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Challenges and Opportunities in Monitoring and Mitigating Sea Turtle Bycatch in Tuna Regional Fisheries Management Organizations
Reviews in Fisheries Science & Aquaculture
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Delineating spatial boundaries that accurately encompass complex, often cryptic, life histories of highly migratory marine megafauna can be a significant conservation challenge. For example, marine turtles range across vast ocean basins and coastal areas, thus complicating the evaluation of relative impacts of multiple overlapping threats and the creation of coherent conservation strategies. To address these challenges, spatially explicit ‘regional management units’ (RMUs) were developed in 2010 for all marine turtle species, globally. RMUs were intended to provide a consistent framework that organizes conspecific assemblages into units above the level of nesting rookeries and genetic stocks, but below the species level, within regional entities that may share demographic trajectories because they experience similar environmental conditions and other factors. From their initial conception, RMUs were intended to be periodically revised using new information about marine turtle distributions, life history, habitat use patterns, and population structure. Here, we describe the process used to update the 2010 RMU framework by incorporating newly published information and inputs from global marine turtle experts who are members of the IUCN Marine Turtle Specialist Group. A total of 48 RMUs for 6 of 7 marine turtle species and 166 distinct genetic stocks for all 7 species are presented herein. The updated RMU framework reflects a significant advance in knowledge of marine turtle biology and biogeography, and it provides improved clarity about the RMU concept and its potential applications. All RMU products have been made open access to support research and conservation initiatives worldwide.
The State of Mediterranean and Black Sea Fisheries 2022 is the fourth edition of the biennial report prepared by the General Fisheries Commission for the Mediterranean (GFCM), providing an up-to-date overview of fisheries status, trends and governance in the region. This report describes the current composition of the fishing fleet (Chapter 1), the overall capture fishery production (Chapter 2), the economic performance and socioeconomic characteristics of capture fisheries (Chapter 3) and bycatch (Chapter 4) and analyses the status of fishery resources (Chapter 5). It also provides insights on small-scale fisheries (Chapter 6) and focuses on the fisheries management measures put in place by the GFCM to support the sustainability of fisheries and the conservation of the marine environment and ecosystems (Chapter 7).
Data and information are presented mostly up to 2020, although when possible, 2021 information is also included. The information contained in this report is based on data officially submitted by GFCM contracting parties and cooperating non-contracting parties (CPCs) in line with binding decisions through a number of established data submission tools or on estimates based on the best available data obtained from other sources or through standard methodologies. Thanks to the consolidation of quality standards over the last two years, The State of Mediterranean and Black Sea Fisheries 2022 analyses trends in the fisheries sector at the regional level for the first time.
The State of Mediterranean and Black Sea Fisheries 2022 unveils the characteristics of a sector that remains under stress despite some positive trends for key fishery resources.
Small-scale fisheries are economically and culturally important throughout the world’s coastal waters. These fisheries, however, often have high bycatch rates of protected marine species. Bycatch in small scale gillnet fisheries is thought to be a major driver behind the declines of several sea turtle populations. Recent studies addressing this issue have identified net illumination as a potentially effective bycatch reduction technology (BRT) to reduce sea turtle interactions with gillnet fisheries. In Southeast Asia, small-scale gillnet fisheries make up a large components of fishing effort often in areas that overlap with important sea turtle habitat. We conducted controlled experiments of net illumination as a potential BRT to reduce sea turtle bycatch in a coastal gillnet fishery based in Paloh, West Kalimantan, Indonesia. Results indicated that net illumination significantly reduced multi-species sea turtle bycatch by 61.4% and specifically green sea turtles (Chelonia mydas) by 59.5%, while the CPUE of total catch and target species remained similar. Moreover, this study suggests that Indonesian fishers can increase their overall market value when using net illumination as the market value per unit effort (MVPUE) of both the total catch and target catch showed significant increases. These results suggest that net illumination could be an effective sea turtle conservation tool for small-scale coastal gillnet fisheries in Indonesia and potentially throughout Southeast Asia. In addition, data from the control treatments of this study also provided the first observer based sea turtle bycatch estimate for a small-scale gillnet fishery in Southeast Asia. Challenges to the broad scale implementation of net illumination to reduce this bycatch of sea turtles include the cost, availability of the technology, socialization of the BRT to fishers, and government interest and support for net illumination as a tool for bycatch reduction.
The Western and Central Pacific Fisheries Commission (WCPFC) has a responsibility to assess the impact of fishing on non-target species. In this report, we estimate the bycatch of the large-scale purse seine fishery operating primarily in tropical waters of the WCPFC Convention Area east of 140°E. These large vessels, typically greater than 500 tonnes carrying capacity, have been responsible for approximately 85% of the purse seine catch of tropical tunas in recent years, a catch that has varied between 1.7 and 2.2 million tonnes annually since 2010. This report provides an update to the equivalent report prepared in 2018 and submitted to WCPFC SC14.
We summarise bycatches for 45 species and/or species groups that provide comprehensive coverage of finfish, billfish, shark and ray, sea turtle and marine mammals observed in purse seine catches. We do not report on seabird bycatch due to the low number of observed catch events.
Available observer coverage for 2020 represented 29% coverage of total sets, compared with annual coverage rates ranging from 62-78% for the period 2010-2019. This is partially due to incomplete loading of 2020 observer trips at the time of preparing the report, as well as difficulties in placing observers caused by the Covid-19 pandemic. As such, the bycatch estimates of 2020 should be considered preliminary.
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.
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.
This publication offers an overview of historical and current trends in the bycatch of five
important groups of vulnerable species in the Mediterranean and the Black Sea: seabirds, sea turtles, elasmobranchs, marine mammals and macrobenthic invertebrates. Interactions between these groups and fisheries are known to occur in the context of nearly all commonly used types of fishing gear and can result in injury or death to the animals. Each chapter in this review focuses on one of the five groups of vulnerable species, describing and presenting data from surveys and studies conducted over recent decades. The chapters are further subdivided according to fishing gear and GFCM subregion (western, central and eastern Mediterranean, the Adriatic Sea and
the Black Sea). The incidental catch records included in this review are derived from a variety of approaches. Surveys completed by onboard observers, while demanding more time and resources, represent the most comprehensive and accurate of these methods. Less reliable data come from non-systematic, opportunistic data collection, such as questionnaire surveys answered by fishers. Though many geographic areas and vessel groups remain underrepresented in the available data, coverage has generally increased in recent years and insight continues to emerge on the key dynamics governing
the bycatch of vulnerable species in the Mediterranean and Black Sea. Seabird bycatch has mainly been recorded from the western Mediterranean and in longline fisheries. Bottom trawlers, on the other hand, have the greatest impact on sea turtles, especially
in the northern Adriatic Sea, Tunisia, Egypt and Turkey. The vessel groups most implicated
in elasmobranch bycatch vary by subregion, with longliners accounting for nearly 80 percent of incidental captures in the central Mediterranean, for example, while pelagic trawlers are responsible for an even greater majority of incidental captures in the neighbouring Adriatic Sea. Historically, marine mammals were often caught in large-mesh driftnets, but the incidental capture of these species has declined since bans on driftnets were put in place in the late 1990s. Unsurprisingly, macrobenthic invertebrates, including soft and hard corals, sponges, echinoderms and molluscs, are most affected by bottom trawls, as they are dragged across the seafloor these species inhabit.
