Mud Crab Aquaculture | Challenges faced in the traditional pond system
Mud crab prices have increased by at least 10% from 2018, due to increased demand and lack of supply.
Peak prices can reach up to USD 30/kg, enticing many to invest in the mud crab business. Despite the high prices, investors are still struggling to attain profitability due to challenges faced. Typical problems faced include cannibalism, maintaining water quality, and crop theft.
Mud crabs (Scylla spp) are known for its aggressiveness, contributing to their cannibalistic behavior. When overcrowded, mud crabs would cannibalize each other resulting in high mortality. Mortality can reach up to 50-75%, resulting in to substantial financial losses. To reduce cannibalism, farm operators would reduce the stocking density to 1-1.5m2/crab. This reduces crop yield and erodes the profitably of farms with a high land cost. Other methods involve placing used tires or coconut leaves that provide hiding spots for mud crabs. It is also noteworthy to mention that different species of mud crabs have different aggression levels. For instances, Scylla olivacea commonly known as the red clawed mud crab is very aggressive and aquaculture efforts are usually met with high losses.
Mud crabs are a brackish water species requiring a salinity of 10-25 ppt (between fresh and seawater). In earthen ponds, water from river mouths is used for culturing mud crabs via tidal water exchange. Water quality needs to be managed to ensure optimal growth of mud crabs in earthen ponds. Due to pollution caused by agriculture runoffs, farm operators located at downstream of plantations are affected. The problem is aggravated during the monsoon season in which high run-off rates are expected. The deterioration of the environment impacts both wild mud crabs and the cultured mud crab species further reducing supplies. To avoid drawing water from polluted rivers, seawater and municipal water are mixed to attain the desired salinity. This increases the capital and operating cost for farm operators that otherwise have no other means of solving this problem.