KARACHI, May 3: A chemical analysis of the fish which were found dead in large numbers in the backwaters of the harbour last month has shown no traces of toxicity in the meat and the results indicate that all values as normal.
The National Institute of Oceanography’s lab findings confirmed the results of the biological investigation conducted earlier which found that the fish died of anoxia due to a high concentration of organic matter in the backwaters of the harbour.
NIO Director-General Dr Mohammad Moazzam Rabbani said: “There were no traces of biological accumulation of toxics in the fish meat as all values are found normal. This means that the fish didn’t consume toxic elements but anoxic conditions due to highly polluted waters caused their sudden death. The fish is safe to be used in poultry feed,” he said.
He said that anoxic conditions were caused due to the decomposition of organic matter, the huge quantity of which came into the creek along with sewage from Lyari River. Suspended organic matter may itself be harmless but harbours bacteria and lessens the supply of oxygen in water.
“This acute lack of oxygen supply was responsible for death of the fish,” he said, adding that the phenomenon was a routine occurrence.
Untreated waste
Expressing concern over the discharge of untreated waste into the sea, the director-general said that about 400 million gallons of waste, including domestic and industrial waste, was discharged into the Lyari River that ended up in the sea. Only 15 per cent of this waste was treated; so one could well imagine the high concentration of toxics at the harbour where oil spillage was a common phenomenon.
“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 organic matter in the backwaters of the Karachi harbour,” he said.
The Red Tide
However, he said that no evidence had been found to support the idea that thousands of fish mostly Mugil Cephalus, locally known as Boei, died due to the ‘Red Tide’ phenomenon. He explained that the red tide 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.
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