Fishermen raise concern over invasive species of mussel in Ennore and Pulicat

They say the the mussel prevents prawns from grazing by spreading over the riverbed like a carpet; its spread is wiping out the locally prevalent yellow clams and green mussels

Fishermen of Pulicat and Ennore are worried over the spread of an invasive species of mussel that is a threat to the prawns of both waterbodies. Known as kakka aazhi among the fishermen, they say it is a South American mussel species that is spreading due to the discharge of ballast waters from ships visiting the ports of Kattupalli.

Ennore fishermen say the mussel spreads like a carpet over the riverbed, preventing prawns from grazing or burying themselves in the sediment. Its spread is wiping out the locally prevalent yellow clams ( manja matti) and green mussels ( pachai aazhi).

According to S. Kumaresan, a fisherman of Ennore, activists of the Save Ennore Creek Campaign and the fishermen contacted marine biologist Naveen Namboothri of Dakshin Foundation, who identified the problem mussel as Mytella strigata or Charru mussels. Native to South America, these mussels have invaded tidal wetlands in several parts of the world, including Vembanad in Kerala, by travelling across continents in the ballast waters of ships. This is the first time this invasive species has been found in the Eastern coast, according to Mr. Namboothri.

The fishermen and researchers have demanded that the two ports take steps to remedy the situation. Mr. Kumaresan said the mussels were first spotted some two decades ago in the Ennore wetlands by local fishers. Human interference in the wetlands, pollution and nature’s actions have turned this insignificant incidence into a full-fledged infestation.

As more and more roads and conveyor bridges were built in the area, small patches of these mussels were noticed. They were stuck to the bridge columns and debris. After Cyclone Vardah in December 2016, the mussels began to intensify and spread far north towards the Pulicat waters. The firm, ash-covered riverbed is also helping the kaaka aazhi expand its territory. The problem has become very severe since April 2022, Mr. Kumaresan said. According to the study, the infestation has already spread to 11 out of 52 fishing sites ( paadu).

“Scientists and regulators are disconnected from local communities that have an intimate understanding of local landscapes. That and the low value placed on local expertise and knowledge means that no action is taken until it is too late despite the early warnings sounded by local communities,” said Nityanand Jayaraman, a volunteer with the Save Ennore Creek Campaign and co-author of the study.

Save Ennore Creek Campaign and the Ennore-Pulicat fishers have written to the State Wetland Authority and Fisheries Department requesting urgent intervention to save the fisheries, and initiate action against those responsible for the harm to ecology and fisher economy.