Spatial Distribution and Abundance of Large Green Turtles on Foraging Grounds in the Florida Keys, USA.

Discerning distribution, density, and abundance of organisms is essential for conservation and management of imperiled species. However, simple counts of sampled individuals are often not adequate to make such estimates, this is especially true for large and highly mobile marine animals. Green turtles (Chelonia mydas) are a highly migratory, long-lived, late-maturing, marine megafauna, that is beginning to recover from severe global population declines. Distance sampling techniques can be used to generate estimates of abundance of green turtles in foraging grounds which have been relatively unstudied in the Northeastern Atlantic basin, filling in important data gaps in a species that is of critical conservation concern. The Quicksands foraging grounds located west of Key West, Florida, USA is used by both sub-adult and adult green turtles. Standardized transects were performed 18 times between 2006 – 2018, and using the collected data; abundances, spatial distribution and evidence of spatial segregation were generated through density surface models and null mode analysis. Densities of foraging green turtles rival some of the largest densities known in the world. Spatial segregation of the two size classes is evident on the foraging ground and may be attributed to differing predator detection and avoidance strategies of the size classes Finally, given the high densities of animals found on the foraging grounds and the rise in general population levels of green turtles and drop in population of green turtle predators (i.e. large sharks), concern is raised for the long term sustainably of the Quicksands seagrass pastures