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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 An assessment of global national and regional plans of action on sharks (NPOAs) found: most are out of date; limited use of specific, measurable and timebound objectives and activities; no outcome objectives; and few performance assessments.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]

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]

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]

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]

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]