Farmed ahi isn’t quite ready to become Hawaii’s newest export, though an ambitious venture to raise yellowfin tuna is getting close to launching after eight years and several million dollars invested in the effort.

Hawaii Oceanic Technology Inc. has endured a lengthy regulatory process and still faces challenges rearing yellowfin from eggs. But company CEO Bill Spencer said last week an initial pool of young fish may finally start swimming in sea cages off Hawaii island next year.

"No one has done this before," said Spencer, former president of the Hawaii Venture Capital Association. "Though additional work needs to be done, company officials and research partners are confident that success with egg-to-plate tuna rearing is at hand."

Spencer established Hawaii Oceanic in 2006 and has spent the last several years obtaining permits, working on cage technology and trying to rear ahi.

He expects construction of the first of the company’s patented "oceanspheres" by the end of this year. Testing in the sea is scheduled to begin in 2015, he said.

Oceanspheres are designed to hover anchorless about 65 feet below the surface and about 1,250 feet above the ocean floor using a combination of ballast, thruster control and surface buoys.

Each oceansphere is 177 feet in diameter, about half the length of a football field, and provides about 3 million cubic feet of interior space. Spencer said the structures will comfortably hold 20,000 fish growing up to 100 pounds each.

"The idea is to create an environment where the fish are happy and healthy — not squeezed in like sardines," he said.

The intended harvest size is about 90 pounds, which will take about 18 months to reach, Spencer projected.

However, raising the fish beyond a larval stage has proved difficult.

Hawaii Oceanic is working with fish-rearing firm Pacific Planktonics Inc. to grow yellowfin from eggs. To date, Pacific Planktonics has been able to get adult fish to spawn, though the offspring have survived only up to an advanced larval stage.

Syd Kraul, owner of Pacific Planktonics, believes he’s on the right track to growing larvae into fish about 3 inches long known as fingerlings. "That’s really hard," he said. "That’s the weakest link."

Kraul added that catching and keeping adult tuna alive in holding tanks is expensive and that the fish sometimes bang into walls and die.

Spencer said if he can’t get young yellowfin by the time the cages are ready for stocking next year, then he plans to instead use moi or kampachi.

If Hawaii Oceanic is successful, Spencer said additional cages could be deployed about two years after the first one.

At full capacity, Hawaii Oceanic anticipates being able to harvest 12 million pounds of ahi from six of 12 cages annually. The company plans to trademark its fish King Ahi and supply Hawaii, Japan and the West Coast. Spencer expects to sell the fish at a premium around $12.50 per pound, or $150 million a year.

Spencer said the global market for farmed seafood by 2020 is expected to surpass $200 billion, of which open-ocean fish farming would represent more than $75 billion.

"This is an incredible opportunity for the U.S., and Hawaii in particular, due to our extensive exclusive economic zone," he said.

The company also intends to sell its oceansphere technology for which it holds patents in the United States, Australia, Canada and the Philippines. Patents are also pending in Europe and Japan.

Open-ocean fish farming has raised concerns that include uneaten food and fish waste degrading ocean ecology, the impact on wild populations if fish escape, and cages attracting or being a hazard to other sea creatures.

Existing and past farm operators have said years of monitoring demonstrate no significant negative environmental impacts. And though raising fish in submerged ocean pens is still largely pioneering work with challenges, potential rewards include creating a major export for Hawaii, reducing pressure on fisheries and satisfying consumer demand in a state where about 85 percent of seafood is imported.

"Generally we need more mariculture in Hawaii," said Maria Haws, director of the Pacific Aquaculture and Coastal Resources Center at the University of Hawaii at Hilo. "We’re importing all this seafood. I think there’s sort of a moral imperative to raising the fish ourselves."

Spencer’s company is zeroing in on commercial production amid a burgeoning resurgence in Hawaii open-ocean fish farming after a couple of big failures.

Earlier this month Mamala Bay Seafood LLC filed an environmental report seeking approval to start a moi farm in waters next to the Honolulu Airport reef runway, and Blue Ocean Mariculture LLC filed a similar report seeking to more than double the size of its existing kampachi farm off Kona International Airport.

The Mamala Bay venture led by Randy Cates comes about two years after another Oahu moi farm started by Cates, Hukilau Foods, was shut down in bankruptcy after an investment firm took over the company and tried to execute an expansion plan.

Blue Ocean started production two years ago after acquiring assets of a prior kampachi farm, Kona Blue Water Farms, that had quit production in 2009.

Spencer’s company completed an environmental impact statement in 2009, and a year later obtained a lease from the state Department of Land and Natural Resources to deploy up to 12 cages below a 247-acre sea surface area three miles off Kawaihae north of West Hawaii resorts and a mile outside the Hawaiian Islands Humpback Whale National Marine Sanctuary.

Several other permits necessary to begin farming were obtained, including an Army Corps of Engineers permit that took four years to get in part because it required consultation with the National Oceanic and Atmospheric Administration to address impacts on endangered species and protected habitats.

"It was an excruciating, long process," Spencer said.

The Army Corps permit, obtained last year, allows Hawaii Oceanic to deploy just one cage, which will be tested for six months before adding fish.