Open ocean fish farming can produce healthier fish and less pollution
An EU-funded project aims to make fish farming more sustainable and cost efficient by taking it away from coastlines and out into the open ocean. OCEANFISH, due to end in April 2018, has allowed Israeli SME Gili Ocean Technologies (GOT) to adapt its existing system to withstand the harsh conditions of the open seas and to introduce several technological innovations. Saltwater aquaculture is usually done in sheltered areas near land ‘because it is easier; you do not have to fight the ocean,’ says project coordinator Josef Melchner, CEO of GOT. ‘But you lose the natural effect of the ocean — oxygen saturation and the flow of micro-elements such as micro algae which help fish nutrition.’ Moreover, near-shore aquaculture can cause pollution due to fish feed and faeces as well as antibiotics, often used intensively to fight disease. Less pollution OCEANFISH has adapted its Subflex system to allow fish farming to take place in much deeper waters than previously possible. This will allow fish farmers to grow their fish in better quality water while significantly reducing their environmental impact. The system is a flexible array of cages held together by ropes. It is attached to a single mooring unit which means the system can rotate with sea currents, thereby reducing wear and tear. ‘The main advantage with this is that it disperses organic matter over a large area, so if you add to this the ocean current, you have a natural dispersing mechanism,’ says Mr Melchner. Farming fish in better quality water makes them healthier and means that antibiotics do not need to be used as frequently. The structure is equipped with a mechanism which allows it to quickly submerge in the event of a storm, thereby protecting fish and the assembly from harm. ‘The system can withstand waves 17 metres high or more’ says Mr Melchner. The OCEANFISH team used computer simulations to calculate the buoyancy needed to keep the system hovering several metres below the surface of the water regardless of conditions above. Tracking the growth rates of farmed fish can be difficult. OCEANFISH used image processing techniques to produce a camera which shows the size and biomass of fish as well as the number of dead ones. It is now being tested in the open ocean. ‘We haven’t yet reached the accuracy we are aiming for — 1 % deviation — but we are not far off,’ says Mr Melchner. Small submarine The team also came up with a new way of feeding fish which works even when the cages are submerged. This consists of a feeding capsule much like a mini submarine, fitted with sensors and remotely operated, which allows fish to feed and keep growing no matter what the current weather conditions are. Following successful trials at sea, the final design is now ready for production. The need to make aquaculture more cost-efficient led the team to try adding a rectangular cage to the array of traditional round ones. Adding corners gave 33 % more capacity without increasing the system’s drag force. The first full-size cage is now being tested at a depth of 70–80 metres 15 km off the Israeli port of Ashdod. GOT aims to have most of these technological developments ready for commercialisation by April 2018 and is already talking to companies around the world about the potential opportunities for new joint ventures.
Keywords
OCEANFISH, aquaculture, fish farming, Subflex, GOT
