Green turtles (Chelonia mydas) foraging at Arvoredo Island in Southern Brazil: Genetic characterization and mixed stock analysis through mtDNA control region haplotypes

We analyzed mtDNA control region sequences of green turtles (Chelonia mydas) from Arvoredo Island, a foraging ground in southern Brazil, and identified eight haplotypes. Of these, CM-A8 (64%) and CM-A5 (22%) were dominant, the remainder presenting low frequencies (< 5%). Haplotype (h) and nucleotide (π) diversities were 0.5570 ± 0.0697 and 0.0021 ± 0.0016, respectively. Exact tests of differentiation and AMOVA ΦST pairwise values between the study area and eight other Atlantic foraging grounds revealed significant differences in most areas, except Ubatuba and Rocas/Noronha, in Brazil (p > 0.05). Mixed Stock Analysis, incorporating eleven Atlantic and one Mediterranean rookery as possible sources of individuals, indicated Ascension and Aves islands as the main contributing stocks to the Arvoredo aggregation (68.01% and 22.96%, respectively). These results demonstrate the extensive relationships between Arvoredo Island and other Atlantic foraging and breeding areas. Such an understanding provides a framework for establishing adequate management and conservation strategies for this endangered species

Photographic identification of sea turtles: method description and validation, with an estimation of tag loss

Recognition of individual sea turtles is mostly achieved by checking artificial tags previously attached to them, a method which is made difficult by the considerable tag loss rate and which requires repeated manipulation of the marked individuals. We describe an individual recognition method for sea turtles of the family Cheloniidae based on a mark-recapture study that relied on both artificial tagging (Inconel tags, style 681) and natural marks (facial profile photographs). Juvenile green Chelonia mydas and hawksbill Eretmochelys imbricata turtles were manually caught at Arvoredo Island, southern Brazil, and through visual comparison of facial profile photographs we were able to identify recaptured individuals with 2, 1, or no artificial tags. Additionally, Bayesian inference based on tag loss information indicated that the way a tag is attached (position and distance from the flipper edge) affects significantly the probability of its loss. We encourage the use of photographic identification (facial profile) as a reliable method for individual recognition in studies of cheloniid turtles

Green turtle (Chelonia mydas) mixed stocks in the southwestern Atlantic, as revealed by mtDNA haplotypes and drifter trajectories

Genetic analyses have the potential to elucidate many aspects of juvenile green turtle (Chelonia mydas) biology and ecology, such as foraging ground composition, hatchling dispersal and migrations. To evaluate genetic structure and assess natal origins of mixed stocks in Southern Brazil, we analyzed mitochondrial DNA control region sequences from Arvoredo Island (n = 115) and Cassino Beach (n = 101), comparing them to other mixed stocks and examining their composition in terms of Atlantic Ocean stocks (nesting areas). In order to compare natal origin estimates (obtained through Bayesian Mixed Stock Analysis) with oceanographic data and develop novel informative priors for this analysis, surface drifter trajectories in the Atlantic Ocean were analyzed. Each study area presented twelve haplotypes, of which ten were shared at extremely similar frequencies. Haplotypes CM-A8 and CM-A5 were most frequent, representing respectively around 60% and 20% of samples from both areas, and remaining haplotypes were present in less than 5% of samples. Genetic structuring was not observed between the study areas. Arvoredo Island and Cassino Beach also did not present structuring in relation to Ubatuba and Rocas/Noronha, in the southwestern Atlantic, but were structured when compared to farther feeding areas in Brazil, the Caribbean, and North America. Analysis of drifter trajectories revealed that drifters from Ascension and Trindade Islands are dominant at the eastern coast of Brazil. Informative priors developed for Mixed Stock Analysis did not greatly alter stock estimates; we do, however, consider them to be ecologically more realistic. According to the Bayesian mixed stock analyses applied here, Ascension, Aves and Trindade Islands, as well as Gulf of Guinea, were the main contributors to the Southern Brazil mixed stock. This analysis has important implications for the conservation of this species, since impacts on mixed stocks along the coast may affect some reproductive stocks which are frequently thousands of kilometers away