The popularity of tuna is growing as more people from Boston to Beijing learn the pleasures of succulent raw fish. But the heavy fishing of wild tuna to meet this demand is rapidly shrinking the global supply.

Now a Hawai'i company wants to build the world's first commercial bigeye tuna farm so the masses may savor sashimi without further reducing tuna populations.

"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."

If successful, the startup could blaze the way toward the environmentally sound farming of one of the world's most in-demand sushi ingredients. But the potential challenges are significant, highlighting the difficulty of relying on farmed fish.

Hawaii Oceanic aims to build a 12-pen farm just under 3 miles off the west coast of the Big Island in two years. The farm would produce 6,000 tons of bigeye a year when fully operational, serving Hawai'i, the Mainland and Asia. In 2007, fishermen caught 224,921 tons of wild bigeye in the Pacific.

Bigeye and other tunas are called 'ahi in Hawai'i, where they're commonly grilled or eaten raw in several ways.

In Japan, bigeye is called mebachi maguro. It's hugely popular as a sushi topping and as sashimi, bite-size slices of raw fish, usually dunked in soy sauce.

Bigeye is the second-most-coveted tuna after bluefin. But bluefin has been so heavily hunted for its soft, buttery meat that the species' population in the Atlantic and Mediterranean has plummeted more than 80 percent in 30 years.

Now, bigeye is becoming the favorite catch, said Mark Stevens, a senior program officer at the World Wildlife Fund. In the Eastern Pacific, humans are capturing bigeye faster than the species can reproduce and replace what we eat. The situation is almost that bad in the Western Pacific, he said.

"The fishing industry has turned to bigeye because it's the closest meat when it comes to quality," Stevens said. "Pressure has switched to bigeye, not just in the Pacific but everywhere."

Aquaculture has great appeal amid overfishing, but environmentalists and scientists note its dangers: Fish farms can pollute the ocean, hurt fish lower on the food chain and lead to problems when farm-raised fish escape into the wild.

At some farms, tightly packed fish cages have become breeding grounds for disease. Fish waste, uneaten feed and antibiotics fed to sickly fish have collected under pens, suffocating marine life on the sea floor.

Spencer says his farm will avoid these pitfalls because his pens will be in waters 1,300 feet deep, where strong currents sweep away waste.

Hawaii Oceanic initially plans to feed its bigeye fish meal, and eventually switch to feed made of soybeans, algae or fish oil recycled from the bigeye.