Alien mussel invades Ennore wetlands

CHENNAI: An ecological catastrophe is silently spawning in Ennore and Pulicat wetlands where an invasive mussel species from South American coasts called Charru mussel, locally known as Kakka Aazhi, is threatening to wipe out commercial prawn fishery and native mussels.

S Kumaresan, a fisherman from Kattukuppam, said Charru mussels (Mytella Strigata) were first spotted around 15-20 years ago in Ennore wetlands. As more road and conveyor bridges started coming up, the fishers noticed small patches of these mussels stuck to bridge columns and debris. “We think the December 2016 Vardah cyclone had something to do with the spread, as they began spreading to stretches far north towards Pulicat. The firm, ash-covered river bottom is also helping the mussel expansion,” he said.

Spreading like a carpet at the bottom of the river, these mussels prevent prawns from grazing or burying themselves in the sediment. Fishers said the alien species is wiping out the locally prevalent yellow clams (manja matti) and green mussels (pachai aazhi).

“Earlier, fishers from my village would catch around one tonne of prawns from the wetland. Presently, we’re able to get only 100 to 200 kg a day,” he said, noting about 10,000 families are dependent on catch from Pulicat lake.

Nityanand Jayaraman of Save Ennore Creek Campaign said the discharge of ballast waters from ships visiting Kattupalli and Kamarajar ports has resulted in the spread of the invasive species.

“This species will wipe out commercially important prawn fisheries in Ennore-Pulicat wetlands,” he warned, noting it has already invaded Vembanad backwaters in Kerala, a Ramsar site, replacing Asian green mussel and an oyster called muringa.