The Experts below are selected from a list of 13989 Experts worldwide ranked by ideXlab platform
Jeffrey E Moore - One of the best experts on this subject based on the ideXlab platform.
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bayesian inference and assessment for rare event Bycatch in marine fisheries a drift gillnet fishery case study
2015Co-Authors: Stephen M Stohs, Summer L Martin, Jeffrey E MooreAbstract:Fisheries Bycatch is a global threat to marine megafauna. Environmental laws require Bycatch assessment for protected species, but this is difficult when Bycatch is rare. Low Bycatch rates, combined with low observer coverage, may lead to biased, imprecise estimates when using standard ratio estimators. Bayesian model-based approaches incorporate uncertainty, produce less volatile estimates, and enable probabilistic evaluation of estimates relative to management thresholds. Here, we demonstrate a pragmatic decision-making process that uses Bayesian model-based inferences to estimate the probability of exceeding management thresholds for Bycatch in fisheries with <100% observer coverage. Using the California drift gillnet fishery as a case study, we (1) model rates of rare-event Bycatch and mortality using Bayesian Markov chain Monte Carlo estimation methods and 20 years of observer data; (2) predict unobserved counts of Bycatch and mortality; (3) infer expected annual mortality; (4) determine probabilitie...
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bayesian inference and assessment for rare event Bycatch in marine fisheries a drift gillnet fishery case study
2015Co-Authors: Stephen M Stohs, Summer L Martin, Jeffrey E MooreAbstract:Fisheries Bycatch is a global threat to marine megafauna. Environmental laws require Bycatch assessment for protected species, but this is difficult when Bycatch is rare. Low Bycatch rates, combined with low observer coverage, may lead to biased, imprecise estimates when using standard ratio estimators. Bayesian model-based approaches incorporate uncertainty, produce less volatile estimates, and enable probabilistic evaluation of estimates relative to management thresholds. Here, we demonstrate a pragmatic decision-making process that uses Bayesian model-based inferences to estimate the probability of exceeding management thresholds for Bycatch in fisheries with < 100% observer coverage. Using the California drift gillnet fishery as a case study, we (1) model rates of rare-event Bycatch and mortality using Bayesian Markov chain Monte Carlo estimation methods and 20 years of observer data; (2) predict unobserved counts of Bycatch and mortality; (3) infer expected annual mortality; (4) determine probabilities of mortality exceeding regulatory thresholds; and (5) classify the fishery as having low, medium, or high Bycatch impact using those probabilities. We focused on leatherback sea turtles (Dermochelys coriacea) and humpback whales (Megaptera novaeangliae). Candidate models included Poisson or zero-inflated Poisson likelihood, fishing effort, and a Bycatch rate that varied with area, time, or regulatory regime. Regulatory regime had the strongest effect on leatherback Bycatch, with the highest levels occurring prior to a regulatory change. Area had the strongest effect on humpback Bycatch. Cumulative Bycatch estimates for the 20-year period were 104-242 leatherbacks (52-153 deaths) and 6-50 humpbacks (0-21 deaths). The probability of exceeding a regulatory threshold under the U.S. Marine Mammal Protection Act (Potential Biological Removal, PBR) of 0.113 humpback deaths was 0.58, warranting a "medium Bycatch impact" classification of the fishery. No PBR thresholds exist for leatherbacks, but the probability of exceeding an anticipated level of two deaths per year, stated as part of a U.S. Endangered Species Act assessment process, was 0.0007. The approach demonstrated here would allow managers to objectively and probabilistically classify fisheries with respect to Bycatch impacts on species that have population-relevant mortality reference points, and declare with a stipulated level of certainty that Bycatch did or did not exceed estimated upper bounds.
