‘Big golden mahseer to small kudremukh barb, freshwater fish are richly diverse’

Vidyadhar Atkore

is a landscape ecologist at the Salim Ali Centre for Ornithology and Natural History (SACON). Speaking to

Times Evoke

, he discusses vibrant river biodiversity — which faces human impacts:
I am a freshwater fish biologist. My research seeks to understand the causes and consequences of the degradation of freshwater systems, due to anthropogenic pressures like illegal fishing, sand mining, hydropower dams, etc. I try in particular to provide the baseline data we currently lack on these topics but which is essential to deepen our understanding. My fascination with riverine or freshwater systems began in my postgraduate years. When I joined the

Wildlife Institute of India

in Dehradun for my

Masters

, one of the first field trips I went on was along the Himalayas, travelling by mountain tracks, walking through hill forests and wading into streams along the Shivaliks. I realised how much I liked these streams and exploring life in them. But I found comparatively less ecological information on riverine systems. Filling these gaps in our knowledge became my focus.

THE TREASURES THEY HOLD: Freshwater ecosystems (above) like the Moyar river, Tamil Nadu, are troves of diverse fish species while the

Kudremukh barb

(below), an entirely new kind of fish, was discovered in the

Tunga

riverine system in 2015 (and put back into the waters by scientists). Photos Courtesy: V. Atkore

For my Masters, I studied the fish community of the Corbett National Park where my colleagues and I researched the golden mahseer, a freshwater fish which is migratory in nature. It can weigh upto 55 kgs but it is hard to find a fish of that size now. This sparked my interest. I’ve since been working on the overall fish community in the hills and peninsular India.

WELCOME TO MY HOME: River fish like the Channa (belowR) reside within the tributaries of the Ranganadi (above), Arunachal Pradesh. Photo Courtesy: V. Atkore Significant findings emerged from my doctoral research which spanned four major river basins, the Malaprabha, Mhadei, Tunga and Bhadra systems in Karnataka. I’ve covered 152 riverine stream landscapes in these areas, documenting over 90 species of fish. My colleagues and I compared the Tunga and Bhadra riverine structures which were free-flowing versus those modified by humans like Mhadei and

Malaprabha

— we found the latter were highly disturbed in terms of the number of check dams built on them, the quality of the water, the degradation of vegetation along the river banks, etc.

I’ve also found that free-flowing riverine systems had nearly 50% more fish species endemic to these habitats, compared to hydrologically modified systems which had more generalist species found across diverse habitats. Endemic and habitat specialist fish require certain conditions, like an ambient temperature, vegetation, etc., to survive — they could only find these in areas which had minimal human disturbance or no check dams, water diversions and fishing pressure.

Dams being barriers standing in the way of fish impact the composition of species found naturally in numerical abundance. Mhadei and Malaprabha had many barrages too, leading to changes in water flow. When the flow is disturbed by human activity, surface-dwelling fish are significantly affected. Human modifications of hydrology have enormous impacts also on river sediments, vegetation and water surfaces — we found more insectivore species living in the Tunga and Bhadra regions since more insects survived there while the modified sites had more omnivorous and carnivorous fish. But mitigations can also help species — retaining undammed tributaries enables fish to recover even downstream of such dams.

A JOURNEY OF DISCOVERY: Scientists release a radio-tagged golden mahseer in river Nayar, Uttarakhand, the non-invasive technology helping them track the mahseer and learn about the fish’s habits and habitat. Photo Courtesy: V. Atkore

There have been other discoveries too — including an entirely new fish! I came across a fish we named

Kudremukh

barb, swimming along in the headwaters of the Tunga. Never seen before, this fish, taxonomically named Pethia striata, had a remarkable colour, the male shaded red and the female, grey, and a unique cross-stripe pattern. We have a lot to learn about its distribution, habitat and life — but meeting this fish for the first time was wonderful.


There are many challenges in riverine research, including getting permits on time and travelling to remote locations. I start my fieldwork very early in the mornings, reaching a forest site, camping there, walking upstream and downstream, measuring the habitat, studying environmental patterns like the presence of chemicals, etc. I spend four hours in the morning collecting data, stop at lunch and resume at another site, returning in the evening to screen all the data.

Freshwater riverine systems are powerfully linked to human wellbeing. We should read more about freshwater biodiversity to appreciate the huge variations of species, their extraordinary colours, abilities and migratory behaviour. This can inspire us to join campaigns for river cleaning. We should also minimise plastic usage as microplastic is a major threat affecting freshwater systems now. And we should discuss the removal of obsolete dams which is taking place worldwide to save freshwater species.

Also, those interested in ornamental fish — please don’t buy these and release them into streams. This adversely impacts native fish. Often unknown to us, human activity changes the lives of fish living miles away. We need to tread far more carefully around freshwater systems to preserve their wondrous inhabitants.

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