Distribution patterns of nearshore aggregations of olive ridley sea turtles (Lepidochelys olivacea) in Rushikulya, Odisha, India: Implications for spatial management measures

Abstract

Abstract Sea turtles are known to migrate large distances between their foraging and breeding grounds. Olive ridley turtles migrate annually in November to the east coast of India from their foraging grounds in the Bay of Bengal and form large aggregations at Gahirmatha and Rushikulya, two globally significant mass nesting rookeries in Odisha. However, little is known about the spatial and temporal variation in their nearshore distribution prior to the mass nesting events, which typically occur between February and April. Inter‐ and intra‐annual variations in the density and distribution of olive ridley turtles were examined in the nearshore waters of Rushikulya from 2012 to 2022. The densities of turtles were estimated for each field season and aggregations were spatially delineated using minimum convex polygons. There was considerable interannual variation in turtle abundance, which typically increased from December to February in Rushikulya. Turtle densities in nearshore waters did not correspond to the presence or absence of mass nesting, thus suggesting that management decisions cannot be based only on nesting beach estimates. Turtle aggregations in Rushikulya were spatially and temporally dynamic and were typically concentrated around the nesting beach. However, they occupied only a small fraction of the area designated as a no‐fishing zone, which suggests that these regulations need to be reassessed. As the no‐fishing zones impose high costs on fishers, it is critical to look at alternative protection measures, such as dynamic spatial closures, developed in consultation with local fishers.