How a researcher found a snow trout near Thar desert – and why it’s vital to study it further
This biological puzzle could be the key to deepen our geological understanding of the region.
The fish that Raza Tehsin found in Rajasthan in 1987. | Arefa Tehsin
In the summer of 1987, the naturalist Raza H Tehsin was collecting biodiversity data at Matoon Mines near Udaipur city just east of the Thar desert in Rajasthan. Hindustan Zinc Limited was excavating rock phosphate here and had hired Tehsin – my father – to survey the fauna of this region.
Tehsin’s fascination with caves led him to ask the staff about unexplored caverns in that area. The chief engineer took him to a 50-foot shaft, which was said to have been formed because of copper being mined here several centuries before.
On an impulse (and much to the consternation of the three other researchers accompanying him), Tehsin climbed down the shaft without a rope or gas mask – or even a torch.
Little did Tehsin know that his adventure that day would lead him to a discovery that opened questions about the course of evolution and about the possibility that an ancient Himalayan waterway may have run its serpentine path in the Thar before the movement of the tectonic plates changed its course.
The bottom of the shaft, he told me later, was covered with debris and there was a pitch dark passage into the mine. He picked up a stone and threw it inside, trying to determine if the drop was steep. He heard a plop. There was water ahead.
After a tedious ascent clinging to the wall, he informed the engineer about the water source. This was good news for the company. The mill to grind the phosphate had halted operations because it had run out of water. Now it could resume work.
Tehsin made one request, though: could they please tell him if they found any fish?
Abuzz with activity
A month on, when Tehsin visited again, the shaft was transformed. There were ladders, electric fittings and pumps. The chief engineer was pleased. He had been praised by his seniors for restarting work. Though water was being pumped from the underground reservoir for 12 hours every day, it would fill up again during the night.
There were plenty of fish, the staff told him. But to Tehsin’s dismay, he was told that many kilograms of fish had been gathered – and eaten.
He found only one remaining specimen. The mine workers had helped him catch it by pumping out the water. At the time the fish was captured, the water in the cave had a temperature of 18°C. The team took photographs of the fish and preserved it in formalin.
Raza Tehsin in 2006.
It was sent to VS Durvey, the head of department of fisheries at Mohan Lal Sukhadia University, Udaipur. He was an expert of limnology or the study of inland waters, both fresh and saline.
Durvey tentatively identified the cave fish as belonging to the Schizothoracine family of snow trout, a type of carp that are normally restricted to the cool mountain streams of the Himalayas. The closest members of this family of fish lie several hundred kilometres away on the far side of the Thar Desert.
It was most mysterious. How did a fish swim from the great mountains to the great desert?
As it turned out, that wasn’t the only mystery. Durvey noted that some of the characteristics of the specimen did not coincide with that of the snow trout.
To try to get a firm identification, the specimen was sent to Bombay Natural History Society in January 1988 and they forwarded it to the marine biology expert BF Chhapgar. But the Society, it seemed, did not have adequate literature on the subject. In search of more definite information, the speciment was sent to the British Museum. After that, the specimen went missing. Despite repeated reminders by Bombay Natural History Society, there has not been a response from the British Museum till date.
In a video interview in 2006, Durvey said that snow trout is found in Kashmir, Himachal Pradesh, Uttarakhand and the higher reaches of Himalayas. “It was not something new,” he said. “But to get the fish in the plains, that too in the region of Rajasthan was something unimaginable and absolutely new.”
He had a theory about how Tehsin could have come to find the specimen in the mine outside Udaipur: “The significance of this find to me is that, sometime or the other in the past geological history of the region, a Himalayan river must be flowing through Rajasthan.”
In 1988, Tehsin, Durvey and a student named M Kulshreshtha, who had accompanied Tehsin on his second trip to Matoon Mines, published a research note in the Journal of the Bombay Natural History Society.
“Schizothoracine fishes inhabit hilly streams and lakes in the Himalayan and sub-Himalayan region extending to China,” they wrote. Such fishes had also been observed in Kashmir, Punjab, Afghanistan, Pakistan, Tibet, and Nepal, they said.
As a consequence, “the occurrence of a Schizothoracine fish in the region south of Aravalli hills in Rajasthan is intriguing”, they wrote. “Presently there is no river or seasonal stream in this region connecting the drainage of the sub-Himalayan region of Punjab and Jammu Kashmir. Since the cave does not receive any surface drainage, the presence of Schizothoracine fish in the cave could be a case of geographical isolation.”
They added: “It is almost certain…that the river and streams of western Rajasthan…had Himalayan connections in former days. There could also be an underground drainage of the sub-Himalayan watershed connecting the streams and rivers of the region south of Aravalli ranges. Obviously, the water of this drainage could be cold.”
