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- 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.
- Individual strategies and phenotypic plasticity of sea turtles in response to environmental changes: Loggerhead turtles nesting in Cabo VerdePublication . Martins, Samir; Loureiro, Nuno de Santos; Marco, AdolfoThe archipelago of Cabo Verde probably hosts the largest loggerhead turtle (Caretta caretta) rookery in the world. Nesting activities occur in all islands, with emphasis on Boa Vista, with more than 55% of the nest’s activities. The ecology of this population is still poorly understood and the studies presented here, carried out in the Sea Turtle Natural Reserve, aims to contribute to overcoming some relevant gaps. Our attention focused on: i. the influence of body size, estimated through the curved carapace length (CCL), the possible indicator of age on the fecundity of nesting females; ii. the influence of parameters such as temperature and moisture of the sand related to clutch location for the survival of offsprings; iii. the influence of nest location characterised by their proximity to the upper limit of the beach and to the water for the predation of hatchlings during their crawl to the sea; iv. the influence of hatcheries on hatching success and viability of hatchlings; and v. the impact of small-scale fishery on the nesting loggerhead turtle. We observed that: i. females nested along the entire width of the beach with a preference for the open area to the detriment of proximity to the tide line and vegetation; ii. only 8% of nesting females had CCL > 90 cm, laying less than 12% of the total annual number of clutches; iii. for higher values of temperature and moisture, the hatching success was lower and produced weaker offsprings; ghost crab predation decreased with increased hatchling group size; iv. hatcheries contributed to the hatching success without causing phenotypic differences; vi. small-scale fishery in Cabo Verde has relevant impacts on the population of C. caretta.
- Effect of body size on the long-term reproductive output of eastern Atlantic loggerhead turtles Caretta carettaPublication . Martins, Samir; Cardona, L.; Abella, E.; Silva, E.; Loureiro, Nuno de Santos; Roast, M.; Marco, A.We assessed the relationship between body size and several important life history parameters to understand the demographic significance of interpopulation variability in the body size of loggerhead turtles Caretta caretta nesting on Boa Vista Island (Cabo Verde). The adult growth rate (0.34 +/- 0.60 cm yr-1), annual mortality rate (0.13, 95% CI: 0.12-0.15) and remigration interval (3.1 +/- 1.2 yr) were independent of curved carapace length (minimum curved carapace length [CCLmin]). Conversely, the body condition index decreased significantly with female CCLmin. The clutch size, mean egg mass, mean hatchling straight carapace length and mean hatchling mass increased significantly with female CCLmin. However, there was no relationship between female size and hatching success. Randomization and bootstrapping were used to incorporate variability when calculating the average individual fecundity over 20 yr, a period that accumulated, on average, 94% of the adult mortality. The overall fecundity during this period increased with carapace length at first maturity (71 cm CCLmin: 815 eggs, 95% CI: 653-863; 80 cm CCLmin: 906 eggs, 95% CI: 822-959; 90 cm CCLmin: 1089 eggs, 95% CI: 926-1415). However, only 8% of the adult females nesting on Boa Vista Island are larger than 90 cm CCLmin, and they produce less than 12% of the total annual egg production. The scarcity of large females might result from a shortage of high-quality foraging grounds where females may reach first sexual maturity at a large carapace length and from the combined effect of a small carapace length at first sexual maturity, low adult somatic growth and high adult mortality.
- 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.
- 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.
- High variability in nest site selection in a loggerhead turtle rookery, in Boa Vista Island, Cabo VerdePublication . Martins, Samir; Patrício, Rita; Clarke, Leo J.; Loureiro, Nuno de Santos; Marco, AdolfoAmong sea turtles, nest site selection is a crucial factor for hatching success and population viability. The relocation of otherwise doomed clutches to safe hatcheries has been widely promoted as a conservation strategy, although this may promote artificial selection of poorly adapted genotypes. In this study, we used multiyear spatial nesting data of individual loggerhead turtles (Caretta caretta) from one of the largest Atlantic rookeries, in Cabo Verde, across six consecutive nesting seasons (2013-2018), to identify spatial nesting patterns, assess how individual nest site selection is influenced by female size and age, and estimate the impacts on the reproductive output. Although females nested across the entire beach width, they preferentially nested in the middle of the beach, avoiding to nest both close to the tideline and close to the vegetation line. Hatching success decreased towards the waterline, while the risk of nest inundation or predation was high, regardless of nest location. In general, females showed high variability in nest site selection, except larger females (> 93 cm curved carapace length) that showed higher repeatability (r = 0.50, SE = 0.14, 95% CI: 0.16-0.72) in distances to the vegetation. We therefore suggest that the relocation of doomed clutches should be considered for this endangered rookery, as clutch relocation should not substantially distort the gene pool, assuming nest choice is a heritable trait. In addition, we recommend the preservation of beach vegetation, particularly in areas with human development.
- 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.