Twenty Years of Sea Turtle Strandings in New Caledonia.

In this study, we investigated cause-specific temporal and spatial trends in sea turtle strandings in New Caledonia. Five species of sea turtles were recorded in the 406 strandings documented between January 1999 and March 2021. Green turtles represented the majority of the stranded species (68%), reflecting the importance of the resident green turtle population in New Caledonian waters. Nearly half of the individuals stranded were juveniles (48%). The great majority of strandings were recorded in the South Province, the most populous province of New Caledonia (73%). The main causes of the strandings were classified as unknown (50%), followed by poaching (17%), by-catch (15%), collision (10%), natural (8%), plastic ingestion (0.5%) and other (0.5%). This study contains the first official record of the presence and relative importance of fibropapilloma in New Caledonia, but we could not determine if it was the cause of death for the stranded individuals. Two individuals, after necropsies, were found to have ingested plastic (one in 2011 and the other in 2020). This is the first record of plastic ingestion for sea turtles in New Caledonia. Three significant trends were also found during the study: an increase in the number of individuals reported in the study since 2004; a seasonal effect, with most strandings occurring in summer (November to January); and stranding hotspots. Rehabilitation allowed for 35% of individuals found alive to be released back into the wild. This study suggests that mitigation strategies such as "go slow" zones and a robust stranding network should be put in place in New Caledonia.

Migrations of green turtles (Chelonia mydas) between nesting and foraging grounds across the Coral Sea.

Marine megafauna tend to migrate vast distances, often crossing national borders and pose a significant challenge to managers. This challenge is particularly acute in the Pacific, which contains numerous small island nations and thousands of kilometers of continental margins. The green sea turtle, Chelonia mydas, is one such megafauna that is endangered in Pacific waters due to the overexploitation of eggs and adults for human consumption. Data from long-term tagging programs in Queensland (Australia) and New Caledonia were analysed to investigate the migrations by C. mydas across the Coral Sea between their nesting site and their feeding grounds. A review of data collected over the last 50 years by different projects identified multiple migrations of C. mydas to and from New Caledonia (n = 97) and indicate that turtles foraging in New Caledonia nest in the Great Barrier Reef (Australia) and vice versa. Several explanations exist for turtles exhibiting this energetically costly movement pattern from breeding to distant foraging grounds (1200-2680 km away) despite viable foraging habitat being available in the local vicinity. These include hatchling drift, oceanic movements and food abundance predictability. Most of the tag recoveries in New Caledonia belonged to females from the south Great Barrier Reef genetic stock. Some females (n = 2) even showed fidelity to foraging sites located 1200 km away from the nesting site located in New Caledonia. This study also reveals previously unknown migrations pathways of turtles within the Coral Sea.