Exploring the demography and conservation needs of hawksbill sea turtles Eretmochelys imbricata in north-west Mexico

Abstract

The hawksbill sea turtle Eretmochelys imbricata is categorized as Critically Endangered on the IUCN Red List and its population has declined by over 80% in the last century. The Eastern Pacific population is one of the most threatened hawksbill populations globally. Western Mexico is the northern distribution limit for hawksbill sea turtles in the Eastern Pacific and recent research indicates that the Mexican Pacific portion of the population is a separate management unit because of the restricted movements of these turtles. Here we use the most complete database of sighting records in the north-west Pacific of Mexico to identify sites where hawksbill turtles are present. We also develop a conservation index to determine the conservation status of hawksbill turtle sites. Our results demonstrate the importance of this region for juveniles and the relevance of rocky reefs and mangrove estuaries as habitats for hawksbill turtles. We identified 52 sites with records of hawksbill turtles. Most of these sites (71%) are not protected; however, sites with high conservation value included islands and coastal sites along the Baja California peninsula that are established as marine protected areas. Reefs and mangrove estuaries relevant for hawksbill turtles are probably also significant fish nursery areas that are important for local fishing communities, creating opportunities for conservation strategies that combine science, local engagement and policy to benefit both local fishing communities and hawksbill sea turtle conservation.

Diet of hawksbill turtles (Eretmochelys imbricata) in the Gulf of California, Mexico

“…Turtle body size ranged from 33.8 to 82.6 cm SCL (mean: 48.2 ± 9.6 cm) (Supporting Information Table S2). Most of the turtles (54 of 56, 96%) fit within the size range estimates for juveniles (Table 1), whereas two individuals (76.6 cm and 82.6 cm SCL) were classified as putative adults based on the mean nesting female hawksbill size reported for the region (CITES, 2002; Van Houtan et al, 2016b; Martínez‐Estévez et al, 2022a).…”

“…Based on abundance estimates in foraging sites of north‐west Mexico, including the Gulf of California (Martínez‐Estévez et al, 2022a), the San Jose foraging ground appears to be one of the most important developmental hotspots for hawksbills in the Mexican Pacific. The smallest turtle captured in the study was 33.8 cm, supporting the idea that turtles in this population transition into this area as later juveniles after spending some amount of time in offshore, pelagic regions during their earliest, post‐hatching, juvenile stage.…”

Ethnobiological methods enhance our capacity to document potential climate sentinels: a loggerhead sea turtle (Caretta caretta) case study

“…Leatherback sea turtles (Dermochelys coriacea), which forage in Monterey Bay, were ruled out due to their distinctive morphology (Benson et al, 2020). Hawksbill sea turtles (Eretmochelys imbricata) were also ruled out due to their restricted range (e.g., tropical coral reefs and mangroves) and restricted movements (Martıńez-Estevez et al, 2022). Each composite image contained photographs of a single species from multiple angles, with clearly visible distinctive features to aid in their characterization (Pozzi and Ladio, 2023).…”