Search

There is growing concern over the conservation status of sharks and relatives exposed to fishing mortality. The Food and Agriculture Organization of the United Nations in 1999 adopted the International Plan of Action for the Conservation and Management of Sharks (IPOA), which provides nations with advice on adopting and implementing national plans. An assessment of global national and regional plans of action on sharks (NPOAs) found: most are out of date; limited use of specific, measurable and timebound objectives and activities; no outcome objectives; and few performance assessments. This makes most NPOAs inadequate for planning and assessing efficacy. Over 33% of the annual retained catch of sharks and relatives was from countries without NPOAs and less than 12% was from countries with current NPOAs. NPOAs identified fisheries management framework deficits, ecology knowledge gaps, institutional capacity and coordination shortfalls, and budget constraints as the largest obstacles to implementation and are improvement priorities. We recommend how to amend the IPOA to better support the adoption and effective design and implementation of NPOAs for evidence‐informed conservation and management. [ABSTRACT FROM AUTHOR]

Data required from fisheries monitoring programmes substantially expand as management authorities transition to implement elements of ecosystem-based fisheries management (EBFM). EBFM extends conventional approaches of managing single fishery effects on individual stocks of target species by taking into account the effects, within a defined ecosystem, of local to regional fisheries on biodiversity, from genotypes to ecological communities. This includes accounting for fishery effects on evolutionary processes, associated and dependent species, habitats, trophic food web processes, and functionally linked systems. Despite seemingly insurmountable constraints, through examples, we demonstrate how data routinely collected in most observer programmes and how minor and inexpensive expansions of observer data fields and collection protocols supply ecological data underpinning EBFM. Observer data enable monitoring bycatch, including catch and mortality of endangered, threatened and protected species, and assessing the performance of bycatch management measures. They provide a subset of inputs for ecological risk assessments, including productivity-susceptibility analyses and multispecies and ecosystem models. Observer data are used to monitor fishery effects on habitat and to identify and protect benthic vulnerable marine ecosystems. They enable estimating collateral sources of fishing mortality. Data from observer programmes facilitate monitoring ecosystem pressure and state indicators. The examples demonstrate how even rudimentary fisheries management systems can meet the ecological data requirements of elements of EBFM. [ABSTRACT FROM AUTHOR]

Fisheries bycatch is the foremost threat to the conservation of many marine species. Evaluation of alternative bycatch management strategies can account for the relative strength of evidence, contribution to achieving objectives, costs to commercial viability, likelihood of compliance and tradeoffs from multispecies conflicts. This study describes benefits and limitations of a complementary approach of applying a sequential mitigation hierarchy to develop evidence-informed bycatch policy. Measures that avoid bycatch are considered before those that minimize catch risk. These are then followed by remediation interventions that reduce fishing mortality and sublethal impacts. Finally, direct, compensatory banking or in lieu fee-based offsets of residual impacts that were not possible to avoid, minimize and remediate can be implemented as a last resort. However, offset activities can be socioeconomically unjust, and some bycatch impacts are irreversible and cannot be offset. Air-breathing bycatch are exposed to a wide range of anthropogenic hazards across ontogenetic stages, presenting more options for offset conservation activities than fishes. Averted loss offsets, which avoid foregone losses predicted to occur had an intervention not occurred, implemented in combination with true offsets can achieve at least an equivalent gain and contribute to meeting broad, population- and species-level conservation objectives. Robust metrics are needed to determine equivalency, such as in relative reproductive value and population viability, between residual impacts and in-kind versus out-of-kind and on-site versus offsite offsets. Bycatch management strategies guided by a sequential mitigation hierarchy promise to achieve ecological and socioeconomic objectives, including going bycatch-neutral or bycatch-negative through a net biodiversity gain. • Fisheries bycatch is the leading threat to many marine species. • Evidence-informed bycatch policy should apply a sequential mitigation hierarchy. • Identifies benefits and risks of a mitigation hierarchy for bycatch management. • Direct and compensatory offsets can obtain equivalent gains for bycatch losses. • Robust metrics are needed to determine equivalency. [ABSTRACT FROM AUTHOR]