Vulnerable species are not the only ones to come out the worse for wear from their interactions with fishing activities. Fishers also risk economic losses resulting from damage done to their nets by entrapped individuals or from the depredatory behaviour of species that feed on bait meant to lure target species. Raising awareness amongst fishers and relevant stakeholders of the threats currently facing vulnerable populations across the Mediterranean and the Black Sea, as well as their importance to local ecosystems, will help to improve relations between fisheries and these species and to ease transitions toward safer practices. New technologies that can mitigate
the bycatch of vulnerable species must continue to be tested and implemented in fisheries and standardized procedures for data collection should be established to better understand the many factors influencing bycatch in the region.
Over the past 3 years, the IATTC staff have worked together with CPCs to incrementally refine the data reporting requirements for large-scale tuna longline fishing vessels (LSTLFVs) to enable IATTC scientific staff to enhance the reporting of non-target species (i.e. “bycatch”) for the Ecosystem Considerations report and the Fishery Status Report. However, these improved data are also intended to be used to improve the quality of scientific research and assessments involving the fishery, in particular ecological risk assessment, and to improve the transparency of data for compliance under relevant IATTC Resolutions.
In 2017, the IATTC staff proposed the establishment of minimum data standards for longline observer programs under Resolution C-11-08 (SAC-08-07e). At the eighth meeting of the Scientific Advisory Committee, the proposal was adopted, and CPCs agreed to provide those data for 2013–2017, and for subsequent years. The measures were subsequently incorporated into Resolution C-19-08 that entered into force in July 2019.
There have been positive advances in longline data reporting over the past two years. The most notable improvement in data reporting has been the agreement by IATTC Members to submit operational-level observer data using an expanded set of data fields, which have been required of IATTC CPCs by the WCPFC since 2016 (WCPFC, 2016; Attachment F) when reporting observer data for sets made in the WCPO. Further data reporting improvements include the adoption of number of hooks as the metric by which longline fishing effort is to be measured in the EPO, as well as the use of a standardized reporting template that summarizes key elements of observer activities that is transparent in demonstrating compliance under Resolution C-19-08. In particular, this relates to the mandates of a minimum of 5% observer coverage of the total annual effort by each CPC’s fleet of longline vessels greater than 20 m length overall (LOA), and that the coverage is “…representative of the activities of its fleet, including in terms of gear
BYC-10 INF-D - Longline observer data - DRAFT 2
configuration, target species and fishing areas representing of the activities of the fleet”.
The current requirement of 5% observer coverage of the longline fleet has been a concern for IATTC research staff for several years given the results of studies conducted as far back as 1996 that recommended a minimum observer coverage of 20% for the Hawaii-based longline fleet (Skillman et al. 1996). Since this time, the recommended minimum coverage levels have been increased to be 40% and 80% to sufficiently monitor the catch rates for bycatch species that have a low incidence of capture in the American Samoa longline fishery (McCracken 2006) and the Hawaiian shallow-set longline fishery (McCracken 2012), respectively. Consequently, since 2017 the staff has annually recommended to the SAC that observer coverage for the longline fleet should be increased to 20% (IATTC-92-04c; p. 4), which has not been supported by the Members.
Considering growing evidence of the potential inadequacy of current observer coverage in the EPO, the objectives of this paper were to:
i) fulfil the recommendation by the SAC at its tenth meeting to provide a summary of the operational-level longline observer data for LSTLFVs >20m LOA received to date by the IATTC, and reporting of the percent observer coverage for 2020 as required under Resolution C-19-08 (see Annex A),
ii) determine whether the current requirement of 5% observer coverage of LSLFVs under Resolution C-19-08 is sufficient to characterize the activities of LSTLFVs in the EPO and facilitate the reliable estimation of total annual catches for bycatch species for inclusion in the IATTC’s annual Ecosystem Considerations report and Fishery Status Report.
This third edition of the State of Mediterranean and Black Sea Fisheries provides a comprehensive overview of the status of fisheries in the region, looking at their main features and trends, in order to better inform their management and better examine current and future challenges that they will face in the near future. The aim of this report is to produce a document that could provide useful analysis and direction for decision-making and future action. In this respect, this publication also represents a convenient source of information for the FAO Committee on Fisheries and offers a practical complement to the data provided in the State of World Fisheries and Aquaculture published by the FAO Fisheries and Aquaculture Department. This volume includes seven chapters divided into two sections: a first part on the status and trends of different aspects of Mediterranean and Black Sea fisheries, including fleet, catches, socio-economic variables and bycatch, and a second part that focuses on the management of Mediterranean and Black Sea fisheries, including an overview on small-scale fisheries. This report is based to a large extent on the most up-to-date data available submitted by GFCM contracting and cooperating non-contracting parties, including information on stock status, national catches, fleet and socio-economic information up to 2018. It is also complemented with information from other sources.
Tunas sustain important fisheries that face sustainability challenges worldwide, including the uncertainty inherent to natural systems. The Kobe process aims at harmonizing the scientific advice and management recommendations in tuna regional fisheries management organizations (RFMOs) toward supporting the sustainable exploitation of tunas globally. In this context, we review the similarities and differences among tuna RFMOs, focusing on stock assessment methodologies, use of information, characterization of uncertainty and communication of advice. Also, under the Kobe process, tuna RFMOs have committed to a path of adopting harvest strategies (HSs), also known as management procedures (MPs), which are the series of actions undertaken to monitor the stock, make management decisions, and implement the management measures. The adoption of HSs for tuna stocks is supported by Management Strategy Evaluation (MSE), which is considered the most appropriate way to assess the consequences of uncertainty for achieving fisheries management goals. Overall, notable progress has been made in achieving some of the Kobe objectives, but there are still some aspects that are inconsistent and need to be agreed upon, due to their management implications. First, not all RFMOs report on stock status based on maximum sustainable yield (MSY) as a reference. Instead, some use depletion level to represent the available fish biomass. Also, the definition of overexploited is not common in all oceans. Finally, very few stock assessments characterize all major sources of uncertainty inherent to fisheries. With regards to HSs, two different approaches are being followed: One is designed to adopt an automatic decision rule once the stock status and management quantities have been agreed upon (harvest control rules (HCRs), not strictly an HS) and the other aims at adopting all the components of HSs (data, use of information and decision rule).
Here, we outline actions taken by Tuna Regional Fisheries Management Organizations on the science of marine turtle’s conservation. The Inter-American Tropical Tuna Commission (1949), the International Commission for the Conservation of Atlantic Tunas (1966), the Indo-Pacific Tuna Program (prior to 1980) the Indian Ocean Tuna Commission(1993), and the Western and Central Pacific Fisheries Commission (2004), supported by their respective Scientific Committees, cover all oceans and main seas (including most sea turtle ranges), are responsible for data collection, monitoring and management of tuna and tuna-like resources, including associated bycatch of sea turtles. The scientists working with these organizations provide annual information on turtle bycatch, promoting several recent initiatives, including impact assessments. These efforts to protect turtles and reduce their bycatch are illustrated by the Bycatch Mitigation Information System, launched by the Western and Central Pacific Fisheries Commission and later expanded and supported by the FAO Common Oceans Tuna Project and the Bycatch Working Group meeting organized in December 2019 in Porto, Portugal, to rejuvenate the process of coordination between the organizations on bycatch issues.
