Mud crabs have four species which are Scylla serrata, S. tranquebarica, S. paramamosain and S. olivacea. The majority of their commercial output is sent to market live, making them one of the most expensive crab species in the world. Aquaculture of mud crabs has risen in popularity as a result of its high nutritional value, rapid growth rate, and strong market demand. Crab farming exploded in popularity, resulting in an overabundance of wild crablets. Mud crab breeding and larvae rearing have proven unsuccessful in Malaysia, resulting in poor mud crab production (Tan, 1997, Linh et al., 2017). Mud crab farming began in Malaysia in 1991, and they were raised in ponds or pens amid the mangrove trees (Tan, 1997).
Currently, the most prevalent mud crab culture techniques involve growing, fattening, and producing soft-shell crabs from seeds collected mostly from the wild. In the natural environment, mud crab output in Malaysia has fallen from 623 tonnes in 1995 to 162 tonnes in 2005 due to over-exploitation and uncontrolled plucking of juvenile crab by fishermen. Mud crab seed gathered in the wild, on the other hand, is inadequate to keep mud crab output at current levels.
It is not easy to site a hatchery since it must consider the land availability, expense, existing infrastructure, and proximity to the grow-out field. There are a few basic characteristics needed for a mud crab hatchery site which include a clean supply of freshwater and marine saltwater; ability to discharge hatchery effluent streams that have been treated; a location with adequate terrain for the development of hatchery structures; staff and products have appropriate access to transportation.
For the grow-out, earthen ponds can be used for farming mud crabs. The characteristics of soil for pond building are critical, especially because pond construction is a commercial operation's greatest capital expenditure. Maintenance, repair, leaking, and pumping expenses may all be reduced with good soil. Soil should be evaluated for its physical and chemical characteristics. Besides, cellular systems can be used for grow-out or fattening also. Cellular systems are the system where the crabs are placed in individual boxes or containers. For such operations, water quality is a must.
Figure 1: Dead Mud Crabs that Died Due to Molting Failure (above) and Lost Limbs (below) in RAS Aquaculture.
In Malaysia, there are a lot of mud crab culture systems which include ponds, stock control netting, mangrove pens, dry raised feeding platforms or mounds, crab fattening, canal systems, and cellular systems. These cultural systems have their own pros and cons. Moreover, all these farms need health management to maintain their production and reduce the chance of disease. All essential operational difficulties should be addressed in a health management program such as water quality management, feed management, health monitoring, site management, and source of supplier.
REFERENCE
1) Tan ESP, 1997. Malaysia crab research. In: Keenan, C.P. and Blackshaw, A. Mud crab aquaculture and biology. ACIAR proceeding. 78: 216.