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global patterns of marine mammal seabird and sea turtle Bycatch reveal taxa specific and cumulative megafauna hotspots
2014Co-Authors: Rebecca L Lewison, Bryan P. Wallace, Jeffrey E Moore, Larry B Crowder, Tara M Cox, Ramunas Zydelis, Sara L Mcdonald, Andrew Dimatteo, Daniel C Dunn, Connie Y KotAbstract:Recent research on ocean health has found large predator abundance to be a key element of ocean condition. Fisheries can impact large predator abundance directly through targeted capture and indirectly through incidental capture of nontarget species or Bycatch. However, measures of the global nature of Bycatch are lacking for air-breathing megafauna. We fill this knowledge gap and present a synoptic global assessment of the distribution and intensity of Bycatch of seabirds, marine mammals, and sea turtles based on empirical data from the three most commonly used types of fishing gears worldwide. We identify taxa-specific hotspots of Bycatch intensity and find evidence of cumulative impacts across fishing fleets and gears. This global map of Bycatch illustrates where data are particularly scarce—in coastal and small-scale fisheries and ocean regions that support developed industrial fisheries and millions of small-scale fishers—and identifies fishing areas where, given the evidence of cumulative hotspots across gear and taxa, traditional species or gear-specific Bycatch management and mitigation efforts may be necessary but not sufficient. Given the global distribution of Bycatch and the mitigation success achieved by some fleets, the reduction of air-breathing megafauna Bycatch is both an urgent and achievable conservation priority.
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cumulative estimates of sea turtle Bycatch and mortality in usa fisheries between 1990 and 2007
2011Co-Authors: Elena M Finkbeiner, Bryan P. Wallace, Jeffrey E Moore, Rebecca L Lewison, Larry B Crowder, Andrew J. ReadAbstract:Sea turtles interact with a variety of fishing gears across their broad geographic distributions and onto- genetic habitat shifts. Cumulative assessments of multi-gear Bycatch impacts on sea turtle populations are critical for coherent fisheries Bycatch management, but such estimates are difficult to achieve, due to low fisheries observer effort, and a single-species, single-fishery management focus. We compiled the first cumulative estimates of sea turtle Bycatch across fisheries of the United States between 1990 and 2007, before and after implementation of fisheries-specific Bycatch mitigation measures. An annual mean of 346,500 turtle interactions was estimated to result in 71,000 annual deaths prior to establish- ment of Bycatch mitigation measures in US fisheries. Current Bycatch estimates (since implementation of mitigation measures) are 60% lower (137,800 interactions) and mortality estimates are 94% lower (4600 deaths) than pre-regulation estimates. The Southeast/Gulf of Mexico Shrimp Trawl fishery accounts for the overwhelming majority of sea turtle Bycatch (up to 98%) in US fisheries, but estimates of Bycatch in this fishery are fraught with high uncertainty due to lack of observer coverage. Our esti- mates represent minimum annual interactions and mortality because our methods were conservative and we could not analyze unobserved fisheries potentially interacting with sea turtles. Although consid- erable progress has been made in reducing sea turtle Bycatch in US fisheries, management still needs improvement. We suggest that sea turtle Bycatch limits be set across US fisheries, using an approach sim- ilar to the Potential Biological Removal algorithm mandated by the Marine Mammal Protection Act.
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an interview based approach to assess marine mammal and sea turtle captures in artisanal fisheries
2010Co-Authors: Jeffrey E Moore, Andrew J. Read, Rebecca L Lewison, Larry B Crowder, Rhema Bjorkland, Sara L Mcdonald, E Aruna, I Ayissi, P Espeut, C JoynsonhicksAbstract:Recent case studies have highlighted high Bycatch mortality of sea turtles and marine mammals in artisanal fisheries, but in most countries there are few data on artisanal fishing effort, catch, or Bycatch. With artisanal fisheries comprising >95% of the world’s fishermen, this knowledge gap presents a major challenge to threatened species conservation and sustainable fisheries initiatives. We report on results from an intensive pilot study to evaluate whether interview surveys can be effective in assessing fishing effort and threatened species Bycatch. Fisheries and Bycatch data from interviews with >6100 fishermen in seven developing countries were collected in <1 year for approximately USD $47,000, indicating that this approach may rapidly yield coarse-level information over large areas at low cost. This effort provided the first fisheries characterizations for many areas and revealed the widespread nature of high Bycatch in artisanal fisheries. Challenges to study design and implementation prevented quantitative estimation or spatial comparisons of Bycatch during this pilot research phase, but results suggested that annual sea turtle Bycatch may number at least in the low thousands of individuals per country. Annual odontocete Bycatch may number at least in the low hundreds per country. Sirenian Bycatch occurred in all study areas but was frequent only in West Africa. We discuss lessons learned from this survey effort and present a revised protocol for future interview-based Bycatch assessments.