Industrial and small-scale coastal (i.e., ‘artisanal’) pelagic fisheries in the eastern Pacific Ocean (EPO) interact with one of the most vulnerable fishery bycatch species, the East Pacific (EP) stock of leatherback turtle (Dermochelys coriacea). As a result of the species’ longevity, slow growth, low reproductive output, and critically low population size, it is currently classified as “Critically Endangered” by the IUCN. EPO tuna fisheries have been mandated since 2008 (Resolution C-07-03) to ensure, by all practical means, the safe handling and release of captured sea turtles. On 1 January 2021 a revised resolution on sea turtles (C-19-04) will enter into force that will subject EPO tuna fisheries to various measures designed to reduce the bycatch of sea turtles, in particular the use of circle hooks and finfish baits in shallow longline sets. The low encounter rates of sea turtles by fishing vessels make these “rare event” data difficult to analyze statistically using conventional approaches of assessing the status of sea turtle populations. Consequently, alternative means to assess vulnerability status and better understand the potential efficacy of different conservation and management measures (CMMs) for effective fisheries management. In response, the spatially-explicit ecological risk assessment (ERA) approach—Ecological Assessment for the Sustainable Impacts of Fisheries (EASI-Fish)—was developed by Inter-American Tropical Tuna Commission (IATTC) staff to quantify the vulnerability of bycatch species, such as the EP leatherback stock, to the cumulative impacts of multiple fisheries in the EPO and to simulate hypothetical CMMs scenarios that may mitigate fishery-imposed risks to the species. This paper describes a collaborative research project between the IATTC, the Inter-American Convention on the Protection and Conservation of Sea Turtles (IAC), and international sea turtle experts where EASI-Fish was used to explore the changes in the vulnerability status of the EP leatherback turtle stock under 39 different hypothetical CMM scenarios simulated for EPO industrial (purse-seine and longline) and artisanal (longline and gillnet) fisheries for 2018. CMMs involved decreasing post-capture mortality (PCM), implementing the use of circle hooks in longline fisheries, and various spatial and temporal closures adjacent to important nesting beaches of the EPO. The “status quo” scenario revealed a proxy for fishing mortality (F ̃_2018) and the spawning stock biomass per recruit (BSR2018) exceeded precautionary biological reference points (F80% and BSR80%), classifying the EP leatherback turtle stock as “most vulnerable”. Of the 39 scenarios, only 14 resulted in the species being classified as “least vulnerable”. Only one scenario involved a single CMM—that achieved an estimated PCM of 20% or less¬—changed the status the “least vulnerable”. This involved imposing an EPO closure period of at least 270 days per year for industrial fisheries; a measure that is unlikely to be feasible. The remaining effective CMMs involved using multiple strategies in concert, with the most effective being closure of coastal fishing grounds adjacent to nesting areas coupled with the use of circle hooks in all longline fisheries and exercising best handling and release practices in all fisheries. This modelling exercise provided an important first step towards assessing the potential effects of CMMs described in the recently approved IATTC Resolution C-19-04. The results of the EASI-Fish models can inform strategies to implement these CMMs within the IATTC Convention Area to reduce bycatch impacts on EP leatherbacks.
Bycatch and mortality in fishing gear poses a conservation threat worldwide to many marine species. Resource managers and conservation scientists face challenges in identifying bycatch mitigation solutions that work for multiple taxa while maintaining acceptable levels of target fish catch. The most successful mitigation measures to address bycatch concerns are those that (1) minimize bycatch with limited or no impact on target species catch, (2) have been proven through at-sea experimental research, (3) are practical, affordable, and easy to use, and (4) do not risk the safety of the fishing vessel crew or the bycaught animals. We conducted a review of mitigation measures in fishing gears that target tuna and tuna-like species and that either prevent capture of non-target species in fishing gear or facilitate alive post-capture release, and evaluated these against 4 defined criteria: effective, proven, practical, and safe. This paper outlines the most effective bycatch mitigation measures, as based upon the best scientific information available, in commercial and artisanal pelagic longline and purse seine fisheries, specifically those that target tuna and tuna-like species. This review includes information on gear and operational changes to fishing practices that reduce bycatch for protected and threatened species across taxonomic groups, with a focus on cetaceans, sea turtles, seabirds, sharks, and istiophorid billfishes. The information provided can guide future research and management efforts in Regional Fisheries Management Organizations that are specific to tuna fishing and that aim to minimize impacts to protected and threatened species while maintaining viable commercial fisheries.
Tuna Regional Fisheries Management Organizations (RFMOs) have been given an arduous mandate under the legal framework of the United Nations Fish Stocks Agreement. Member states with different interests and objectives are required to cooperate and collaborate on the conservation and management of tuna and tuna-like species, which includes the allocation of fishing opportunities. It is well understood that the main RFMO allocation disagreements are the inability to agree on a total allowable catch, the lack of willingness to accept new members, disagreement on who should bear the conservation burden, and non-compliance with national allocations owning to perceived inequities. Addressing these elements is crucial for any organization if it is to sustain its credibility stability and legitimacy. This paper identifies additional barriers facing an equitable allocation process at the Indian Ocean Tuna Commission (IOTC). These challenges are multi-faceted and include institutional, political, and scientific barriers in the ongoing allocation negotiations, and further inhibit effective negotiation and resolution adoption as a whole. After almost 10 years of negotiations, the process has progressed little, and without agreement on these barriers it will be a challenge to adopt a stable systematic allocation process.
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.
Decompression sickness (DCS) was first diagnosed in marine turtles in 2014. After capture in net fisheries, animals typically start showing clinical evidence of DCS hours after being hauled on-board, often dying if untreated. These turtles are normally immediately released without any understanding of subsequent clinical problems or outcome. The objectives of this study were to describe early occurrence and severity of gaseous embolism (GE) and DCS in marine turtles after incidental capture in trawl gear, and to provide estimates of on-board and post-release mortality. Twenty-eight marine turtles were examined on-board fishing vessels. All 20 turtles assessed by ultrasound and/or post-mortem examination developed GE, independent of season, depth and duration of trawl and ascent speed. Gas emboli were obvious by ultrasound within 15 minutes after surfacing and worsened over the course of 2 hours. Blood data were consistent with extreme lactic acidosis, reduced glomerular filtration, and stress. Twelve of 28 (43%) animals died on-board, and 3 of 15 (20%) active turtles released with satellite tags died within 6 days. This is the first empirically-based estimate of on-board and post-release mortality of bycaught marine turtles that has until now been unaccounted for in trawl fisheries not equipped with turtle excluder devices.
Priority setting approaches for widely distributed and long-lived species can be challenging. This is especially true for sea turtles, which are species of conservation concern. The aim of this study was to conduct a detailed analysis of threats to identify, quantify and prioritize the main impacts to the loggerhead (Caretta caretta) population in the South West Atlantic (SWA) region. A matrix of relative threats was constructed. Threats were identified and classified for 8 different life stages (nesting females, eggs, hatchlings, swim-frenzy transitional stage, juveniles neritic, juvenile oceanic, adult neritic, adult oceanic) and ecosystems inhabited by sea turtles (terrestrial, neritic and oceanic). Results indicated that fisheries bycatch represents a major threat for loggerheads in the SWA. The trawl fishery was identified as the main source of mortality for neritic juvenile and adult turtles, whereas juveniles in oceanic areas were mostly impacted by the surface longlines. In terrestrial environments, eggs and hatchlings are mainly affected by habitat alteration, and by native and exotic predators. Loggerheads have shown a positive nesting trend at their main nesting beaches in the SWA, probably due to long-term conservation efforts to reduce the mortality of the different life-stages within the terrestrial zone. However, the high mortality rates of juveniles and sub-adults documented at some known foraging grounds represent a reason for concern as this may affect the overall population trend in the future. In conclusion, this threat analysis provides a tool to review the goals of national action plans, prioritize actions, and optimize the allocation of management resources.
