KARACHI: A 3.8-metre-long tiger shark weighing 550 kilograms was accidentally caught about 186km south of Karachi in the Indus Swatch area off Keti Bunder, four days ago. It was already dead when it was retrieved from the water, said Noor Mohammad, a fisherman trained by the World Wide Fund for Nature, Pakistan (WWF-P) to collect data for tuna fisheries.

“The male shark was too large to be handled and preserved. Fishermen used a mechanical device to lift it to the harbour where it was weighed and auctioned for Rs55,000,” he said.

According to him, its liver weighed about 150kg and around 120 litres of oil was extracted from it which would be used to smear the hull of fishing boats to keep them smooth and free from fouling organisms.

Tiger sharks are listed as a near threatened species in the International Union for Conservation of Nature (IUCN) Red List because of excessive hunting pressure on the species for finning and demand for its meat.

Once common along Pakistan’s coast, tiger sharks are now hard to find. Their numbers, as well as of other shark species, have dwindled drastically due to over-exploitation.

“The introduction of bottom set gillnetting mainly targeting shark species during the period between 1987 and 2002 was a major reason behind their reduced number. Unfortunately, their population could never be rehabilitated since then,” pointed out WWF-P technical advisor on marine fisheries Mohammad Moazzam Khan, adding that catching a tiger shark of more than 200kg was now very rare in Pakistan.

According to him, larger specimens of sharks have already diminished and it is very rare that they are caught. The tiger shark is a prolific breeder and a female produces about 10 to 80 pups in a litter but due to excessive fishing, stocks have declined seriously.

“Every month, few specimens of tiger sharks are caught but they are of small size with weight ranging between 50kg and 150kg.”

Locally known as Narmani in Balochi and Aiyan in Sindhi, tiger sharks are caught mainly by bottom set gillnet, longlines and handline with the help of live bait and pelagic gillnets.

The tiger shark is a requiem shark (one of the biggest shark families including the only freshwater species) known for its ferocious nature, and is widely distributed in tropical and subtropical waters of the Indian, Pacific and Atlantic Oceans.

The hot spots of tiger sharks in Pakistan are the Indus Swatch area and the waters off Ormara and Jiwani. The Indus Swatch is a deep canyon at the mouth of the Indus river and has a maximum depth of more than 1,000 meters.

Shark concentrations have been reported from both sides of the canyon up to a depth of 300m. They are also reported in the shallow coastal waters and in estuary and lagoon areas along the Pakistan coast.

Considering the over exploitation of sharks, the governments of Sindh and Balochistan recently enacted a ban on catching a number of shark species including rare silky, oceanic whitetip, thresher, whales and hammerhead sharks as well as guitarfish and mobulids, which are shark relatives.

Senior director programmes at WWF-P Rab Nawaz said that sharks such as tiger sharks were apex predators of the ecosystem of coastal and offshore waters, and their decline had disturbed the tropic balance resulting in the appearance of some species (for instance Indian mackerel) which were not found in abundance in the past.

“A 2012 study showed that major shark stocks in the offshore waters are depleting whereas sharks harvested by fleets in coastal waters are also under serious threat,” he said, urging the government to implement relevant laws to ensure protection of shark species.

Published in Dawn, October 14th, 2016