Impact Of Bycatch Research Articles

Blue shark vertical movement patterns in the Central Mediterranean: bycatch mitigation windows revealed from pop-up satellite archival tag data

In the Mediterranean Sea, pelagic longline fisheries, targeting tuna and swordfish, have contributed significantly to the bycatch of threatened chondrichthyan species, such as blue shark (Prionace glauca). The Mediterranean blue shark population is assessed as critically endangered, making a timely implementation of mitigation measures crucial. A comprehensive understanding of blue shark habitat use dynamics is essential for deriving appropriate mitigation measures. This study aimed at evaluating vertical movement behaviour and investigating factors potentially influencing the movements of blue sharks in the Mediterranean Sea. Twenty-six blue sharks, bycaught in a longline fishery in the southern Adriatic, were tagged with pop-up satellite archival tags. Analysis of data from thirteen recovered tags revealed a distinctive diel movement pattern. Blue sharks used shallower waters during the night and deeper waters during the day, characterised by steep ascents and descents during sunset and sunrise, respectively. In addition, lunar phases were also influencing the depth of blue shark movements, with sharks using deeper waters right before and during full-moon. Shark size, salinity, currents, spatial location and time of the year were additional factors influencing blue shark depth use. The observed tendency of blue sharks to use deeper areas at daytime and prior and during the full moon period offers possibilities to develop and test bycatch mitigation strategies. Aligning longline fishing schedules and fishing depths with blue shark behaviour during the fishing seasons could hold promise to effectively reduce spatio-temporal overlap between fishing and blue shark distribution and may ultimately decrease the bycatch impact of the fishery.

Sea turtle bycatch in Argentina: A qualitative assessment in commercial vessels

Abstract1. The Northern Argentine continental shelf is a sea turtle feeding ground that overlaps with important fisheries. Few studies assessed bycatch impact, especially on commercial vessels. 2. This work documents sea turtles' bycatch, fishery involved, species captured and crew actions. 3. Bycatch in four fisheries were registered at the 107 interviews to fishers conducted between 2021 and 2023, showing the urgency to research bottom trawling for demersal multi‐species. Fishers frequently recognize Caretta caretta, and positive and negative practices towards animals have been documented on‐board. 4. These results will help focus researches on fisheries with the greatest impact on sea turtles in the region. They also underscore the necessity for implementing commercial vessel monitoring programmes and improving on‐board handling practices.

Nowhere to hide: Sea turtle bycatch in Northwest Africa

Abstract Fisheries bycatch is considered the largest threat to sea turtle populations globally. However, it has been challenging to assess the impact of bycatch on sea turtles in some regions such as Northwest Africa (i.e. Cabo Verde, Guinea, Guinea–Bissau, Mauritania, Senegal, Sierra Leone and The Gambia) owing to large data gaps. This hampers effective management actions and interferes with conservation efforts in the region. Five sea turtle species occur in Northwest Africa (i.e. green turtle Chelonia mydas, hawksbill Eretmochelys imbricata, leatherback Dermochelys coriacea, loggerhead Caretta caretta and olive ridley Lepidochelys olivacea). The region has regionally and globally important sea turtle nesting and foraging habitats and is a global fishing hotspot, with high and increasing fishing pressure. Available information on sea turtle bycatch in Northwest Africa was compiled from peer‐reviewed and grey literature from 2010 onwards to determine the impact of artisanal and industrial fisheries (by gear type) on regional sea turtle populations and assess the level of threat to individual species. All sea turtle species occurring in the region are impacted by bycatch. Reports suggest that green turtles and loggerheads have the highest bycatch rates, probably owing to their regional abundance and widespread distribution. Some of the potentially highest reported global bycatch rates (14,000–90,000 turtles/year/country) are noted, particularly in gillnets, longlines and handlines. However, further research is needed to understand mortality levels from artisanal fisheries and assess the impact of trawl fisheries operating in the region. Additional sources of mortality include deliberate capture for consumption or trade. To strengthen regional sea turtle conservation and reduce sea turtle bycatch and mortality, urgent action is needed to implement and enforce national protection, establish a bycatch reduction framework (including gear modifications and spatio‐temporal closures), improve fisheries data collection and build capacity.

