CHENNAI: Unprecedented scenes were witnessed on Tuesday at Adyar river mouth where thousands of fish washed ashore dead. This is the second mass fish kill incident being reported within two years at the same spot, which throws up several questions on the ability of Adyar Creek to support life.
The last incident happened on December 31, 2014. It was a rude shock for fisherfolk dependent on Adyar estuary for livelihood. Among the dead, five species were spotted and the majority were mullet with eggs inside.
Though the exact reason for the disaster is yet to be ascertained, local fishermen said it was because of high influx of raw sewage from upstream residential localities, industries and hospitals. The State fisheries department has written to Central Institute of Brackishwater Aquaculture (CIBA) to investigate. Even scientists from Central Marine Fisheries Research Institute (CMFRI) visited the spot and collected fish and water samples for toxicology study.
CIBA director K Vijayan ruled out the possibility of mortality being caused by any pathogen-induced disease. “If it is any disease, the death would have been slow. This is clearly a case of fish suffocating to death due to reduction in oxygen and it would be either due to substantial increase in pollutants entering the water body or low tide minimising the sea water ingress into estuary or a combination of both. Our animal health division is doing sampling, but it would be difficult to establish the true picture since the samples were collected almost 5-6 hours after the mass kill occurred. Sea water might have entered in between diluting the nutrient concentration in the water,” he said.
S Palayam, president of Ururkuppam Fishermen Cooperative Society, said the fish began dying in lumps from the wee hours of Tuesday. “I went to the river mouth to lay my net around 4 am and by then, I found scores of fish washed ashore dead. Due to some disturbance in the sea, lots of fish came close to shore. Fishermen on Monday had dream catch. During high tide, the fish from the sea must have moved inside the estuary, which is considered safe. But at the same time, a large quantity of sewage must have been covertly discharged laying a death trap,” he rued.
Besides madavai (mullet), other fish species like oodan (Indian goat fish) and silepi (Tilapia) were also found dead. Joe K Kizhakudan, scientist, CMFRI, said mullets are tolerant to high salinity levels and can survive in both sea and estuaries. “Something has terribly gone wrong. Only a thorough investigation would reveal facts. Pollution is definitely one of the causes.”
Local fishermen also said in Urur Kuppam and Odai Kuppam, two large fish — Raa Paarai (a kind of mackerel), each worth about `20,000 were caught from the shore. These fish are usually found only mid sea.
Locals allege that some of the industries in SIPOT at Irungattukottai, Pallipattu, Somangalam, Amarambedu and Chembarambakkam release untreated effluents into the neighbouring water streams during monsoon period, which eventually flow into the Adyar estuary. Marine biologist Rahul Muralidaran said, “Except for Tilapia, which is mouth-breathing, no other fish can survive the polluted Adyar waters. These fish must have come with the tide.”