Mapping the past for the future: Spatial and temporal patterns and long-term trends of sea turtle strandings in Hong Kong and wider East Asian waters

Sea turtle strandings provide critical insights into population health and anthropogenic threats, yet long-term data remain scarce for East Asia region, including Hong Kong waters. Here we retrospectively analysed 23 years (2002–2024) of 223 (58 live, 165 deceased) sea turtle stranding records to characterize species composition, demographics, temporal trends, spatial hotspots, and causes of stranding. Standardized Level A data were compiled, complemented since 2019 by virtopsy-integrated necropsy (postmortem CT, 3D surface scanning), and analysed using generalized additive models (GAMs; Poisson family) for temporal trends; kernel density estimation (KDE) and Getis-Ord Gi* statistics for spatial clustering and hotspot detection. Green turtles (Chelonia mydas) dominated (76.7%, n = 171), primarily juveniles, with hawksbill (Eretmochelys imbricata; 7.2%), loggerhead (Caretta caretta; 5.4%), olive ridley (Lepidochelys olivacea; 3.6%), leatherback (Dermochelys coriacea; 0.8%), and unidentified (6.3%). GAMs revealed a significant nonlinear increasing trend over the study period (adjusted R² = 0.595, p < 0.001), with the fitted smooth visually levelling after 2018, and seasonal peaks in spring (Mar–May) and autumn (Sep–Nov). Spatial hotspots concentrated in eastern and southern waters, including marine protected areas. Cause of stranding was determined conservatively based on pathognomonic lesions identified through virtopsy-integrated necropsy; undetermined cases predominated (78.5%, n = 175), followed by anthropogenic causes (17.5%, n = 39), other causes (typhoon entrapment, buoyancy disorder) (2.7%, n = 6), and natural causes (1.3%, n = 3). The most common anthropogenic cause of stranding was fishery interaction including bycatch and fishing gear entanglement (n = 23/39), vessel collision (n = 9/39), and pollution (n = 7/39). Limitation of this study included the majority of cause of strandings were classified as undetermined, underscoring the urgent need for enhancements in stranding investigation methodologies. This first long-term assessment for Hong Kong integrates advanced postmortem imaging with spatial and temporal modelling. Eastern and southern spatial hotspots and spring/autumn seasonal peaks warrant priority fishery bycatch mitigation, vessel speed restrictions, and targeted stranding patrols to enhance East Asian sea turtle conservation. © 2024. Published by Elsevier B.V.