Sea turtle strandings in the temperate Southwest Atlantic: Analysis of drivers and potential causes

Abstract

Marine megafauna are subject to several threats due to the increasing exploitation ofmarine ecosystems. Mortality is frequently evidenced by the occurrence of strandedindividuals in coastal zones; however, conclusive identification of its drivers andcauses is challenging. In this study, we explore the hypothesis that bycatch intrawling is one of the anthropic drivers of sea turtle strandings in the temperateSouthwest (SW) Atlantic, where green (Chelonia mydas), loggerhead (Caretta caretta)and leatherback (Dermochelys coriacea) turtles forage seasonally. Beach survey dataduring March, April and May from 2014 to 2018 were used to characterizestrandings and relate their spatio-temporal distribution to physical and anthropicvariables. Loggerhead (47.4%) and leatherback turtles (49.3%) were the mostcommon stranded species, whereas green turtles were recorded only occasionally(3.3%). Based on the size distribution, strandings reflected both juvenile and adultmortality, with variations between species. Generalized linear models showed thatsea turtle strandings were influenced by winds and sea surface temperature, whilethere was no evidence of a relationship with fishing effort. Further studies shouldassess drowning due to bycatch as a cause of turtle death, since interaction withfisheries is commonly reported in the area and drowned animals may or may notwash ashore. This study raises awareness and assesses, for the first time, themortality of threatened sea turtle species in a poorly known region of its distribution.