Fishermen Interviews: A Cost-Effective Tool for Evaluating the Impact of Fisheries on Vulnerable Sea Turtles in Tunisia and Identifying Levers of Mitigation.

Fisheries bycatch is considered one of the main threats to sea turtles. To provide an updated assessment of the bycatch impact on loggerhead turtles in Tunisia, 483 interviews were conducted with fishermen in 19 ports along the Gulfs of Gabes and Hammamet. The interview questions included data on vessel and fishing gear characteristics, monthly fishing effort, and monthly sea turtle bycatch of the last year. Results revealed that sea turtle bycatch per unit effort (BPUE) was the highest for ray nets (0.73 turtles/vessel/day, 95% CI [0.02-1.15]), followed by pelagic longlines (0.6 turtles/vessel/day, 95% CI [0-4.23]) and shark nets (0.4 turtles/vessel/day, 95% CI [0-2.12]). However, due to the trawlers' high fishing effort, the cumulative impact of the trawl nets was the highest with an estimated number of 11,740 (95% CI [0-41,525.75]) turtles caught per year in Tunisia. Factors influencing the bycatch risk were gear characteristics (mesh size for nets, hook size for longlines, vertical opening for trawls), as well as season and location of operations. These factors will guide the research of mitigation solutions. The interviews with fishermen proved to be a cost-effective approach for the rapid assessment of sea turtle interactions with fisheries in the context of Tunisia.

Bycatch of Amboina Box Turtle (<i>Cuora amboinensis</i>) by Fishermen in Rawa Aopa, Southeast Sulawesi

Rawa Aopa is a permanent swamp ecosystem that serves as one of the suitable habitats for amboina box turtles (Cuora amboinensis). Some of the area is part of a national park (Rawa Aopa Watumohai National Park) and is designated as a traditional zone for fishing activities, where local fishermen sometimes reported accidental catch C. amboinensis in their fishing gear. The aims of this study were to record the existence of C. amboinensis bycatch, size and age structure of bycatch, characteristic of fishing activity, and to discuss the conservation implication of bycatch. The number of bycatch was recorded by direct observation of 7 selected fishermen in 14 days. The C. amboinensis caught accidentally were measured and weighed. A total of 38 individuals of C. amboinensis were accidentally caught by fishermen during the study, having a size ranged of 7.4 to 18.5 cm (juveniles, young adults, and old adults; no hatchling), and weighed 248 to 996 g. Based on sex, there was no significant difference between morphological size of male and female, although bycatch for females (59%) tend to be slightly higher than males (41%). Most of fishermen lives in Pewutaa Village and used bubu traps to catch fishes. C. amboinensis are the most common bycatch compared to other species. In order to minimize the impact of bycatch of the C. amboinensis by fishermen, we need to ensure that the turtle that accidentally trapped in the fishermen’s fishing gear would be released unharmedly to their habitat.

A stochastic model for estimating sustainable limits to wildlife mortality in a changing world.

Human‐caused mortality of wildlife is a pervasive threat to biodiversity. Assessing the population‐level impact of fisheries bycatch and other human‐caused mortality of wildlife has typically relied upon deterministic methods. However, population declines are often accelerated by stochastic factors that are not accounted for in such conventional methods. Building on the widely applied potential biological removal (PBR) equation, we devised a new population modeling approach for estimating sustainable limits to human‐caused mortality and applied it in a case study of bottlenose dolphins affected by capture in an Australian demersal otter trawl fishery. Our approach, termed sustainable anthropogenic mortality in stochastic environments (SAMSE), incorporates environmental and demographic stochasticity, including the dependency of offspring on their mothers. The SAMSE limit is the maximum number of individuals that can be removed without causing negative stochastic population growth. We calculated a PBR of 16.2 dolphins per year based on the best abundance estimate available. In contrast, the SAMSE model indicated that only 2.3–8.0 dolphins could be removed annually without causing a population decline in a stochastic environment. These results suggest that reported bycatch rates are unsustainable in the long term, unless reproductive rates are consistently higher than average. The difference between the deterministic PBR calculation and the SAMSE limits showed that deterministic approaches may underestimate the true impact of human‐caused mortality of wildlife. This highlights the importance of integrating stochasticity when evaluating the impact of bycatch or other human‐caused mortality on wildlife, such as hunting, lethal control measures, and wind turbine collisions. Although population viability analysis (PVA) has been used to evaluate the impact of human‐caused mortality, SAMSE represents a novel PVA framework that incorporates stochasticity for estimating acceptable levels of human‐caused mortality. It offers a broadly applicable, stochastic addition to the demographic toolbox to evaluate the impact of human‐caused mortality on wildlife.

