Rivers of life

MARINE BIODIVERSITY

Vidyadhar Atkore visits the Shiwalik region of the Himalayas and observes the rich biodiversity of the region, from its many rivers to the variety of species the rivers are home to. Giant fish species such as the mahseer are endangered because of threats such as sand-boulder mining, illegal fishing and use of dynamite.

The Shiwalik region of the Himalayas is one of the most fascinating landscapes in India. I would often visit the nearby forest during my post-graduate study at the Wildlife Institute of India, Dehradun. Rajaji National Park was one such destination. I visited the area just before autumn, when the monsoon had receded. Nonetheless, the forest still carried the freshness of the monsoon.

Lush grass and many small herbaceous plants bobbed their heads along forest trails. Streams flowed abundantly through the forest. Grassy patches were crowded with cattle. Cattle egrets were busy catching grasshoppers amidst a herd of buffaloes. I was lucky enough to travel with AJT Johnsingh, among India’s foremost wildlife biologists and the then WII dean.

In one big pool along a river in the park, Johnsingh pointed to a big school of golden mahseer, a giant sporty fish of the Himalayan waters. The fish is golden in colour with big scales on its body. It has two larger barbels in front of the eyes which act as sensory organs. Mahseer migrate a long distance. They travel from lower stream to higher stream to lay their eggs at the onset of the monsoon. They seem to prefer fresh oxygen with minimum disturbance from humans. They mostly feed on benthic insects, diatoms and algae.

Soon I learned that these giant fish are endangered because of sand-boulder mining, illegal fishing and use of dynamite. The river bed comprising sand, boulder and gravel forms the main breeding habitat for many fish species. Any slight alteration to their habitats may destroy their population.

Inspired by what I learnt about this fish and its habitat, I turned my attention to river ecology. I studied the Ramganga river basin in the Shiwalik Himalayas. Khoh, Kolhu and Mandal rivers are its tributaries flowing in the Lansdowne Forest and Corbett National Park.

Adapting to the Himalayas

Slowly, I learnt that fishes in the Himalayas have adapted to their habitats well, especially torrential streams. How did fish species adapt to such harsh environments? I found that many bottom-dwelling Himalayan fishes have a special apparatus on their body.

For instance, stone sucker fish (garra gotyla) have an adhesive apparatus below its mouth which helps them to cling to rocky surfaces in turbulent waters. Stone suckers are algivores and scrape off algal moss on rocks and boulders. Crossocheilus latius latius (Gangetic latia) is another bottom dwelling fish which also has an adhesive apparatus.

I made notes about the fish caught by my field assistant in Khoh river near the town of Kotdwar in the Pauri-Garhwal district of Uttarakhand. On one occasion, two Gangetic latia caught my attention.

I was stunned to see that the two fish were actually crawling out of the water on a stretch of rock less than a meter in length, and had reached a height of almost 80 to 85-cm from the river floor. They were out of water for nearly 120-125 seconds. After some time, they slipped into the water and started climbing again.

Riverine fishes require a free flow of water to complete their life cycle. Any hydrological barrier on a river can have detrimental effects on such habitat-specialist fish. We still do not know the appropriate height at which such species would climb a certain barrier. It is crucial to understand species biology before planning dams or other hydrological barriers on our rivers.

Apart from fishes, I have often encountered elusive animals in this landscape. Returning from the Mandal river, at one junction, my field assistant showed me otters. There were three or four smooth-coated otters swimming in a big pool and catching fishes and crabs. Otters are very sensitive to human disturbances. Rivers in the Corbett and Lansdowne reserve forest seem to have good otter populations.

Rich resources

Kolhu river is about 16 to 18-km long and flows through the hilly terrains of the Shiwaliks. It joins Khoh river and meets the Ramganga downstream in Uttar Pradesh. After completing fish sampling in the Khoh river, I turned my attention to Kolhu. River Kolhu forms an S-shape in the Kolhuchaur reserve forest. At one such bend, we spotted as many as 32 elephants including a two-week-old calf, sub-adults and mature adult elephants. There was a small animal trail coming from a hillside, later joining Kolhu.

The elephants had all followed this trail and entered the river for a few minutes. We walked a few meters ahead and came to a point where we had to cross the river. All elephants we saw in the morning were feeding on the leaves of mallotus philippinensis (commonly known as ‘Kamala’ or ‘Kapila’) trees. Mandal river forms part of the boundary of the northern part of Corbett National Park.

I wanted to measure the river width at one location where the Mandal joins the Ramganga and decided to cross the river. As soon as I got into the water, I realised that the water was freezing, probably close to zero degrees. I stepped forward gingerly bracing myself against the cold of the flowing river. Halfway across, I reached a point where the water current accelerated. At this point, I felt that getting into the river was a mistake. But it was too late to return. After my footwear got washed away in the water, I caught my breath and recovered from the experience.

Downstream, I discovered that the river plunged into a deep gorge which went further into the core areas and was the ‘restricted zone’ of the Corbett National Park. Fearfully, I decided to descend into the core zone. There was no question of a proper trail. From one side of the hill, I alighted gingerly clutching at plants for support.

While returning, I noticed a fresh tiger pugmark filled with water. The tracks led to a partially hidden cave. “That’s it”, I said. With alacrity, I moved away and stopped only after reaching a safe place. Later, a forest guard said the restricted zone was home to crocodiles!

Perils

Rivers in India are in a precarious state and Himalayan rivers are no exception. Engineers have often tried to tame the river, but in recent times, it is alarming to see the number of hydro-electric projects mushrooming in the hilly regions.

The Ganga has been accorded the status of a national river, a welcome sign from the government. At the same time, this raises many questions. Do we have a detailed knowledge of the biodiversity of this river? Do we have effective methods to curb river pollution? .

A recent study of the Teesta in Sikkim highlighted the importance of river flow and biodiversity associated with it. If we want to preserve freshwater habitats and save the livelihoods of fisher-folk, we need to act wisely.