The goal of this study was to assess the consequences of single versus multiple paternity by identifying paternity of clutches per female to identify whether there were detectable costs or benefits. Multiple mating can occur when the benefits of mating outweigh the costs, but if costs and benefits are equal, no pattern is expected. Previous research on loggerhead sea turtle (Caretta caretta) populations found male‐biased breeding sex ratios and multiple mating by many females nesting in southwestern Florida. A sample of nesting loggerhead females who laid more than one nest over the course of the season and a subset of their hatchlings were examined from 36 clutches in 2016 on Sanibel Island, Florida. Males that fathered hatchlings in the first clutch sampled were identified in subsequent clutches. Interestingly, 75% of the females analyzed had mated singly. No male was represented in more than one female's clutches. The results suggest that females likely mate at the beginning of the season and use stored sperm for multiple clutches. Evidence for mating between laying events was limited. There was no consistent pattern across the subsequent multiple paternity clutches, suggesting benefits to loggerhead females likely equal their costs and subsequent mating is likely determined by female preference. The focus of this paper is to examine and describe the costs and benefits of multiple mating across taxa and then focus on a case study by examining repeating nesting of loggerhead sea turtles (Caretta caretta) nesting in the Gulf of Mexico. We identified in all nests, males that were present in the first nest were also present in subsequent nests (confirming sperm storage). We also found instances of possible sperm depletion and weak evidence for remating events, but no evidence of male genotypes in multiple female's nests (polygyny).
Overlap of small-scale fisheries with sea turtle high-use areas is of growing concern, but the extent to which these endangered species interact with fishing gear is rarely known. Structured face-to-face interviews with 22 longline vessel captains were used to make a rapid assessment of sea turtle bycatch by the artisanal longline fleet of Barbados in the eastern Caribbean. Extrapolated estimates suggested that an average of 284 sea turtles yr-1 were caught on 1896200 hooks, a bycatch per unit effort of 0.15. Based on extrapolation of the percentage of the observed vessels to the entire fleet, an estimated average of 374 sea turtles yr-1 are caught. The majority of captains (86%) reported leatherback turtles Dermochelys coriacea to be the predominant species. The Barbados longline fleet operates in sea areas through which leatherbacks pass on their way to and from important nesting beaches in Trinidad and Tobago, Grenada, and the Guianas, and in which they reside during the pre-nesting period as well as throughout the nesting season. Although most sea turtles caught as bycatch were released alive, they often remained hooked with trailing lines. The majority of captains expressed their willingness to be trained in safe-handling and release of hooked and entangled turtles, to increase the probability of their survival.
In fisheries, vulnerability assessments—also commonly known as ecological risk assessments (ERAs)—have been an increasingly popular alternative to stock assessments to evaluate the vulnerability of non-target species in resource- and data-limited settings. The widely-used productivity−susceptibility analysis (PSA) requires detailed species-specific biological information and fishery susceptibility for a large number of parameters to produce a relative vulnerability score. The two major disadvantages of PSA are that each species is assessed against an arbitrary reference point, and PSA cannot quantify cumulative impacts of multiple fisheries. This paper introduces an Ecological Assessment of the Sustainable Impacts of Fisheries (EASI-Fish), a flexible approach that quantifies the cumulative impacts of fisheries on data-limited bycatch species, demonstrated in eastern Pacific Ocean (EPO) tuna fisheries. The method first estimates fishing mortality (F ) based on the ‘volumetric overlap’ of each fishery with the distribution of each species. F is then used in length-structured per-recruit models to assess population vulnerability status using conventional biological reference points. Model results were validated by comparison with stock assessments for bigeye and yellowfin tunas in the EPO for 2016. Application of the model to 24 species of epipelagic and mesopelagic teleosts, sharks, rays, sea turtles and cetaceans and identification of the most vulnerable species is demonstrated. With increasing demands on fisheries to demonstrate ecological sustainability, EASI-Fish allows fishery managers to more confidently identify vulnerable species to which resources can be directed to either implement mitigation measures or collect further data for more formal stock assessment.
The WCPFC Bycatch Management Information System (BMIS) is an online resource for fisheries managers, scientists, fishers, educators and the public (see Figure 1). The database consolidates information on the mitigation and management of species of special interest, including seabirds, sharks and rays, marine turtles and marine mammals, incidentally caught in the pelagic tuna and billfish fisheries of the Western and Central Pacific Ocean (WCPO).
The Bycatch Data Exchange Protocol (BDEP) is a format standardised public domain regional bycatch data summary. The WCPFC BDEP tables now are updated annually and available at www.wcpfc.int/node/29966. This work has improved the quality of, and access to WCPFC bycatch data.
BMIS has been significantly expanded and redeveloped with funding from the FAO Common Oceans (Areas Beyond National Jurisdiction - ABNJ) Tuna Project over the period 2015-2019 (Clarke and Smith, 2019). This project has also funded development and improvements of the WCPFC BDEP tables. This paper provides an update on project tasks related to BMIS and BDEP in the final year of funding (to 31 August 2019). Further detail about the previous developments can be found in Fitzsimmons et al. (2015, 2017, and 2018), Williams et al. (2016 and 2017), and Williams (2018).
Sea turtles are vulnerable immediately after emerging from nests and before they reach the surf. Mortality rates during this brief period are largely unknown. Many sea turtle monitoring programs measure hatchling production from nest inventories. These inventories rarely account for post-emergence mortality, leaving an unknown bias in hatchling production estimates. This study addresses the nest-to-surf data gap for Florida’s east coast nesting assemblages of loggerhead sea turtles (Caretta caretta). Five locations were surveyed during the 2016-nesting season. Across all beaches, 7.6% of the observed hatchlings did not survive to reach the water. Mortality sources varied by location. Observed predators include: mammals, birds, and crabs. Hatchling disorientation and misorientation due to photopollution occurred more frequently in urban areas than natural areas. Factors identified as important in hatchling mortality included numbers of hatchlings emerging, nest-to-surf distance, and level of urbanization. The results of this study may help sea turtle nesting managers address nest-to-surf mortality and improve hatchling production estimates.
The Shrimp Trawl Observer Program, which is administered by NOAA Fisheries Southeast Fisheries Science Center (SEFSC) Galveston Laboratory, assigns observers to shrimp otter trawl vessels in both the Gulf of Mexico (GOM) and the waters off the U.S. east coast within the jurisdiction of the South Atlantic Fishery Management Council (SATL), and vessel participation has been mandatory since 2007. We applied integrated Bayesian models to the observer data to estimate sea turtle bycatch. We also estimated mortality, defined as the total number of sea turtles that were caught in shrimp trawls and died at the time
of capture. The total bycatch mortality was estimated by multiplying the probability of mortality for turtles caught in shrimp trawl nets by the total bycatch estimated from a linear model of catch per unit effort (CPUE) per strata (area, season, depth zone, time period) multiplied by the total effort in each stratum. For rare species, the bycatch rate was estimated by modeling CPUE of all species together, and multiplying this by the species composition to get species-specific CPUE. Total bycatch mortality was estimated separately for the GOM and the SATL, and for standard shrimp otter trawl nets versus “try”
nets, which are small nets fishers deploy in front of the primary nets to test catch rates. About 30% of sea turtles caught in standard nets were dead, while less than 1% of sea turtles caught in try nets were dead. Thus, although many Kemp’s ridley, loggerhead, and green sea turtles were caught in try nets in both regions, few of them were killed. For example, in the GOM in 2015, we estimated 95% credible intervals of 54-256 Kemp’s ridley, 173-495 loggerhead and 22-114 green sea turtles caught in try nets, but only 0-7 Kemp’s ridley, 0-17 loggerheads, and 0-3 green sea turtles were estimated to be killed. On the other hand,
for standard nets in the GOM, we estimated 95% credible intervals of 63-369 Kemp’s ridley, 18-105 loggerhead and 75-226 green sea turtles captured, corresponding to mortality of 19-130 Kemp’s ridley, 5-36 loggerhead and 22-81 green sea turtles killed. In addition, we found 95% credible intervals of 24-99 turtles classified as unknown/other species killed in standard nets in the GOM. The unknown category includes sea turtles that were not identified by the observers, as well as leatherback and hawksbill sea turtles, which could not be modeled separately because there were only 3 leatherbacks and 1 hawksbill recorded. Total bycatch mortality of Kemp’s ridley and loggerhead sea turtles in standard nets decreased from 2007 to 2015 in the GOM, but green sea turtle bycatch stayed constant. In the SATL, the sample
sizes were lower, fewer turtles were observed, and total effort was not as well estimated. Thus, total bycatch rates were estimated with wide credible intervals. There was no trend over time in the SATL from 2007 to 2016, and total mortality in standard nets in 2016 was on the order of 5-111 Kemp’s ridley turtles, 9-139 loggerhead turtles, 2-86 green sea turtles, and 13-168 of unknown/other species of turtles. These estimates of total bycatch mortality include only sea turtles that are dead at the time of capture; there may be additional mortality due to stress or injuries after live release.
