Anthropogenic threats associated with mortality and biomass of stranded sea turtles on the northern coast of São Paulo State, Brazil

Abstract

ABSTRACT Beach monitoring programmes along the Brazilian coast in recent years have provided stranding data which can be analysed to show the effects of human impacts on sea turtle populations. In Brazil, the five species recorded are threatened with extinction. In this study, data from strandings of sea turtles on the northern coast of the State of São Paulo, Brazil, over six years (2015–2021), were used to evaluate whether human activities are associated with impacts on the populations and to analyse the effects of seasonality on abundance. There were 6411 strandings of sea turtles, the majority being Chelonia mydas, followed by Caretta caretta, Lepidochelys olivacea, Eretmochelys imbricata and Dermochelys coriacea. Strandings occurred mainly during winter and spring. Where it was possible to determine the cause of death of an individual, there were several associations with anthropogenic factors, mainly solid waste, fishing gear, collisions with vessels, injuries and dredging. The high incidence of strandings of sea turtles on the Brazilian coast, mostly juveniles, and the great impact of anthropogenic factors in the causa mortis indicate the need to adopt ocean education strategies and public policies that can establish effective management and conservation plans of marine ecosystems.