A large quantity of dead fish was washed ashore along the coastline from Srinivasapuram up to Ashtalakshmi temple in Besant Nagar on Wednesday.

Fisherfolk, dependent on the Adyar estuary for their livelihood, were shocked by this sudden surge of dead fish.

R. Suresh, a fisherman from Nadukkuppam, said release of untreated hazardous wastewater from a couple of hospitals could have caused the death of the aquatic life. “Since yesterday, we have been sensing a stench and then, this morning, saw the huge quantity of dead fish on the shore,” he said.

S. Palayam, president, Oorurkuppam Fishermen Cooperative Society, said he, along with five other fishermen, could earn nearly Rs, 2,000 by spreading their nets at the mouth of the estuary. Similarly, a good quantity of prawn was also caught in the bay, he said, adding that the release of untreated hazardous waste into the Adyar River had led to the death of fish.

“It not only affects the fish, but even the prawn fingerlings get wiped out due to contamination by polluted waste. So far, we have not had such a large-scale death of fish in our area,” he said. Mullet, sardine and milk fish were the three species found in abundance in the area, he added.

Pooja Kumar, of Coastal Resource Centre, Besant Nagar, said they got the call from fishermen around 3 a.m. on Wednesday about the dead fish washed ashore. A drainage pipe on the old Adyar bridge had got damaged in some portions, from which the sewage seems to have leaked into the river. Thus, the water passing through Adyar Creek before reaching the Bay of Bengal could have become contaminated, resulting in the mass death of fish, she explained.

Nearly five lorry loads of dead fish were collected by unidentified persons, who said they would sell them to units manufacturing poultry feed.

Mr. Palayam said that, on several occasions, the fishermen had complained to authorities about the release of untreated raw sewage into Adyar River. But, so far, no action had been taken. The rise of new hotels and residential apartments near the coast along Foreshore Estate exacerbated the issue, he said.

Sources with the fisheries department said eutrophication (presence of excessive nutrients due to increased presence of algae) could have caused the death.