Pelagic longline fisheries affect both market and vulnerable bycatch species and can have broad effects on community structure and processes., Observer data from the Palau longline fishery were analysed to identify opportunities to mitigate vulnerable species bycatch, determine temporal trends in local abundance, and assess changes following a ban on shark retention and wire leaders. Catch and haulback condition data for bigeye and yellowfin tunas, blue and silky sharks and pelagic stingrays were fitted to standardized catch and survival rate models., The fishery caught silky and blue sharks, olive ridley sea turtles and other species of conservation concern., Changing from shallow sets to deep daytime sets might reduce shark and sea turtle catch rates but increase turtle haulback mortality rates, maintain economically viable tuna catch rates, but increase catch rates of pelagic stingrays, a lower conservation concern than main caught species of sharks and turtles., Focusing fishing effort during the middle of the calendar year would maximize yellowfin tuna and minimize silky shark standardized catch rates, but maximize blue shark catch rates., A large decline in shark fishing mortality rate very likely occurred following a ban on shark retention and wire leaders. This was due to large reductions in the nominal shark catch rate and shark retention, partially offset by decreases in the shark haulback survival rate and pre-catch survival rate. Significantly higher blue shark and lower pelagic stingray nominal catch rates occurred on wire vs. monofilament leaders. Significantly higher blue shark and lower yellowfin tuna nominal catch rates occurred on sets using shallow 'shark lines'. It is a research priority to compare the probability of shark pre-catch survival after escaping from monofilament leaders with an ingested hook and trailing line to the survival probability when captured on wire leaders., Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A performance assessment was conducted of regional fisheries management organizations' ( RFMOs') bycatch governance, one element of an ecosystem approach to fisheries management. Obtaining a mean score of 25%, with a 64% CV, collectively the RFMOs have large governance deficits. Individually, there has been mixed progress, with some RFMOs having made substantial progress for some governance elements. There has been nominal progress in gradually transitioning to ecosystem-based fisheries management: controls largely do not account for broad or multispecies effects of fishing, and cross-sectoral marine spatial planning is limited. Regional observers collect half of minimum information needed to assess the efficacy of bycatch measures. Over two-thirds of RFMO-managed fisheries lack regional observer coverage. International exchange of observers occurs in one-third of programmes. There is no open access to research-grade regional observer data. Ecological risk assessments focus on effects of bycatch removals on vulnerable species groups and effects of fishing on vulnerable benthic marine ecosystems. RFMOs largely do not assess or manage cryptic, generally undetectable sources of fishing mortality. Binding measures address about one-third of bycatch problems. Eighty per cent of measures lack explicit performance standards against which to assess efficacy. Measures are piecemeal, developed without considering potential conflicts across vulnerable groups. RFMOs employ 60% of surveillance methods required to assess compliance. A lack of transparency and limited reporting of inspection effort, identified infractions, enforcement actions and outcomes further limits the ability to assess compliance. Augmented harmonization could help to fill identified deficits. [ABSTRACT FROM AUTHOR]

Abstract: To support implementing an ecosystem approach to fisheries management, ecological risk assessment (ERA) methods have recently been developed for the continuum of data-deficient to data-rich fisheries. A semi-quantitative ERA was conducted for the Marshall Islands longline bigeye tuna (Thunnus obesus) fishery. The study used information from analyses of observer data, surveys of captains and crew and inventories of gear and equipment. Relative risks were evaluated through a consideration of phylogenetic uniqueness, risk of population extirpation, risk of species extinction and importance in ecosystem regulation. The fishery presents a highest relative risk to leatherback (Dermochelys coriacea), hawksbill (Eretmochelys imbricata), green (Chelonia mydas) and olive Ridley (Lepidochelys olivacea) sea turtle Regional Management Units that overlap with the fishery, in that order. The next highest relative risk is to affected stocks of oceanic whitetip (Carcharhinus longimanus), blue (Prionace glauca), and silky (Carcharhinus falciformis) sharks, in that sequence. Seabird bycatch is likely not problematic. There was inadequate information to assess risks to cetacean populations. Risks to stocks of market and non-market species of marine fishes with r-selected life history characteristics were not assessed. This is because estimates of critical threshold levels of local and absolute abundance and current biomass are not known for many of these stocks. Several best practice gear technology methods to mitigate problematic catch of vulnerable species groups are currently employed: monofilament leaders, whole fish for bait, single-hooking fish bait, no lightsticks, and no fishing at shallow submerged features. Setting terminal tackle below 100m and carrying and using best practice handling and release equipment were methods identified to reduce fishing mortality and injury of vulnerable species. More information is needed to determine if weaker hooks should be prescribed to mitigate cetacean bycatch. The large benefit to sea turtles of replacing remaining J-shaped hooks with circle hooks might outweigh a possible small increase in elasmobranch catch rates. The consumption of 2024l of fuel per tonne of landed catch, which is within the range of available estimated rates from similar fisheries, could be reduced, reducing greenhouse gas emissions, through more frequent maintenance and upgrading vessel equipment and materials. Observer data quality may be adequate to support a quantitative Level 3 ERA to determine the significance of the effect of various factors on standardized catch rates and to estimate population-level effects from fishing mortality. [Copyright &y& Elsevier]

