New deep-sea fish discovered off Kerala, corrects long-standing taxonomic error

Indian Council of Agricultural Research (ICAR)’s Central Marine Fisheries Research Institute (CMFRI) has discovered a new deep-sea fish from the Arabian Sea off southern Kerala.

The findings of the research have been published in the latest issue of the Indian Journal of Fisheries. It underlines the rich, yet largely unexplored, marine biodiversity hidden in the deep waters off India’s southwest coast.

Named Cyttopsis indica (Indian dory), it was found at depths of 350-500 metres along the continental slope of the eastern Lakshadweep Sea. The newly identified fish belongs to the genus Cyttopsis, a primitive group of marine fishes commonly known as "dories." The discovery is based on six specimens collected from deep-sea trawl landings at Sakthikulangara fishing harbour in Kollam.

Researchers led by CMFRI Scientist Dr Ratheesh Kumar R confirmed the fish as a new species after carrying out traditional taxonomic analysis combined with advanced molecular tools. Until now, the fish seen in the Indian Ocean was believed to be Cyttopsis rosea, a species with distribution now confined to the Atlantic Ocean after this study. The DNA analysis revealed a stark genetic divergence from all other known species in its genus, correcting a long-standing taxonomic error.

The specimens of Cyttopsis species were collected from commercial deep–sea trawl landings at Sakthikulangara Fisheries Harbour, Kollam, Kerala, one of the major fishing harbours along the south-west coast of India. The specimens were obtained from the landings of multi-day otter-trawl vessels operating at depths ranging from 350 to 500 m over the continental slope of the eastern Lakshadweep Sea. Collection was conducted during regular fisheries landing monitoring surveys carried out by the Marine Biodiversity and Environment Management Division (MBEMD) of ICAR-CMFRI, Kochi.

According to the researchers, the discovery underscores the considerable taxonomic and biogeographic complexity that remains to be resolved within the family Parazenidae and provides further evidence of cryptic diversity among deep-sea Zeiformes.

The research paper written by A. Sreeja, R. Ratheesh Kumar, Aju K. Raju, A. X. Treasa, Augustina and S. Anand observes that the recent discoveries of everal deep-sea fish species from the continental slope off the south-west coast of India further highlight the eastern Lakshadweep Sea and northern Indian Ocean as underexplored region for fish diversity, emphasising the need for dedicated studies in the region.