Toxic mussels alien to Indian waters have invaded the Ennore and Pulicat wetlands, threatening the prawn fisheries in the vicinity. A collaborative study conducted by the fishers of Ennore, Bengaluru-based scientist Naveen Namboothri, and the Save Ennore Creek campaign activists has highlighted the issue. The South American mussel species, identified as Mytella Strigata or Charru mussels, has reportedly stretched like a carpet across six to seven kilometres underwater.

Fishers have noted that the clear water column in the region is the result of the mussels sucking in and processing hundreds of litres of water every day. The river bottom is also suffocated with a foot-deep sludge of black, slimy, and foul-smelling excreta. “We refer to this species as kaaka aazhi. Since it has completely covered the muddy river bottom, the water is clear. We (fishermen) cannot fish in clear water because the fish will avoid visible nets. Moreover, Kattukuppam fishermen are dependent on prawns for their livelihood. With this mussel covering the muddy river bed, prawns, which usually bury themselves in the mud when predators approach, are not able to survive,” S Kumaresan from the Kattukuppam fisher panchayat told TNM.

Since prawns are unable to protect themselves, two fishers alone extracted Rs 1,04,000 worth of prawn over 12 days from a fishing site in Konamudukku. “If this continues, the Ennore-Pulicat wetlands which are commercially important for prawns will suffer in the coming years,” said Kumaresan.

According to the study, the mussel has infested 11 out of 52 fishing sites in the Ennore-Pulicat stretch. However, the collaborative study has confirmed that the spread is yet to affect Pulicat as severely as the Ennore backwaters.

Meanwhile, Kumaresan said that the community had noticed small patches of mussels stuck to the bridge columns in 2015. However, it began to intensify in 2017 after the Vardah cyclone in the year before. “The invasion was prevalent even in 2021, but it had only spread across two kilometres. Over the past year, the problem has become severe,” he said.

Researchers have concluded that the mussel has travelled in the ballast waters of ships which had set sail from South America. Additionally, lack of both ballast water regulations for ships from South America and environmental impact assessment processes at the Kamarajar and Kattupalli ports are being cited as the main reasons for the alien invasion.

“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 the co-author of the fisher-led study.

Fisher activists believe that the ports need to rectify the situation, and have demanded compensation for the region’s fishers. “Firstly, the spread of this mussel needs to be contained. Secondly, we need some government intervention to help eradicate it since our livelihood is on the line,” added Kumaresan.