Mud crab

  • Name of species:
    mud or mangrove crabs (Scylla spp).
  • Primary potential:
    Aquaculture. There is limited scope for stock enhancement.
  • Attributes for aquaculture/stock enhancement :

    · Once mud crab are through their larval stage they appear to have robust health. In many areas throughout Southeast Asia juvenile mud crabs are collected from the wild and stocked into ponds or enclosures for grow-out

    · Once through the larval stage survival through grow-out is high, if ponds are stocked at appropriate densities. Mud crabs can grow from juvenile to adult size in 4-6 months, dependent upon species and water temperature, providing the potential for 2 crops (grow-out) per year.

    · Live mud crabs fetch market prices of around AUD10 per kg, whilst higher prices can be obtained for soft-shell mud crab in Asian markets from smaller crabs of 100-150 g. For crabs picked for crab meat for canning, a price of around AUD3 per kg is common. Premium prices, of around AUD20 per kg, can be obtained for hard shell crabs in excess of 1 kg for the banquet market in restaurants, with particularly high prices during the New Year and Chinese New Year periods

    · In Indonesia and Philippines the price paid for crablets for farming is rising every year as the supply situation from the wild worsens

    · Mud crabs are quite hardy organisms. Little is known of disease problems in the juvenile or grow-out phase of their culture. It is only during larval culture that susceptibility to bacteria has been identified

    · Mud crabs (S. serrata) have a high fecundity, producing several million eggs per individual. They are easily bred in captivity, which means that selective breeding (e.g. for rapid growth) can be introduced in the near future

    · Broodstock husbandry is simple

    · Mud crabs are easily transported either as larvae in water, or dry once they have reached the crab stage

  • Culture methods :

    · Juveniles/seed can be collected from the wild or be produced in the hatchery

    · Seedstock for most mud crab farms in Southeast Asia is harvested from the wild. Hatchery production has only recently started to contribute to seedstock production. The future of the industry is in hatchery produced seedstock, as wild seedstock will always be a limiting factor

    · Issues for grow-out cover such issues as scope for using simple, low-cost technology, suitability for small-scale operations, ease of management, possible environmental impacts and opportunities for employing women

    · Mud crab grow-out takes place either in ponds (with or without mangroves) or in enclosures within mangrove forests in Southeast Asia. Whilst some pelletised feeds are available, little R&D has yet gone into their formulation. Trash fish and agricultural wastes (in some areas) are currently used as feeds for mud crabs

    · In Australia the grow-out of mud crabs in mangrove enclosures by Aboriginal communities is seen as a farming practice that can complement traditional fishing and gathering activities. The husbandry of mud crabs in the enclosures is seen as an activity in which women can play an important role

  • Current production status :

    · Whilst many groups are still working to develop reliable commercial mud crab aquaculture systems, commercial production of crablets for farming has already commenced in Vietnam and the Philippines on a relatively small scale. In Australia, crabs from hatchery production have been grown out in a commercial prawn farm on an experimental basis, and government institutions, together with the private sector, are working on commercialisation of their technology

    · The main constraint to mud crab farming development is the reliable supply of crablets. Larval rearing of mud crabs on a commercial scale has proven to be more difficult than for some other crustaceans. Their larvae are particularly sensitive to bacteria and related water quality parameters

    · Mud crab farming is a significant industry in the Philippines, Vietnam, Indonesia, Sarawak and elsewhere in Southeast Asia

    · There are active mud crab fisheries from Africa, through Southeast Asia and into the Indo-Pacific

  • Marketing :

    · The international market for crabs is generally strong. Mud crabs are reasonably tough animals and can be transported live, packed dry in boxes. This makes marketing and transportation much simpler than for many other organisms. In addition to the live mud crab trade, there is also a market for soft-shell crab (particularly in Southeast Asia). Niche markets can be developed for 'egg crab' (females with eggs), all male crabs (as they grow faster and larger, with bigger claws than females) and for crab meat. Special markets exist for banquet size mud crabs (over 1 kg), which have their highest demand around New Year and Chinese New Year celebrations. There is also a market for crablets for farming throughout Southeast Asia

    · Most Pacific nations have a significant domestic demand for mud crabs. In many countries over fishing of mud crabs has left depleted stocks which cannot meet local demand

    · Throughout Southeast Asia considerable effort is being put into the development of environmentally friendly production systems based on simple enclosures being constructed in existing mangrove forests (or revegetated mangroves) to culture crabs. It may be feasible for such crabs to obtain eco-labelling

    · Development of mud crab farming will have spin-offs, as associated with most seafood enterprises. There will be an increased demand for transport/freight services, packaging, processing (if the product is cooked or meat picked) and feeds, all of which will provide employment and business development opportunities. Processing of blue swimmer crab meat from wild fisheries has led to considerable investment in processing plants in Indonesia and the Philippines. The market for pasteurised, tin crab meat is very large. One US company alone, Phillips, has a need for 30,000 tons per annum

    · Farmed production of mud crabs can meet market demand outside of seasonal catches from mud crab fisheries and provide a better continuity of supply to the market. Similarly, harvesting from farms can be timed to meet peak demand

  • Comparative advantages/disadvantages (risks) of producing the species in the Pacific:

    · Countries in the region can benefit from investment in this species already undertaken elsewhere. Technology can be transferred

    · There are good local markets for mud crab in most Pacific Island countries

    · Many Pacific Island nations have extensive mangroves that can be used for farming crabs in simple enclosures

    · Tending/operating a mud crab farm in mangrove enclosures requires minimal technical training

    · Some Pacific Islands have good links to significant markets such as Hawaii, Guam, New Zealand, Australia and the USA

    · Hatchery production of mud crab can be used for restocking of wild mud crab fisheries

    · Income developed from mud crab farming can assist in poverty alleviation

    · Mud crab farming (and fishing) can complement and provide a secondary source of income from mangrove silviculture

    · There is already an established marketing network in many countries for mud crab from fishing

    · Harvested stock can be stored without refrigeration



    · Airfreight options and capacity may be limited, making it difficult to take advantage of live trade

    · Many Pacific Islands have limited land area available for pond-based farming systems

    · Technical staff will need to be trained or recruited to run hatcheries to support mud crab farming

    · If crablets are moved between islands without adequate health checks, there is the risk of spreading disease

    · If fisheries enforcement is not effective, there may be a temptation to collect juvenile crabs from the wild for farming, which will be contrary to current best practice management for mud crab fisheries

    · In some Pacific states international trade in mud crabs is controlled by legislation, as part of their wild fisheries management control. This would have to be amended to allow product to be exported, perhaps by a marking system to make them distinguishable from wild stock

    · If pond culture is utilised, discharge will have to be well managed to avoid harm to fragile coral ecosystems

    · If ranching or restocking of wild stocks is attempted, professional genetic advice will be required to ensure genetic diversity is maintained and genetic contamination from non-local stock does not occur

Research & Development