- The IUCN has red-listed the hump-backed mahseer, believed to be endemic to river Kaveri, as critically endangered following a taxonomic evaluation and a scientific name, Tor remadevii.
- At Galibore fishing camp, near Bengaluru, the ratio of hump-backed to blue-finned mahseer was 1:4 in 1998, by 2012 this was 1:218, researchers say.
- Destructive fishing methods, building of dams that reduced the flow rates in the river, over-abstraction of water and pollution are cited as reasons for the dwindling numbers.
The orange-finned mahseer or hump-backed mahseer, believed to be endemic to the Kaveri river that flows through the states of Karnataka and Tamil Nadu, has been an enigma for anglers all over the world and a source of much debate among ichthyologists and environmentalists. Most recently, the red-listing of the fish as a Critically Endangered species by the International Union for Conservation of Nature (IUCN) in 2018, sparked differences of opinion among experts.
A type of carp of the family Cyprinidae, the hump-backed mahseer can grow to a length of 1.5 metres, the size of a small human. The biggest one caught so far — by British angler Ken Laughran in Valnoor, in Kodagu district of Karnataka, in 2012— weighed close to 60 kilograms. Some say that the name ‘mahseer’ was derived from the Sanskrit words ‘maha’, meaning big, and ‘seer’ meaning head; others conjecture that the name is Indo-Persian, from the words ‘mahi’, meaning fish, and ‘sher’, meaning tiger.
The most sought-after game fish in the world, the hump-backed mahseer is also called the Tiger of Kaveri for the fight it puts up, giving anglers the thrill they seek.
The sobriquet of ‘tiger’ seems to fit even more perfectly with the IUCN’s critically endangered species status, the highest threat status – just a step short of ‘Extinct in the Wild’.
Ironical, for a fish that is believed to have divine protection. For devotees of temples on the banks of the Kaveri, the ‘kempu gari bilimeenu’ (red-finned white fish), is God’s emissary and spotting one among the black and white ones that congregate at the fish sanctuaries of temples like Vahni Pushkarani in Ramanathapura, Karnataka, is the rarest of rare sights, they believe. Scientific studies, however, suggest reasons other than the mystical for the rare sightings of the orange-finned hump-backed mahseers, in a river that was once considered a hotbed for this megafauna.
Conflicting views on taxonomic classification
Belonging to the genus Tor, this fish was earlier confused with Tor Putitora or golden mahseer found in Himalayan rivers. However, a detailed taxonomic evaluation in 2018 by ichthyologists from the Kerala University of Fisheries and Ocean Studies (KUFOS), the Indian Institute of Science Education and Research, Pune (Maharashtra) and Bournemouth University, United Kingdom (UK), revealed that the orange-finned mahseer, native to river Kaveri, is, in fact, different and possesses the same genetic and morphological characteristics of another mahseer species, Tor remadevii, which was earlier identified by a group of researchers from Cochin University of Science and Technology during their study of juvenile mahseer specimen in the Pambar river, one of the tributaries of the Kaveri, in the early 2000s.
But some experts in the field believe that the hump-backed mahseer is a subspecies of Tor mussullah, a mahseer species found in the rivers of the Deccan region, including Maharashtra.
Shashank N. Ogale, former head of environment and corporate social responsibility, Tata Power, who spearheaded the mahseer conservation efforts for four decades at Tata Power’s hatchery in Lonavla, Pune, is certain that the hump-backed mahseer in the Kaveri is Tor mussallah. “Tor mussallah too is hump-backed. Colour is not a criterion to identify a fish species because it changes due to various reasons like seasonal changes and melanism. The Tor mussallah population is also on the decline but the fish is not endemic to the Kaveri,” he says.
What’s in a name?
According to Steve Lockett, education and outreach officer, Mahseer Trust, a U.K.-registered charity set up to conserve mahseers, a formal taxonomic name for this iconic but endangered mahseer species could mean a lot.
“Without a valid scientific name, species do not qualify for international conservation status assessment. So, this has been a crucial milestone in getting the animal formally recognised and protected,” adds researcher Adrian Pinder of Bournemouth University, who was involved in the study.
Just as well since, in the absence of any study of this fish in the wild, very little is known about it other than its physical features.
