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Sand Mining Behind Cauvery Basin’s Humpbacked Mahseer Fish’s Extinction?

Mahseer fish, found only in Cauvery basin, is on the brink of extinction, going by a joint study by Indian and UK biologists, who attribute the cause to pollution, sand mining and upcoming hydel power projects on the river Cauvery, especially the Mekadatu dam.

First mentioned in HS Thomas’s ‘A Rod in India’ in 1873,  the giant fish of the carp family has been known to anglers around the globe as ‘one of the largest and hardest fighting freshwater fish in the world’ and its distribution has been limited to South India’s River Cauvery.

Rajeev Raghavan of the Conservation Research Group of St Albert’s College in Kerala and his British counterparts from the Bournemouth University studied logbooks maintained by 3 angling camps on the Cauvery to come to this conclusion.

The Humpback Mahseer - internal

The Humpback Mahseer (Photo: https://www1.bournemouth.ac.uk)

These proxy indicators of the eroding population of the orange-finned fish in the Cauvery river show that the fish can survive maximum one more generation and become extinct soon. “This fish is now believed to be so endangered it may be extinct in the wild within a generation,” said Raghavan.

Out of 17 species of Mahseer fish species, 4 are already listed as ‘Endangered’ on the International Union for Conservation of Nature (IUCN) Red List and soon the ‘Humpback Mahseer’ of cauvery basin would join the list, going by these researchers.

Another interesting angle of their research was the introduction of Maharashtra’s blue-finned Mahseer in the Cauvery basin the in the 1980s that made the species survive in abundance but at the cost of native Mahseer, said researchers.

“Without a doubt, their (Maharashtra) success has been at the expense of the humpbacked Mahseer that historically occurred throughout the entire river catchment,” said Adrian Pinder of Bournemouth University in the UK.

Another feature going against humpbacked Mahseer is that it was not named as an entirely different species and hence its extinction will not even make its presence in the records, said Pinder.

“The state of confusion surrounding Mahseer taxonomy means the humpback Mahseer currently lacks a valid scientific name and could potentially go extinct before being named,” he noted and said that it is not too late to obtain DNA from this fish species and name it and include it in ‘critically endangered’ on the IUCN Red List.

Their findings have been published in the journal Endangered Species Research.


  1. Siddhartha, your comment is very interesting. I would appreciate knowing more about this so we can include your thoughts as part of our future studies & negotiations. Perhaps you can email me on: steve@mahseertrust.org with more specifics? Especially dates (years) of introductions.

  2. Other than the reasons mentioned above, one of the main reasons for this impending threat of extinction of the Giant Humpbacked Mahseer Fish in the Cauvery would be the stealthy and unscientific (and possibly unauthorized) introduction of hatchling, juvenile and young crocodiles from Bannerghatta and surrounding areas brought in by the wildlife forest guards /officials and dropped in places like Sangama, Mekedatu, Bommasandra, etc. in the Cauvery Wildlife Sanctuary vicinity area of Kanakapura Taluk. I have indisputable first-hand information & evidence of this. This used to be the area where this particular Mahseer species was most protected and flourished. This part of Cauvery used to have crocodiles before too, but the characteristics and nature of the crocodiles introduced later are very different from the original local ones. The later introduced crocodiles are relatively more aggressive in nature, less afraid of humans and have started to threateningly dominate the river space here. They have disturbed the sensitive balance of the eco-system here. I am a local and a keen observer of this place and have personally experienced the fast deteriorating situation of the Cauvery due to outside introduced crocodiles in this particular space that used to be a heaven for Mahseer and other riverine species. A detailed scientific study and corrective action in this regard is Highly Urgently needed to restrict further damage to the eco-system here

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