New deep-sea catshark species identified off India's southwest coast

Scientists from the Zoological Survey of India have described a new species of deepwater catshark, Apristurus drona, based on four specimens collected off the coast of Kerala in the southeastern Arabian Sea. The first specimen was found in 2022 during examination of bycatch from deep-sea shrimp trawlers operating at depths of 400 to 650 metres on the Kollam slope, an area designated as an Important Shark and Ray Area. Three additional specimens were collected in 2024 during monitoring surveys at Sakthikulangara Fisheries Harbour in Kollam.

The research team, led by Sweta Beura and corresponding author Bineesh K.K. of the Marine Biology Regional Centre in Chennai, used both morphological examination and DNA barcode analysis to confirm the species was distinct. Genetic sequencing showed a 5.5 to 5.7 percent difference from its closest known relative, Apristurus nayakai from the southwestern Pacific Ocean, well above the typical 3 percent threshold used to delineate shark species. The new species belongs to the Apristurus brunneus subgroup within the genus Apristurus, which contains 42 recognised species worldwide.

Prior to this description, only one Apristurus species — A. investigatoris from the Andaman Sea — had confirmed occurrence in Indian waters. Four other species recorded from India have questionable taxonomic status due to scant records. The genus is considered taxonomically difficult because species show subtle physical differences, making molecular analysis essential for accurate identification.

Apristurus drona is a small, slender-bodied black catshark with an angular, pointed snout and striking white eyes. Researchers note the species has no commercial value due to its small size and high water content. Specimens caught incidentally were previously discarded but are now sometimes processed into fish meal for poultry. The species was absent from bycatch records between 2008 and 2022, appearing only after fishers increased trawling depths to target deep-sea shrimp such as the red ring shrimp (Aristeus alcocki).

Because the species is known from only four specimens collected at two locations — Kollam slope and Wadge Bank — its abundance, distribution, biology, and mortality rates remain unknown. The researchers classify it as data-deficient. Bineesh K.K. noted that if the species is micro-endemic, restricted to a small area, increased fishing pressure at those depths could pose a significant extinction risk.

Over one-third of chondrichthyan species (sharks, rays, and chimaeras) are threatened with extinction globally, primarily due to overfishing, according to the International Union for Conservation of Nature. Deep-sea sharks are particularly vulnerable because of slow growth, low fecundity, and late maturation. While deep-sea fisheries in India remain limited and are monitored by the ICAR-Central Marine Fisheries Research Institute, the expansion of trawling to greater depths raises conservation concerns.

The study was conducted under the Ministry of Earth Sciences' Deep Ocean Mission, which aims to explore deep-sea chondrichthyan diversity and resolve taxonomic uncertainties. Researchers plan systematic monitoring surveys to gather data on the species' distribution, breeding, and natural and fishing-related mortality. This information would be needed to propose any conservation measures.

Independent experts note that three new marine species, including Apristurus drona, were described from Indian waters in 2026 alone, underscoring how much deep-sea biodiversity remains undocumented. The authors suggest future research could also investigate whether the species hosts useful microbes or antimicrobial peptides with potential human applications.