Apart from maintaining good water quality, it is also crucial for operators to find a suitable feed for the mud crabs. Utilizing the proper feed will allow the mud crabs to grow faster, reduce mortality and prevent the outbreak of diseases. In this post, we will be discussing the 5 common types of feed that are used in mud crab aquaculture.
#01 FEED- Trash Fish
The most popular option opted by many farms is the usage of low-value trash fish. These trash fishes are often unwanted by-catch that has low economic value, making them a cost-effective option. Farm operators typically buy them daily from the local fisherman, as storing them in large quantities are difficult. Trash fish is commonly used throughout India, Bangladesh, Philippines, etc. Depending on the size of the crabs, the fish are processed and cut into smaller pieces and fed to the crabs. Blood from the fish acts as an attractant to the crabs, and crabs rely heavily on chemoreception that detects changes in water chemistry. Most farm operators prefer trash fish for reasons associated with availability and cost.
#02 FEED- Formulated Feed
Formulated feed has also gained popularity for the past few years. Like trash fish, the bulk of formulated feed is made up from fish meal with excellent amino acid profiles. Unlike trash fish, formulated feed in their dried form can be transported and stored efficiently until use. This reduces logistical cost by the economy of scale and reduces the need for freezing during storage. Furthermore, the shape of the formulated feed can be made for different sizes of the crab. This reduces the additional labor cost associated with feed preparation. The formulated feed is also often at a higher protein content due to the reduction in moisture. Nevertheless, mud crabs can be quite reluctant to feed as formulated feed is not native to their diet. In this case, it is important to slowly wean off the mud crabs from the trash fish diet to a fully formulated feed diet. Formulated feeds are also sterilized, hence reducing the risk of the spread of diseases.
Body- Shellfish
#03 FEED- Shell Fish
Shellfish and mollusks are the favorite foods for mud crabs, marked by their aggressive appetite for them. Typical shellfishes that are used to feed mud crabs include cockles, marsh clams, and mussels. Mud crabs can use their powerful crusher claws to open these shellfish, making these slow-moving creatures ideal for consumption. Apart from providing protein to the crabs, shellfish are also rich in fats (lipids) that are crucial to the development of the mud crabs. Despite their preference for shellfishes, many farms refrain from using them as feed due to the several factors. Shellfish prices have been increasing throughout the years due to production problems. Furthermore, it is common for diseases like Vibro spp. which is commonly found in shellfish to spread to mud crabs.
#04 FEED- Squid
Apart from protein, the mud crab diet also requires fat (lipids) to promote growth. Trash fish and formulated feed are often lacking in the required fats, while shellfish are too expensive and might contain pathogens common to the mud crab. A viable option is to incorporate squid as a part of the diet for mud crabs. Squids contain high protein levels and fats, which are commonly extracted to make squid oil. Apart from growth, squid also encourages the development of mature ovaries in female crabs. Squids are rotated between trash fish and the formulated feed diet for extra nutrition.
#05 FEED- Natural Food
Another crucial type of feed that is excellent for the growth of mud crab aquaculture are the results of natural productivity of the ponds. Pond culture that is exposed to sunlight will often develop algae that tend to flocculate together. Higher-level organisms like amphipods, copepods, and nematodes will feed on the flocculated algae. The algae and the higher organisms are natural food sources for mud crabs. It is not quite understood how natural food sources perform in comparison with other feeds, but it is generally the cheapest option among the rest.
In aquaculture, feed cost typically accounts for 50-60% of operating cost. Hence, it is important to ensure that you pick the optimal feed that feeds your business goals. Typical considerations include availability, cost, and performance. Many researchers are also looking into other alternative protein sources that could potentially improve the growth of mud crabs. That includes the usage of biofloc technology, black soldier flies, plant-based protein, etc