Observations on the mortality of olive ridley sea turtles (Lepidochelys olivacea) and associated factors along Ganjam coast, east coast of India

Abstract

The Odisha coast along the east coast of India is home to three mass nesting sites (Gahirmatha, Devi and Rushikulya) and several sporadic nesting sites for olive ridley sea turtles. The coastline in the Ganjam district of Odisha has more than nine beaches that report olive ridleys (Lepidochelys olivacea) nesting, including one mass nesting site i.e the Rushikulya estuary. To develop a better understanding of beach habitat conditions along the Ganjam district's 60-km-long coastline, a survey was conducted and data on the extent of olive ridley mortality, associated threats (both direct and indirect), and factors affecting habitat loss, were collected. The survey was carried out entirely on foot between March and April 2020, visiting nine separate sites three times each. Dead turtle carcasses were seen on only seven out of the nine beaches. The major threats observed were fishing activities and predation; while plastic contamination, topographical changes (shifting in Rushikulya river mouth), vehicular movements, and artificial lighting were the factors associated with habitat degradation. The highest incidences of mortality were caused by fishing activity. In addition, maximum turtle mortality was seen at lower elevations (3 – 6 m above MSL) as compared to beaches with higher elevations. The current survey on olive ridley turtle mortality is the first of its kind along the Ganjam coast and the findings underscore the importance of solidifying conservation efforts on the olive ridleys' habitat.