Mud crab farming is very popular in some Asian countries like Bangladesh, India, Thailand, Philippine etc. Mud crab has huge demand and price in international market. Crab is very tasty and many countries of the world import huge amount of crabs for consumption every year. As a result, there are huge possibilities of earning foreign currencies by exporting crabs. The main benefits of crab farming are, labor cost is very low, production cost is comparatively lower and they grow very fast. Commercial crab farming business is developing the lifestyle of the people of coastal areas. By proper care and management we can earn more from crab farming business than shrimp farming. And small scale crab farming is gaining popularity day by day. Mud crab farming systems in coastal areas are described below.
Types of Mud Crabs
Mud crab can be found on estuaries, backwaters and coastal ares. They are member of Scylla genus. There are two species of crabs available that are suitable for commercial production. Two species of crabs are red claw and green mud crab.
Green Mud Crab
- Green mud crabs are larger in size.
- A green mud crab can grow to a maximum size of 22 centimeter carapace width. And it can weights about 2 kg.
- These are free living and distinguished by the polygonal markings present on all appendages.
- Generally red claws are smaller in size than green mud crab.
- A red claw can grow to a maximum size of 12.7 centimeter carapace width. And it can weights about 1.2 kg.
- It has a burrowing habit and there are no polygonal markings on it.
Both species are suitable for commercial crab farming business. And both have good value and huge demand in the foreign market.
Mud Crab Farming Methods
You can raise mud crabs in two systems. Grow out farming and fattening systems. The systems of farming in this two methods are shortly described below.
Grow Out System
In grow out farming system, young crabs are raised and grown for a certain period of 5 to 6 months till they reach marketing size and weight. This type of crab farming system is generally pond based. The pond size depends on the production type. Generally ponds for crab farming sized between 0.5 to 2 hectors. Proper bunds and tidal water exchange is a must. Small sized ponds are very suitable for crab farming. Because they are easily maintained. Make a suitable fence if the size of pond become small. In larger sized ponds where natural conditions are prevailing, strengthening is necessary along the outlet area. You can stock wild collected juvenile crabs that weights around 10 to 100 grams. Depending on the size of crabs and available facilities the duration of production may varies between 3 to 6 months. In commercial production with supplementary feeding you can stock 1-3 crabs per square meter. You can feed your crabs low cost fish, shrimps, small sized crabs etc. You can visit your nearest local market and collect rotted fish and innards of birds and animals from slaughter house. Provide the crabs 5% feed daily of their total body weight. For example, if there are 100 kg crabs in the pond then feed 5 kg food daily. Collect some crabs and try to determine an average weight. Regular sampling is very necessary for monitoring the growth and general health, and to adjust the feeding rate. Keep some pipes in the pond for shelter and the purpose of reducing mutual attacks and cannibalism. Within 3 to 5 months they will reach marketing weight and become suitable for selling.
Raising soft shelled crabs for a certain period until their exoskeleton gets hardened is known as crab fattening system. Hard shelled crabs has four to five times more value in the market than soft shelled crabs. Farming crabs in this system take less time and the process is very profitable. You can do crab fattening business in two systems that are described below.
- Fattening in Pond: Fattening can be done in any types of ponds between 0.025 to 0.2 hector size. Small tidal ponds with a depth of 1 to 1.5 meter is very suitable for crab farming. Prepare the pond perfectly before stocking crabs in the pond. Pond preparation can be done by draining the pond water, sun-drying and adding sufficient quantity of lime. Make a fence around the pond for fattening purpose. Because the crabs have a tendency to escape by making hole and digging the soil. Reinforce the inlet areas with bamboo matting inside the bund. For stocking, collect soft crabs from local fisherman or crab merchants. Collect the crabs in morning. 1-2 per squire meter stocking density is ideal for crab fattening purpose. Divide the pond into different compartments according to the size of crabs if it is big sized. Keeping male and female crabs separated from each other will make good results and reduce mutual attacks and cannibalism. Depending on your location and crabs availability 8 to 12 fattening cycles can be done in a year. Generally, crabs weight between 300 grams to 500 grams have high demand and value in the market. Collect and sell all the crabs when they reach the marketing weight. Always try to sell the crabs when they are in hard shelled condition. This will ensure high profit form crab farming business.
- Fattening in Pens or Cages: Crab fattening can also be done in pens, floating net cages, bamboo cages in shallow estuarine waterways and inside large shrimp ponds with good tidal water influx and in tanks. You can use bamboo splits, netlon or HDPE as netting material. 3 m * 2 m *1 m (3 m long, 2 m wide and 1 m height) is ideal cage size for crab fattening. Arrange the cages in a row so that you can easily feed and monitor the crabs. Stocking density of 10 crabs per squire meter in cage and 5 crabs per squire meter in pens is ideal. Maximum stocking density can result mutual attacks and cannibalism. Fattening in cages or pens in only used in small sale production. For commercial production fattening in ponds is perfect and more profitable.
Between these two crab farming methods, fattening system is more profitable than grow out system and has many advantages. Grow out crab farming system takes more time than fattening system. But fattening system is very popular to the farmer as it take less time and highly profitable.
Water quality plays an important role in the production of crabs. Change water occasionally if possible or apply proper medicines or chemicals. See the following chart.
For commercial purpose, crabs need 5-8% food of their body weight. You can feed your crabs low cost trash fish, chicken waste, animal innards collected form slaughter house, brackish water clams etc. Don’t served all the feed at once. Instead give it twice a day. Give major part of the total feeds during evening hours.
After a certain period check the crabs for their hardening. In grow out crab farming system they become suitable for marketing purpose within their 3 to 6 months of age. And in fattening system the time depends on crab’s size. However, collect the crabs when they reach proper weight and when their price remain high. Collect the crabs in the early morning hours or evening hours. You can collect crabs from pond by using scoop net or by using alluring bait. Wash the collected crabs with good brackish water and remove all types of dirt and mud. And then carefully tie the crabs very carefully without breaking its legs. Then try to keep those crabs in moist conditions. Keep them away from sunlight. Because direct sunlight has a negative effect on their survival. After that send them to the market.
Commercial crab farming business is gaining popularity day by day in many coastal areas around the world. Because it is a very easy, profitable and takes less time. Mud crabs have huge demand and high value in international market. So, you can earn some extra money and make an employment opportunity by doing commercial crab farming business. Have a good day!