Incidental capture of marine animals in fishing gear may cause immediate or delayed mortality due to injury. Increasing post-capture survival of these species is very important to reducing the widespread impacts of bycatch, particularly on protected and threatened populations. In this paper, we review recent literature on safe handling of sea turtles, cetaceans, seabirds, sharks, and billfish and summarize the most effective measures for improving survivability of these species after interactions with gillnet, pelagic longline, and purse seine gear. We also review the current tuna Regional Fishery Management Organization (tRFMO) measures on safe handling and release to identify gaps in implementation of safe handling practices. Strategies that increase post-capture survival of marine species can be grouped into 3 primary categories: reducing immediate mortality, minimizing injury that results in delayed mortality, and reducing stress that can lead to death. Routine training of fishermen on safe handling practices greatly improves the effectiveness of these measures. When bycatch does occur, the strategies to increase post-release survival become key for protecting vulnerable marine populations. This inventory highlights the great conservation value that can be provided by the tRFMOs by providing guidance and training on safe handling practices to increase post-release survival across taxa.
Bycatch in fisheries can have profound effects on the abundance of species with relatively low resilience to increased mortality, can alter the evolutionary characteristics and concomitant fitness of affected populations through heritable trait-based selective removals, and can alter ecosystem functions, structure and services through food web trophic links. We challenge current piecemeal bycatch management paradigms, which reduce the mortality of one taxon of conservation concern at the unintended expense of others. Bycatch mitigation measures may also reduce intraspecific genetic diversity. We drew examples of broadly prescribed ‘best practice’ methods to mitigate bycatch that result in unintended cross-taxa conflicts from pelagic longline, tuna purse seine, gillnet and trawl fisheries. We identified priority improvements in data quality and in understanding ecological effects of bycatch fishing mortality to support holistic ecological risk assessments of the effects of bycatch removals conducted through semi-quantitative and model-based approaches. A transition to integrated bycatch assessment and management that comprehensively consider biodiversity across its hierarchical manifestations is needed, where relative risks and conflicts from alternative bycatch management measures are evaluated and accounted for in fisheries decision-making processes. This would enable managers to select measures with intentional and acceptable tradeoffs to best meet objectives, when conflicts are unavoidable.
Overfishing impacts the three pillars of sustainability: social, ecological and economic. Tuna represent a significant part of the global seafood market with an annual value exceeding USD$42B and are vulnerable to overfishing. Our understanding of how social and economic drivers contribute to overexploitation is not well developed. We address this problem by integrating social, ecological and economic indicators to help predict changes in exploitation status, namely fishing mortality relative to the level that would support the maximum sustainable yield (F/FMSY). To do this we examined F/FMSY for 23 stocks exploited by more than 80 states across the world's oceans. Low-HDI countries were most at risk of overexploitation of the tuna stocks we examined and increases in economic and social development were not always associated with improved stock status. In the short-term frozen price was a dominant predictor of F/FMSY providing a positive link between the market dynamics and the quantity of fish landed. Given the dependence on seafood in low-income regions, improved measures to safeguard against fisheries overexploitation in the face of global change and uncertainty are needed.
This study summarizes nearly 20 years (1997-2015) of tracking strandings of sea turtles along the Andalusian coast. In this period 2495 specimens were recorded, most of them loggerhead turtles Caretta caretta (92.6%) and leatherback turtles Demochelys coriacea (7.1%). Two other species were almost insinificant, green turtle Chelonia mydas (0.2%) and Kemp’s ridley Lepidochelys kempi (0.1%). Significant part of the turtles were recorded in the Atlantic coast, although in this area the incidence of alive specimens was low. Spring and summer were the seasons with more specimens stranded, probably related to warmer and more productive waters. The size of the loggerhead turtles observed highlights an important presence of inmature specimens in Andalusian waters, although mature individuals were not rare. In the case of leatherback turtles, adult stage is the only detected in the specimens recorded.These results, combined with the fact that the Atlantic coast has a large continental shelf and a high primary productivity near the coast, suggesting that the gulf of Cádiz may represent a neritic habitat used by the sea turtles. In this case, new and more effective politics of conservation are needed in order to protect sea turtles in this area.
Bycatch remains one of the most significant fisheries issues in the world and its monitoring and reporting is now expected in many regions. This paper provides a global synthesis of the data that are available on one of the most controversial components of bycatch, that associated with the capture and discarding of endangered, threatened and protected (ETP) species in marine commercial and artisanal fisheries. We examine the available literature regarding estimates for the key taxa in this category of bycatch (seabirds, turtles, sea snakes, marine mammals, sharks, rays and teleosts) and use the data to try to provide a total global estimate. We estimate (albeit quite imprecisely) that at least 20 million individuals of such species are discarded annually throughout the world. However, there remain far too many gaps and uncertainties across fisheries and regions in the information to provide any robustness (or variance) around such an estimate, nor to determine the actual fates of these animals (many may survive). This is exacerbated because: (1) the occurrences of such species are often rare and controversial and so go either unnoticed and/or unrecorded; (2) different levels of protection are afforded to different ETP species in different countries and fisheries and; (3) discarding practices vary greatly across a hierarchy of spatio-temporal scales and according to individual fishing conditions and procedures—the latter affecting actual mortalities. Nevertheless, there have been major initiatives established in recent years to provide better data on such interactions in addition to novel fishing methods and practices that reduce them and also improve the survival of discarded individuals. This paper discusses the data currently available and the quite significant gaps that remain.
The available information regarding the 2 sea turtle species breeding in the Mediterranean (loggerhead turtle Caretta caretta and green turtle Chelonia mydas) is reviewed, including biometrics and morphology, identification of breeding and foraging areas, ecology and behaviour, abundance and trends, population structure and dynamics, anthropogenic threats and conservation measures. Although a large body of knowledge has been generated, research efforts have been inconsistently allocated across geographic areas, species and topics. Significant gaps still exist, ranging from the most fundamental aspects, such as the distribution of major nesting sites and the total number of clutches laid annually in the region, to more specific topics like age at maturity, survival rates and behavioural ecology, especially for certain areas (e.g. south-eastern Mediterranean). These gaps are particularly marked for the green turtle. The recent positive trends of nest counts at some nesting sites may be the result of the cessation of past exploitation and decades of conservation measures on land, both in the form of national regulations and of continued active protection of clutches. Therefore, the current status should be considered as dependent on such ongoing conservation efforts. Mitigation of incidental catch in fisheries, the main anthropogenic threat at sea, is still in its infancy. From the analysis of the present status a comprehensive list of re search and conservation priorities is proposed.
