At-sea distribution of juvenile leatherback turtles: new insights from bycatch data in the Atlantic Ocean

Highly mobile marine species can travel long distances, which in some cases extend over entire ocean basins. This is especially true for sea turtles, which have a spatially complex life cycle that for most species comprises initial development in oceanic habitats. Due to the difficulty involved in accessing open ocean waters and the elusive nature of small individuals, very little is known about the distribution of young oceanic-stage sea turtles. This is particularly true for the leatherback turtle Dermochelys coriacea, as studies on this species’ young life stages are lacking and therefore represent one of the top research priorities for this taxon worldwide. Here, we report new records (n = 28) of juvenile leatherbacks (≤100 cm curved carapace length, CCL) incidentally captured by longline fisheries and provide information about their distribution and possible dispersal patterns. Juvenile leatherbacks were found in tropical and subtropical waters in the Atlantic, while small individuals (<80 cm CCL) were restricted to the equatorial central Atlantic, between latitudes 3.5°N and 3.1°S. The incidental capture of a leatherback of 40 cm CCL indicates that individuals can be exposed to this threat approximately 1 yr after nest emergence. Lagrangian drifter data used to explore the possible role of ocean currents on post-hatchling dispersal from the main leatherback rookeries in the Atlantic suggested that small leatherbacks found in the equatorial central Atlantic may come from West Africa. Given the limited data on oceanic-stage sea turtles, this study provides additional information on where to look for young leatherbacks and possibly focus future field-based research.