Venturing into mud-crab farming

WHILE mud-crab farming, based on the collection of crablets or crabs from the wild for fattening or grow-out, has probably taken place for hundreds of years, hatchery production of mud crabs is a relatively recent innovation in Sarawak — thanks to the conducive local environment helping to make Sarawak a mud-crab producing state.

The preferred habitat of mud-crabs is mangrove forest or swamp, typically associated with sheltered tropical to subtropical estuaries and embayments. Mangrove vegetation is important to mud-crabs for providing both habitat and food supply.

Mud-crabs’ salinity tolerance enables the crustaceans to survive in fresh water for a few hours and hypersaline conditions for extended periods, and their ability to breathe air enables them to utilise their habitat effectively, even at low tide, and leave water that has a low oxygen level.

Ginger & Coconut Development Sdn Bhd (G&C) is the first vertically integrated mud-crab farming business in Sarawak and Malaysia, producing hatchery-based crablets, premium live hard-shell crabs and ethically produced soft shell crabs for both domestic and export markets.

Its director, Umang Nangku Jabu, and her husband, Cyrill Eigensatz, chairman of the company, produce their own trademark mud-crabs called ‘neocrabs’. They believe in the rich flora and fauna of the environment, much of which along the coastal areas is vast and unexplored.

Umang said Sarawak has clean and pristine waters and mud-crab farming is extensive but friendly to the environment.

“Where the interest in mud-crab farming is concerned, food production is the main focus. We have looked at many options, including oil palm, fish and fruit orchard. We wanted to do something that would make a difference. And mud-crabs came into the picture.

“We realise that while the size of the crabs in the market are smaller, prices are increasing. We’ve looked further into this and the potential of farming mud-crabs in Sarawak.

“I believe mud-crab farming can help the rural population economically, especially the mud-crab fishing community,” she said, adding that this reflected the current wisdom on mud-crab farming where R&D, significant industry development and extension of technology had occurred in recent years.

According to her, the development of such a manual is indicative of the contributions from major departments and research teams, involved in mud-crab culture development, especially the Agriculture Department.

More aid, however, is needed to further develop the industry.

Inspiration and insight

Crab fisheries and aquaculture over the past couple of years have provided inspiration and insight into the need for such a manual which brings together the whole process of mud-crab farming from broodstocks to high-quality products leaving the farm.

“In this case, we have asked the Agriculture Department to help us and the small farmers who want to venture into mud-crab farming but do not have the means. I believe if help were given, these farmers could help boost crab fisheries in the state.

“For us, in G&C, we can’t do it alone — that’s why we encourage small-time farmers, keen on the industry, to further develop mud-crab farming in Sarawak.

“We also urge the farmers to come together and share their skills but first, help comes from the Agriculture Department, considering mud-crab farming in Sarawak is still at an early stage of development,” Umang said.

For G&C, its three cultured mud-crabs from four famous species are Scylla Serrata, S Tranquebarica and S Olivacea which are the focus of both commercial fisheries and aquaculture production. The company does not culture the fourth type – S Paramamosain.

These species are among the most valuable in the world with the bulk of G&C’s commercial production sent live to Singapore, Taiwan and Hong Kong apart from the local market.

This pioneer venture for Umang and Cyrill has been very challenging but they are committed to doing their best to develop this sector of aquaculture.

“The state government appointing us as the anchor company is a sign of support. Exploring the unknown involves a lot of risks. But every little step achieved brings tremendous satisfaction and motivates us to move to the next level,” she noted.

Life history

The life history of mud crabs (neocrabs) — the whole mud-crab megalopae (final larvae stage before settlement of their life cycle) — appears to be not selective among estuarine habitats (seagrass, mud or sand) and crablets (juvenile mud-crabs). The strong selection of a seagrass habitat indicates living within seagrass beds likely increases the crabs’ survival.

An interesting aspect of the mud-crabs’ maturation is their step-wise maturation process whereby they pass through an apparent physiological maturation before becoming functionally mature.

For mud-crabs, the first stage of maturation for males occurs from CW (carapace width) of 90-110mm. From CW of 140-160mm, males develop their characteristic of large claws, and mating scars on their sternum and front walking legs become apparent.

In females, the characteristic U-shape of their abdominal flap, together with a well-developed fringe of setae around it (plus their pigmented abdomen) are a more obvious sign of maturation. This differs from the more triangular to the more grounded and broad forms of the immature females.

The development of the ovary can be seen by depressing and pushing forward the first abdominal segment next to the carapace. Ovaries change colour as they mature, progressing from transparent through to a yellow and finally dark orange (probably in layman term, we call them eggs).

A mature female mud-crab produces between one million and six million eggs with the larger species laying even larger numbers.

But out of that many, probably 40,000 will be spawned with the survival rate between only one and two per cent.

“If there’s one million eggs, we’re happy to get 10,000 crablets,” Umang revealed.