The presence of the Green Turtle, Chelonia mydas (Linnaeus, 1758) is very rare in Mediterranean French waters. There is no record before 1987. Thirteen records were reported from 1987 to 2014, eight during the five last years (five in 2014). This increase is mainly due to the recent development of survey network. Green Turtles are seen from June to September.
Mediterranean populations of loggerhead Caretta caretta and green sea turtles Chelonia mydas are subject to several anthropogenic threats, with documented mortality from incidental capture in fishing gear. However, how such mortalities actually affect the populations is uncertain without an estimate of population size. We derived a theoretical demographic structure for each species in the Mediterranean, assuming a stationary age distribution in a stable population with constant proportions of turtles in each life stage, using distributions of age-specific vital rates. We incorporated uncertainty into the main vital rate parameters to identify a likely order of magnitude of turtle abundance in different life stages. Through this approach, we aim to (1) provide a rough estimate of all population stage classes, particularly the juvenile classes that are most subject to fisheries interactions, (2) provide an estimate of reproductive life span, (3) identify and review the key demographic parameters, and (4) identify the priority gaps in our information in need of further investigation. The range of population abundance estimates from the models constructed with uncertainty (95% CI) was 0.81-3.38 million loggerheads and 0.26-2.21 million green turtles, Mediterranean-wide. When we calculated the potential biological removal for the segment of the population at risk of fisheries capture, our estimates were comparable to or lower than the estimated bycatch levels in fisheries. Although the model assumes a stable population and provides only a rough estimate of abundance, these results suggest that the current bycatch level should be regarded as unsustainable for Mediterranean turtle populations
Marine turtles spend the majority of their lives at sea; therefore understanding anthropogenic sources of mortality at sea is essential to assess population viability. This Ecological Risk Assessment assesses the risk to turtles from the impacts of tuna fishing in the ICCAT region. We used a Level 2 (semi-quantitative) assessment, within a Productivity-Susceptibility Analysis framework, at the Regional Management Unit (RMU) level; the assessment was hampered by significant data gaps and highly variable bycatch rate estimates. Bycatch rates were scaled to mean annual fishing effort, per RMU. ICCAT longline fishing poses the greater threat to turtles than purse seining. Loggerhead and leatherback turtles potentially encounter the most longline fishing effort (~300 million and >650 million hooks/yr, respectively). The east Atlantic olive ridley, the south Caribbean green turtle and SW Atlantic leatherback turtle RMUs were consistently among the most vulnerable from both gear types. Conversely, the west Atlantic olive ridely turtles showed lowest risk. Regions where turtles are at highest risk included S Caribbean and tropics (20°N-15°S, both gear types), and loggerhead turtles in the Mediterranean (longline only). RÉSUMÉ Les tortues marines passent la plupart de leurs vies en mer ; c'est pourquoi il est fondamental d'appréhender les sources anthropogéniques de la mortalité en mer afin d'évaluer la viabilité des populations. Cette évaluation des risques écologiques (ERA) évalue le risque pour les tortues provenant des impacts des pêcheries de thonidés dans la zone relevant de l'ICCAT. Nous avons utilisé une évaluation de niveau 2 (semi-quantitative), dans le cadre d'une analyse de productivité-susceptibilité (PSA), au niveau de l'unité de gestion régionale (RMU) ; l'évaluation a été entravée par des lacunes considérables dans les données et par les estimations des taux de prises accessoires fort variables. Les taux des prises accessoires ont été échelonnés à la moyenne de l'effort de pêche annuel, par RMU. La pêche à la palangre au sein de l'ICCAT constitue une plus grande menace pour les tortues que la pêche à la senne. Les tortues couannes et les tortues luth sont potentiellement confrontées à l'effort de pêche palangrier le plus grand (~300 millions et >650 millions hameçons/an, respectivement). La RMU de la tortue olivâtre de l'Atlantique Est, de la tortue verte du Sud des Caraïbes et de la tortue luth de l'Atlantique Sud-Ouest se trouvait de manière constante parmi les plus vulnérables avec les deux types d'engins. En revanche, la tortue olivâtre de l'Atlantique Ouest était exposée au risque le plus faible. Les régions où les tortues étaient les plus vulnérables incluaient le Sud des Caraïbes et les tropiques (20°N-15°S, deux types d'engins) et pour la tortue caouanne la Méditerranée (palangre seulement). 2226 RESUMEN Las tortugas marinas pasan la mayor parte de sus vidas en el mar, por tanto, comprender las fuentes antropogénicas de la mortalidad en el mar resulta esencial para evaluar la viabilidad de la población. Esta evaluación del riesgo ecológico evalúa el riesgo para las tortugas procedente del impacto de la pesca de túnidos en la región de ICCAT. Se utilizó una evaluación de nivel 2 (semi-cuantitativa), dentro de un marco de análisis de susceptibilidad-productividad a nivel de unidad de ordenación regional (RMU); la evaluación se vio obstaculizada por las importantes lagunas de datos y por las estimaciones muy variables de tasa de captura fortuita. Se escalaron las tasas de captura fortuita al esfuerzo pesquero medio anual, por RMU. La pesca de palangre de ICCAT supone una amenaza mayor para las tortugas que la pesca de cerco. La tortuga boba y la tortuga laúd son potencialmente las que tienen más encuentros con el esfuerzo pesquero de palangre (~300 millones y >650 millones de anzuelos/año, respectivamente). Las RMU de las tortugas golfinas del Atlántico este, las tortuga verdes del Caribe sur y la tortugas laúd del Atlántico suroccidental fueron de forma continua las más vulnerables para ambos tipos de arte. Por el contrario, las tortugas golfinas del Atlántico oeste presentaban el riesgo más bajo. Las zonas en las que hay más peligro para los tortugas son: el Caribe meridional y tropical (20°N-15°S, ambos tipos de arte), y para las tortugas laúd el Mediterráneo (solo palangre).
The Joint Tuna Regional Fisheries Management Organizations’ (RFMOs’) Bycatch Technical Working Group prioritized adopting minimum data fields and standardized collection protocols to enable interoperability of the tuna RFMOs’ observer-collected bycatch datasets. Standardizing data fields, data collection protocols and database formats enables meaningful comparisons between the RFMOs, facilitates the integration and pooling of datasets within and across regions necessary to support large spatial scale analyses, and allows training materials and courses for observers to be standardized within and across regions. Harmonizing longline observer data and improving the quality of data collection methods across the tuna RFMOs also promises to improve assessments of fishery effects on bycatch species including more robust stock assessments, identify factors that significantly explain catch and survival rates, and evaluate the performance of bycatch mitigation methods. A January 2015 meeting of experts on observer longline bycatch data identified a need for a systematic review of existing information collected by the tuna RFMOs’ longline observer programmes in order to identify priority gaps. The group recommended developing a comprehensive list of variables that could be collected through tuna RFMO human and electronic monitoring onboard observer programmes that have documented significant effects on catch and mortality rates of species of conservation concern that are susceptible to capture in pelagic longline fisheries to facilitate identifying gaps in priority fields collected by each of the tuna RFMOs’ longline observer programmes. A study to implement this recommendation was commissioned by the Western and Central Pacific Fisheries Commission with funding provided by the Areas Beyond National Jurisdiction (Common Oceans) Tuna Project. This report presents the results of this study. A total of 28 priority fields organized into four categories (vessel characteristics and equipment, gear characteristics and fishing methods, catch, and environmental parameters) were identified based on their importance for monitoring and managing catch and survival. For each prioritized variable, a review was presented of evidence of its significant effect on longline catch and survival rates and the mechanism for its significant effect. Existing data collection protocols by each of the five tuna RFMOs were summarized for each prioritized variable, however, it was recommended that these be verified by each tuna RFMO Secretariat. Alternative and recommended harmonized data collection protocols were described for each variable based on current practices by the five tuna RFMOs, practicality for collection in onboard observer programmes and expected data quality.
