Tor remadevii, the orange-finned mahseer, also known as the hump-backed mahseer, is a Critically Endangered species of freshwater fish endemic to the Western Ghats of India.[1] It is restricted to the Kaveri river basin.
It can be distinguished from other mahseer by the prominent hump originating above the pre-opercle, a distinctive kink in the pre-opercule, a terminal mouth position, and its bright orange caudal fin. It is considered a high-quality game fish, and has been proclaimed by anglers as "the largest and hardest fighting freshwater fish in the world".[2]
Among the reasons for the species' extreme threat status is the introduction of non-native mahseers Tor khudree [3] and Himalayan golden mahseer (Tor putitora) [4] to the wider Kaveri river basin. Also endangering this species is the heavy construction of dams along the Kaveri and tributaries, as well as the use of dynamite fishing.[5] These and other factors including loss of riparian cover, industrial and urban pollutions, irrigation and abstraction, plus climatic changes in monsoon weather patterns led to a heavy crash in hump-backed mahseer populations around 2004.
Despite this endangered status, the general lack of a formal scientific name had previously hampered efforts to protect the species. However, a 2018 study found that the orange-finned mahseer was in fact conspecific with Tor remadevii, a little-known species identified in 2007 based on 19 individuals [6] sampled from the Pambar River in 2004.[7] This has allowed the species as known from historic records across the whole river basin to finally gain a scientific name and an updated Red Listing. These will both be of help for future conservation efforts.