A Hawaiian company wants to build the world’s first commercial Bigeye tuna farm, in hope of creating a sustainable alternative to wild-caught big eye.

Bigeye tuna, Thunnus obesus, is the second most coveted tuna after the famous Bluefin tuna and the wild populations have been seriously depleted by commercial fishing fleets. As Bluefin is becoming increasingly rare due to over-fishing, consumers are turning their eyes towards Thunnus obesus – which naturally puts even more stress on this species that before.

In 2007, fishermen caught nearly 225,000 tons of wild Bigeye in the Pacific. Juvenile bigeye tuna like to stay close to floating objects in the ocean, such as logs and buoys, which make them highly susceptible to purse seine fishing in conjunction with man-made FADs (Fish Aggregation Devices). The removal of juvenile specimens from the sea before they have a chance to reach sexual maturity and reproduce is seriously threatening the survival of this tuna species.

“All indications are we’re on a rapid race to deplete the ocean of our food resources,” said Bill Spencer, chief executive of Hawaii Oceanic Technology Inc. “It’s sort of obvious _ well, jeez we’ve got to do something about this.”

Techniques to spawn and raise tuna fry are still being tentatively explored by scientists in several different countries, including Australia and Japan. As of today, most tuna farms rely on fishermen catching juvenile fish for them, but Hawaii Oceanic Technology plans to artificially hatch Bigeye tuna at a University of Hawaii lab in Hilo.

Once the young tunas from the lab have grown large enough, they will be placed in the 12-pen tuna farm that Hawaii Oceanic is planning to build roughly 3 miles off Big Island’s west coast. Each pen will have a diameter of 50 metres (168 feet) and the entire farm will be spread out over one square kilometre (250 acres). If everything goes according to plan, this project will yield 6,000 tons of Bigeye per annum. The fish will not be harvested until it reaches a weight of at least 45 kg (100 lbs).

In an effort to avoid many of the common problems associated with large scale commerical fish farmning, Hawaii Oceanic Technology will place their pens at a depth of 1,300 feet (400 metres) where currents are strong. The company also plans to keep their pens lightly stocked, since dense living conditions are known to increase the risk of disease in fish farms.

Farming pens can cause problems for the environment if fish waste and left-over food is allowed to collect under the pens, suffocating marine life living beneath. Other problems associated with fish farming are the release of antibiotics into the water and the escape of invasive species.

Fish farms can also put pressure on fish further down in the food chain since vast amounts of food is necessary to feed densely packed fish pens, and Peter Bridson, aquaculture manager at the Monterey Bay Aquarium in California, is concerned about how much fish meal the Hawaiian farm will use need to feed its tuna.

“You kind of have to come back to the whole debate on whether these fish are the right thing for us humans to be eating,” said Bridson. “There are lots of other things which have a lower impact in terms of how they are farmed.”

Spencer shares this concern and says Hawaii Oceanic wish to eventually develop other ways of feeding their fish, e.g. by creating food from soybeans or algae. It might also be possible to decrease the need for fish meal by recycling fish oil from the farm itself.

“We’re concerned about the environmental impact of what we’re doing,” Spencer said. “Our whole goal is to do this in an environmentally responsible manner.”