Time filter

Source Type

Las Palmas de Gran Canaria, Spain

Parga M.L.,SUBMON | Pons M.,Research Center y Conservacion Marina | Andraka S.,WWF | Mituhasi T.,Overseas Fishery Cooperation Foundation of Japan | And 5 more authors.
Fisheries Research | Year: 2015

Bycatch by longline fisheries, especially by artisanal small-scale fisheries, is one of the main conservation problems for some sea turtle populations around the world. Since 2004, a network of professionals under the "Eastern Pacific Regional Sea Turtle Bycatch Program" have been working with artisanal longline fishers in the Eastern Pacific Ocean (EPO) to reduce sea turtle bycatch and related mortality. Trials assessing circle hooks of different sizes and shapes, and different baits, have been conducted to determine the effectiveness in the reduction of sea turtle bycatch and changes in hooking location. In this paper, information from 1823 olive ridley sea turtles incidentally captured in the EPO were analyzed to assess how hook type (J, tuna hooks or circle hooks), hook size, bait type (squid or fish), turtle size and target species (tunas, sharks or mahi-mahi) affect hooking location on sea turtles. This were modeled with a Classification and Regression Tree using hooking location as a multinomial variable response (for 6 categories of hooking locations); and also as a binomial response (swallowed vs. non-swallowed) using a Generalized Linear Mixed Model (GLMM). Hook type and size, plus bait type, were the most important factors affecting hooking location, while turtle size and target species did not have any significant effect. J-hooks and tuna hooks had a much greater probability of being swallowed than circle hooks. In addition, as the hook size increased, the likelihood of swallowing it decreased. The use of fish bait in combination with larger circle hooks tended to produce higher proportions of external hookings. An increase in external or lower mandible hookings is preferred since these locations are assumed to be less dangerous for the animal's post-release survival, and because hooks and attached gear are easier to remove by well-trained fishermen. © 2014 Elsevier B.V. Source

Andraka S.,WWF | Mug M.,WWF | Hall M.,Inter American Tropical Tuna Commission IATTC | Pons M.,Research Center y Conservacion Marina | And 13 more authors.
Biological Conservation | Year: 2013

Since 2004, governments and non-governmental organizations, together with the fishing communities from nine countries, from Mexico to Peru, have implemented joint efforts to reduce incidental mortality of sea turtles in artisanal longline fisheries of the Eastern Pacific Ocean (EPO). These countries are involved in a Regional Sea Turtle Bycatch Program to achieve this goal. Circle hooks have been proposed as a way to mitigate incidental mortality of sea turtles. Thus, we analyze the performance of circle hooks in relation to J-style and tuna hooks on the hooking rates of target and non-target species in the artisanal surface longline fisheries of three of the participating countries with the largest sample sizes (Ecuador, Panama and Costa Rica). These fisheries target mahi-mahi, Coryphaena hippurus, or a combination of tunas, billfishes and sharks (TBS), and use different techniques and gear configurations to catch their targets. For the TBS fishery we presented the results of comparisons between tuna hooks and 16/0 circle hooks from Ecuador, Panama and Costa Rica, and between tuna hooks and 18/0 circle hooks in Costa Rica. For the mahi-mahi fishery, we analyzed the performance of 14/0 and 15/0 circle hooks in Ecuadorian vessels and 16/0 circle hooks in Costa Rican vessels vs. the traditional J-style hooks. A total of 730,362 hooks were observed in 3126 sets. Hooking rates for target and non-target species were not consistent for all fisheries and countries analyzed. However, circle hooks reduced sea turtle hooking rates in most of the comparisons. © 2013 Elsevier Ltd. Source

Williard A.,University of North Carolina at Wilmington | Parga M.,SUBMON | Sagarminaga R.,ALNITAK | Swimmer Y.,National Oceanic and Atmospheric Administration
Biology Letters | Year: 2015