Andrew J. Read - One of the best experts on this subject based on the ideXlab platform.
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mitigation of marine mammal Bycatch in u s fisheries since 1994
2013Co-Authors: Christina K A Geijer, Andrew J. ReadAbstract:Bycatch in fishing gear is one of the most pressing conservation issues facing marine mammals today. In the United States a formal regime to address Bycatch of marine mammals was adopted in 1994 as Amendments to the Marine Mammal Protection Act (MMPA). This regime provides quantitative conservation goals and a transparent reporting system, allowing for a unique opportunity to assess the efficacy of Bycatch mitigation within U.S. waters. In the present analysis, we compile Bycatch estimates for each stock of U.S. marine mammals since 1994 to determine whether mitigation efforts under the Amendments have been successful in reducing Bycatch. Bycatch trends were analysed on a national level, and for two regional case studies; harbor porpoises in the Gulf of Maine and common dolphins along the U.S. Pacific coast. The estimated annual marine mammal Bycatch was 4356 (SE 424) and Bycatch levels declined since the MMPA was amended. Harbor porpoise Bycatch in the Gulf of Maine was, however, correlated with landings of cod, suggesting that effort controls in the fishery, rather than porpoise conservation measures, were responsible for initial Bycatch reduction. Bycatch mitigation efforts were more successful in the Pacific, where higher levels of compliance with mitigation measures are known to occur. We conclude that the 1994 Amendments have in general been successful, but that implementation has not always translated into conservation success, as illustrated by the harbor porpoise case study. Further studies are required to determine factors that promote compliance and mitigation success within the MMPA framework.
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to ping or not to ping the use of active acoustic devices in mitigating interactions between small cetaceans and gillnet fisheries
2013Co-Authors: Steve Dawson, Simon Northridge, Danielle M Waples, Andrew J. ReadAbstract:Active sound emitters ('pingers') are used in several gillnet fisheries to reduce Bycatch of small cetaceans, and/or to reduce depredation by dolphins. Here, we review studies conducted to determine how effective these devices may be as management tools. Significant reductions in Bycatch of harbour porpoise Phocoena phocoena, franciscana Pontoporia blainvillei, common Delphinus delphis and striped dolphin Stenella coeruleoalba, and beaked whales as a group have been demonstrated. For harbour porpoise this result has been replicated in 14 con- trolled experiments in North America and Europe, and appears to be due to porpoises avoiding the area ensonified by pingers. Two gillnet fisheries (California-Oregon driftnet fishery for sword- fish; New England groundfish fishery) with mandatory pinger use have been studied for over a decade. Bycatch rates of dolphins/porpoises have fallen by 50 to 60%, and there is no evidence of Bycatch increasing over time due to habituation. In both fisheries, Bycatch rates were significantly higher in nets sparsely equipped with pingers or in which pingers had failed, than in nets without any pingers at all. Studies of pinger use to reduce depredation by bottlenose dolphins Tursiops truncatus generally show small and inconsistent improvements in fish catches and somewhat reduced net damage. Dolphin Bycatch in these fisheries is rare, but still occurs in nets with pingers. Taken together, these studies suggest that the most promising candidates for Bycatch reduction via pinger use will be gillnet fisheries in developed countries in which the bycaught cetaceans are generally neophobic species with large home ranges. We offer a set of lessons learned from the last decade of Bycatch management.