Of the seven mahseer species identified in Indian rivers, the hump-backed mahseer is the largest in size. With a distinct head and a large body, they are omnivorous and can be cannibalistic too. They play a very vital role in balancing the riverine ecosystem by feeding on everything from fish, frogs, crabs, aquatic insects, worms, fruit, seeds, leaves and algae. But the hump-backed has its favourites, such as the fruits from riparian vegetation like mango and cannonballs. They are fast swimmers and are believed to swim into tributaries to breed at the onset of monsoon. It is also speculated that they spawn in the main river water system and multiple times a year. Mahseers are also found to prefer faster flows where oxygen levels are higher and, in the absence of it, could take refuge in deep pools.
Multiple reasons suggested for the decline in population
Although speculative, the general consensus is that there could be multiple reasons for the declining numbers of hump-backed mahseer — destructive fishing methods like gill netting, poisoning and extensive use of dynamite in rivers before regulations were put in place; building of dams that reduced the flow rates in the river and affected fish habitat and migration; over-abstraction of water due to tourism in Coorg; sand mining that has affected the river bed and led to loss of spawning grounds; sewage and other pollutants that have brought down the dissolved oxygen levels in the water, to name a few.
Another reason cited by some experts is that the Tor khudree or blue-finned mahseer, ranched at the Tata Power hatchery in Lonavla was released in huge numbers into the Kaveri by the Karnataka fisheries department from the early 1970s onwards to populate the river. Experts at the Mahseer Trust believe that overstocking of artificially-bred Tor khudree species could have contributed to the decline of the hump-backed mahseer.
Ogale differs, however. He says Tor khudree is not an invasive species. “If it has affected the hump-backed mahseer population, why are other fish not affected? The population of all mahseers including Tor khudree, is affected due to other reasons like loss of natural habitat and breeding grounds,” he adds.
‘Critically endangered’ label contested
C.P. Aiyappa of Coorg Wildlife Society (CWS), an organisation dedicated to protecting the ecology of the Kaveri since the early 1980s, remains unconvinced that a sturdy, fighter fish like the hump-backed mahseer could be endangered.
Sitting on the banks of the Kaveri at Valnoor, where the CWS has taken a 34-kilometre stretch of the river on lease for conservation, Aiyappa says that he stills spots a number of hump-backed mahseer splashing around. According to Aiyappa, the mahseers are too smart for gill netting. He recounts an incident during a study last year when researchers had blocked a long stretch of the river and let the gill nets run zig-zag to catch as many fish as possible. “They couldn’t net a single hump-backed mahseer and the net was torn to shreds by the fish. Mahseer are smart fish. When they see resistance on a line, they let go and don’t come back,” says Aiyappa.
But the larger consensus is that it is difficult to spot this fish now. Says Sandeep Chakrabarti, who has been fishing in the Kaveri the past two decades. “The Kaveri had hump-backed mahseer in abundance in the 1970s, up till the 1990s. It was the predominant species at that time. But there has a sharp decline after that,” he says.
Angler catch data collected to identify the fish, too, points in that direction. “At Galibore fishing camp, near Bengaluru, the ratio of hump-backed to blue-finned mahseer was 1:4 in 1998, by 2012 this was 1:218,” says Pinder, who also believes that prior to stocking of blue-finned mahseer, the mahseer community in the Kaveri consisted only of the endemic hump-backed mahseer.
This is, however, contested by Aiyappa and local fishermen who say that apart from orange-finned mahseer, black-fin and silver-fin species have been in the Kaveri for decades. “Local knowledge is that there have always been three types of mahseers in the Kaveri — kempu gari (red-finned), kappu gari (black-finned) and belli meen (silver fish). We could eat the red one but the black and silver ones made us vomit,” he says.
Rajeev Raghavan, assistant professor, department of fisheries resource management, KUFOS, who was associated with the research says that they based their conclusion that the fish is endangered on the globally-accepted red list category and criteria with the main inference drawn from the study of the distribution and population of the fish. “We looked at the entire Kaveri catchment to study the extent of occurrence (EOO) and small pockets of the river to study the area of occupancy (AOO) of the species. The population was studied on the secondary data collected through angler catch at government-run Jungle Lodges fishing camps at Galibore, Bheemeshwari and Doddamakali. The result of this rigorous study made us conclude that this mahseer species fell into the threshold of critically endangered species,” he explains.
Even as the debate continues, one thing is certain — without concerted efforts on the part of researchers to understand the fish in the wild and the authorities to work towards a feasible solution to conserve them, the Tiger of Kaveri, much like its namesake on the land, will soon be a thing of the past.
Banner image: Fish at Vahni Pushkarani temple. Photo by Abhishek N. Chinnappa.