Ecology of loggerhead marine turtles Caretta caretta in a neritic foraging habitat: movements, sex ratios and growth rates

Much is still to be learned about the spatial ecology of foraging marine turtles, especially for juveniles and adult males which have received comparatively little attention. Additionally, there is a paucity of ecological information on growth rates, size and age at maturity, and sex ratios at different life stages; data vital for successful population modelling. Here, we present results of a long-term (2002-2011) study on the movements, residency, growth and sex ratio of loggerhead turtles (Caretta caretta) in Amvrakikos Gulf (39A degrees 0'N 21A degrees 0'E), Greece, using satellite telemetry (N = 8) and ongoing capture-mark-recapture (CMR; N = 300 individuals). Individuals encountered at sea ranged from large juvenile to adult (46.2-91.5 cm straight carapace length) and demonstrated growth rates within published norms (< 2.7 cm yr(-1)) that slowed with increasing body size. We revealed that an unexpectedly high proportion of animals were male (> 44 % of captures above 65 cm straight carapace length), compared to region-wide female-biased hatchling production, indicating sex-biased survival or possible behavioural drivers for likelihood of capture in the region. Satellite tracking confirmed that some turtles establish discrete, protracted periods of residency spanning more than 1 year, whilst others migrated away from the site. These findings are underlined by CMR results with individual capture histories spanning up to 7 years, and only 18 % of individuals being recaptured.