Voluntary fishing logbooks are essential for unveiling unsustainable bycatch levels and appropriate mitigating measures: The case of sea turtles in the Gulf of Manfredonia, Adriatic Sea

Abstract Studying the impact of bycatch on marine megafauna, including sea turtles, is challenging for a variety of technical and biological reasons. The Mediterranean Sea has among the highest levels of turtle bycatch globally, notably of the loggerhead sea turtle (Caretta caretta), and bottom trawling represents a particularly relevant threat. Bottom trawlers from a recently discovered neritic foraging area, the Gulf of Manfredonia, reported 1,152 loggerhead turtles incidentally caught in the period 2015–2020. Capture locations were available for 497 turtles. These data were complemented by the distribution of fishing effort obtained by the vessel monitoring system. High bycatch rates were observed, leading to more than an estimated 5,600 annual captures and to the death of a minimum of 560 large individuals with high reproductive value. These findings are extremely concerning for the affected population and require immediate action. A strong seasonality of turtle bycatch was observed, with most captures occurring in November–March when fishing effort occurs in shallow waters where turtles concentrate all year round. Therefore, a seasonal approach (e.g. adopting measures only in the high‐turtle bycatch season) can be pursued as long as the spatial distribution of fishing effort varies among seasons. However, such a spatio‐temporal pattern should be monitored; then, in the case of change, although more difficult to implement, an area‐based conservation approach should be pursued. Several recommendations are provided, including the urgent implementation of turtle excluder devices, at least on a seasonal basis. This case shows that identifying the best conservation approaches requires information on the actual spatio‐temporal pattern of turtle occurrence and bycatch. Such information can only be derived from spatial distribution of bycatch and fishing effort obtained through a voluntary collaboration of fishers.

Bycatch in the West Greenland lumpfish fishery, with particular focus on the common eider population

Incidental bycatch is a well-known challenge in gillnet fisheries throughout the world, and the fishery for North Atlantic lumpfish Cyclopterus lumpus roe is no exception. In Greenland, the fishery was Marine Stewardship Council-certified in 2015 but has pending conditions related to bycatch quantification, enforcement and mitigation strategies. To improve this situation and to assess the potential impact of bycatch, we collected independent on-board observer data on non-target fish and seabirds over 2 seasons (2019 and 2021). We recorded 6 fish species, but the only species constituting >1% of the lumpfish landings was the spotted wolffish Anarhichas minor. The bycatch of fish likely had little impact on the involved fish stocks. We recorded 4 seabird species, of which common eider Somateria mollissima was most common. When extrapolated to the entire West Greenland lumpfish fishery, the estimated bycatch of common eider was considerably higher in 2019 (19938; 95% CI: 3486-59661) than in 2021 (9802: 1260-29940) due to a longer fishing season in 2019. On average, for 2019 and 2021, the bycatch was modelled to reduce the growth potential for the West Greenland winter population by 51%. In comparison, the current hunting level (16538 birds yr-1) reduced the growth potential by 30%. The larger impact of bycatch was mainly due to a larger proportion of adults and females being targeted. The common eider bycatch impacts mainly the breeding population in Canada and Southwest Greenland and less so in Northwest Greenland. As mitigation, we recommend temporal closures of the fishery unless modified gillnets, which markedly reduce bycatch, become available.

