Search

Bycatch is considered one of the most significant threats affecting cetaceans worldwide. In the North Sea, bottom-set gillnets are a specific risk for harbor porpoises ( Phocoena phocoena). Methods to estimate bycatch rates include on-board observers, remote electronic monitoring, and fishermen voluntarily reporting; none of these are systematically conducted. Additionally, necropsies of stranded animals can provide insights into bycatch occurrence and health status of individuals. There are, however, uncertainties when it comes to the assessment of bycatch in stranded animals, mainly due to the lack of diagnostic tools specific for underwater entrapment. We conducted a literature review to establish criteria that aid in the assessment of bycatch in small cetaceans, and we tested which of these criteria applied to harbor porpoises retrieved from gillnets in the Netherlands ( n = 12). Twenty-five criteria were gathered from literature. Of these, “superficial incisions,” “encircling imprints,” and “recent ingestion of prey” were observed in the vast majority of our confirmed bycatch cases. Criteria like “pulmonary edema,” “pulmonary emphysema,” and “organ congestion” were also frequently observed, although considered unspecific as an indicator of bycatch. Notably, previously mentioned criteria as “favorable health status,” “absence of disease,” or “good nutritional condition” did not apply to the majority of our bycaught porpoises. This may reflect an overall reduced fitness of harbor porpoises inhabiting the southern North Sea or a higher chance of a debilitated porpoise being bycaught, and could result in an underestimation of bycatch rates when assessing stranded animals.

Made available in DSpace on 2022-04-29T08:29:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Incidental capture is the most common threat to rays worldwide, by both artisanal and industrial fishing. To better understand this threat, we evaluated the capture and handling stress in three incidentally captured benthopelagic ray species: American cownose ray (Rhinoptera bonasus), Brazilian cownose ray (Rhinoptera brasiliensis), spotted eagle ray (Aetobatus narinari), and one benthic species, the longnose stingray (Hypanus guttatus). Through analyzing secondary stress physiological variables (plasma lactate and glucose), our results revealed a similar physiological stress response in benthopelagic rays, suggesting they are resilient to capture using beach seine fishing. We also demonstrated that handling for research can increase the stress in both American cownose and spotted eagle rays, suggesting that more stringent handling protocols for research should be required. Findings from this study expands on the number of ray species for which stress to capture and handling has been evaluated, providing recommendations for appropriate research and management. Universidade de São Paulo Instituto de Biociências Departamento de Fisiologia Laboratório de Metabolismo e Reprodução de Organismos Aquáticos, Rua do Matão, travessa 14, 321, Cidade Universitária Universidade Estadual Paulista Instituto de Biociências de Botucatu Laboratório de Biologia e Genética de Peixes, Rua Professor Doutor Antonio Celso Wagner Zanin, s/n Universidade Estadual Paulista Instituto de Biociências de Botucatu Laboratório de Biologia e Genética de Peixes, Rua Professor Doutor Antonio Celso Wagner Zanin, s/n CAPES: 001 FAPESP: 2014/16320-7 FAPESP: 2016/09095-2

During 2010 – 2015, the Mississippi Sea Turtle Stranding and Salvage Network (STSSN) documented 1,073 sea turtles, primarily juvenile Kemp’s ridleys (Lepidochelys kempii), incidentally caught by recreational anglers. Due to increases in interactions, an angler interview survey was conducted during 2013 at six Mississippi fishing piers. Anglers were interviewed about fishing practices and sea turtle interactions. Interviewers conducted outreach and distributed Rehabilitation Hotline business cards. Angler participation was 86%, and over 60% used J-hooks and were not targeting specific species, which was similar to data collected from incidental captures reported to the STSSN. Over 58% of anglers used dead shrimp followed by cut up fish for bait. This greatly differs from STSSN reported captured sea turtles where 60% were caught on cut up fish and only 6% on dead shrimp. Over 18% of participants captured at least one sea turtle in the last 12 months. Anglers stated that nearly half of the sea turtles were taken for rehabilitation, 41% were released by the angler and 10% broke the line and swam away. Only 60% of anglers reported the capture because many were unaware they should report it. During and after the survey period, there was an increase in reported incidental captures, possibly indicating outreach is an effective means of increasing awareness and reporting. Recently, NOAA Fisheries developed a survey that can be used nationally to conduct similar research. We recommend conducting angler surveys every few years unless there is a noticeable change in incidental capture trends or angler practices.

The Bigeye Thresher Shark Alopias superciliosus Lowe, 1841 is one of the largest shark species found in the Pacific, Atlantic, and Indian oceans. They also have started to be seen in the Mediterranean Sea since the 1980s. The presence of two different species of Thresher sharks in Turkish waters is known, which are A. vulpinus and A. superciliosus. Thresher sharks can easily be distinguished from other shark species with their big tails. A juvenile female specimen of A. superciliosus with a total length of 240 cm was caught incidentally in Mersin Bay in January 2020. Essential measurements of the fish were fulfilled and the specimen was deposited in the Museum of the Systematic, Faculty of Fisheries, Mersin University (catalog number: MEUFC-20-11-127). This study is the first record of A. superciliosus in Mersin Bay.