ABSTRACT Declines in absolute abundance and altered size distributions from size-selective removals of market species of pelagic apex predators in tuna fisheries alters evolutionary characteristics of populations and ecosystem processes and stability. Pelagic fishing at seamounts, where hyperstability of pelagic predators may occur, can exacerbate declining abundance and have high bycatch of species groups that are highly vulnerable to overexploitation., Generalized additive mixed Poisson regression models (GAMMs) were fitted to Hawaii longline tuna fishery observer data to determine temporal trends in standardized catch rates, an index for local, relative abundance. Temporal trends in expectile length distributions were determined through geoadditive expectile GAMMs., Significant declining trends in relative abundance in this fishery were observed for tunas, sharks and billfish. A decline in seabird standardized catch rate occurred concurrently with the uptake of seabird bycatch mitigation technology. Changed spatial distribution of fishing effort and increased use of wider circle hooks likely contributed to a declining sea turtle standardized catch rate., Tuna and billfish mean lengths significantly increased over the time series due to entire distributions of length classes having shifted towards larger fish. Larger tunas comprised a larger proportion of the catch due to fewer small tunas being caught, and to a lesser extent because mean lengths of larger size classes increased. Conversely, billfish largest length classes experienced the largest increases in average lengths. Changes in spatial and seasonal distributions of fishing effort, increased use of wider circle hooks, and possibly increasing purse seine selective removals of juvenile tunas, may have contributed to increased selectivity for larger fish., Significant differences in standardized catch rates and length distributions at a shallow seamount vs. the open ocean confirms the aggregating effect of seamounts on pelagic predators, including juvenile market species of pelagic fish and species groups relatively vulnerable to overexploitation., Wider circle hooks significantly improved valuable tuna standardized catch rates, but also increased unwanted shark and reduced valuable billfish standardized catch rates., Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Overexploitation of bycatch and target species in marine capture fisheries is the most widespread and direct driver of change and loss of global marine biodiversity. Bycatch in purse seine and pelagic longline tuna fisheries, the two primary gear types for catching tunas, is a primary mortality source of some populations of seabirds, sea turtles, marine mammals and sharks. Bycatch of juvenile tunas and unmarketable species and sizes of other fish in purse seine fisheries, and juvenile swordfish in longline fisheries, contributes to the overexploitation of some stocks, and is an allocation issue. There has been substantial progress in identifying gear technology solutions to seabird and sea turtle bycatch on longlines and to direct dolphin mortality in purse seines. Given sufficient investment, gear technology solutions are probably feasible for the remaining bycatch problems. More comprehensive consideration across species groups is needed to identify conflicts as well as mutual benefits from mitigation methods. Fishery-specific bycatch assessments are necessary to determine the efficacy, economic viability, practicality and safety of alternative mitigation methods. While support for gear technology research and development has generally been strong, political will to achieve broad uptake of best practices has been lacking. The five Regional Fisheries Management Organizations have achieved mixed progress mitigating bycatch. Large gaps remain in both knowledge of ecological risks and governance of bycatch. Most binding conservation and management measures fall short of gear technology best practice. A lack of performance standards, in combination with an inadequate observer coverage for all but large Pacific purse seiners, and incomplete data collection, hinders assessing measures'' efficacy. Compliance is probably low due to inadequate surveillance and enforcement. Illegal, unreported and unregulated tuna fishing hampers governance efforts. Replacing consensus-based decision-making and eliminating opt-out provisions would help. Instituting rights-based management measures could elicit improved bycatch mitigation practices. While gradual improvements in an international governance of bycatch can be expected, market-based mechanisms, including retailers and their suppliers working with fisheries to gradually improve practices and governance, promise to be expeditious and effective. [Copyright &y& Elsevier]