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cumulative estimates of sea turtle Bycatch and mortality in usa fisheries between 1990 and 2007
2011Co-Authors: Elena M Finkbeiner, Bryan P. Wallace, Jeffrey E Moore, Rebecca L Lewison, Larry B Crowder, Andrew J. ReadAbstract:Sea turtles interact with a variety of fishing gears across their broad geographic distributions and onto- genetic habitat shifts. Cumulative assessments of multi-gear Bycatch impacts on sea turtle populations are critical for coherent fisheries Bycatch management, but such estimates are difficult to achieve, due to low fisheries observer effort, and a single-species, single-fishery management focus. We compiled the first cumulative estimates of sea turtle Bycatch across fisheries of the United States between 1990 and 2007, before and after implementation of fisheries-specific Bycatch mitigation measures. An annual mean of 346,500 turtle interactions was estimated to result in 71,000 annual deaths prior to establish- ment of Bycatch mitigation measures in US fisheries. Current Bycatch estimates (since implementation of mitigation measures) are 60% lower (137,800 interactions) and mortality estimates are 94% lower (4600 deaths) than pre-regulation estimates. The Southeast/Gulf of Mexico Shrimp Trawl fishery accounts for the overwhelming majority of sea turtle Bycatch (up to 98%) in US fisheries, but estimates of Bycatch in this fishery are fraught with high uncertainty due to lack of observer coverage. Our esti- mates represent minimum annual interactions and mortality because our methods were conservative and we could not analyze unobserved fisheries potentially interacting with sea turtles. Although consid- erable progress has been made in reducing sea turtle Bycatch in US fisheries, management still needs improvement. We suggest that sea turtle Bycatch limits be set across US fisheries, using an approach sim- ilar to the Potential Biological Removal algorithm mandated by the Marine Mammal Protection Act.
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an interview based approach to assess marine mammal and sea turtle captures in artisanal fisheries
2010Co-Authors: Jeffrey E Moore, Andrew J. Read, Rebecca L Lewison, Larry B Crowder, Rhema Bjorkland, Sara L Mcdonald, E Aruna, I Ayissi, P Espeut, C JoynsonhicksAbstract:Recent case studies have highlighted high Bycatch mortality of sea turtles and marine mammals in artisanal fisheries, but in most countries there are few data on artisanal fishing effort, catch, or Bycatch. With artisanal fisheries comprising >95% of the world’s fishermen, this knowledge gap presents a major challenge to threatened species conservation and sustainable fisheries initiatives. We report on results from an intensive pilot study to evaluate whether interview surveys can be effective in assessing fishing effort and threatened species Bycatch. Fisheries and Bycatch data from interviews with >6100 fishermen in seven developing countries were collected in <1 year for approximately USD $47,000, indicating that this approach may rapidly yield coarse-level information over large areas at low cost. This effort provided the first fisheries characterizations for many areas and revealed the widespread nature of high Bycatch in artisanal fisheries. Challenges to study design and implementation prevented quantitative estimation or spatial comparisons of Bycatch during this pilot research phase, but results suggested that annual sea turtle Bycatch may number at least in the low thousands of individuals per country. Annual odontocete Bycatch may number at least in the low hundreds per country. Sirenian Bycatch occurred in all study areas but was frequent only in West Africa. We discuss lessons learned from this survey effort and present a revised protocol for future interview-based Bycatch assessments.
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a bayesian uncertainty analysis of cetacean demography and Bycatch mortality using age at death data
2008Co-Authors: Jeffrey E Moore, Andrew J. ReadAbstract:Wildlife ecologists and managers are challenged to make the most of sparse information for understanding demography of many species, especially those that are long lived and difficult to observe. For many odontocete (dolphin, porpoise, toothed whale) populations, only fertility and age-at-death data are feasibly obtainable. We describe a Bayesian approach for using fertilities and two types of age-at-death data (i.e., age structure of deaths from all mortality sources and age structure of anthropogenic mortalities only) to estimate rate of increase, mortality rates, and impacts of anthropogenic mortality on those rates for a population assumed to be in a stable age structure. We used strandings data from 1977 to 1993 (n = 96) and observer Bycatch data from 1989 to 1993 (n = 233) for the Gulf of Maine, USA, and Bay of Fundy, Canada, harbor porpoise (Phocoena phocoena) population as a case study. Our method combines mortality risk functions to estimate parameters describing age-specific natural and Bycatch mortality rates. Separate functions are simultaneously fit to Bycatch and strandings data, the latter of which are described as a mixture of natural and Bycatch mortalities. Euler-Lotka equations and an estimate of longevity were used to constrain parameter estimates, and we included a parameter to account for unequal probabilities of natural vs. Bycatch deaths occurring in a sample. We fit models under two scenarios intended to correct for possible data bias due to indirect Bycatch of calves (i.e., death following Bycatch mortality of mothers) being underrepresented in the Bycatch sample. Results from the two scenarios were "model averaged" by sampling from both Markov Chain Monte Carlo (MCMC) chains with uniform probability. The median estimate for potential population growth (r(nat)) was 0.046 (90% credible interval [CRI] = 0.004-0.116). The median for actual growth (r) was -0.030 (90% CRI = -0.192 to +0.065). The probability of population decline due to added fisheries mortality, prior to management to reduce Bycatch, was 0.690. Our approach takes into account multiple sources of uncertainty in data and process, and it provides posterior distributions for a rich set of demographic rate parameters that are unknown for most cetaceans. This method should be easily adaptable to other taxa for which fertility and age-at-death data are available.
