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Distribution and growth rates of immature hawksbill turtles Eretmochelys imbricata in Fernando de Noronha, Brazil

Cláudio Bellini, Armando J. B. Santos, Ana R. Patrício, Luís Felipe W. Bortolon, Brendan J. Godley, Maria A. Marcovaldi, Dominic Tilley, Liliana P. Colman*

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ABSTRACT: Knowledge of life history parameters is essential for the effective management of species of conservation concern. For migratory marine vertebrates such as hawksbill sea turtles Eretmochelys imbricata feeding aggregations are important developmental habitats, allowing the study of population dynamics. Here, we use data from a 31-yr mark-recapture study of juvenile hawksbill sea turtles in Fernando de Noronha, Brazil, to estimate key demographic parameters. Turtles recruit to the neritic habitat at similar sizes to those of other Atlantic hawksbill aggregations. The mean curved carapace length (CCL) at the first capture ranged from 28 to 84 cm (mean ± SD 44.6 ± 9.8 cm). Median minimum residence time of turtles captured at least twice was 3.2 yr, whilst long-term minimum residence of up to 14 yr was also observed, with turtles showing site-fidelity within the Archipelago. The mean size of turtles captured was constant throughout time. Turtles grew on average 3.4 ± 2.2 cm yr1, with a monotonic expected growth rate function generally decreasing with increasing size. At these rates, hawksbill turtles in Fernando de Noronha would need to spend ca. 14-18 yr to reach minimum adult breeding size (~74 cm CCL). This mark-recapture study has been essential to understanding the ecology and demographic parameters of this regional hawksbill turtle neritic foraging ground.