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.

"Going with the flow" or not: evidence of positive rheotaxis in oceanic juvenile loggerhead turtles (Caretta caretta) in the South Pacific Ocean Using Satellite Tags and Ocean Circulation Data.

The movement of juvenile loggerhead turtles (n = 42) out-fitted with satellite tags and released in oceanic waters off New Caledonia was examined and compared with ocean circulation data. Merging of the daily turtle movement data with drifter buoy movements, OSCAR (Ocean Surface Current Analyses--Real time) circulation data, and three different vertical strata (0-5 m, 0-40 m, 0-100 m) of HYCOM (HYbrid Coordinate Ocean Model) circulation data indicated the turtles were swimming against the prevailing current in a statistically significant pattern. This was not an artifact of prevailing directions of current and swimming, nor was it an artifact of frictional slippage. Generalized additive modeling was used to decompose the pattern of swimming into spatial and temporal components. The findings are indicative of a positive rheotaxis whereby an organism is able to detect the current flow and orient itself to swim into the current flow direction or otherwise slow down its movement. Potential mechanisms for the means and adaptive significance of rheotaxis in oceanic juvenile loggerhead turtles are discussed.

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.

The coral sea: physical environment, ecosystem status and biodiversity assets.

The Coral Sea, located at the southwestern rim of the Pacific Ocean, is the only tropical marginal sea where human impacts remain relatively minor. Patterns and processes identified within the region have global relevance as a baseline for understanding impacts in more disturbed tropical locations. Despite 70 years of documented research, the Coral Sea has been relatively neglected, with a slower rate of increase in publications over the past 20 years than total marine research globally. We review current knowledge of the Coral Sea to provide an overview of regional geology, oceanography, ecology and fisheries. Interactions between physical features and biological assemblages influence ecological processes and the direction and strength of connectivity among Coral Sea ecosystems. To inform management effectively, we will need to fill some major knowledge gaps, including geographic gaps in sampling and a lack of integration of research themes, which hinder the understanding of most ecosystem processes.