Dredging may not solve charru mussel invasion in Ennore-Pulicat wetlands, says NCSCM

The unchecked spread of charru mussels (Mytella strigata) across the Ennore-Pulicat wetland system continues to raise concern, as government agencies remain without a clear or sustainable plan to contain the invasive species.

Field surveys conducted by the National Centre for Sustainable Coastal Management (NCSCM) in May revealed that mussels had colonised multiple pockets along the 24-km stretch from Ennore Creek to Pulicat Lake.

Mussel presence was confirmed at nearly 24% of 197 sampling points, with the highest densities recorded at over 800 mussels per square metre.

Clusters were found under bridges, around mangroves, near the estuary mouth, and in traditional fishing zones, which are areas critical for local livelihoods. Charru mussels, originally native to Central and South America, are known for rapidly colonising estuarine environments. Their spread in Ennore has damaged fishing nets, outcompeted native shellfish, and disrupted traditional fisheries.

S. Kumaresan, a fisherman from Ennore, says that in some areas, the creek has become deeper after mussel removal, while in others, untouched mussel beds continue to obstruct movement.

He adds that certain paadu (locally designated fishing zones), such as Karukkumaram, Kandachedi, and Jallikuzhi, are completely overrun by the mussels.

Dredging impact

In response to long-standing complaints from fishermen, dredging was initiated in some sections of the creek. A 1,700-metre stretch at Kattupalli and another 500 metres at Puzhuthivakkam were taken up by the Water Resources Department, at an estimated cost of ₹20.85 crore.

However, the NCSCM, in its recent submission to the Southern Bench of the National Green Tribunal, has warned that both manual and mechanical dredging pose serious ecological risks. These include habitat destruction, disruption of sediment layers, loss of native aquatic species, and long-term degradation of water quality.

“Dredging can cause serious and lasting damage, if not carefully planned,” the NCSCM said, adding that disturbed sediments may also release pollutants like heavy metals into the ecosystem. Despite these warnings, no alternative method for removal has been proposed by either the NCSCM or the Tamil Nadu State Wetland Authority.

With no clear removal method and the final NCSCM report still pending, the fishermen are a worried lot. While dredging, despite its potential environmental impact, is still seen as useful by Mr. Kumaresan, he acknowledges that it is not a permanent solution, as the mussels could return. However, the dredging is being carried out unevenly, making it difficult for fishermen to navigate their boats through the affected areas.

Questions over delay

During a hearing on July 9, the Tribunal expressed concern that more than two years after the issue was raised, a conclusive plan for managing the invasive species has still not been formulated.

The Tribunal said: “The NCSCM report does not support dredging, and yet, it offers no alternative. We hope the Member Secretary of the TNSWA will return with a feasible solution and a definite timeline.” It also pointed out that recent desilting operations were carried out to remove fly ash, not Charru mussels, highlighting a disconnect between restoration efforts and the specific problem of bio-invasion.

A value-addition study is underway to explore possible commercial uses for the mussels, such as in animal feed or fertiliser. However, the study remains incomplete and cannot yet support a full-scale removal strategy.