LONG-TERM TREND OF OLIVE RIDLEy SEA TURTLES (LEPIDOCHELYS OLIVACEA) NESTING IN BRAZIL REVEALS ONE OF THE LARGEST ROOKERIES IN THE ATLANTIC

Northeastern Brazil supports an important population of Olive Ridley Sea Turtles (Lepidochelys olivacea) that was historically depleted due to several human activities. Here, we present the long-term trends in numbers of Olive Ridley Sea Turtles nests observed throughout 16 y of beach surveys. From 2003/2004 until 2018/2019 nesting seasons, we recorded annual nest counts along coastline of Bahia and Sergipe states between September and March. These data were compared with previous published data collected between 1991/1992 and 2002/2003 nesting seasons. We also estimated the minimum number of females nesting annually based on clutch frequency. Our results indicate an upward trend in annual nest counts between 2003/2004 and 2018/2019 with a significant increase in annual clutch counts every 2 y. We also observed a 50-fold increase in nesting numbers when comparing the 12,709 nests estimated in 2018/2019 season to the 252 nests counted in 1991/1992. Based on the average number of nests laid in the last three nesting seasons, we estimated that about 11,923 females nested annually over the study area. Our results highlight that Brazil currently supports the second largest population of Olive Ridley Sea Turtles in the Atlantic. The increase in annual nest counts observed between 1991/1992 and 2018/2019 is probably due to conservation actions that maximized hatchling output from the nesting beaches and reduced threats at sea. Despite this increasing trend, a high level of mortality of mature Olive Ridley Sea Turtles due to incidental catch in trawl fishery has been reported and is a matter of concern for the conservation and population stability in Brazil.

Automated summary

Northeastern Brazil has seen a significant increase in the number of Olive Ridley Sea Turtles nests over the past 16 years. The annual nest counts have been trending upwards, with a particularly large increase observed every two years. There has been a 50-fold increase in nesting numbers since 1991/1992. Despite this positive trend, incidental catch in trawl fishery poses a significant threat to the population stability of the Olive Ridley Sea Turtles in Brazil.