Somatic growth rates for a hawksbill turtle population in coral reef habitat around Barbados

A generalized additive mixed modelling approach was used to investigate the somatic growth of hawksbill turtles Eretmochelys imbricata (23.7 to 80 cm curved carapace length [CCL]) on nearshore coral reef sites around Barbados at depths of 12 to 35 m. The effects of body size, sex, sampling year, recapture interval and an indicator of foraging habitat quality on growth rates were investigated. The model accounted for about 60% of the variance in growth rates, but only mean size and sampling year were significant predictors. The growth rate function was nonmonotonic, with peak growth (3.4 cm yr(-1)) occurring in turtles with a CCL between 30 and 35 cm. The lower growth rates recorded for smaller turtles may reflect a period when sea turtles newly recruiting from pelagic to neritic habitats are adapting to a change in diet. The decline in growth rates with sampling year over the 10 yr study may reflect density-dependent effects on growth. Declining growth rates may prompt large juveniles to leave the Barbados foraging ground to settle elsewhere to grow to maturity.