Bycatch of endangered loggerhead turtles in longline fisheries results in high rates of post-release mortality that may negatively impact populations. The factors contributing to post-release mortality have not been well studied, but traumatic injuries and physiological disturbances experienced as a result of capture are thought to play a role. The goal of our study was to gauge the physiological status of loggerhead turtles immediately upon removal from longline gear in order to refine our understanding of the impacts of capture and the potential for post-release mortality. We analysed blood samples collected from longline- And hand-captured loggerhead turtles, and discovered that capture in longline gear results in blood loss, induction of the systemic stress response, and a moderate increase in lactate. The method by which turtles are landed and released, particularly if released with the hook or line still attached, may exacerbate stress and lead to chronic injuries, sublethal effects or delayed mortality. Our study is the first, to the best of our knowledge, to document the physiological impacts of capture in longline gear, and our findings underscore the importance of best practices gear removal to promote post-release survival in longline-captured turtles. © 2015 The Author(s) Published by the Royal Society. All rights reserved. Source

Swimmer Y.,National Oceanic and Atmospheric Administration | Empey Campora C.,Biolintec Consulting LLC | Mcnaughton L.,University of Hawaii at Manoa | Musyl M.,University of Hawaii at Manoa | And 2 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2014

There are few reliable estimates of post-release mortality for sea turtle species because of the many challenges and costs associated with tracking animals released at sea. In this study, the likelihood of sea turtle mortality as a result of interactions with longline fishing gear was estimated based on satellite telemetry data, such as the number of days an animal was successfully tracked, or days at liberty (DAL) and dive depth data, as well as anatomical hooking locations. Pop-up satellite archival tags were deployed on 29 loggerhead sea turtles (Caretta caretta) caught by the North Pacific US-based pelagic longline fishery operating from California and Hawaii between 2002 and 2006. Loggerhead turtles were catagorized by observers as shallow-hooked (55%) if the animal was entangled in the line or the hook was in the flipper, jaw or mouth and could be removed, or deep-hooked (45%) if the hook was ingested and could not be removed. The vertical movements of turtles were used to infer potential mortalities. Of the 25 tags that reported data, the DAL ranged from 3 to 243 days (mean=68 days). The DAL was shorter (by nearly 50%) for shallow-hooked (mean=48 days, range: 3 to 127) compared to deep-hooked turtles (mean=94 days, range: 5 to 243), but these changes were not statistically significant (P=0.0658). Although aspects of these analyses may be considered speculative, these data provide empirical evidence to indicate that deep-hooking is not linked to shorter DAL. DAL, anatomical hooking location, and gear removal were evaluated with inferences about the extent of injuries and rates of infection to estimate an overall post-release mortality rate of 28% (95% bootstrap CI: 16-52%). This range of estimates is consistent with those used to shape some US fisheries management plans, suggesting that conservation goals are being achieved at the expected level and ideally striking a balance between the interests of industry and those of protected species. Copyright © 2013 John Wiley & Sons, Ltd. © 2013 John Wiley & Sons, Ltd. Source

Bulletin of Marine Science | Year: 2012

Six out of seven species of marine turtles are endangered, with longline bycatch considered one of the main causes for the decrease of their populations. Recently, the use of large circle hooks has been shown to reduce the impact of longline fishing on sea turtles, both decreasing the number of sea turtles captured, and shifting the number of hookings to the mouth, as opposed to other anatomical locations. However, little is known about the true post-release mortality of captured turtles in relation to hook location and associated lesions, essential information to adequately determine gear impacts. Here I discuss, from a veterinarian's point of view, the lesions caused by hooks in different locations in captured sea turtles, and their possible effects, combining information gathered from personal experience, longterm studies on captive sea turtles, post-mortem analysis of stranded sea turtles, and results of satellite tagging studies. Although hooks in the mouth are generally considered low risk, there are sensitive structures in this area, such as the glottis or the jaw joint, which should be carefully considered. On the other hand, the esophagus has a strong muscular wall and is somewhat resistant to lesions, unless the hook lodges close to the heart or large blood vessels. Lines left trailing are by far the most dangerous part of the gear, and have very high chance of causing mortality. Adequate training of fishermen by experienced researchers is essential to reduce sea turtle mortality, and more research is urgently needed to confirm the effectiveness of circle hooks. © 2012 Rosenstiel School of Marine & Atmospheric Science of the University of Miami. Source

Discover hidden collaborations