Habitat loss, over-catch threaten mud crab population in coastal Sindh

HYDERABAD: Increasing marine pollution, habitat loss due to depleting mangrove forest and over catch have been contributing to the drop in mud crab (Scylla serrata) population along the 350km long coast of Sindh, fishermen said.

Studies have revealed that close to 10 species of crabs inhabit the coastal areas of Sindh; however, among these, the mud crab is a commercially important species. It is common throughout the Indo-west Pacific region, and in Pakistan is fished by mostly traditional sector for commercial purposes.

People keeping a close eye on marine natural resources reveal that previously, fishermen only caught larger male crabs and avoided catching females or juvenile. This was a sustainable approach and helped maintain the crab population.

Fayaz Rasool, who has been associated with mangrove plantation drives on Sindh and Balochistan coast, said around 30 years back there were plenty of large mud crabs on islands, which the fishermen would catch to sell in the market.

Now, the fishermen catch all sizes of crabs, including females and juveniles. “As a result, the population of mud crabs is declining fast. They (community fishermen) do not let the juvenile crabs grow and catch them for money,” he added.

Female mud crabs carry the egg mass under their belly. They can produce up to 100,000 eggs, which take 12–14 days to hatch, depending on temperature.

Since mud crabs are considered a highly exploited species, associated to mangrove ecosystems in the deltaic region, coastal countries have formulated laws to protect female crabs to increase population. But here, the situation seems different in terms of policies and legislation, Rasool added.

Government authorities as well as institutions and community organisations, which work in the field of natural resource management, have failed to create awareness about sustainable methods among communities that exploit crab populations for commercial use.

Majeed Motani, a senior fisherman of Ibrahim Hydri, Karachi understood the seriousness of the matter.

Recalling the past, Motani said there were enough male crabs on the muddy islands off the coast of Sindh, so fishermen never tried to catch the smaller ones.

He agreed that there was a need to educate the communities and teach them that if they continued to catch female crabs, the population would never reach sustainable levels and ultimately go extinct.

There is a huge demand of crabs in the foreign market, but the supply chain is not perfect. He attributed it to overexploitation of the fertile zones with over catch.

“When fishermen do not find enough fish catch in the sea, they go all out after the crabs of all sizes to make ends meet,” the veteran fisherman said.

Groups of fishermen can be found looking for crabs in the mangrove forests near coastal villages, in Sujawal, Thatta and Karachi districts.

Nawaz Dablo, a fisherman from coastal village Rehri Mayan in Karachi, said whenever fish catch declines due to weather ups and downs, they travel to mangroves on islands to collect crabs to sell and earn a little money for their survival.

Presently, the prices in the local market, mainly at jetties range from Rs100 to Rs300, depending on the size of the crab. The price of the same item goes up during winter. But before winter, many unaware people catch a higher number of crabs from the fields, leaving nothing behind.

Fishermen use two methods for crabbing. In the first method, they put chicken pieces in typical nets to trap seven-eight or more blue crabs. The second is tracing burrows in mangrove fields to catch crabs through iron rods.

Crabs are collected live and then put in a bucket or a cage to avoid injuries. Fishermen have to deal with the crabs carefully, as an injury means the fragile crustaceans could lose a claw or leg, making it inacceptable to customers.

Dablo goes to the open sea for fishing with other crew members. It helps him earn enough to survive. He expressed ignorance as to why they were not catching enough fish these days.

Quoting senior crew members, he said it happens often that fish move to coral reefs at the start of wintering season to avoid coldness. “For the community however, declining fish catch is a helpless situation,” he added.

Noor Muhammad Thahimor, a community activist from Jati, Sujawal district, said the Arabian Sea has witnessed two cyclones, Nisarga and then Amphan quite recently, which might have changed water phenomenon and movement of marine species, including fish. There is a common understanding among fishermen that whenever any changes took place in the sea, it impacted the fish. So, many people take up crabbing as a lucrative business.

Interestingly, not many local people consume crabs at home despite its nutritional value and huge demand in international markets.

Thahimor said mostly fishermen, who took their boats to open sea now go to nearby islands for crabbing. They make small ponds along the beach, where they collect the crabs till they have enough to bring to the market.

Each person earns Rs1,000-Rs1,500 as a share from a trip. In winter, they catch crabs for their traditional business to earn more, he added.

Earlier, some organisations had initiated crab farming, but it could not be sustained by the people, because of lack of awareness about feeding and farm management.