Sea snake (Serpentes: Elapidae: Hydrophiinae) diversity and distribution in Indian waters: Bycatch impacts and cryptic lineages

Sea snakes contribute significantly to food chains and biodiversity in tropical and subtropical marine ecosystems but face threats from bycatch, overfishing, pollution, and habitat loss. Here, we investigate bycatch composition, genetic diversity, and phylogeography of Indian sea snakes. Sea snakes obtained from fishing bycatch from coastal areas of India were surveyed and used to generate population structure, connectivity, and phylogeographic patterns using three mitochondrial markers. Field surveys recorded 117 bycatch specimens, identifying five species, with Hydrophis schistosus being the most abundant (51%) and Hydrophis cyanocinctus the rarest (1%). While Hydrophis platurus exhibits widespread genetic similarity across the Indo-Pacific, several other species, including Hydrophis curtus and Hydrophis schistosus, display deep divergence between eastern and western populations, suggesting possible species-level separation. Hydrophis caerulescens and Hydrophis cyanocinctus exhibit similar marked east–west phylogeographic splits, indicating limited gene flow and historical isolation. Our findings emphasize the importance of widespread sampling in understanding population structuring and the processes underlying genetic divergence over the large distances encompassed by the Indian and western Pacific oceans. Seasonal variation in bycatch and the predominance of bottom trawling suggests that conservation strategies to mitigate fishing impacts and to preserve genetic diversity of sea snakes in this region are needed.