Long-Term Demographic and Spatio-Temporal Trends of Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) Bycatch in Bather Protection Nets off KwaZulu-Natal, South Africa

Bather protection nets have been in place off the coast of KwaZulu-Natal (KZN), South Africa, since the 1950’s. Besides sharks, they also catch a number of other marine vertebrates, including dolphins, the majority of which are Indo-Pacific bottlenose dolphinsTursiops aduncus. Previous analyses of dolphin bycatch in the nets indicated the potential impacts on the local populations, but a lack of information on population structure has to-date hindered a more detailed assessment. A recent re-assessment of the status and population delineations ofT. aduncusoff South Africa prompted a re-examination of demographic, spatial, and temporal patterns of its catches in bather protection nets over a 36-year period (January 1980 to December 2015). In total, 1169 dolphins were caught, including a slightly greater number of females and juveniles than other sex-classes, raising concern about the potential long-term effects on population demographics. More dolphins were caught off the North than the South coast. Temporal trends indicate that the bycatch during June and July every year (peak Sardine Run period) as a percentage of overall dolphin bycatch has been steadily decreasing from 39.8% in 1980 to 13% in 2015. A large inter-annual fluctuation can be seen, probably as a result of the inter-annual intensity of the Sardine Run. Although our results do not indicate a long-term decline of the individual populations as previously predicted, revised abundance estimates and data on the demographics and movement patterns of the animals are urgently required to accurately assess the impact of bycatch on the Indo-Pacific bottlenose dolphin populations off KZN and to advise conservation and management decisions going forward.

Bycatch in local fishery disrupts natural reestablishment of Eurasian otter in western Norway

AbstractLack of proper estimates of nonreported bycatch has made it difficult to evaluate the actual impact of bycatch in many local fisheries. For the Eurasian otter (Lutra lutra), there are no published estimates on the extent to which bycatch is unreported, despite nonreporting being a well‐known issue. Through public outreach efforts in local news and media we collected information from citizen scientists on nonreported otter mortalities of a small‐scale fishery in western Norway along the recent natural expansion front of otters. We compared this to deaths that were properly registered by local authorities. In total, cause of mortality was determined from 218 otters between 2003 and 2018. We found that the chances of a mortality being properly reported varied between type of death. Drowning in fyke and gillnets were the most common cause of mortality, and at least 61 and 69% of these deaths were never reported, respectively. The high level of bycatch occurring in the otters' current region of expansion is likely to have demographic impacts and hinder otter reestablishment in the area. Banning the use of fyke nets and setting a minimum fishing depth for gillnets would enhance otter recovery and simultaneously alleviate bycatch of other nontarget species in the region, while having little economic impact on a fishery which is mostly noncommercial. The case of the otter is a classic example of lack of communication between government agencies which have so far failed to establish platforms where issues like this can be discussed and solved by adequate law implementation.

Evaluating elicited judgments of turtle captures for data‐limited fisheries management

AbstractWe compare judgments of green turtle (Chelonia mydas) captures elicited from local gillnet skippers and not‐for‐profit conservation organization employees operating in a small‐scale fishery in Peru, to capture rates calculated from a voluntary at‐sea observer program operating out of the same fishery. To reduce cognitive biases and more accurately quantify uncertainty in our experts’ judgments, we followed the IDEA (“Investigate,” “Discuss,” “Estimate,” and “Aggregate”) structured elicitation protocol. The elicited mean monthly estimates of green turtle gillnet captures within summer and winter fishing seasons were higher than the equivalent green turtle capture rates calculated from the fisheries observer data; however, no statistically significant differences were identified when comparing the means of the datasets using bootstrap hypothesis tests (winter observed difference‐in‐means: 83.15, adj mean ± SD = 42.39 ± 32.59; summer observed difference‐in‐means: 68.58, adj mean ± SD = 54.06 ± 41.22). We investigated respondent performance in relation to the observer data capture rates. The not‐for‐profit employees scored high on accuracy and calibration performance metrics. The gillnet skippers’ judgments ranked higher on informativeness yet lower on accuracy and calibration, potentially reflective of overconfident judgments. This research presents a new context for using the IDEA protocol, which may prove helpful for rapid, exploratory evaluations of capture and bycatch impact in data‐limited small‐scale fishery management scenarios.

