Mud crab aquaculture

Market and industry

Mud crabs have good export potential due to:

• fast growth
• price
• new products
• positive market acceptance.

New mud crab products being developed for domestic and overseas markets are creating opportunities for farmers. Despite this potential, mud crab aquaculture requires significant capital input during breeding and grow out phases.

Mud crab farming requires expertise in:

• crustacean husbandry and nutrition
• water quality control and pond management
• food processing and marketing.

Culture and production systems

Mud crab grow out requires a large area of earthen ponds with access to quantities of brackish water. Mud crab farm design is very similar to marine prawn farms and production systems.

Mature, female mud crabs extrude eggs when kept in large tanks or ponds under suitable conditions in hatcheries. Each egg batch contains about 2–5 million eggs and a female may extrude more than one batch in her life.

Grow out

Growout of juvenile mud crabs is a common practice overseas, but in Australia it has not yet progressed beyond pilot–scale operations. Growout can be done to a limited extent on prawn farms, that require only minor changes to their facilities to accommodate mud crabs.

This grow out method is being explored as an enterprise option for remote northern communities. In aquaculture farms, post–nursery crabs reach marketable size and maturity in 6–7 months compared with 18–24 months under natural conditions.

Read the mud crab aquaculture and biology manual for:

• production methods
• rearing larvae
• grow out using ponds
• aquaculture research around the world.

Water quality and temperature

Juvenile and adult crabs are more tolerant of temperature and salinity changes than larvae. However, the water temperature should still be kept between 20°C– 32°C. This reduces issues with water quality and helps ensure healthy growth rates, as growth slows significantly at lower temperatures.

Salinity does not seriously affect crab survival if it is kept above 10 parts per thousand (ppt) and does not exceed 45ppt. The ideal salinity range for optimum growth is 15–25ppt.

Shelter

Crabs need shelter to reduce the risk of attack and cannibalism during the short, vulnerable time when their shells are hardening during the moulting process. As grabs grow, they shed their exoskeleton and expand the new, soft shell by inflating it with water and then harden the new larger shell. During moulting, the crab may be attacked and cannibalised by hard-shelled crabs.

You can place items in ponds to create shelter, suitable materials include:

• onion bags or shade cloth
• masonry blocks
• short lengths of pipe
• car tyres.

Providing shelter in the pond improves survival and productivity but can complicate pond management. The amount of shelter in the pond may be affected by the maintenance of pond quality, labour and harvesting.

Stock density

Moult-related cannibalism limits the density at which crabs can be grown in ponds. The maximum density for crab growth also depends on the crab size at harvest. The smaller the size, the greater the number produced. Separating and sorting crabs by size and sex may also help reduce cannibalism.

Feeding

In the natural environment, mud crabs eat mainly shellfish and crustaceans, which is difficult to achieve in aquaculture conditions. Feeding with raw animal material is not recommended, as it can foul the water. We recommend using formulated, dried pellet-style feed rations. Good results have been achieved using pellets designed for marine prawn aquaculture.