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Tasty Idea

Sustainable ahi farming powered by sustainable energy

Graphic: courtesy Hawaii Oceanic Technology

Think of Hawaii Oceanic Technology’s project as renewable energy meets sustainable fish farming. The company, called HOT for short, plans on installing self-propelled spherical fish cages off the Big Island’s Kohala Coast to harvest bigeye tuna. HOT plans to raise $10 million in funding to deploy the first three Oceanspheres. The first of the spheres could be operational by 2010. But Bill Spencer, CEO of HOT, says long-term goals are to license the technology to worldwide users.


Spherical Miracle
The netting is made of Kevlar (the same material used to make bullet-proof vests), which means fish and other marine animals won’t break through, inside or out. Each Oceansphere has 21 patent-pending technologies, including a hybrid ocean thermal energy conversion (OTEC) power plant. OTEC is a sustainable source of energy, producing energy by harnessing the power between warm, shallow waters and cold, deep-ocean water.

Steady Waters
Similar projects are tethered to the shoreline in shallow waters. HOT’s approach is 2.6 miles away from the nearest shoreline at ocean depths of 1300 feet. This allows for more space and more fish, making it more economically viable. The top of the Oceansphere will hover at 60 feet below surface level using geostatic positioning technology, powered by OTEC. A pump reaching 600 feet below sea level will draw cold water into the OTEC power plant.

Full Circle
To be a truly sustainable HOT will run a closed loop system. Fish will be raised from eggs in a hatchery for six months. Afterwards, they will be transferred to the Oceansphere and allowed to mature up to 100 pounds. All other tuna aquaculture operations employ a catch-and-fatten method that depletes natural wild tuna stocks. Because the sphere is enclosed, the fish will only eat what is provided to them, which could potentially lower mercury levels in ocean fish. “You can control the diet and make sure that it’s got a proper balance of protein and fat to achieve the kind of quality the market expects,” Spencer says.

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Hawaii Business,November