Interactions between small-scale fishery activities and sea turtles were investigated in coastal fishers' population of the South and Northeast Brazilian coast, Western Atlantic. Data were collected using semi-structured questionnaires (N=418). The presence of four sea turtle species was confirmed in the studied areas: Chelonia mydas, Caretta caretta, Eretmochelys imbricata and Dermochelys coriacea. Adults are commonly seen in the water, and nesting females and hatchlings on beaches, especially at the Northeast region. The presence of the three most easily distinguishable ontogenetic phases (hatchlings, juveniles and adults) confirms the importance of the estuaries and adjacent areas for sea turtles feeding, gathering, nesting, growing and resting grounds. Fishing was considered the most important threat to sea turtles (77%). Gillnets with small mesh sizes (<60 mm) more frequently interact with sea turtles (65%), and mortality was mostly related to gillnets with larger mesh sizes (>60 mm) (100%) (p<0.01). Although poaching is a cultural habit still practiced by many people, fishers did not openly assume it. In addition, most fishers (82%) (p<0.01) do not know that it is possible or how to recover sea turtles drowned in fishing gears. Conservation measures should be adopted by fishers to reduce sea turtle mortality such as monitoring soak gillnets more frequently, avoiding nets with larger mesh sizes and thicker threads, and an awareness campaign to provide recovery procedures for turtles drowning in fishing gears. This would be the basis of the design of desirable mitigation actions enhancing conservation efforts and benefiting marine diversity as a whole.
This publication is the third in a series on bycatch in global tuna fisheries. Dealing with longline fisheries, its scope is defined taxonomically to comprise only non-tuna and non-tuna-like species. The history of longline fishing illustrates the role of new technologies, the expansion of fishing grounds, and the operational characteristics of the fleets in shaping today’s fishery. More recently, management regulations, the price of oil, the cost of labour, and market demand have also exerted an influence. No more than 23 percent of the tuna in each ocean is longline-caught. However, there may be up to 7 500 tuna longliners globally with almost 60 percent of them less than 24 m in length. Available data suggest that elasmobranch catches have fallen 14 percent since their peak in 2003. In longline fisheries, shark catch rates may be determined by bait type, soak time, hook shape, leader length and material, depth at which the hook is fished, and whether special gear is deployed to target sharks. Vulnerability to hooking, and resilience to haulback and handling, vary by species, size, area and fleet operational practices. Tuna regional fisheries management organizations (t-RFMOs) assess the status of shark populations but data limitations often hinder firm conclusions. There is little information on the implementation or effectiveness of finning bans and no-retention measures. Mitigation measures have been tested but results vary. Six of the seven species of sea turtles are threatened with extinction, and while longline fisheries may have less impact than net-based fisheries, significant populationlevel impacts may be occurring in some regions. The greatest concern is associated with loggerhead–longline interactions in the Atlantic. Circle hooks and using finfish bait have proved effective mitigation techniques either by reducing hooking or hook swallowing. Other methods require further development. Interactions with pelagic longline fisheries kill 50 000–100 000 seabirds annually. Many of these species, particularly albatrosses, are threatened with extinction. Recent advances in tracking technologies have facilitated mapping of where interactions are most likely. The Western and Central Pacific contains more than 45 percent of the global total albatross and giant petrel breeding distributions. The most promising mitigation methods appear to be night setting, side-setting, line weighting and streamer lines, but further research is needed. All five t-RFMOs require use of one or more of these methods in areas that overlap albatross distributions. However, compliance data are limited and improved observer coverage is essential. Marine mammals’ interactions with longline fisheries are detrimental to the fishery but may be positive or negative for the mammals. Although it is often unclear which species are involved, pilot whale interactions in the western Atlantic and false killer whale interactions off Hawaii have triggered national mitigation plans. No t-RFMO has adopted management measures for marine mammal interactions. Research and testing of mitigation measures continue in order to ameliorate both marine mammal impacts and economic losses to industry from depredation. At least 650 species of other bony fishes may be caught in association with pelagic longline fisheries, e.g. dolphinfish, opah, oilfish, escolar and ocean sunfish. Some of these stocks are important as local food supplies. However, it is unclear whether these stocks or the ecosystem they help structure is at risk. More attention should focus on improving fishery statistics and initiating basic monitoring of these stocks’ status. The diversity of pelagic longline gear designs and fishing methods, the variety of habitats they are deployed in, the thousands of marine species they may interact with, v and the different mechanisms and behaviours that govern those interactions provide an array of topics to be addressed in any discussion of bycatch mitigation. Scientific and technical issues in mitigation including effects across taxa, effects of combinations of measures, economic and safety considerations, underlying biological mechanisms, handling and post-release mortality, and non-fishery impacts must all be addressed. In addition, it is also necessary to consider issues such as who takes the lead for ensuring mitigation is sufficient for the population as a whole, how to devise effective mitigation implementation strategies, and whether gear modification should be used in concert with more sweeping measures.
Significance
Loss of megafauna, termed trophic downgrading, has been found to affect biotic interactions, disturbance regimes, species invasions, and nutrient cycling. One recognized cause in air-breathing marine megafauna is incidental capture or bycatch by fisheries. Characterizing megafauna bycatch patterns across large ocean regions is limited by data availability but essential to direct conservation and management resources. We use empirical data to identify the global distribution and magnitude of seabird, marine mammal, and sea turtle bycatch in three widely used fishing gears. We identify taxa-specific hotspots and find evidence of cumulative impacts. This analysis provides an unprecedented global assessment of the distribution and magnitude of air-breathing megafauna bycatch, highlighting its cumulative nature and the urgent need to build on existing mitigation successes.
This report provides a review of our knowledge of the bycatches, defined as discarded dead, from the tropical tuna purse seine fisheries of the world. The major fishing grounds involved (eastern and western Pacific, eastern Atlantic, and western Indian Oceans) share the gear, the ways of fishing, and the structure of the pelagic communities. Because of that, the species taken in association with tuna schools tend to be the same in all regions. After describing the gear and fishing operations, it discusses the reasons why bycatches happen, and explores the options to mitigate them. The types of sets used to capture tunas and the detection methods used to locate the schools are a major factor to determine which are the catches and the bycatches. The main bycatches are tunas, sharks and rays, pelagic bony fishes, billfishes, and sea turtles. The total discards amount to one to five percent of the total tonnage captured, and tunas of the species targeted amount to over 90–95 percent of those bycatches. The silky shark is the most common shark species by far, followed by the oceanic whitetip sharks. Marlins and sailfishes are also taken but in reduced numbers. Olive ridley sea turtles are the most common turtle captured, but the majority of them are released alive and unharmed. Rainbow runners, mahi-mahis, wahoos and amberjack yellowtail are the major pelagic bony fishes taken with the tunas. They are being retained in increasing numbers for utilization. Besides discussing problems of estimation, the report presents most of the ideas proposed or in different stages of testing, to mitigate those bycatches, including ways to avoid the captures, or to release the individuals from the net or from the deck. Finally, the known or potential ecological impacts of the rapidly increasing fishery on fish aggregating devices (FADs) are reviewed, emphasizing some of the uncertainties that still prevail
Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact (CUI) on marine predators by combining electronic tracking data of eight protected predator species (n=685 individuals) in the California Current Ecosystem with data on 24 anthropogenic stressors. We show significant variation in CUI with some of the highest impacts within US National Marine Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied in planning the use of marine resources.
