Giant cages submerged in the ocean off Hawai'i are a growing venue for farming fish — and now a research team plans to study the viability of adding Hawaiian lobster and shrimp to the mix.

The idea is that bottom-feeding crustaceans can conveniently live off the waste and uneaten food falling from the fish into a separate cage below.

The setup, if feasible, would blunt one of the chief criticisms of open-ocean aquaculture — that it produces concentrated levels of fish feces that harm the environment.

Adding higher-value co-crops to ocean fish farms also could drive faster expansion of an industry considered by some to be the answer to a growing global appetite for seafood even as stocks of wild fish continue to dwindle.

Some observers see a potentially enormous financial payoff if the research leads to commercial lobster farming — especially if it includes the Hawaiian lobster, a delectable and pricey creature that has become scarce in fish markets and restaurants because of commercial fishery restrictions and depletion.

"This is a little bit of a long shot, but the potential is there," said Spencer Malecha, a professor of animal sciences at the University of Hawai'i's College of Tropical Agriculture and Human Resources.

Malecha, a former North Shore shrimp farm owner, is the principal researcher for the project, which tentatively is being awarded a $25,000 grant from the state Department of Agriculture to begin research.

Partnering with Malecha are Waikiki Aquarium director Andrew Rossiter, UH aquaculture extension agent Clyde Tamaru and local ocean fish cage farmer Randy Cates, who raises moi (Pacific threadfin) off 'Ewa Beach.

Malecha proposes to study six animals native to Hawaiian waters — two kinds of spiny lobsters, two kinds of slipper lobsters, marginated shrimp and giant mantis shrimp.

Each animal has its own advantages and drawbacks for fish cage co-cultivation, Malecha said.

The spiny lobsters probably are on the extreme end of the spectrum with the biggest potential reward but also the biggest obstacles, he said.

Purple and green varieties of Hawaiian spiny lobster, or ula, have been scarce since the federal government closed Hawai'i's main lobster fishery around the Northwestern Hawaiian Islands in 2000 because of declining populations.

From 1984 to 1990, Hawai'i's annual lobster catch averaged 331,000 pounds, or about 1 million predominantly spiny lobsters, and had become a major export to the Mainland and Asia before off-and-on fishery closures and catch quotas began in the 1990s. Two years ago, the designation of the Northwestern Hawaiian Islands as a national marine sanctuary permanently closed the fishery.

'ALMOST NOTHING'

Today, most lobsters are caught by hand by divers around the main Hawaiian Islands. The state Department of Land and Natural Resources said commercial fishermen in each of the past two years caught close to 7,500 pounds of spiny lobster, or around 3,600 animals — down from 11,800 pounds and 5,900 animals in 2005.

"What's on the market is almost nothing," said Guy Tamashiro of Tamashiro Market in Palama. "The catch has been really poor."

Tamashiro said he hasn't had spiny lobster in his family's fish market in many months.

At John Dominis, the fine-dining restaurant in Kaka'ako that once ran its own lobster fishing boats, Hawaiian spiny lobster is still printed on the menu, but it hasn't been available for years.

"We wish we had it," said restaurant general manager Al Yim. "It's not like the old days."

Tamashiro guesses that if spiny lobster was available for retail sale, it might cost $15 to $20 per pound.

But if someone were able to raise the animals commercially, they would essentially corner the market.

"If they can do it successfully, they could basically set their own price," he said.

However, breeding Hawaiian spiny lobster in cages is a tall order because the animal has to survive about 50 larval stages over as many as 150 days before it reaches a stable young maturity.

Joe Wilson, a lobster hatchery pioneer who has successfully reared cold-water Maine lobster on the Big Island and attempted to breed Hawaiian spiny lobster off and on over the past 20 years, said he knows of no one who can keep alive more than five warm-water lobsters out of 1 million eggs.

Wilson, co-owner of Kona Cold Lobsters Ltd., said he applauds Malecha's team for attempting to solve a puzzle that he said could make someone a billionaire if they find the solution.

But he also said it's an immense challenge to keep a viable number of lobsters alive to make warm-water lobster a viable commercial aquaculture crop.

"Nobody knows what it is (that keep lobster larvae alive)," he said.

Another long shot is raising mantis shrimp, a crustacean that typically grows up to a foot long. Five years ago, the species made local and national news when workers dredging the Ala Wai Canal caught and ate several of the creatures, the largest of which was 15 inches long and weighed 1.35 pounds.

HOUSING CHALLENGE

Malecha said a big consumer market exists in Japan for mantis shrimp, but a challenge is housing high enough numbers of maturing shrimp in limited space. That's because mantis shrimp — unlike Hawaiian spiny lobsters that live together peacefully — are like cold-water lobsters that kill each other with their powerful claws.

Smaller, more docile marginated shrimp and slipper lobsters have a greater likelihood of becoming a successful fish cage co-culture, according to Malecha.

For marginated shrimp, or 'opae lolo, Malecha said there are established land-based cultivation methods and markets, though it's uncertain how the animals would do in undersea cages. Slipper lobsters tolerate high population densities and have good market value, but it takes a long time for them to grow to commercial size, Malecha said.

Diversifying open-ocean fish farming with more species is expected to become a trend, according to a report last year by a task force convened by the Massachusetts-based nonprofit Woods Hole Oceanographic Institution with support from the Pew Charitable Trusts.

The report said aquaculture in 2004 was a $70 billion global business dominated by China and other Asian countries producing mostly carp and other fish. U.S. aquaculture production in 2005 was estimated at about $1 billion.

$25 MILLION IN ISLES

In Hawai'i, aquaculture production of fish, shellfish and algae has been valued around $25 million annually in recent years, and industry players have been leaders in sea cage farming.

Cates, who now does business as Hukilau Foods, in 2001 became the first in the U.S. to lease ocean space for commercial aquaculture. Kona Blue Water Farms LLC on the Big Island was the second, and produces kahala, or amberjack, marketed under the trademarked name Kona Kampachi.

Both companies are in the process of expanding operations to raise more fish for harvest.

Malecha and his research team expect to tackle mounds of existing research on the six crustaceans and try to breed them in captivity as a first step.

"It's exciting," said Cates, who used to be a commercial Hawaiian lobster fisherman. "If we can get them to grow to a certain point, then we have a shot."

Malecha, who intends to seek a second $25,000 state grant later this year or next year and is counting on $25,000 in matching funds from UH, said he hopes initial work will lead the team to focus on one or two animals for further research and development — for which he would need to seek much more funding.

"It has a lot of potential," he said. "There's a lot of material that's not being used (in fish cage farms) that can be used by something else."

Reach Andrew Gomes at agomes@honoluluadvertiser.com.