Why do fish matter?

Health of the Cauvery

It is a strange thing. If we find a man walking by with a dead deer on his shoulder, we would be horrified. However, the same reaction does not occur if he were carrying fish. This is understandable as fish is commonly seen as a harvestable food source. But what it also reflects is our lack of understanding that there are many complex ecosystems in the wild, with several endangered species nested within. Rivers, for one, get very little attention. What lies underwater remains unseen, unknown.

A riverine ecosystem faces some unique challenges. Apart from the usual anthropological pressures, it also falls into the twilight zone of clearly defined ownership. No one is really sure who has holistic ownership for the health of a river. The forest department does a great job of policing the stretches that flow through protected areas. But they have their hands full, monitoring big fauna and the forests.

Various government bodies, such as the irrigation department and PWD, are primarily concerned with the use of water for human benefit. Fisheries tend to be focused on fish as a food source. So, who really is concerned about the overall health of the freshwater ecosystem? How much do we understand about its delicate balance? Do we even notice when an important species goes extinct or becomes endangered? The answer is no. While a handful of scientists have worked on freshwater species, the reality is that many of our species remain poorly studied even from a basic taxonomical perspective.

This brings us to the story of an iconic fish. The Mahseer or ‘Mahi Sher’ derives its name from its strength and endurance. Hence it is considered the ’tiger’ among freshwater fish in India. This beautiful species belongs to the carp family and represents the apex fish species in many of our rivers. In terms of cultural importance and popularity in folklore, it is probably matched only by the Hilsa of Eastern India.

The Mahseer gained fame in India and abroad from pre-colonial times because of its strength and ability as one of the world’s top “fighting fish”, sought after by anglers. Its size and power are legendary, with documented records of fish that can grow to the length of a fully-grown man and weigh as much. The power of such a fish in fast flowing waters is the stuff of legends, with everyone from Jim Corbett to a Viceroy of India and a Maharaja of Mysore documenting thrilling encounters with the Mahseer.

It is estimated that there are over 15 species of Mahseer in India. The largest and most impressive of them is the ‘hump backed’ Mahseer, found only in River Cauvery in South India. Here, it grows to sizes not seen anywhere else in the world. Recent studies have taxonomically identified it as Tor Remadevii, but work continues on this front.

The heaviest fish on record is one landed by British angler Ken Loughran at over 130 pounds in 2011. Most modern anglers practice strict “catch and release” angling, where the fish is released back alive into the water. Research shows that there is minimal impact of catch-and-release angling to the health of the fish.

However, the same cannot be said of other anthropological pressures that have been decimating this fish. Since Independence, we have ravaged our rivers on multiple fronts. Dams are built and courses are changed, blocking historical migratory routes and submerging key spawning sites. Water is diverted to our cities and for irrigation, leading to low water levels and reduced rate of flow. This affects oxygenation and several large species simply perish.

There is indiscriminate netting, dynamiting and poisoning of water outside protected areas. Lastly, several invasive species such as the African Catfish, Tilapia, and even Alligator Garr and Piranha have been introduced into our waters. Some misguidedly as food sources. These species are often predatory and decimate native species completely. Herein also lies the danger of poorly studied plans such as river linking.

The story of the mighty hump backed Mahseer is no different. This iconic fish has been in rapid decline and no one has seen a monster-sized fish in recent times. The only data we have are historical catch records from anglers. They tell a worrying tale. The data indicates a massive decline in catch ratio of the hump backed Mahseer from 1:4 in 1998 to as little as 1:218 by 2012. This clearly indicates a population crash that could lead to the extinction of the fish. What a pity it would be if it were to be lost forever from the Cauvery!

Conservation efforts

The good news is, there is still hope. Groups of committed conservationists continue to work on protecting the species and have been tracking its health since the 1970s. Recent studies indicate that the species still exists in the river and its tributaries. So, rehabilitation may be possible. But it will require significant public and political will to protect a fish that should rightfully be considered the pride of Karnataka.

Much needs to be done to ensure that the specific reproductive and survival needs of the fish are safeguarded. That means ensuring the availability of deep rock pools for wintering, fast flowing and highly oxygenated water to trigger spawning and the availability of clean sandy banks for the demersal eggs to be deposited. All of which are major challenges in a scenario where multiple states are fighting over the scarce water.

Meanwhile, silt and effluents continue to enter the river from outside protected areas and dynamiting is on the rise. The good news is that the Cauvery tribunal has stipulated that 10 tmc of water must be reserved for the environment. But a lot more would need to be done if this species is to survive.

One can only hope that the powers that be realise that the Mahseer is a direct marker for the health of the river. If the Mahseer dies, the river is dying. And if the river dies, human populations in the millions will face the consequences. For our own good, we need to recognise the warning signs and moderate the insatiable demands that we are placing on the Cauvery.

(The writer is Secretary, Wildlife Association of South India)