Rebecca L Lewison - One of the best experts on this subject based on the ideXlab platform.
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addressing fisheries Bycatch in a changing world
2015Co-Authors: Lisa M Komoroske, Rebecca L LewisonAbstract:Fisheries Bycatch is a threat to species of marine megafauna across the world’s oceans. Work over the past several decades has greatly advanced our understanding of the species affected, the magnitude and the spatial extent of Bycatch. In the same time period, there have been substantial advances in the development of mitigation strategies and best practices to reduce Bycatch. In this paper, we take stock of Bycatch knowledge and science to address the critical question “Where do we go from here?” First, we review the current state of global Bycatch science, including Bycatch rate estimation and biological effects of Bycatch, and Bycatch mitigation practices and gear. We then identify knowledge gaps as well as socio-cultural constraints that hamper effective knowledge transfer or implementation, and discuss emerging transdisciplinary approaches to address these issues. Finally, we discuss the need to consider Bycatch in a changing ocean and socio-cultural context where species, ecosystems, and people are responding to multiple stressors and dynamic conditions. As the field of Bycatch research moves into the 21st century, a new perspective is needed to develop responsive strategies that effectively address the shifting ecological, social, cultural and economic contexts of the global Bycatch seascape.
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global patterns of marine mammal seabird and sea turtle Bycatch reveal taxa specific and cumulative megafauna hotspots
2014Co-Authors: Rebecca L Lewison, Bryan P. Wallace, Jeffrey E Moore, Larry B Crowder, Tara M Cox, Ramunas Zydelis, Sara L Mcdonald, Andrew Dimatteo, Daniel C Dunn, Connie Y KotAbstract:Recent research on ocean health has found large predator abundance to be a key element of ocean condition. Fisheries can impact large predator abundance directly through targeted capture and indirectly through incidental capture of nontarget species or Bycatch. However, measures of the global nature of Bycatch are lacking for air-breathing megafauna. We fill this knowledge gap and present a synoptic global assessment of the distribution and intensity of Bycatch of seabirds, marine mammals, and sea turtles based on empirical data from the three most commonly used types of fishing gears worldwide. We identify taxa-specific hotspots of Bycatch intensity and find evidence of cumulative impacts across fishing fleets and gears. This global map of Bycatch illustrates where data are particularly scarce—in coastal and small-scale fisheries and ocean regions that support developed industrial fisheries and millions of small-scale fishers—and identifies fishing areas where, given the evidence of cumulative hotspots across gear and taxa, traditional species or gear-specific Bycatch management and mitigation efforts may be necessary but not sufficient. Given the global distribution of Bycatch and the mitigation success achieved by some fleets, the reduction of air-breathing megafauna Bycatch is both an urgent and achievable conservation priority.
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impacts of fisheries Bycatch on marine turtle populations worldwide toward conservation and research priorities
2013Co-Authors: Bryan P. Wallace, Larry B Crowder, Andrew Dimatteo, Rebecca L LewisonAbstract:Fisheries Bycatch is considered the most serious threat globally to long-lived marine megafauna (e.g., mammals, birds, turtles, elasmobranchs). However, Bycatch assessments to date have not evaluated population-level Bycatch impacts across fishing gears. Here, we provide the first global, multi-gear evaluation of population-level fisheries Bycatch impacts for marine turtles. To compare Bycatch impacts of multiple gears within and among marine turtle populations (or regional management units, RMUs), we compiled more than 1,800 records from over 230 sources of reported marine turtle Bycatch in longline, net, and trawl fisheries worldwide that were published between 1990–2011. The highest Bycatch rates and levels of observed effort for each gear category occurred in the East Pacific, Northwest and Southwest Atlantic, and Mediterranean regions, which were also the regions of highest data availability. Overall, available data were dominated by longline records (nearly 60% of all records), and were non-uniforml...
