Mechanical system design of automatic sub-surface floating fish cage

The culture of fish in cages has become a practical and successful method in oceans to get good yield in fish production without going to deep sea. Our system contains a fish cage and an electronic system which makes the cage system submerge to a desired depth to protect fish during adverse weather condition. An automatic sub-surface floating fish cage has been developed for deployment in the coastal waters to safeguard the cage during bad weather condition. The prototype fish cage system consists of a rigid HDPE pipe assembly, net cage, variable ballast tank, submersible pump, air control system, floats, mooring ropes, anchors, and control station. The variable ballast tank is used to change the buoyancy of the system so that the fish cage can either be surfaced or submerged. The cage is free to move vertically in a water column by adjusting the weight and the buoyancy with an automatic control system. The system was tested in a test tank facility and sea trail was conducted off Chennai in Bay of Bengal to verify the operability of the fish cage.