Overexploitation is currently the main cause of marine defaunation. Vulnerability to overexploitation varies across populations. Determining which populations are of highest ecological risk from fishing mortality guides management. Because no single approach is optimal across taxonomic groups, a multi-model ensemble of relative risk estimates for a data-poor Pacific Ocean tuna longline fishery was obtained from two semi-quantitative Productivity-Susceptibility Analyses (PSAs) and from a quantitative approach that estimates instantaneous fishing mortality to compare to reference points of yield-per-recruit models. Individual estimates were combined to produce a pooled mean relative risk rank order. The study identified stocks below biological limits for which the contribution from this fishery to cumulative anthropogenic mortality may warrant intervention. Relative risks in descending order were for populations of albatrosses, cetaceans, mesopelagic sharks, rays, marine turtles, epipelagic sharks and teleosts. The fishery's contribution to cumulative fishing mortality of western central north Pacific Ocean striped marlin warrants a more rigorous assessment to determine absolute risks. The study identified the disparate factors explaining relative risk from an individual fishery versus absolute risk from cumulative anthropogenic mortality sources. Improved risk assessments are possible by addressing identified deficits with PSAs, obtaining information on variables that explain catch and post-capture survival risks that was unavailable for this assessment, improving electronic monitoring data quality and filling gaps in life history traits. Findings support stakeholders to design integrated bycatch management frameworks that mitigate fishing mortality of the most vulnerable taxa and account for multispecies conflicts that result from some bycatch mitigation methods. • A risk assessment identified most vulnerable taxa caught in a tuna longline fishery. • An ensemble of assessment approaches accounted for differences between taxa. • Relative risks were highest for albatrosses, mesopelagic sharks and cetaceans. • Mortality of a striped marlin stock warrants determining absolute risks. • Addressing assessment method deficits and filling information gaps are priorities. [ABSTRACT FROM AUTHOR]

Abstract: Substantial ecological, economic and social problems result from shark interactions in pelagic longline fisheries. Improved understanding of industry attitudes and practices towards shark interactions assists with managing these problems. Information on fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers. A study of 12 pelagic longline fisheries from eight countries shows that incentives to avoid sharks vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. Shark avoidance practices are limited, including avoiding certain areas, moving when shark interaction rates are high, using fish instead of squid for bait and deeper setting. Some conventionally employed fishing gear and methods used to target non-shark species contribute to shark avoidance. Shark repellents hold promise; more research and development is needed. Development of specifically designed equipment to discard sharks could improve shark post release survival prospects, reduce gear loss and improve crew safety. With expanding exploitation of sharks for fins and meat, improved data collection, monitoring and precautionary shark management measures are needed to ensure that shark fishing mortality levels are sustainable. [Copyright &y& Elsevier]

The reduction of sea turtle mortality in fisheries may contribute to recovering populations. To reduce turtle interactions, regulations for the Hawaii-based longline swordfish fishery required vessels to switch from using a J-shaped hook with squid bait to a wider circle-shaped hook with fish bait. Analyses of observer data showed that, following the introduction of the regulations, significant and large reductions in sea turtle and shark capture rates occurred without compromising target species catches. Capture rates of leatherback and loggerhead turtles significantly declined by 83% and 90%, respectively. The swordfish catch rate significantly increased by 16%. However, combined tuna species and combined mahimahi, opah, and wahoo catch rates significantly declined by 50% and 34%, respectively. The shark catch rate significantly declined by 36%, highlighting the potential for the use of fish instead of squid for bait to contribute to addressing concerns over the sustainability of current levels of shark exploitation. There was also a highly significant reduction in the proportion of turtles that swallowed hooks (versus being hooked in the mouth or body or entangled) and a highly significant increase in the proportion of caught turtles that were released after removal of all terminal tackle, which may increase the likelihood of turtles surviving the interaction. A quarter of turtle captures were in clusters (>1 turtle caught per set and consecutive sets with turtle captures), which is substantially higher than predicted by chance if the events were independent. This suggests that turtles aggregate at foraging grounds and that instituting methods to avoid real-time turtle bycatch hotspots may further reduce turtle interactions. There was no significant correlation between turtle and swordfish catch rates (vessels with high swordfish CPUE do not necessarily have high turtle CPUE), indicating that there may be a fishing practice or gear design causing some vessels to have low turtle catch rates without compromising swordfish catch rates. [Copyright &y& Elsevier]