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cumulative estimates of sea turtle Bycatch and mortality in usa fisheries between 1990 and 2007
2011Co-Authors: Elena M Finkbeiner, Bryan P. Wallace, Jeffrey E Moore, Rebecca L Lewison, Larry B Crowder, Andrew J. ReadAbstract:Sea turtles interact with a variety of fishing gears across their broad geographic distributions and onto- genetic habitat shifts. Cumulative assessments of multi-gear Bycatch impacts on sea turtle populations are critical for coherent fisheries Bycatch management, but such estimates are difficult to achieve, due to low fisheries observer effort, and a single-species, single-fishery management focus. We compiled the first cumulative estimates of sea turtle Bycatch across fisheries of the United States between 1990 and 2007, before and after implementation of fisheries-specific Bycatch mitigation measures. An annual mean of 346,500 turtle interactions was estimated to result in 71,000 annual deaths prior to establish- ment of Bycatch mitigation measures in US fisheries. Current Bycatch estimates (since implementation of mitigation measures) are 60% lower (137,800 interactions) and mortality estimates are 94% lower (4600 deaths) than pre-regulation estimates. The Southeast/Gulf of Mexico Shrimp Trawl fishery accounts for the overwhelming majority of sea turtle Bycatch (up to 98%) in US fisheries, but estimates of Bycatch in this fishery are fraught with high uncertainty due to lack of observer coverage. Our esti- mates represent minimum annual interactions and mortality because our methods were conservative and we could not analyze unobserved fisheries potentially interacting with sea turtles. Although consid- erable progress has been made in reducing sea turtle Bycatch in US fisheries, management still needs improvement. We suggest that sea turtle Bycatch limits be set across US fisheries, using an approach sim- ilar to the Potential Biological Removal algorithm mandated by the Marine Mammal Protection Act.
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global patterns of marine turtle Bycatch
2010Co-Authors: Bryan P. Wallace, Rebecca L Lewison, Sara L Mcdonald, Richard K Mcdonald, Connie Y Kot, Shaleyla Kelez, Rhema K BjorklandAbstract:Fisheries Bycatch is a primary driver of population declines in several species of marine megafauna (e.g., elasmobranchs, mammals, seabirds, turtles). Characterizing the global Bycatch seascape using data on Bycatch rates across fisheries is essential for highlighting conservation priorities. We compiled a comprehensive database of reported data on marine turtle Bycatch in gillnet, longline, and trawl fisheries worldwide from 1990 to 2008. The total reported global marine turtle Bycatch was ∼85,000 turtles, but due to the small percentage of fishing effort observed and reported (typically <1% of total fleets), and to a global lack of Bycatch information from small-scale fisheries, this likely underestimates the true total by at least two orders of magnitude. Our synthesis also highlights an apparently universal pattern across fishing gears and regions where high Bycatch rates were associated with low observed effort, which emphasizes the need for strategic Bycatch data collection and reporting. This study provides the first global perspective of fisheries Bycatch for marine turtles and highlights region–gear combinations that warrant urgent conservation action (e.g., gillnets, longlines, and trawls in the Mediterranean Sea and eastern Pacific Ocean) and region–gear combinations in need of enhanced observation and reporting efforts (e.g., eastern Indian Ocean gillnets, West African trawls).
Elliott L. Hazen - One of the best experts on this subject based on the ideXlab platform.
