The adverse weather conditions have caused sediment in the sea to mix with the water, leading to contamination in the mangrove areas and coastal regions of Karachi Harbor.

Species such as mullet and spotted skate are among the thousands found dead along the coast.

According to WWF Technical Director Maaz Khan, the fish deaths are a “localised event and not widespread.” Fishermen are reportedly collecting the dead fish to sell to poultry feed plants.

Khan warned against using such fish, as they have “died due to pollution and may be unhealthy for consumption.”

A cyclonic storm is also predicted to hit the southern coast, bringing with it torrential rains and possible flooding, the Sindh province disaster authority said.

More than 300 people have died across Pakistan in rain-related incidents since the start of the monsoon in July.

Most deaths have occurred in northwestern Khyber Pakhtunkhwa and neighbouring Punjab, according to official figures.

“The deaths were a result of lightning, electrocution and collapse of mud or dilapidated houses,” a statement from Punjab’s disaster management agency said on Friday.