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‘Tigers’ of River Cauvery: Earth’s Most Iconic Freshwater Fish Named After 150 Years!

Can a name save an endangered species of fish from extinction? Ask these researchers, they’ll say “Yes! Definitely!” In fact, their research is solely based on resolving the naming issue of one of the most iconic yet endangered fish in India.

In 1873, a British civil servant named Henry Sullivan Thomas released a book called “The Rod in India”, which documents various game fish caught in India.

One of the iconic game fish showcased in the book is the humpback mahseer, found in the Cauvery basin. The huge carp that is known to grow up to 1.5 metres in length and weighing about 55 kg is also known as “Tigers of the Water”, due to the fight it puts up!

That documentation is one of the few records of the fish ever being caught. In fact, the fish is known to be very elusive, so much so that game hunters would come all the way to catch the magnificent beast.

For the longest time, the mammoth fish was thought to be extinct. It was only in 1977 when the Trans World Fishing Team – comprised three Englishmen –travelled to India to explore the country’s rivers before reaching the Cauvery, when they found the humpback mahseer in its glory and very much alive.

Martin Clark of the Trans World Fishing Team with one of the fish caught in 1978. Trans World Fishing

Soon, its popularity grew, and people all around flocked to see the humongous fish, but the species were very less in number already, due to earlier practices of fishing– dynamite fishing where sticks of dynamites were blown up in the water to catch the fish.

Coupled with that, the expanding rate at which dams were being constructed and the industries’ contribution to the water pollution, the species had limited place to migrate to, hence inhibiting the growth of the fish.

The humpback mahseer, as it was unofficially called, was also nearly exhausted due to the introduction of new species into the Cauvery basin. A paper published in 2015 outlined how the humpback mahseer is under threat of imminent extinction.

But the fish was not classified as an endangered species till June of 2018. Why? It’s because of the name.

The iconic hump-backed mahseer. Credit: J. Bailey
The iconic hump-backed mahseer. Credit: J. Bailey

The IUCN Red List of Threatened Species is known for being the most comprehensive and objective global approach for evaluating the conservation status of plant and animal species.

For a species to be classified, it needs a taxonomic name so that its categorisation is not mixed. For this, researchers had to find the wild specimens to analyse the DNA. Finding the species itself was a burdensome task for the team.

Restricted to the Cauvery basin, the fish’s prominent feature by which it can be distinguished is the hump present on its back.

What makes the research much harder is that the last time the fish were spotted was on the River Pambar in Kerala, back in 2007. Unfortunately, these were juvenile specimens, and neither a photograph nor an illustration accompanied the description.

Despite this, the researchers used literature and previous photographs to study the fish. And the classification is not that easy as it sounds.

For this, scientists needed tissue and voucher samples collected from different sources, from markets to inland streams as well as samples of other fish of the same genus.

With permissions from the Department of Forests and Wildlife, Government of Kerala, to Rajeev Raghavan and the Government of Tamil Nadu, the group set out to find the fish and give a name to the species that was discovered 150 years ago.

The researchers found different species of the same genus in River Krishna and its tributaries in Maharashtra, River Chaliyar in Kerala and River Pambar in Kerala. But it was only in River Moyar in Tamil Nadu, that they found the elusive humpback mahseer.

They also found the same species in the River Cauvery at Dubare, Karnataka.

The Cauvery and its tributaries flow through the states of Karnataka, Kerala and Tamil Nadu.  Central Ground Water Board, India
The Cauvery and its tributaries flow through the states of Karnataka, Kerala and Tamil Nadu. Central Ground Water Board, India

Coming back to the lab, the scientists conducted tests in a molecular analysis to Morphometrics, and they finally pinned down the genus as Tor and gave it the name Tor Remadevii.

And currently, the fish is classified as an endangered species, this will allow the organisation to take action against it endangerment, so that the mysterious fish may not end up on the walls of museums.

Reading about the work, it gives a sense of dedication depicted by the researchers and their commitment towards saving endangered species.

(Edited by Shruti Singhal)

Hey, you may also like: WWF Cameras Capture Endangered Snow Leopards in Sikkim for The First Time. Check Out the Pics!

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