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Comprehensive Bycatch assessment in US fisheries for prioritizing management
2020Co-Authors: Matthew S. Savoca, Stephanie Brodie, Heather Welch, Aimee Hoover, Lee R. Benaka, Steven J. Bograd, Elliott L. HazenAbstract:The sustainability of wild fisheries is limited by the capture of non-target species. This study estimates that such ‘Bycatch’ from US fisheries totalled 1.93 million tonnes in 2010–2015, with a 10.5% discard rate. Despite considerable improvements, certain longline, trawl and gillnet fisheries have persistent Bycatch issues. Wild-capture fisheries help provide food security to billions of people, yet Bycatch of non-target species threatens ecosystem health and fishery sustainability. Appropriate monitoring and fisheries management can mitigate Bycatch but require standardized Bycatch data to be robustly recorded and effectively disseminated. Here we integrated and analysed 30,473 species-specific Bycatch records from 95 US fisheries in 2010–2015. We examined patterns in fish and invertebrate, marine mammal, seabird and sea turtle Bycatch and developed a standardized scoring system, the relative Bycatch index, to assess Bycatch performance of each fishery. The estimated amount of fish and invertebrate discards totalled 1.93 million tonnes (4.26 billion pounds) over the 6-year period. We found that the national discard rate is 10.5%, considerably lower than past estimates. Results from our relative Bycatch index analysis can be used to facilitate management intervention strategies for particular fisheries or gear types, such as shrimp and otter trawls and several pelagic longline and gillnet fisheries, which had the poorest Bycatch performance. These findings underscore the need for continued, high-quality, easily accessible Bycatch information to better support fisheries management in the United States and globally.
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oceanographic determinants of ocean sunfish mola mola and bluefin tuna thunnus orientalis Bycatch patterns in the california large mesh drift gillnet fishery
2017Co-Authors: Nick Hahlbeck, Steven J. Bograd, Elliott L. Hazen, Kylie L Scales, Heidi Dewar, Sara M MaxwellAbstract:Abstract The reduction of incidental capture of non-target species in a fishery (Bycatch) is a key objective of ecosystem-based fisheries management (EBFM) and critical to the conservation of many marine species. Predicting Bycatch events can inform targeted ecosystem-based management approaches to reduce risk. Here, the probability of ocean sunfish ( Mola mola ) and bluefin tuna ( Thunnus orientalis ) Bycatch in the California large-mesh drift gillnet fishery is predicted using a suite of remotely-sensed environmental variables. Generalized additive models (GAMs) were used to model Bycatch probability for these species in 8045 observed sets from 1990 to 2011, and predictive capabilities were assessed using k -fold cross validation. Bycatch probabilities for both species were elevated in regions of cool sea surface temperatures ( Mola Bycatch occurred primarily in late fall, at moderate eddy kinetic energy values (0.006–0.008 m 2 /s 2 ) and in areas of high seafloor rugosity. Bluefin tuna Bycatch rates were higher west of the Southern California Bight, also in late fall, and appear to be associated with the seasonal upwelling frontal zone. These models can be used with near-real time satellite data by both fishers and managers for Bycatch avoidance, providing a tool for more dynamic ocean management strategies.
Kylie L Scales - One of the best experts on this subject based on the ideXlab platform.
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oceanographic determinants of ocean sunfish mola mola and bluefin tuna thunnus orientalis Bycatch patterns in the california large mesh drift gillnet fishery
2017Co-Authors: Nick Hahlbeck, Steven J. Bograd, Elliott L. Hazen, Kylie L Scales, Heidi Dewar, Sara M MaxwellAbstract:Abstract The reduction of incidental capture of non-target species in a fishery (Bycatch) is a key objective of ecosystem-based fisheries management (EBFM) and critical to the conservation of many marine species. Predicting Bycatch events can inform targeted ecosystem-based management approaches to reduce risk. Here, the probability of ocean sunfish ( Mola mola ) and bluefin tuna ( Thunnus orientalis ) Bycatch in the California large-mesh drift gillnet fishery is predicted using a suite of remotely-sensed environmental variables. Generalized additive models (GAMs) were used to model Bycatch probability for these species in 8045 observed sets from 1990 to 2011, and predictive capabilities were assessed using k -fold cross validation. Bycatch probabilities for both species were elevated in regions of cool sea surface temperatures ( Mola Bycatch occurred primarily in late fall, at moderate eddy kinetic energy values (0.006–0.008 m 2 /s 2 ) and in areas of high seafloor rugosity. Bluefin tuna Bycatch rates were higher west of the Southern California Bight, also in late fall, and appear to be associated with the seasonal upwelling frontal zone. These models can be used with near-real time satellite data by both fishers and managers for Bycatch avoidance, providing a tool for more dynamic ocean management strategies.