The time to hatching and release of larvae is temperature-dependent with a shorter time to release at a higher temperature within the animal’s natural temperature range, and longer time at a lower temperature.

Once released, the longevity of each larval stage is similarly temperature-dependent with survival rates linked to both temperature and salinity.

As a result, the time of the five zoeal stages and the one megalopa larval stage found in planktons can vary considerably before settlement to the first crablet stage, also known as C1/C2.

As the crablets grow, they can moult up to 15 times to reach their size of 150mm.

Mud-crab behaviour includes cannibalism, a trait that threatens the lives of mud-crabs growing-out.

So in the culturing stage, they are placed in individual containers as in fattening operations. In this way, survival can be improved compared to pond-reared crabs where cannibalism is prevalent.

For G&C, the hatchery of mud-crabs is in Sematan (next to Palm Beach Resort) where broodstocks are brought and mother crabs allowed to lay eggs which will be cultured or reared until they become small crabs and thereafter, transferred to the nursery and reared into mature crabs.

“Having the hatchery will allow us to do sustainable farming and help with the conservation of mud-crabs in the wild. After hatching, they become larvae.

“There are small five zoeae stages, followed by the megalopa stage before the larvae become crablets (C1/C2). From the zoeae stages to newly-settled crablets, it will take about one month to become a crab.

“The reason we put them back in the nursery (at Rambungan, Loba Stoh) is to make them bigger to ensure their survival.

“From the hatchery, the size of C1/C2 is about 6mm. We then grow them 10 days to 14 days to reach 14mm. That’s when we will put them into farms or sell to those who want to be in the industry,” Umang said.

Nursery development

G&C has further developed a mud-crab nursery at Rambungan (Loba Stoh) where it has 13 ponds from phases 1 and 10 and phases 2 and 8.

Its second phase gate, a second farm at Telaga Air, uses the five ponds from phase 1, and 23 ponds from phases 2, 3 and 4 for a total of 41 ponds.

From the hatchery, C1/C2 crablets are brought to the nursery and left in the ponds between 10 and 20 days to allow them to grow. At the end of the period, they will fall into C3, C4 categories — a time for harvesting.

Explained Umang: “Once they have grown into these sizes, they’re ready to be sold to our clients and vendors. In fact, even for the crablet size, we have clients from Johor who would buy these crablets for their farms, and we sell them according to their sizes — at USD0.10 per crablet (C1/C2 between 4 to 6mm); USD0.15 per crablet (C2/C3 between 7 to 9mm) and USD0.25 per crablet (C3/C4 between 10 to 14mm) with a minimum order of 3,000 pieces of crablets.”

On marketing, she said their premium hard-shell mud-crabs were in high demand, especially from locals, while some were exported to countries like Korea, Japan and Singapore.

G&C is also adding to its production pool a soft-shell crab (ketam nipah) which is becoming popular.

“The demands for these crabs are quite high, and currently, we also export to Singapore and Korea. For instance, Korea has requested we export to them five tonnes a month but that’s not achieveable as now, we can only produce 500 kg every month.

“We can’t achieve what we’re targetting because for five tonnes, more than one hectare of ponds are required to produce the numbers. So we cannot meet the five tonnes target,” she said.

The reason is that a mud-crab requires a space of at least one sq metre for itself.

Umang pointed out that they were happy with the present sales volume despite insufficient ponds, noting that approval for the utilisation of land near the coastal areas was being awaited.

“We’re contented with what we can sell for now – a minimum of 100 to 200 kg locally to fishermen and restaurants per month while some is exported.”

MoU signing

This year, G&C signed a Memorandum of Understanding (MoU) with the state government through the Agriculture Department to develop mud-crab farming and produce crablets and hard-shell and soft-shell crabs in Sarawak — plus the whole supply and value chain.

“The market opportunities for hatchery-based mud-crab farming are promising due to overfishing of the world stock and increasing world market demand.

“We want to work with contract farmers. The company will provide crablets and technical guidance, and during harvest, the farmers will provide back to G&C for quality assurance, packing, processing and distribution,” Umang added.

At the MoU signing, G&C said it could help grow the industry albeit with assistance from the Agriculture Department as the company’s role was to help the local people.

“I understand they’re supposed to give grants to contract farmers but till now, we haven’t heard anything. Hopefully, the industry will have the opportunity to further develop its potential.

“The problem with contract farmers is that they want to be part of the industry but do not have the money to dig ponds. They’re interested but financially constrained. They have the land but not the means to proceed as it’s not cheap.

“We also asked for one hatchery site in case our present one is infected with diseases. So we applied for one more hatchery at the Sematan station belonging to Department of Fisheries (DOF) but they already have fish and prawns.

“We need the whole station for our operation,” she said.

Purchases of mud-crabs or soft shell crabs can be made via the G&C office (tel: 082-575763, email [email protected] or website www.neocrab.com.