DESIGN A GRADER FOR Peneaus vannamei NURSERY

Traditionally the shrimp farmers used to stock pl (post larvae) of Penaeus vannamei shrimps in to grow out ponds directly but they faced many problems such as, running mortality syndrome, retarded growth, high FCR, increased production cost and lower profit. So, a new system of farming was introduced wherein a new phase is introduced in between hatchery and grow out i.e. called a nursery system or nursery phase. The main advantage of nursery phase is to remove the weaker post larvae and transfer the stronger ones to attain a compensatory growth in grow out ponds. In nursery systems pl is used to grow up to 0.5 to 2 g and then transferred to grow out ponds. But during the transfer of seeds due to the "heterogeneous growth " of the shrimp seeds it is quite difficult to attain the compensatory growth at an expected phase. So a grader was designed to separate the uniform size seeds which weigh above 0.5 g from small size seeds from L.vannamei nursery systems. During testing of the designed grader, it showed more than 75% efficiency in the separation of seeds that weighed 0.5 g and above. Thus, the results showed significant difference between the seeds that were graded and non-graded.

SUMMARY AND CONCLUSION:

In nursery farming, the common process involves the grading of the shrimp seeds of required size to transfer it to the grow out ponds. The machine has a dimension of which is suitable for all type of nursery systems. The various components were selected after appropriate design of those components. After assembling the parts, a test was carried out to grade the appropriate size shrimp seeds with respect to the time taken to complete the grading operation and to find out the efficiency of the machine. Results showed that the machine has an efficiency of 75% and 25% for quantity retained in the mesh plate and quantity collected down respectively when 2 kg of shrimp seeds are loaded and the grading process completed within 7 minutes. So, a Farmer can transfer the shrimp seeds using this portable grading machine effectively. The portable grading machine has been found to be effective and efficient for the purpose of grading the shrimp seeds of weight 0.5 g from small size seeds. The designed machine has been made simple so that it could be understood and operated by even an unskilled person. Most materials used for the fabrication of the machine are locally available and affordable making the machine very cheap to fabricate and to maintain. Furthermore, it saves energy and time as it operates electrically.