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

Erik A. P. Santos*, Augusto C. C. D. Silva, Roberto Sforza, Fabio L. C. Oliveira, Marilda I. Weber, Jaqueline C. Castilhos, Maria de los Milagros L. Mendilaharsu, Maria A. A. G. Marcovaldi, Renata M. A. Ramos, Andrew DiMatteo

*Corresponding author:

ABSTRACT: Sergipe and Bahia states comprise the main nesting beaches for olive ridley Lepidochelys olivacea turtles in Brazil. Between February 2014 and March 2015, 40 L. olivacea turtles were equipped with Argos Platform Transmitter Terminals (PTT). A state space model (SSM) was applied to Argos location data to investigate the animals’ spatial ecology and identify areas of restricted movements (ARM) and directional movements. The inter-nesting ARM included the continental shelf from the south of Alagoas state to the north of Bahia state, 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 Guyana (turtles = 4), (2) neritic South/Southeastern (S/SE) Brazil (turtles= 16), or (3) oceanic (turtles = 19) from Brazil to West Africa. ARM consistent with foraging areas were identified for 24 olive ridleys: 15 along the continental shelf of southeastern Brazil, 2 adjacent to Ceará and Maranhão states (between the 25 and 75 m isobaths), and 7 off the African countries of Cabo 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 or near high use areas. These results can be used as a basis for spatial management measures to protect this endangered species.