Browsing by Author "Abella, Elena"
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- Evaluating loggerhead sea turtle (Caretta caretta) bycatch in the small-scale fisheries of Cabo VerdePublication . Martins, Samir; Tiwari, Manjula; Rocha, Fernando; Rodrigues, Edson; Monteiro, Ravidson; Araújo, Sónia; Abella, Elena; Loureiro, Nuno de Santos; Clarke, Leo J.; Marco, AdolfoThe incidental or target capture of sea turtles by small-scale fisheries (SSF) has been receiving increasing attention in recent years due to its high impact. Here, we evaluated the impact of the SSF on sea turtles in Cabo Verde, which hosts the largest rookery of the endangered Eastern Atlantic loggerhead turtle (Caretta caretta) population. This is the most comprehensive study evaluating the impact of SSF on sea turtles in the Cabo Verde Archipelago involving more than 85% of boats and more than 20% of the fishermen registered in the archipelago. Between the years of 2011 and 2014, 763 artisanal fishermen were interviewed at all the main ports and fishing communities of seven islands. Artisanal fishermen reported a mean annual capture of 1.5 turtles per boat indicating that a minimum of 1675 sea turtles could be landed per year in this fishing sector alone, with 65% in Santiago Island (which host the country's capital, Praia). Most captures (95.7%) occurred from May to September and coincided with the loggerhead turtle nesting season. These results suggest a severe impact of the SSF on adult loggerheads turtles in Cabo Verde as well as green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) juvenile turtles. To mitigate this impact, measures such as revising the current legislation for fisheries, the supervision and control of landings, especially in the most remote ports of the Archipelago, the regulation of the SSF during the nesting season around the main nesting areas, awareness-raising campaigns, sustainable activities, and alternative sources of income in fishing communities are recommended.
- Hatchery efficiency as a conservation tool in threatened sea turtle rookeries with high embryonic mortalityPublication . Martins, Samir; Ferreira-Veiga, Nádia; Rodrigues, Zuleika; Querido, Adélcio; Loureiro, Nuno de Santos; Freire, Kátia; Abella, Elena; Oujo, Carolina; Marco, AdolfoSea turtles are globally endangered and facing anthropogenic threats. To mitigate the negative impacts on sea turtle populations, different conservation strategies have been developed and implemented. For instance, when an endangered population suffers a high embryonic mortality from predation, human poaching, beach flooding or erosion, the relocation of clutches to safer and controlled areas can lower these threats. However, the use of hatcheries is controversially discussed, with some previous studies reporting negative results such as low hatching success, skewed sex ratio or phenotypic alterations of hatchlings. In this study, we evaluated the efficiency of beach hatcheries compared to in-situ incubation in Cabo Verde using data from six nesting seasons (2013-2018). During this study, several thousand high-risk clutches from loggerhead turtle (Caretta caretta Linnaeus, 1758) were relocated to a hatchery constructed within the Sea Turtle Natural Reserve (STNR, Boa Vista Island). Our findings confirmed that the in-situ nests within the STNR have extremely high egg mortality that is usually over 70%. Mean hatching success of clutches relocated to hatcheries was significantly higher than in-situ clutches with mean values between 70 and 85%. No significant differences were observed in the incubation period, the size and the behavioural response of hatchlings between relocated and in-situ clutches. As long as a sea turtle population is endangered and hatching success is low, clutch relocation programs which are designed to have an impact at the population level, are considered an efficient tool that contributes to its recuperation. Nevertheless, strict recommendations that increase hatching success while maintaining natural hatchling phenotype must be implemented.
- Hatchery efficiency for turtle conservation in Cabo VerdePublication . Martins, Samir; Ferreira-Veiga, Nádia; Rodrigues, Zuleika; Querido, Adélcio; Loureiro, Nuno de Santos; Freire, Kátia; Abella, Elena; Oujo, Carolina; Marco, AdolfoThis paper evaluated the efficiency of beach hatcheries as a conservation tool for threatened sea turtle clutches. During six nesting seasons (2013 to 2018), several thousand high-risk clutches from loggerhead turtles (Caretta caretta) were relocated to a hatchery constructed on the same beach, within the Sea Turtle Natural Reserve (STNR, Boa Vista Island, Cabo Verde). Some parameters like hatching success; incubation period, hatchlings’ morphology and their behavioral response were compared to in-situ clutches.
- Warmer incubation temperature influences sea turtle survival and nullifies the benefit of a female-biased sex ratioPublication . Martins, Samir; Silva, Elton; Abella, Elena; Loureiro, Nuno de Santos; Marco, AdolfoClimate change plays a key role in the development and survival of oviparous ectotherms such as sea turtles. Higher environmental temperatures are expected to lead to increased production of female hatchlings and potential feminization of many populations, as well as reduced hatching success and hatchling fitness. We investigated how different sand temperatures affect sea turtle embryo mortality, hatchling phenotype, and hatchling predation during their crawl to the sea. the study was conducted in Cabo Verde, the only rookery of the endangered loggerhead turtle (Caretta caretta) in the Eastern Atlantic. During three consecutive seasons (2015-2017), 240 loggerhead clutches were exposed to three different incubation temperature regimes created by different sand colours. the warm treatment (mean = 32.3 degrees C +/- 0.5) killed 33% more embryos than the cold treatment (mean = 29.7 degrees C +/- 0.6). Hatchlings from the warm treatment were mostly females, smaller in size, and had lower performance. Hatchling predation by ghost crabs during seaward transit was higher for hatchlings incubated in the warm treatment. Combining embryo mortality and hatchling predation, the rate of female hatchling arrival at the sea was more than twice as high in the cold treatment (34.4 females per 100 eggs) than in the warm treatment (16.0 females per 100 eggs). This increase in mortality caused by warmer incubation temperatures may cancel any potential benefit of a female-biased sex ratio. Conservation planners should consider behavioural adaptations and the potential dispersal of the nesting areas to colder areas to increase resilience of loggerhead turtles to climate change.