Implementation of Precautionary Principleon Bycatch Management in Indonesian Policy

Food and Agriculture Organization estimates that around 7 million tons of bycatch discard by the sea. FAO Code of Conduct for Responsible Fisheries require to suppress the number of bycatch and environmental impact from their fishing methods. The precautionary principle proposed as guides in environmental decision making. This research aimed to analysedthe precautionary principle to implement for fisheries especially for bycatch management. The research method used is normative juridical research, that is documenting the by catch impact and analyzed suitable with the existing regulations, combined with the legal event occurs and interview with the relevant officials to complete the existing document. The results showed that precautionary principle needed as one of procedures to prevention which should be done before the fishermen fishing. Precautionary principle with four element are taking preventive action in the face of uncertainty; shifting the burden of proof to the proponents of an activity; exploring a wide range of alternatives to possibly harmful actions; and increasing public participation in decision making. The procedure of precaution to keep the environment conserved and with efficient cost should be headed. Keywords : Precautionary principle, bycatch, efficient cost, national policy.. DOI : 10.7176/JLPG/93-06 Publication date: January 31 st 2020

Additive effects of climate and fisheries drive ongoing declines in multiple albatross species

Environmental and anthropogenic factors often drive population declines in top predators, but how their influences may combine remains unclear. Albatrosses are particularly threatened. They breed in fast-changing environments, and their extensive foraging ranges expose them to incidental mortality (bycatch) in multiple fisheries. The albatross community at South Georgia includes globally important populations of three species that have declined by 40-60% over the last 35 years. We used three steps to deeply understand the drivers of such dramatic changes: (i) describe fundamental demographic rates using multievent models, (ii) determine demographic drivers of population growth using matrix models, and (iii) identify environmental and anthropogenic drivers using ANOVAs. Each species was affected by different processes and threats in their foraging areas during the breeding and nonbreeding seasons. There was evidence for two kinds of combined environmental and anthropogenic effects. The first was sequential; in wandering and black-browed albatrosses, high levels of bycatch have reduced juvenile and adult survival, then increased temperature, reduced sea-ice cover, and stronger winds are affecting the population recovery potential. The second was additive; in gray-headed albatrosses, not only did bycatch impact adult survival but also this impact was exacerbated by lower food availability in years following El Niño events. This emphasizes the need for much improved implementation of mitigation measures in fisheries and better enforcement of compliance. We hope our results not only help focus future management actions for these populations but also demonstrate the power of the modelling approach for assessing impacts of environmental and anthropogenic drivers in wild animal populations.

Preliminary estimates of the abundance and fidelity of dolphins associating with a demersal trawl fishery

The incidental capture of wildlife in fishing gear presents a global conservation challenge. As a baseline to inform assessments of the impact of bycatch on bottlenose dolphins (Tursiops truncatus) interacting with an Australian trawl fishery, we conducted an aerial survey to estimate dolphin abundance across the fishery. Concurrently, we carried out boat-based dolphin photo-identification to assess short-term fidelity to foraging around trawlers, and used photographic and genetic data to infer longer-term fidelity to the fishery. We estimated abundance at ≈ 2,300 dolphins (95% CI = 1,247–4,214) over the ≈ 25,880-km2 fishery. Mark-recapture estimates yielded 226 (SE = 38.5) dolphins associating with one trawler and some individuals photographed up to seven times over 12 capture periods. Moreover, photographic and genetic re-sampling over three years confirmed that some individuals show long-term fidelity to trawler-associated foraging. Our study presents the first abundance estimate for any Australian pelagic dolphin community and documents individuals associating with trawlers over days, months and years. Without trend data or correction factors for dolphin availability, the impact of bycatch on this dolphin population’s conservation status remains unknown. These results should be taken into account by management agencies assessing the impact of fisheries-related mortality on this protected species.