International audience; Skewed adult sex ratio (ASR) has been proposed as a common pattern in birds, frequently biased towards males and with larger biases in globally threatened species. In albatrosses and petrels, it has been suggested that differential mortality of one gender in fisheries is caused either by sexual size dimorphism giving males a competitive advantage, which allows more access of the larger sex (i.e. males) to discards and/or baits, or to at sea segregation of sexes. Here, we tested these hypotheses by determining ASRs in albatrosses and petrels trapped at sea when attending longline fishing vessels for discards in the southwestern Atlantic Ocean, and searched in the literature for patterns in ASR in albatrosses and petrels killed by fisheries in this area and elsewhere. We show that skewed ASR is common in albatrosses and petrels in the community attending vessels for discards, confirming results found for birds in general. There was no correlation between skewed ASR and conservation status, or between ASR and sexual size dimorphism. Our review of the sex of birds incidentally killed in fisheries found skewed ASR toward males, females or parity to be equally reported. Thus, sexual dimorphism in size does not explain skewed ASR in the community we sampled or in incidental captures in fisheries in the review. Differential at-sea distribution of sexes appears to be a better explanation of the patterns found in the community sampled at sea as well as skewed ASR in seabird fatalities, particularly distant from breeding areas.

Mediterranean populations of loggerhead Caretta caretta and green sea turtles Che- lonia mydas are subject to several anthropogenic threats, with documented mortality from inci- dental 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 popula- tion 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) pro- vide 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 con- structed 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.

The western Mediterranean Sea is an important fishing area for the Spanish drifting longline fleet, targeting swordfish (Xiphias gladius), bluefin tuna (Thunnus thynnus) and albacore (T. alalunga). Some seabird species can be captured incidentally as bycatch marine fauna. From July 1999 to August 2000 information on 554 surface longline sets was collected by onboard observers of the Spanish Oceanographic Institute (IEO) on 18 longline fishing boats working within the Spanish Mediterranean fishing area. Eleven yellow-legged gulls (Larus cachinnans), 9 Cory´s shearwaters (Calonectris diomedea) and 1 Northern gannet (Morus bassanus) were captured incidentally. Bycatch rates ranged from 0.002 to 0.023 birds/1000 hooks. El mar mediterráneo occidental es una importante área de pesca para la flota palangrera de deriva española, centrando su actividad sobre el pez espada (Xiphias gladius), el atún (Thunnus thynnus) y la albacora (T. alalunga). Algunas especies de aves marinas pueden ser capturadas accidentalmente por estas artes de pesca. Desde julio de 1999 hasta agosto de 2000 se recogió información en 554 palangres de superficie por observadores de abordo del Instituto Oceanográfico Español (IEO) en 18 barcos palangreros trabajando en la zona de pesca mediterránea española. Resultaron capturadas accidentalmente 11 gaviotas patiamarillas (Larus cachinnans), 9 pardelas cenicientas (Calonectris diomedea) y un alcatraz (Morus bassanus). Las tasas de capturas oscilaron entre 0,002 a 0,023 aves/1000 anzuelos.

Large oceanic migrants play important roles in ecosystems, yet many species are of conservation concern as a result of anthropogenic threats, of which incidental capture by fisheries is frequently identified. The last large populations of the leatherback turtle, Dermochelys coriacea , occur in the Atlantic Ocean, but interactions with industrial fisheries could jeopardize recent positive population trends, making bycatch mitigation a priority. Here, we perform the first pan-Atlantic analysis of spatio-temporal distribution of the leatherback turtle and ascertain overlap with longline fishing effort. Data suggest that the Atlantic probably consists of two regional management units: northern and southern (the latter including turtles breeding in South Africa). Although turtles and fisheries show highly diverse distributions, we highlight nine areas of high susceptibility to potential bycatch (four in the northern Atlantic and five in the southern/equatorial Atlantic) that are worthy of further targeted investigation and mitigation. These are reinforced by reports of leatherback bycatch at eight of these sites. International collaborative efforts are needed, especially from nations hosting regions where susceptibility to bycatch is likely to be high within their exclusive economic zone (northern Atlantic: Cape Verde, Gambia, Guinea Bissau, Mauritania, Senegal, Spain, USA and Western Sahara; southern Atlantic: Angola, Brazil, Namibia and UK) and from nations fishing in these high-susceptibility areas, including those located in international waters.

Surface longline gears are used to fish different species, mainly albacore Thunnus alalunga (Bonnaterre, 1788), bluefin tuna Thunnus thynnus (Linnaeus, 1758), and swordfish Xiphias gladius Linnaeus, 1758, and are considered highly dangerous for threatened marine turtles. Loggerheads Caretta caretta (Linnaeus, 1758) can be incidentally captured by surface longlines. A number of captured individuals die during the fishing operation, which we consider direct mortality due to fishing. We analysed the relative loggerhead by-catch and direct mortality associated with each type of boat and gear from April to December during the period 1999-2004 in the Spanish surface longline fleet that fishes in the western Mediterranean Sea, an important fishing area for this fleet. We used different indices to compute the catch per unit effort (CPUE) according to the number of hooks and to the number of fishing operations for each type of boat and gear. Both by-catch and direct mortality differed significantly according to the type of boat and gear. With respect to the number of hooks, boats longer than 12 m not using a roller and targeting bluefin tuna captured the highest number of loggerheads, whereas boats longer than 12 m with a roller that targeted swordfish caused the highest direct mortality. With respect to the number of fishing operations, boats longer than 12 m without a roller that targeted albacore captured the highest number of loggerheads; the highest direct mortality was caused by this type of boat and by boats longer than 12 m using a roller and targeting swordfish., Sí