KARACHI, April 7: An initial probe into the causes of the death of a large number of fish found on Sunday revealed that a high concentration of toxics in the backwaters of the Karachi harbour was responsible for the killing thousands of fish.
The investigation was carried out by the National Institute of Oceanography (NIO) and the results of a chemical analysis will be released within 10 days.
No evidence has been found to support the idea that the fish—belonging to the same species and without any injuries—died due to the red tide phenomenon.
The NIO director, Dr Mohammad Moazzam Rabbani, said that the initial tests conducted on the fish samples collected from the Natives Jetty, Boating Basin, Chinna Creek, and Clifton showed that the fish got trapped in an ebb tide and died of anoxia due to a high concentration of toxics in the backwaters of the Karachi harbour.
He said that a high tide early Sunday morning at the harbour pushed tons of thousands of fish mostly Mugil Cephalus, locally known as Boei, from the sea into the channels. This coastal fish is widely used in the chicken feed. In search of food, it enters the creeks and gets caught by fishermen.
“Their number was high because of a low activity at the harbour on that day and also because the tide was recorded to be at the maximum level. It started rising in the early hours of Sunday and began receding later in the day. By 11am, a large number of fish had already died. They got trapped in the receding waters, which is highly polluted due to the release of toxic waste, and died of suffocation due to depleted oxygen supply,” he said.
“About 400 million gallons of waste, including domestic and industrial waste, is discharged into the Lyari River that ends up in the sea. Only 15 per cent of this waste is treated so one can well imagine the high concentration of toxics at the harbour where oil spillage is a common phenomenon,” Dr Rabbani said.
Dr Rabbani said that the test results showed no trace of oil contaminants on their body or the toxic algae, which were linked to the red tide phenomenon. Explaining the red tide phenomenon, he said that it was caused by a rapid growth of unicellular microscopic phyto-planktons (toxic algae). As the algae multiplied, they caused a discolouration in the water near the shoreline.
“With the rise in tide, the red algae detach from the bottom of the sea floor and rises towards the surface. The red colour attracts fish, which eats the poisonous algae and washes ashore dead.”
He, however, dispelled that notion that some of the big trawlers operating in the coastal areas might have had thrown the fish load as trash.
Dr Rabbani recalled that tide fluctuation had also caused large-scale death of fish on July 30 last year. “We are fortunate that marine pollution has so far remained limited to the Karachi coast where enormous human activities take place. So the fish caught from the deep waters and other areas is safe for human consumption,” he said.
He said that such coastal fish, which were found in shallow waters, were widely used in the preparation of chicken feed and fish meal, and the quality of these fish was highly degraded. Dr Rabbani was of the view that in order to check the situation, industries must be made to follow the rules and regulations pertaining to the environment.
The expert said that the NIO could predict the occurrence of tide fluctuation that might lead to the likely killing of fish. However, such incidence could only be prevented if authorities concerned make arrangements for the proper disposal of toxic waste.
Interestingly, the officials of the Sindh Environment Protection Agency (Sepa) told Dawn they had no idea of what had actually happened.
An official of the Karachi Port Trust, Usman Yahya, heading the Marine Pollution Control Department, said that almost 80 per cent of the area had been cleared of the dead fish, which had been properly disposed of at a landfill site in Keamari Town, Jungle Shah.
