishes, guitarfishes and devil rays. “I don’t think the public has ever been this supportive of conservation of sharks,” she says. “We’re trying to get them to expand their horizons to include rays when they think about the needs of sharks.” The strategy document itself outlines four key areas where it says progress needs to be made: saving sharks and rays from extinction; managing fisheries sustainably; ensuring responsible trade; and encouraging responsible consumption of shark and ray products. It also has a very specific overall goal: “by 2025, the conservation status of the world’s sharks and rays has improved—declines have been halted, extinctions have been prevented, and commitments to their conservation have increased globally.” Beyond that, the strategy also outlines dozens of smaller goals to save the most at-risk species, learn more about the species for which scientific information is lacking, preserve coastal habitats, improve trade reporting and certification, block illegal or unsustainable products, and work with retailers and consumers to improve the demand for sustainable products. “We’re not shying away from the fact that these are complicated problems and there’s no one solution,” Fordham says. “But the time is now and there are many, many concrete steps that could be taken without any more data. There are also many government commitments that need to be fulfilled.” Fordham has been working in shark conservation since 1991 and says that even with the threats that sharks face, she now feels generally hopeful about the future. “My career has seen incredible progress, both with the way the public sees sharks and the tools that we have available to address overfishing,” she says, pointing to her favorite example, the spiny dogfish (Squalus acanthias), a species that was in bad shape at the turn of the century but was declared recovered in 2011 thanks to science-based fisheries management. With that type of progress in mind, Fordham says “there are really no excuses not to move forward to pick up the pace.” The conservation coalition has already started advocating this strategy to the governments of the world. It’s also pushing for agencies to fulfill previous commitments and turn them into action. “The tools and resources are available to take those steps,” she says.