Habitat use of juvenile green sea turtles along the North Pacific coast of Costa Rica

Understanding how threatened marine species use coastal areas and the extent of connectivity across different spatial and temporal scales is important for identifying critical habitats that can enhance conservation efforts in other regions of their distribution. In this study, we investigated the site fidelity and habitat use of juvenile yellow morphotype green sea turtles ( Chelonia mydas ) in the Gulf of Santa Elena, north Pacific coast of Costa Rica. Fifteen juvenile green sea turtles (49 – 83 cm curved carapace length; CCL) were monitored for 19 – 629 days with an array of 11 acoustic receivers placed within 5 main habitat types: muddy areas, reef patches, macroalgae, rocky reefs, and mangroves. Daily and seasonal locations of the turtles were estimated using a positioning estimation algorithm to determine the site fidelity and habitat use within the study area. Large juveniles (≥ 65 CCL) were detected disproportionally in the macroalgae habitat during the upwelling season (43.9% detections) from December – April, and in the reef patch habitat during the non-upwelling season (36.0%) from May to November. Small juveniles (< 65 cm CCL) had more detections in the reef patch habitat during both seasons (Upwelling: 35.4%, non-upwelling: 45.4%) relative to other habitats sampled. More than half of the turtles monitored (67%) showed strong site fidelity to the study area, ranging from 68.9 to 100% from October 2020 to September 2022. Our results suggest that juvenile green sea turtles, particularly larger individuals, have a strong association with coral / rocky reef patches and macroalgae habitats, similar to adults. Our finding suggested that protecting similar habitats in other areas along the Central American coast will help rebuild the Eastern Pacific Ocean green sea turtle population.