Olive ridley inter-nesting and post-nesting movements along the Brazilian coast and Atlantic Ocean

Abstract

The states of Sergipe and Bahia comprise the main nesting beaches for olive ridley sea turtles Lepidochelys olivacea in Brazil. Between February 2014 and March 2015, 40 L. olivacea were equipped with Argos platform transmitter terminal tags. A state-space model was applied to Argos location data to investigate the animals’ spatial ecology and identify areas of restricted movements (ARMs) and directional movements. The inter-nesting ARMs included the continental shelf from the south of Alagoas state to the north of Bahia, totaling 7244 km2 (kernel density estimation, 90% isopleth) and generally extended up to 22 km from the coast or to the 50 m isobath. The post-nesting directional movements were classified as either (1) neritic north/northeastern (N/NE) Brazil to French Guiana (n = 4 turtles), (2) neritic south/southeastern (S/SE) Brazil (n = 16), or (3) oceanic (n = 19) from Brazil to West Africa. ARMs consistent with foraging areas were identified for 24 olive ridleys: 15 along the continental shelf of SE Brazil, 2 adjacent to Ceará and Maranhão states (between the 25 and 75 m isobaths), and 7 off the African countries of Cape Verde, Senegal, Gambia, Guinea-Bissau, and Sierra Leone. The results demonstrated the complexity of olive ridley movements from northern Brazil, raised questions about connectivity, and highlighted threats such as fisheries, ports, and hydrocarbon exploration fields overlapping with, or near to, high-use areas. These results can be used as a basis for spatial management measures to protect this endangered species.