In Kuttanad, this underwater wall 'kills' fish

Kuttanad: The Thanneermukkam Barrage or Bund across the Vembanad lake might have allowed Kuttanad farmers to harvest two crops a year but deep inside the water, as though the Vembanad had suffered a massive emotional upheaval, the world has turned topsy-turvy. The telltale sign of this internal churning is the dramatic fall in the population of two aquatic species – the black clam (kakka) and the giant freshwater prawn (aattu konchu) – that thousands of coastal families in Kuttanad depend on for their livelihood.

Innumerable official studies have confirmed the gradual depletion of the two species. Both are freshwater species but require saline water for breeding. The giant freshwater prawn is a migratory species, which moves to more brackish areas to breed. The baby prawns or the postlarvae then travel back to settle in the fresh water areas. The bund exists as an underwater wall that divides the northern brackish areas from the southern freshwater zone. At least four studies, including that by Centre for Water Resoruces Development and Management (CWRDM), have found that the annual production of giant freshwater prawn in Vembanad had dwindled considerably, to about 33 tonnes from a high of 300 tonnes during the late seventies.

The bund, which came into being in 1975, was an artificial barrier created to stanch the intrusion of seawater into the low-lying paddy fields between November and May. During other months, the rivers and lakes swell with freshwater that it keeps the sea water at bay. Once the rain dries up by the end of November, salt water flows in causing serious farming disruptions. "It was to save farmers, and also to allow them to have two harvests a year, that the bund was constructed," said Gopan Mukundan, a Kerala Sasthra Sahithya Parishad activist.

The realisation that the bund had wrecked underwater life came much later, when the major commercial catches like prawn and clam dropped to noticeable levels. The depletion is more alarming in the case of black clam, the lifeline of thousands of coastal folk in Kuttanad. Black clam production, which was once 57,000 tonnes, has come down to 32,000 tonnes. The black clam is also a freshwater species but its ideal breeding ecosystem should be a bit saline; it requires 10-12 ppt (parts per thousand) salinity for breeding. When there was no bund, the clams got its salinity when the seawater began flowing into freshwater areas in early December. "Now, the barrage is closed from December, depriving the clam the salinity it requires during its breeding season," said Jojo TD of Ashoka Trust for Research in Ecology and the Environment (ATREE), a Bangalore-based NGO active in Kuttanad.

Kuttanad's western bank, along which falls places like Muhamma, Aryad, Mannanchery, has been traditionally known to be the haven of clam collectors (kakka piduthakkar). "Now, black clam is virtually non-existent in these areas," Jojo said. These areas from where black clam has vanished are also the stretches now wildly colonised by weeds and freshwater sponges called spongilla. "Black clams are natural bio-filters that consume planktons and spongilla. It purifies the waterbody and maintains its pH level. So, when black clams vanish, the water becomes acidic and would be taken over by weeds that snuff out aquatic life," said Ashish, an ecologist who works for ATREE.

A fight back is now on. The Central Marine Fisheries Research Institute and the Fisheries Department, in association with ATREE, are implementing what has been called the 'Clam Relaying' project. Under this project, black clams found in the northern part of the bund are collected and scattered along the western bank from where its vanished. "Clams live for three hours out of water and so we can quickly transport them from one area to other," said Jojo.

A Fisheries Department study revealed that the black clam population has gone up after the 'relaying' Clam farmers in the western bank, therefore, are now back in business.

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