Offshore fish cages can be submerged to avoid storms

The SeaFisher fish cage system includes 12 cubic cages anchored to the seabed, which can sink to a depth of 20 m to keep them safe during storms .

A research team led by professor Chien Ming Wang at the University of Queensland and professor Joerg Baumeister at Griffith University developed SeaFisher, an offshore fish cage system that can withstand storms , New Atlas reported on March 7. The project was commissioned by the Australian Green Economy Cooperation Research Center. New research published in the journal Marine Science and Engineering.

The SeaFisher system includes 12 fish cages that float near the water surface when the waves are not too high. (Photo: University of Queensland)

Each SeaFisher system is 120m long, consisting of 12 cubic cages made of polyester mesh divided evenly into two rows. The cage frame is made from high-density, light-weight polyethylene pipes bonded together. The entire system is held in place by a seabed suction anchor at the front of the system. This is the only connection point to the seabed. Thanks to that, SeaFisher can continuously rotate around the anchor to always follow the direction of the waves. A front shield helps deflect incoming trash.

If the waves are not too big, the SeaFisher will still float close to the water's surface. But when the weather begins to deteriorate, water is pumped into the system's polyethylene pipes. This process helps the SeaFisher sink to a maximum depth of 20m and stay there to safely ride out the storm. The cages have a mesh cover on top, so the fish will remain in the cage when the SeaFisher sinks. When the storm passes, water is pumped out of the pipes, helping the system float again.

The team of scientists is testing small-sized prototypes, after which they will build full-sized prototypes. Each SeaFisher system is estimated to cost about 6 million USD , lower than many offshore fish farms today. The team hopes the system will have a relatively short payback period.

"We estimate each cubic cage can hold about 24,000 adult fish weighing 5kg. The system can be used to grow multiple species of fish side by side, and can even be adapted to grow seaweed, utilizing waste from fish cages to provide nutrients to plants ," Wang said.