Sea Turtle Distribution and Abundance on the East Coast of the United States

Spatially explicit estimates of species distribution and abundance are required to quantify potential impacts from human activities, such as military training and testing. On the US East Coast, four protected species of sea turtles can commonly be found and require impact assessments. An area of 1.2 million kilometers of line transect surveys from seven different survey organizations were collated to create spatial density models for these species. Almost a third of the available sightings were unidentified turtles. A random forest model was used to assign these unidentified sightings to the species level. Hardshell turtles were predicted to be farther south in cool months, moving northwards in late spring and early summer to occupy seasonal nearshore habitats. Leatherback turtles were predicted to be in high abundance off Florida year-round and at low-to-moderate densities off the continental shelf and in the Gulf of Maine year-round. The models presented here are the first to apply availability bias estimates that have been developed in or near the study area and to classify unidentified sightings to the species level in the region, providing an updated, critical tool to managers responsible for the conservation of these species.