Bell, Ian, Schwarzkopf, Lin, and Manicom, Carryn (2012) High survivorship of an annually decreasing aggregation of hawksbill turtles, Eretmochelys imbricata, found foraging in the northern Great Barrier Reef. Aquatic Conservation: marine and freshwater ecosystems , 22 (5). pp. 673-682.

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Abstract

An 8-year study of the foraging abundance of an Eretmochelys imbricata aggregation, found on 13 reefs (Howick Group) within the northern section of the Great Barrier Reef Marine Park was undertaken. A CormackJollySeber method within program MARK was used to: (1) compare survival and recapture probabilities among age and sex classes of turtles; and (2) estimate survival and recapture rates for male and female adults and sub-adults from 665 capturemarkrecapture profiles of E. imbricata. Mean annual population density estimates were consistently greater for adult female E. imbricata (n=333.7; SD=135.6; R=221-581) than for adult males (n=32.4; SD=33.4; R=8-98), with both adult males and females displaying high survivorship rates (71.1%; 92.2%, respectively). This was also apparent in immature age-classes, with male and female turtles showing similarly high survivorship likelihoods (78.0%; 93.0%, respectively). Both sexes exhibited a similar overall trend with a peak population density being displayed in the first two years of the study, followed by a general decline in the female stock and stable male population. These are the only reliable long-term abundance time-series data for a population that includes all age-classes of E. imbricata in the western Pacific and provide good baseline data for the detection of possible climate change induced trends.

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