The use of the territorial sea by Lepidochelys olivacea (Eschscholtz, 1829) in front of nesting beaches in Oaxaca, Mexico

Abstract

Scientific research focused on sea turtle monitoring and management has relied on nesting beaches, but little attention has been paid to surveying turtles in the territorial sea off nesting beaches. This study aimed to evaluate how the Olive Ridley turtle, Lepidochelys olivacea, uses the territorial sea off the nesting beaches in Puerto Escondido, Puerto Ángel, Santa María Huatulco, and Morro Ayuta, in Oaxaca, Mexico. Between December 2017 and August 2018, 2394 individuals were sighted in the territorial sea engaged in the following activities: feeding (6 individuals), mating (164 individuals), swimming (2172 individuals), and resting (49 individuals). We analyzed the diet and body condition of L. olivacea and identified which biophysical factors affect the distribution of these sea turtles in the region. We also recorded direct interactions with fishers and tourism service providers. We captured 40 individuals, collected morphometric data, and analyzed esophageal content to characterize feeding habits, which were correlated with a body condition index. Diet items included crustaceans, tunicates, four commercially important fish species, jellyfish, mollusks, and algae. Approximately 95% of turtles exhibited very good body condition. The largest turtle aggregations were recorded in Morro Ayuta (898 individuals) and Puerto Ángel (808 individuals). In situ sea surface temperature and chlorophyll-a concentrations from satellite images were used to characterize the territorial sea. Sea surface temperature was negatively correlated with turtle abundance. Management and conservation actions are needed for sea turtles that address the negative interactions with fishers (e.g., competition for commercially important fish species) and tourism service providers that occur in the territorial sea off nesting beaches to protect these crucial reproductive habitats in the long term.