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What’s in a name? Unravelling the scientific identity of an iconic game fish

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Martin Clark with a hump-backed mahseer of 92lb captured from the middle Cauvery in 1978
Martin Clark with a hump-backed mahseer of 92lb captured from the middle Cauvery in 1978   (Photo: MaTrans World Fishing Team)

Confusion in species names not only impacts our understanding of how a species is faring under a range of anthropogenic threats, but also hampers conservation efforts for sustaining future populations in the wild. Such has been the case for the hump-backed mahseer, which after 145 years of first being publicised, has finally achieved clarity in terms of its scientific nomenclature. A recent study, led by Adrian Pinder from Bournemouth University, UK, used multiple lines of enquiry to resolve the taxonomy of this iconic fish.

This study was carried out in collaboration with scientists across several institutes in India, including Bharathiar University and Zoo Outreach Organization (ZOO), Coimbatore, Mahatma Gandhi College, Thiruvananthapuram, Nirmalagiri College, Kannur, Indian Institute of Science Education and Research (IISER), Pune, Kerala University of Fisheries and Ocean Studies, Kochi and the Ministry of Environment, Forest and Climate Change.

Mahseers, commonly referred to as “tigers of the water”, are large fish endemic to freshwater habitats in continental Asia. As a genus which can attain large sizes, these fish have been popular targets for recreational angling. However, variation in size and body coloration in these fish has resulted in taxonomic confusion.

The hump-backed mahseer, native to south India, is a prized catch and has iconic status with anglers across the globe. However, the species had existed without a proper scientific identity since it was first mentioned under its common name in a 1873 book about sport fishing in India. “This was perhaps because it was never recognized as being different and consequently there was no formal scientific description,” says Pinder, who is also the Director of Research at Mahseer Trust.

Pinder and colleagues carried out systematic body size measurements and molecular analysis for a range of mahseer specimens (Genus Tor). The authors included specimens from museum repositories and live fish samples of four different mahseer species: Tor khudree, Tor malabaricus, Tor remadevii and Tor putitora. They also sieved through historical photographs to decipher similarities in body size and colouration of the hump-backed mahseer with other mahseer species.

The researchers found that the hump-backed mahseer showed morphological and taxonomic characteristics similar to Tor remadevii, a species first described in 2007. Genetic studies, phylogenetic analyses and morphometric measurements confirmed these results. “Thus concluding that the giant hump-back is the same as T. remadevii,” says Pinder.

Adrian Pinder and Steve Lockett from Mahseer Trust measuring morphology of various Tor specimens at Natural History Museum London

This is good news for conservation efforts directed towards protecting this iconic fish. “The hump-backed mahseer now having a valid scientific name means it can be Red Listed,” says Pinder. Tor remadevii is endemic to India, with a restricted distribution within the Western Ghats (Cauvery basin). In recent times, this habitat has been threatened by anthropogenic activities such as destructive fishing.

“Our recent interviews with local fishers suggest that the population of larger fish has drastically reduced in recent years,” says Pinder. The authors are already in the process of enlisting the species as Critically Endangered, which would be vital to conserve critical habitats and the existing populations.

“Unfortunately, there is dearth of a clear database on the status of several megafaunal fish species in tropical river systems, especially for countries like India, where studies on freshwater systems and their fauna are already sparse,” says Anuradha Bhat, Indian Institute of Science Education and Research (IISER), Kolkata, a freshwater ecologist who was not associated with this study. “The recent work by Pinder et al. is a much needed and timely study on a critically endangered group of fishes.”

Now that the hump-backed mahseer finally has a scientific identity, it is anticipated there will be earnest efforts to conserve and secure the future of its remaining populations in the Cauvery basin.

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Chandrima is a PhD survivor and a full time mom. She is trying to bridge the science and communication divide by being a more communicative scientist