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, multigear 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 nonuniformly distributed, with significant data gaps around Africa, in the Indian Ocean, and Southeast Asia. We found that bycatch impact scores—which integrate information on bycatch rates, fishing effort, mortality rates, and body sizes (i.e., proxies for reproductive values) of turtles taken as bycatch—as well as mortality rates in particular, were significantly lower in longline fishing gear than in net and trawl fishing gears. Based on bycatch impact scores and RMU-specific population metrics, we identified the RMUs most and least threatened by bycatch globally, and found wide variation among species, regions, and gears within these classifications. The lack of regional or species-specific patterns in bycatch impacts across fishing gears suggests that gear types and RMUs in which bycatch has the highest impact depend on spatially-explicit overlaps of fisheries (e.g., gear characteristics, fishing practices, target species), marine turtle populations (e.g., conservation status, aggregation areas), and underlying habitat features (e.g., oceanographic conditions). Our study provides a blueprint both for prioritizing limited conservation resources toward managing fishing gears and practices with the highest population impacts on sea turtles and for enhancing data collection and reporting efforts.
The effectiveness of recovery plans for threatened and endangered species has been questioned in academic and political domains. A comprehensive assessment of species recovery plans concluded that quantification and prioritization of threats have received insufficient attention, which contributes to the failure of some plans. On the basis of this assessment, we developed and implemented a detailed analysis of threats in the Recovery Plan for the Northwest Atlantic Population of the Loggerhead Sea Turtle (Caretta caretta), produced by the National Marine Fisheries Service and US Fish and Wildlife Service. The analytical approach that we designed and summarize here provides an objective process for quantifying known threats and prioritizing recovery actions in terms of their relative impact on population growth rate (λ) of the loggerhead sea turtle. Although this process was developed for loggerhead sea turtles, it can be applied to other species.
Pakistan is an important gillnet coastal state with a well-known marine biodiversity. Around 709 tuna fishing vessels are operating in Pakistani waters. These boats have high of ETP/ CITES-listed bycatch species such as whale shark, mobulids and sea turtles. these bycatch animals protected by several national and international instruments and encouraged their safe releases to ensure the survivability of these protected species. the data of the crew-based observer programme help into the development of guidebook for safe handling and release of these bycatch species in tuna gillnet fisheries. This guidebook focuses on three main possible levels of entanglement of animals in fishing operations. It follows and guides the target group to follow the 'key' of different precautionary and handling and steps for every situation. The guidebook also encourages the user for the collection of the information and reporting of the entangled animal including the recording of the whole process of operation. This guidebook can be served and adopted by conservation institutes and organization as best practices of safe handling and release of bycatch animals in ghost nets/ gillnet fisheries.
The western Mediterranean Sea is an important fishing ground for the Spanish surface longline fleet targeting swordfish, bluefin tuna, and albacore. Spanish Mediterranean waters, including contiguous international waters, are important feeding areas for thousands of juvenile and sub-adult loggerhead turtles. Due to the spatial overlap in fishing grounds between different longline métiers and loggerhead distribution, in the early 2000s, an estimated minimum of 60,000 loggerhead sea turtles were caught as bycatch in Mediterranean longline fisheries, including all countries operating in the area. The Spanish surface longline fleet is continually introducing technological and strategic innovations to improve the economic benefits of the fishery. These innovations lead to high variability in fishing gear and operational strategies from year to year. During the study period, there was a change in the specific contribution of each métier to total effort. Thus, since 2000 to the present, the Spanish traditional home-base surface longline targeting swordfish has been gradually modified or in other cases replaced by other métiers, and in most vessels it has been replaced by a new deeper semipelagic longline targeting the same species; which has led to a dramatic decrease in sea turtle mortality. The main result of this study is that loggerhead turtle post-release mortality due to the bycatch by the Spanish surface fleets using different longline métiers has significantly decreased during the last 8 years of the study period. We estimate an average post-release mortality around 1800 loggerheads sea turtles per year. The observed decrease in turtle mortality was an indirect effect of the introduction of changes in technology and fishing strategies in the fleets in the attempt to improve their economic objectives.
The closest interaction of an organism with its environment is the ingestion of a subset of that environment and the subsequent alteration and absorption of that subset as it passes through the digestive tract of the organism. The absorbed nutrients fuel the productivity — both growth and reproduction — of the organism. The pivotal 200role that nutrition plays in the productivity of individuals and populations — and thus to the conservation of species — has often been overlooked.
Over the last several years, a great deal of emphasis has been given to the use of participatory research to enhance knowledge co-production between fisheries stakeholders, involving fishers in the sampling of their catches both for scientific and control purposes. Indeed, this approach could complement data collection through trawl surveys and onboard observers, which is usually expensive and thus, does not allow much spatio-temporal coverage. Within the EU participatory research project, GAP2, electronic logbooks were installed on board otter-trawlers to collect haul-by-haul geo-referenced catch data in the Adriatic Sea (NW Mediterranean Sea). Between September 2012 and December 2013, catches of some of the most important otter-trawl target species (8 species including teleosts, cephalopods, and crustaceans) were recorded in 3588 self-sampled hauls. Because a major concern for the use of these data is related to their quality, self-sampling was run concurrently with a scientific observers’ program, which allowed the detailed monitoring of catches from 249 hauls. The latter dataset was used to test the reliability of fishers’ self-sampled data and for their validation. In all species, no significant disagreement between the two datasets was observed. The full self-sampled dataset was thus used to describe the spatio-temporal changes in catches, as derived by observers’ data, allowing important insights into species’ life cycles. Results agreed with available literature information and fishers’ experience-based knowledge, which was thus embedded in the process of data validation and results interpretation. The collaboration between scientists and fishermen was demonstrated to be a valuable approach for generating reliable fisheries data, allowing a better understanding and quantitative descriptions of species’ life cycles and the attainment of a common base of knowledge for the enforcement of spatially explicit fisheries management.
ish water forms (e.g. Truchetn~x .scriptcc. Chr~xv~~~s picta, Mulacl~~r~~~~.s trrrupin, C'hel~~dru .wrpmtinu) as useful models. and extrapolate to marine species. Because of these constraints, generalizations about sea turtle biology need to be viewed with some reservation. The basic sea turtle life history strategy is. how- ever, similar in all species (Fig. I; see Miller, 1997 for review). Female turtles mate in near-shore waters. probably storing sperm for several weeks after a single mating. They lay eggs in nests dug on tropical, subtropical or warm-temperate beaches. Parental care beyond the energetic contribution to each egg is limited to choice of nesting site and stereotyped burial and smoothing of the nest area. Egg number per clutch is very high by reptilian standards (roughly 50-200 eggs. depending on species, subpopulation and individual; IUCN, 1982) and females of most species appear to lay several clutches per nesting season (16-7 in green turtles) at intervals of 9 -30 days, but usually do not breed every year. Eggs, much larger as well as more nu- merous than most freshwater species, incubate for about 2 months. They hatch at any time of the day or night, but usually emerge from the nest at night, the hatchling turtles crawling down the beach and swimming rapidly and continuously ("swimming frenzy") out to sea. Much of their subsequent life is still enigmatic, though Atlantic loggerhead turtles spend several years (perhaps as many as IO 12) drifting with oceanic currents (Caldwell, 1968: Carr and Meylan, 1980; Stoneburner et d.. 1982; see also Musick and Limpus, 1997 for review) before