Caught in the Same Net? Small-Scale Fishermen's Perceptions of Fisheries Interactions with Sea Turtles and Other Protected Species

Small-scale fisheries are responsible for high numbers of animals caught as bycatch, such as turtles, cetaceans and seals. Bycatch and its associated mortality is a major conservation challenge for these species and is considered undesirable by fishermen. To gain insights on the impact of bycatch on small-scale fishermen and put it in context with other financial and environmental challenges they face, we conducted questionnaire-based interviews on fishermen working on Crete, Greece. We investigated fishermen’s perceptions of sea turtle and other protected species interactions, and the impacts of such interactions on their profession and livelihoods. Our results indicate a connection between declining fish stocks, related increased fishing effort, and reported increased frequency of interactions between fishermen and sea turtles. Respondents believed that their livelihoods were endangered by industrial fishing and environmental problems, but thought that combined interactions with turtles and other marine megafauna species were a larger problem. Responses suggested that extending compensation to fishermen may be a good conservation intervention. Small-scale fishermen hold a wealth of knowledge about the marine environment and its resources. This may be of help to researchers and policy makers as it could be used to achieve a better managed, sustainable fishery. Including small-scale fishermen in the process of developing regulations will both enhance those regulations and increase compliance with them.

Varying demographic impacts of different fisheries on three Mediterranean seabird species.

Fisheries have an enormous economic importance, but reconciling their socio-economic features with the conservation and sustainability of marine ecosystems presents major challenges. Bycatch mortality from fisheries is clearly among the most serious global threats for marine ecosystems, affecting a wide range of top predators. Recent estimates report ca. 200,000 seabirds killed annually by bycatch in European waters. However, there is an urgent need to rigorously estimate actual mortality rates and quantify effects of bycatch on populations. The Mediterranean Sea is one of the most impacted regions. Here, we estimate for the first time both bycatch mortality rates and their population-level effects on three endemic and vulnerable Mediterranean taxa: Scopoli's shearwater, Mediterranean shag, and Audouin's gull, that die in different types of fishing gears: longlines, gillnets andsport trolling, respectively. We use multi-event capture-recapture modelling to estimate crucial demographic parameters, including the probabilities of dying in different fishing gears. We then build stochastic demography models to forecast the viability of the populations under different management scenarios. Longline bycatch was particularly severe for adults of Scopoli's shearwaters and Audouin's gulls (ca. 28% and 23% of total mortality, respectively) and also for immature gulls (ca. 90% of mortality). Gillnets had a lower impact, but were still responsible for ca. 9% of juvenile mortality on shags, whereas sport trolling only slightly influenced total mortality in gulls. Bycatch mortality has high population-level impacts in all three species, with shearwaters having the highest extinction risk under current mortality rates. Different life-history traits and compensatory demographic mechanisms between the three species are probably influencing the different bycatch impact: for shearwaters, urgent conservation actions are required to ensure the viability of their populations. Results will be very useful for guiding future seabird conservation policies and moving towards an ecosystem-based approach to sustainable fisheries management.

Seasonal residency of loggerhead turtles Caretta caretta tracked from the Gulf of Manfredonia, south Adriatic

A detailed knowledge of sea turtle distribution in relation to anthropogenic threats is key to inform conservation measures. We satellite tracked five loggerhead turtles incidentally caught in the Gulf of Manfredonia, where a high turtle occurrence and high bycatch levels have been recently reported. Turtles were tracked for a period ranging from 27 to 367 days, with a minimum travel distance ranging from 151 to 4,300 km. With the caution due to the small sample size, results suggest that: (i) the area may host residential loggerhead turtles at least in summer, while they probably move elsewhere in winter due to the low temperatures occurring in shallow waters, (ii) turtles may have very small home ranges in the area, (iii) turtle occurrence may be higher in shallow waters along the coast. Moreover (iv) one turtle showed remarkable fidelity to the same spot after seasonal migration and constant migration paths. If confirmed and further detailed, such movement patterns may guide effective conservation strategies to reduce the impact of bycatch in the area.

