KAILUA, Kona, Hawai'i — A Kona open-ocean fish farm is facing opposition as it seeks to double its capacity.

The company says its fish are raised without significant environmental impact and as a source of omega-3 fatty acids with no detectable mercury or other contaminants.

Opponents say the giant underwater operation goes against Native Hawaiian traditions and will harm the ocean environment around it.

Kona Blue Water Farms LLC has applied for permits to increase the size of its eight submersible net pens off Unualoha Point to help meet the growing demand for fish as wild stocks are being depleted.

The aquaculture company, which has 38 employees in its Kona hatchery operation, currently raises Kona Kampachi, the trademarked name for its cultivated kahala, a native fish also known as Hawaiian yellowtail or amberjack.

The company, with administrative offices in San Francisco, has applied for use of an additional 13 acres in a conservation district which is managed by the state Land Division. The move would increase the operation's total lease area to 103 acres near Keahole Point, said Neil Sims, Kona Blue president and co-founder.

Its submersible pens would increase in size, from 2,800 and 3,200 cubic meters to slightly more than 6,200 cubic meters.

The open ocean fish farm, which uses two grids containing six- and two-net pens, would be consolidated into a single grid, accommodating all eight pens.

At a Board of Land and Natural Resources hearing last week in Kailua, Sims said studies have shown the pens have no significant negative impact on the water quality, the surrounding area or marine mammal life.

Opponents, however, voiced concerns about the lack of a monitoring, reporting and enforcement program; pollution from overfeeding or fish waste; behavioral changes of underwater creatures; parasites and fish health; and the effects of potential fish escapes.

Kale Gumapac, representing the Big Island alliance Mano O Ku Hawaii, said the group plans to petition the state for a contested case hearing and called for a cultural impact statement. He claimed the submerged lands Kona Blue wants to lease are ceded lands, former Hawaiian Kingdom land now administered by the state.

"Native Hawaiians have an interest separate than the general public, and we have not been involved," he said. "What has not been addressed has been the impact to customary practices and cultural traditions."

Gumapac urged an environmental impact statement, which would include an evaluation of the effects on cultural practices.

The group has until Jan. 28 to file a formal petition requesting a hearing. The company already has completed a draft environmental assessment.

The expansion plan also had its supporters at last week's hearing.

Charter boat Capt. Jeff Rogers, who primarily catches wild kahala, said the area where Kona Blue wants to expand never has been good for fishing, although he has noticed the company's pens have brought back the ono.

"It's kind of like a desert," he said, adding the expansion's impact would be "like putting more ash on the volcano."

The company has met with federal, state, county and community groups to discuss concerns about water quality; accumulation of fish feces and feed; impacts on wild fish stocks, sharks and dolphins; and conflicts with fishing and recreation activities, Sims said.

"In aquaculture, you always have to be flexible, but we certainly would like to move ahead as quickly as possible," he said.

Sims said traditional Hawaiian fish pond management is a good model and Hawai'i can be a global leader in fish farming and aquaculture.

"We see this as an opportunity to start to do things together. We are taking the traditional Hawaiian concept of sustainability and marrying it with new really exciting technology and growing native fish," Sims said.

The company projects sales of $9 million this year, mostly on the Mainland, and aims to harvest 30,000 pounds per week by mid-2008.

Kona Kampachi is now available locally at KTA Super Stores, Safeway, Whole Foods Market, Costco and high-end restaurants, Sims said.

The company also has announced plans to explore a possible operation in the Sea of Cortez in Mexico.