SEAFDEC Opens Gates to Mud Crab Domestication

TIGBAUAN, Iloilo – The complete life cycle of the mud crab is now documented, opening the gates for its domestication.

That’s big time: next to China, the Philippines is the world’s second largest mud crab producer; it harvested 14,437 metric tons of mud crabs from aquaculture in 2010.

“The study on the domestication of mud crab is the first ever reported in the Indo-west Pacific region,” said Dr. Emilia T. Quinitio, Scientist and Head of the Technology Verification and Demonstration Division of the Southeast Asian Fisheries Development Center’s Aquaculture Department (SEAFDEC/AQD). “The initial results would serve as guide to understand and eliminate the barriers to mud crab domestication.”

“The breeding technology will support the production of good-quality seedstock for farming and eventually lessen the dependence on wild stock,” she said in an interview.

“Genetic selection for desirable traits focusing on fast growth and better reproductive performance will be done while maintaining the healthy status of the stock and genetic diversity in succeeding generations,” Quinitio told Malaya Business Insight.

For her research on the domestication of the mud crab (Scyllla serrata), Dr. Quinitio received the 2011 Department of Science and Technology-Elvira O. Tan Memorial Award for Best Published Paper in Aquaculture and Inland Fisheries.

SEAFDEC/AQD has actually closed the life cycle of three of the country’s mud crabs: S. serrata, S. tranquebarica and S. olivacea.

The S. serrata – or the mud crab locally known as alimango, bulik, banhawan and kinis – is now a good candidate for domestication. This is because its life cycle can be completed within a year and its seed production in the hatchery and nursery has reached the commercial level.

S. serrata is the preferred species for farming by crab growers because it is larger and less aggressive than the other two species. It is sourced from the estuaries along the country’s Pacific Ocean side: Cagayan, Catanduanes and other parts of Bicol, Samar and Surigao.

The most widely distributed species in the Indo-west Pacific region, S. serrata is found in estuaries and sheltered coasts and in soft muddy bottoms where it digs deep burrows.

Courtship and mating occur in estuaries, then the mature S. serrata migrates up to 50 kilometers offshore to spawn (the three other species prefer less saline water). It may spawn any time in a year, producing from 1 million to 6 million eggs in a single spawning.

A crab muolts several times before it matures fully. A male grows up to 3 kilograms; a female has dark orange ovaries that fill the cavity under the carapace and which is much valued in Philippine cuisine.

“Although the technology for the hatchery, nursery and grow-out has been developed, there remains a need to integrate all stages of production to develop a complete and reliable technology that can be used for the production of quality broodstock and seedstock” Quinitio said.

Successful implementation of the breeding program requires a network of facilities. Broodstock for hatcheries, for example, are currently sourced from crab trading centers or directly from commercial ponds.

S. serrata produces an average of 2 million larvae per hatching. A survival rate of 3 percent translates to 60,000 crab instar (<1 centimeters). Several hatchery runs can be undertaken in a year. Due to the cannibalistic behavior of crabs, much space is required for the nursery and grow-out phase.

Mud crabs from the wild are mostly depleted because they are overharvested even when they are smaller than 3 centimeters, Quinitio said.

Several municipalities in major collection sites have issued ordinances banning the collection and transport of crablets less than 3 cm in size. In recent years, overexploitation and habitat degradation have reduced the quantity and the mean size of crabs caught. The key is to conserve what remains of crabs in the wild.

“Conservation of the natural population of crabs is thus essential to sustain the industry,” Quinitio said. “Another solution is to source the crablets from the hatcheries using SEAFDEC technology.”

With only slight modifications, shrimp hatcheries can be utilized for rearing mud crabs.

To increase the availability of seedstocks for farming, the Department of Science and Technology (DOST) has approved a joint proposal of SEAFDEC/AQD and the University of the Philippines Visayas for a national mud crab science and technology program.

The goal is to establish mud crab hatcheries and nurseries and maintain or improve the country’s status as the world’s second largest producer of mud crabs.

“Mud crab R&D will be a major activity for AQD especially that it is the lead agency for the DOST’s National Mud Crab R&D Program starting this year,” said Dr. Felix Ayson, head of SEAFDEC AQD.

“Our mud crab activity will also be in support of the national program of the Bureau of Fisheries and Aquatic Resources and the Department of Environment and Natural Resources on mangrove rehabilitation. In this particular program, mud crab is one of the commodities that they plan to introduce in the mangrove areas. As such, we should be ready with the appropriate technologies for mud crabs.”

Source: Malaya