Hawaii regulators have approved a Honolulu startup company's plan to build the nation's first tuna farm in waters off the Big Island.

Hawaii Oceanic Technology aims to create an environmentally friendly open ocean farm for bigeye tuna, a favorite source for sushi and sashimi that's overfished in the wild.

The state Board of Land and Natural Resources voted 4-1 on Friday to give Hawaii Oceanic permission to install three large underwater cages for the tuna.

"I'm concerned on a global level and a local level that we have severe overfishing going on, and something needs to be done," said board member John Morgan, who voted in favor of the project.

Unlike many tuna farms around the world which capture immature tuna and fatten them until they're ready for harvest, Hawaii Oceanic plans to artificially hatch bigeye at a University of Hawai'i lab in Hilo.

After the fry grow, the company will take the fish to giant ocean pens about three miles offshore where they will grow until they reach 100 pounds.

Hawaii Oceanic expects to avoid the disease problems that have plagued other fish farms because its ocean pens will be large and its fish won't be as densely packed in the cages.

The ocean is 1,300 feet deep where the cages will be. This will allow strong currents to sweep away fish waste and uneaten food, preventing the pollution of the ocean floor.

The farm would produce 6,000 tons of bigeye a year when fully operational, serving Hawaii, the U.S. Mainland, Japan and other parts of Asia. In 2007, fishermen caught 224,921 tons of wild bigeye in the Pacific.

Hawaii Oceanic projects it will generate $120 million in annual export revenues, more than six times the value of Hawaii's current aquaculture output.

Several critics told the board they're worried diseased farm fish would escape and contaminate wild stocks, and others said they're worried about where Hawaii Oceanic would obtain its fish feed.

The project won't be sustainable if it imports its feed and exports about 90 percent of its product, said Rob Parsons, a board member of the environmentalist group Maui Tomorrow. The venture looks like it will suffer from the same pollution and disease problems as cattle farms, he said.

"This is not a farm," Parsons said. "It's an industrial feed lot."

The company has vowed to only purchase feed made from sustainably harvested fish and has said it won't feed its tuna any antibiotics.

Board members noted Hawaii Oceanic conducted an environmental impact statement that said the farm wouldn't significantly affect the environment.

No one has challenged the study in court, Department of Land and Natural Resources staff told the board.

Several board members said they were concerned that Hawaii Oceanic planned to use solar and ocean thermal energy to operate its giant ocean pens, something that hasn't been done before.

Given the untested technology and the large scale of the project, the board required the company to report on its progress and return for permission to deploy the remaining nine cages it aims to build.