Ictiofauna acompanhante da pesca de arrasto para embarcações acima de 45 hp no litoral do Paraná, Brasil

A pesca de arrasto de camarões é considerada muito impactante aos sistemas bentônicos por ser pouco seletiva. O objetivo do presente trabalho foi caracterizar a ictiofauna acompanhante da pesca de arrasto das embarcações com potência acima de 45 HP. Foram realizadas amostragens mensais, entre agosto de 2000 e julho de 2001 para barco e agosto de 2004 e julho de 2005 para bote no litoral do Paraná. Foram capturados, com barco e bote, 45.277 e 57.387 peixes, respectivamente. Com ambas embarcações foram capturaram 99 táxons. A famí­­lia Sciaenidae foi a mais representativa em número de espécies e indiví­­duos. Houve diferenças na ictiofauna entre as estações do ano e entre as áreas ao sul e ao norte da desembocadura do Complexo Estuarino de Paranaguá tanto para barco como para bote. As diferentes frotas atuam sobre o mesmo recurso, mas incidem de maneira distinta com relação í­Â riqueza de espécies e abundí­¢ncia ictiofauna acompanhante e medidas de gestão, como a implementação de dispositivos de redução da captura acidental, devem levar em consideração as caracterí­­sticas não somente da embarcação mas também do petrecho de pesca utilizado.

Assessing sea turtle bycatch in Northeast Brazil through an ethnozoological approach

Bycatch in artisanal fisheries poses a significant threat to sea turtles populations globally, evidencing need for studies aimed at analyzing the impact of bycatch of sea turtles and their conservation. Considering the decentralized nature of artisanal fisheries, limited infrastructure for research and monitoring, collecting data on bycatch through interviews is recognized as an alternative method for estimating the magnitude of bycatch in artisanal fisheries. Using an ethnozoological approach, this work aimed to obtain data on the bycatch of sea turtles along the coast of the state of Paraíba (Northeast Brazil). The study focused on the following hypotheses: 1) the bycatch of sea turtles on the Paraíba coast is associated with different fishing techniques, and gillnets have the most impact on the animals; and 2) large-mesh gillnets that have higher bycatch than small-mesh gillnets. The results revealed that bycatch caused by gillnets was significantly greater in comparison with other fishing gear. Gillnets with a mesh size of more than 50 mm caused more bycatch of sea turtles than one with a smaller mesh size. Recommendations to reduce bycatch and mortality of sea turtles are proposed.

Potential bycatch impact on distinct sea turtle populations is dependent on fishing ground rather than gear type in the Mediterranean Sea

Bycatch is one of the main threats affecting marine megafauna worldwide, not only because of its prevalence, but also because the impact of high levels of bycatch in small oceanic regions may spread over whole oceans due to the complex dispersal patterns of bycaught species. Here, we use intrinsic and genetic markers to understand the impact of bycatch on the Atlantic and Mediterranean populations of the loggerhead turtle sharing the same foraging grounds in the western Mediterranean Sea. Turtles of Atlantic origin settle on the continental shelf later and at a larger size than turtles of Mediterranean origin and hence have been suggested to be more vulnerable to pelagic fishing gears, whereas those of Mediterranean origin would be more vulnerable to neritic ones. To assess whether this hypothesis holds true, we compared the genetic make-up of turtle bycatch from drifting longlines and bottom trawl/trammel nets in three different regions (eastern mainland Spain, southern Balearic Islands and southern Italy). A total of 176 incidentally caught turtles were considered, and size and habitat use, as revealed by stable isotopes, were incorporated to the analysis. No genetic, size or isotopic differences were found between turtles caught with drifting longlines and bottom trawl/trammel nets within any of the three regions. However, genetic, size and isotopic differences were detected among regions, regardless of the fishing gear. Thus, the population make-up of loggerhead bycatch depends on the area where the fishing operations are conducted, but not on the fishing gear used. Accordingly, the actual impact of loggerhead bycatch in the Mediterranean Sea will depend not only on the total number of turtles taken, but also on the geographic distribution of the fishing effort.