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.”

An important step in the ground-breaking Clean Seas Tuna breeding program was taken today when millions of dollars worth of Southern Bluefin Tuna was airlifted from sea pens off South Australia’s Eyre Peninsula to an on-shore breeding facility at Arno Bay.

The Southern Bluefin Tuna is a highly appreciated food fish and the remaining wild populations are continuously being ravished by commercial fishing fleets, despite the species status as “critically endangered” on the IUCN Red List of Threatened Species.

The Australian tuna breeding program is the first of its kind and will hopefully help ease the strain on wild populations. The air transfer was made to provide the breeding program with an egg supply ahead of the spawning period.

As reported earlier, the Australian company Clean Seas Tuna managed to successfully produce Southern Bluefin Tuna fingerlings in March this year and they are now hoping to commence commercial production of the species no later than October.

WWF Australia’s fisheries program manager Peter Trott says any advancement that would reduce pressure on wild tuna stocks is welcome, but he also cautions against the environmental problems associated with large-scale aquacultures. It is for instance common to use other fish to feed farmed fish, which can put pressure on wild fish populations.

In a world first, the Australian company Clean Seas Tuna has managed to successfully rear Southern bluefin tuna (Thunnus maccoyii) in captivity. This breakthrough opens up the way for the development of an alternative to wild-caught tuna.

Clean Seas Tuna announced on April 20 that their tuna broodstock had spawned continuously during a 35-day period from March 12 to April 16, and that the company now had succeeded in raising 28-day-old 2.5 cm tuna fingerlings. During the breeding period, over 50 million fertilised eggs and 30 million larvae were produced by the captive held tunas.

“This is equal to Armstrong walking on the moon,” says an elated Hagen Stehr, chairman of Clean Seas Tuna. Clean Seas Tuna now hope to breed tuna in their facilities off Port Lincoln. “The achievements are world firsts and major stepping stones to present the world with a sustainable tuna resource for the future. There are a number of other hurdles to overcome, but Australia can now achieve total sustainability in tuna.“

According to Fisheries Research and Development Corporation executive director Dr Patrick Hone, farm raised tuna can be a solution to the problem of falling world-wide fish stocks and increased seafood consumption.

“Australia uses 450,000 tonnes of fish a year of which 70 per cent is imported,” says Dr Hone. “Our goal is to lift farmed finfish production from about 50,000 tonnes to 100,000 tonnes annually by 2015.”

Large-scale commercial fish farming is however not a completely unproblematic endeavour from an ecological point of view and farmers will be forced to find solutions for sustainable water management, run-off handling, and food procurement if they truly wish to make farmed tuna an environmentally friendly alternative to wild caught fish.  It is however no doubt that it could provide the wild tuna population with a well needed chance to recover.