ORIGIN OF LEATHERBACKS (DERMOCHELYS CORIACEA) AT FEEDING GROUNDS OFF THE RÍO DE LA PLATA IN SOUTH WESTERN ATLANTIC

PROSDOCIMI L.,; VELEZ-RUBIO, G.; FALLABRINO, A.; LÓPEZ-MENDILAHARSU, M.; LACASELLA, E.; RODEN, S.; DUTTON, P.H.

Simposio; 41th Annual Symposium on Sea Turtle Biology and Conservation.; 2023

ISTS

The leatherback turtle, Dermochelys coriacea, like other species of marine turtles, undertakes long-distance migrations between tropical/subtropical nesting beaches and distant temperate foraging areas. Globally, leatherback status according to IUCN is listed as Vulnerable, but the Southwest Atlantic subpopulation is classified as Critically Endangered. Satellite telemetry studies have demonstrated that the coastal waters off South America provide important feeding grounds for large juveniles and adult leatherbacks in the western South Atlantic. For the past 20 years, the NGO Karumbe in Uruguay and PRICTMA in Argentina has investigated the biology and habitat use of this species in waters off the Rio de la Plata estuary, a nearshore foraging area with jurisdiction shared between Uruguay and Argentina. Previous genetic studies using Mixed Stock Analysis (MSA) with mtDNA data have demonstrated that the leatherbacks foraging off Uruguay and Argentina come primarily from the West African breeding populations, primarily the large Gabon rookeries. New approaches are now available to assign stock origin of individual turtles using nDNA analysis with greater precision. This study builds on previous mixed stock analysis, by incorporating nDNA genotyping using a suite of 16 informative microsatellite markers combined with mtDNA analysis of an expanded sample set (n= 130), including 56 new samples from stranded animals of the Río de la Plata. Results of the MSA are generally consistent with previous findings, with an estimated 90% belonging to the West Africa rookeries. It was unclear whether the minor contributions estimated by MSA from Caribbean and South African rookeries were statistical artifacts resulting from shared common mtDNA haplotypes among these source populations. Results from our individual assignments using nDNA genotype data confirmed that at least five turtles originated from Caribbean rookeries, providing new insights into potential connectivity between the breeding populations in the Northwest Atlantic and the foraging populations in the Southwest Atlantic. Taken together these findings advance our understanding of the connectivity between these breeding and foraging areas on opposite sides of the ocean in the South Atlantic.