The collection of accurate fisheries catch data is critical to ensuring sustainable management of tuna fisheries, mitigating their environmental impacts and for managing transboundary fish stocks. These challenges are exemplified by the western Pacific tuna longline fishery, who's management includes >26 nations, but is informed by critically low coverage of fishing activities by scientific observers. The gap in observer data could be filled by electronic monitoring (EM), but there are few trials that span multiple nations. A large-scale trial of EM systems on tuna longliners based in Palau, Federated States of Micronesia and the Republic of the Marshall Islands, is reported on. Comparisons are made of catch rates of market and bycatch species in corresponding EM, logbook and human observer data. Retained species were under-reported in logbooks by up to three times and discards of many species were not reported in logbooks. Discards identified in the EM data included threatened species such as marine turtles. Catch rate estimates from EM data were comparable to those estimated by human observers. EM data recorded a higher species diversity of catches than logbook data. Analysis of the EM data indicated clusters of bycatch that were associated with specific fishing practices. These results suggest further expansion of EM could inform improved management of both target and bycatch species. Ultimately greater coverage of EM data could contribute to reconciling debates in international stock allocation schemes and support actions to reduce the impacts of the fishery on threatened bycatch species. • Electronic monitoring of longline fisheries in three Pacific nations was trialled. • Catches were underreported in logbooks compared to the corresponding electronic monitoring data • Catch records from logbooks reported fewer species than the corresponding electronic monitoring data • Clusters of catch on some longline sets suggest opportunity for bycatch mitigation • Expanding trials offers significant opportunities to improve longline monitoring and overall sustainability [ABSTRACT FROM AUTHOR]

Accurate data on discards, the proportion of the catch that fishers do not retain, is necessary to achieve socioeconomically and ecologically sustainable fisheries. We review conventional and emerging approaches to monitor and manage discards. At-sea human observer programs currently produce the most accurate data on discards. Electronic monitoring may become the most effective method to monitor discards, as it has the capacity to overcome most sources of statistical sampling bias of conventional human onboard observer programs. Other monitoring approaches, including logbooks, fishery-independent surveys and fisher interviews, produce relatively unreliable discard estimates, while port sampling only provides information on landed catch. Modifications to fishing practices and gear to increase selectivity are main approaches used to reduce discards. Managing the temporal and spatial distribution of fishing effort by employing tools such as dynamic spatial management and fleet communication are additional discards management tools. Landing obligations, retention bans, bycatch caps, effort limits and size restrictions are additional approaches for which strengths and weaknesses are discussed. Continual evaluation is necessary to understand ever-changing causes of fishers' discarding decisions so that important factors can be accounted for in designing monitoring programs and discard models, and guide the adaptation of measures to manage and reduce discards. • Accurate data on discards are necessary to achieve sustainable fisheries. • New technologies and approaches are emerging to effectively monitor and manage discards. • We review the strengths and weaknesses of conventional and emerging approaches. • Continual evaluation is necessary to understand variable causes of discarding. [ABSTRACT FROM AUTHOR]

There has been a recent proliferation of large‐scale marine protected areas (MPAs) containing pelagic habitats. These contribute substantially toward meeting the area‐based goal of Aichi Biodiversity Target 11 and to managing pelagic ecosystem pressures, including fishing. We assessed theoretical and empirical evidence for the achievement of ecological objectives by static and dynamic spatial management of pelagic fisheries. Exceptionally few studies have assessed ecological responses to MPAs that constrain pelagic fisheries, leaving substantial uncertainty over their efficacy. Assessments have provided a limited basis for causal inferences and have not evaluated whether other management tools would be more effective. Pelagic MPAs have relatively high promise to mitigate fisheries bycatch of species of conservation concern with "slow" life history traits and that form temporally and spatially predictable hotspots, and for some species, to protect habitats important for critical life history stages. It would be challenging to design MPAs to maintain absolute biomass levels of target stocks near targets and above limits: MPAs would need to be extensive to account for broad and variable distributions, and account for catch risk outside of the MPA, including from displaced fishing effort and fishing‐the‐line. For non‐overexploited stocks, which is the status of most target pelagic species and their prey, there would likely be little response in absolute stock biomass to an MPA. While pelagic MPAs have a higher promise of increasing target stocks' local abundance, evidence with a robust basis for inferring causality is needed. Reducing fishing mortality of prey species might not affect the biomass of their pelagic predators because prey species experience light fishing pressure and because there may be a weak correlation between the absolute abundance of forage fish and their predators. There is an especially limited basis for predicting the effects of MPAs on fisheries‐induced evolution (FIE) in pelagic species. We describe how pelagic MPAs could be designed to achieve five ecological objectives without causing cross‐taxa conflicts and exacerbating FIE. To fill substantial gaps in knowledge, we prescribe counterfactual‐based modeling of time series data of standardized catch records to infer causation in assessments of ecological responses to pelagic MPAs. [ABSTRACT FROM AUTHOR]