VS Durvey and Raza Tehsin in 2006.
As for specimen’s unconventional appearance, they explained that the “peculiar assemblage of different generic characters in the specimen studied could be the sequel of interbreeding and long isolation, thereby inducing speciation”.
After the publication of the research note, the acclaimed professor of geology SS Mehr, who worked for 25 years in the Himalayas, contacted Durvey. He told them that their findings confirmed his findings about the course of older rivers.
“He brought certain samples of stones from Rivers Luni and Ghaggar, and he told me that it was almost certain that a few thousand years back Himalayan rivers were flowing through Rajasthan and joining the Arabian Sea,” said Durvey. “While we have the geological evidence to show that these rivers were flowing through Rajasthan, this is a biological evidence. That too of a higher order. To get an evidence at a micro level, bacterial level or algae level is possible. But to get a higher level of animal kingdom is something very important.”
In 2006, two Australian scientists, behavioural biologist Culum Brown and ecological geneticist Felicity Brown, launched an expedition called “Lost in the Desert” with Raza Tehsin to try to collect further specimens of the fish from the cave complex. They were funded by Australian Geographic. But they were unable to find any more fish.
“When we came over to search for further specimens there was an incredibly bad drought,” said Brown, who is now Director Higher Degree Research (Biology) at the Macquarie University and assistant editor of the Journal of Fish Biology. “We had trouble finding water, let alone any fish, so this still remains something of a mystery.”
He added:“There is no doubt that historically a Himalayan river once flowed through Rajasthan. That has been noted several times by geologists. Due to slight uplifts in the landscape, the river was diverted east. But there are still substantial subterranean water flows in the region and it is certainly possible that these waterbodies act as refugia for fish that are no longer present on the surface. The surface water that exist today are simply too hot for snow trout, but below ground it is substantially cooler.”
Durvey remarked during the video documentation of the expedition that the underground caves in this part of the Aravallis have not been charted.
“Adivasis have told me that there are underground caves that contain water,” he said. “But then how to do it is a problem. It is a big project which has to be funded by a big organisation. Quite likely in other caves which we have not surveyed so far, they [the fish] must be there. It requires a real scientific investigation of high order with adventurous people getting into it and confirming this.”
Australian researcher Culum Brown enters the shaft at the Matoon Mine.
Brown was one of those adventurous ones who followed Tehsin’s footsteps and ventured into the underground caves. “I’d say that it remains an intriguing possibility that snow trout exist in these underground systems,” he said. “Having said that, open cut mining in the area is draining the water table so these activities pose a great threat to subterranean water ecosystems.”
In 2015, Tensin gave an interview to PTI recalling his find. “This area lies in the Aravalli hills, one of the oldest ranges of the world,” he said. “There is no geological evidence from the historical era of a glacial river originating in the Aravallis or human memory of a Himalayan river flowing through this region. A major part of the drainage of the Aravalli region today is connected to the Gangetic system and some flows south, towards the Arabian Sea. It is possible that several thousand years back the drainage of Mewar was flowing towards the west and a tributary of a larger Himalayan river could have joined this drainage.”
He added: “The fishes of the Himalayan region might have migrated through its tributaries towards Mewar. Due to geological changes, a fish species from the cold streams could have been cut off from their main water body, got trapped and survived in cooler underground water.”
At the time of its discovery, the prevalent opinion of geologists as well as fish experts was that it was the first live biological evidence that the Saraswati river mentioned in the Vedas once flowed through the Thar desert of Rajasthan. However, a recent research in hydrology published in the Proceedings of the National Academy of Sciences, the official journal of the National Academy of Sciences in the US, points that no glacial-fed rivers flowed between the Indus and Ganges basins during the Holocene – the epoch that began 11,650 years ago. All these rivers were rain-fed.
The snow trout that my father discovered is a biological indicator of a Himalayan cold-water stream or a river tributary that would have flowed through the Indus-Yamuna region, possibly very close to the Aravalli hill ranges. It may well be closely related to snow trout; however, it is likely to be a new species, specially adapted to life in caves as it lived in apparent isolation for thousands of years.
The spate of debates and research into the myth of the Saraswati has gained ground after the Indian government’s multi-million project to “revive” the river. While the scientific basis of this project is questionable and its political aspect is evident, the discovery of a cave fish needs to be pulled out from the distant haze of the 1980s.
This biological puzzle could be the key to deepen our geological understanding of the region and the story of how it came to be.
Arefa Tehsin is the author most recently of Steed of the Jungle God & Amra and the Witch. Visit her website here.