KARACHI: Thousands of fish died have been found mysteriously along the shores of Karachi port, which the marine experts linked to the depleted oxygen and toxics, Business Recorder learnt Monday.
The dead fish species surfaced over the Karachi seaport navigational channel soon after the fishermen ended their protest blockade to let the ships move to wharfs last week, according to Karachi Port Trust (KPT).
Experts attributed the dead fish phenomenon to limited circulation of oxygen during neap tide period, saying that it was restricted to one specific sea area and not a general occurrence to spill over into other shores of the city.
The dead fish were mullets, which are locally called “Boi”, teeming in the waters off the Karachi harbour. In schools, mullets move in-and-out of the harbour under the influence of tidal flow.
Experts however believe that the mass mortality of fish on this occasion may be from chemical-contamination of sewerage that flows through the Sindh Industrial Trading Estate (SITE) forming low oxygen water in the Arabian Sea.
“This is not the first case of mass fish killing at Karachi harbour,” Muhammad Moazzam Khan, Technical Adviser on Marine Fisheries at WWF-Pakistan, told Business Recorder.
The release of chemicals by the SITE industries into sea has resulted in mortality of mullets and other fish in Karachi harbor’s navigational channel over the several occasions in the past, he said.
A major mortality of mullets occurred on August 4 and August 5, 2013 in the Karachi Port area because of the similar causes, he pointed out. “This fish mortality is not because of harmful algal bloom (HAB), which are frequently reported from coastal and offshore waters of Pakistan, resulting at times in fish mortality,” Moazzam Khan said that there are no reports of any algal bloom in coastal waters in the recent days. Sewage flowing through the Lyari River and Gizri Creek, which receives sewage through Malir River, has already turned the Karachi Fish Harbour into azoic zones, where there is no marine life, he said.
“Around 450 million gallon per day (mgd) sewage is dumped into the sea through these two rivers, resulting in extreme high levels of pollution,” he said. Nearly 90 percent of untreated sewage is released into the sea resulting in mortality, bio-accumulation and depletion of area with animals and plants, he added.
He lauded the KPT for its efforts to initiate an operation cleanup to remove the dead fish from water. But, he also urged the port authorities not let fishermen to collect the dead fish and use them for fish meal purpose.
“It is expected that on the completion of S-3 project which is being implemented by KWSB, KPT, Sindh and federal governments will help reduce pollution in coastal area of Karachi,” Moazzam Khan hoped.
The KPT said that it is cleaning up the shore and harbour waters from dead fish and seeking information from the relevant organisations to ascertain the cause of death.
It said that its marine pollution control staff has collected about 1000 kilograms of dead mullets and dumped safely. It also advised the beach goers, visitors and picnickers to avoid fishing or collecting dead fish.
Every year from January to February, low oxygen water prevails over major part of coastal and offshore areas, as Arabian Sea is known for having one of the world’s largest Oxygen Minimum Zone (OMZ), which migrates to coastal areas during winter, experts said.
Mullets are considered important commercial species that are relished by the locals especially the fishermen community. “The use of dead species even for production of fish meal is highly undesirable,” experts warned.
Copyright Business Recorder, 2022