Despite intense interest in conservation of marine turtles, spatial ecology during the oceanic juvenile phase remains relatively unknown. Here, we used mixed stock analysis and examination of oceanic drift to elucidate movements of hawksbill turtles (Eretmochelys imbricata) and address management implications within the Caribbean. Among samples collected from 92 neritic juvenile hawksbills in the Cayman Islands we detected 11 mtDNA control region haplotypes. To estimate contributions to the aggregation, we performed 'many-to-many' mixed stock analysis, incorporating published hawksbill genetic and population data. The Cayman Islands aggregation represents a diverse mixed stock: potentially contributing source rookeries spanned the Caribbean basin, delineating a scale of recruitment of 200-2500 km. As hawksbills undergo an extended phase of oceanic dispersal, ocean currents may drive patterns of genetic diversity observed on foraging aggregations. Therefore, using high-resolution Aviso ocean current data, we modelled movement of particles representing passively drifting oceanic juvenile hawksbills. Putative distribution patterns varied markedly by origin: particles from many rookeries were broadly distributed across the region, while others would appear to become entrained in local gyres. Overall, we detected a significant correlation between genetic profiles of foraging aggregations and patterns of particle distribution produced by a hatchling drift model (Mantel test, r = 0.77, P < 0.001; linear regression, r = 0.83, P < 0.001). Our results indicate that although there is a high degree of mixing across the Caribbean (a 'turtle soup'), current patterns play a substantial role in determining genetic structure of foraging aggregations (forming turtle groups). Thus, for marine turtles and other widely distributed marine species, integration of genetic and oceanographic data may enhance understanding of population connectivity and management requirements.

The impact of recreational SCUBA diving on coral reefs of the Cayman Islands, British West Indies, was assessed from 63 10-m video transects, filmed on reefs in the West Bay area of Grand Cayman. Three high use and three low use dive sites were sampled at distances of c. 15, 55 and 200 m from mooring buoys, in addition to three sites where no diving occurs. Both diver numbers and distance from buoys were found to show highly significant (P< 0.01) effects on hard coral cover and cover of the major reefbuilding coral, Montastrea annularis. Diver numbers also increased the amount of dead coral and coral rubble. Relative to overall hard coral cover, the proportion of massive corals was smallest at heavily dived sites, but there was a larger proportion of Agaricia spp. corals, dead coral and coral rubble at these sites. Our findings suggest the need for a new management approach if the Islands are to conserve the ecological and aesthetic qualities of their most popular dive sites.

We present detailed results of a satellite tracking project following 10 adult female turtles from the Cayman Islands, thought to have once been one of the world's largest rookeries. By tracking the movements of 7 green turtles Chelonia mydas and 3 loggerhead turtles Caretta caretta from now critically reduced rookeries we defined key habitats for internesting movement, migration, and foraging in a range of Caribbean jurisdictions. Turtles tracked from the Cayman Islands traveled to foraging grounds in Belize, Guatemala, Honduras, Mexico, Nicaragua and the USA. This range encompasses a > 2000 km stretch of Caribbean coastline and the Florida Keys, highlighting the need for international cooperation in identifying and mitigating foraging ground threats. For one of the green turtles, foraging site fidelity was elucidated over the course of two reproductive seasons, and oceanic internesting intervals/post-nesting oceanic circles were defined for the first time in Atlantic loggerhead turtles. In addition to fundamental and applied insights into the biology of the 2 species, this research elucidates geographic scale for potential ecological effects of past decimation of rookeries in the Cayman Islands and highlights the effectiveness of community efforts in support of conservation research.

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