LAST OF 2 PARTS

After years of trial and error, researchers finally proved what many thought wasn’t possible.

Now they’re working to overcome the next major hurdle: making the process more commercially viable.

Just over three years ago, scientist Chad Callan and his research team at Oceanic Institute of Hawaii Pacific University were able to successfully raise yellow tang, Hawaii’s iconic aquarium fish, in aquaculture tanks in Waimanalo.

The female fish spawned at the facility, the eggs hatched there and the juveniles grew to adulthood, all under the watchful eyes of Callan and his team.

It was a milestone. Yellow tang juveniles never before had been produced in captivity.

The longest-surviving ones are now 3-1/2 years old and going strong, with the females producing thousands of eggs that the researchers are using to try to repeat the process again and again.

“It became apparent that it’s not impossible to do this,” Callan, Oceanic’s finfish program manager and head of the yellow tang project, told the Honolulu Star-Advertiser. “There just needs to be more effort to make it more commercially feasible.”

The initial success has enabled Biota Aquariums, which partnered last year with Oceanic on the project, to ship about 3,000 of the cultured fish to retailers around the country. The first batch went out in December. All the fish eventually ended up in home and public aquariums.

“Feedback has been incredible,” Tom Bowling, Biota’s chief executive officer, said in an email to the Star-Advertiser from the island of Palau, where he is based. “People cannot believe how quickly they settle into the tank and start eating whatever is offered to them.”

For now the aqua-cultured specimens come with a hefty price tag.

LiveAquaria, an arm of Petco, sells the Waimanalo-raised tangs for $99.99 per fish — roughly double the cost of a comparably sized wild-caught tang from Hawaii, according to its website. Yellow tang are found throughout the Pacific, but most come from Hawaii.

“Based on consumer feedback, we believe marine aquarium hobbyists understand captive-bred yellow tangs are more accustomed to conditions found in home aquariums,” Petco spokeswoman Ventura Olvera said in an email. “As a result, captive-bred yellow tangs were priced higher than wild- harvested ones.”

Because the fish essentially are quarantined from birth, they carry very low risk of introducing disease and pathogens into a home aquarium, according to Bowling. “This is very important when you have thousands of dollars invested in your home reef,” he said.

The captive-bred fish also are not stressed from being removed from the wild.

The fish can produce tens of thousands of eggs during the several days a month they spawn. But the vast majority don’t last long — either in the wild or in aquaculture tanks.

At the Oceanic facility, researchers are trying to improve the process so more larvae can survive, bringing down the per-fish production costs. To make it more commercially viable, the survival rate has to reach at least 5 to 10 percent, according to Callan.

Currently it’s about 1 percent, still far greater than in the wild, he added.

“If you can improve that number by just a few percent, it changes the ballgame completely because the amount of effort you put in doesn’t really change,” Callan said. “If you get 1,000 fish out or 5,000 fish out, you’re still putting the same amount of effort to culture them.”

If Oceanic and Biota are able to make the process more economically viable, giving consumers a competitively priced alternative to wild-caught specimens, that has the potential to lessen demand for yellow tang from Hawaii’s reefs — and potentially other fish as well, experts say.

Oceanic and Biota have a second joint project in which they are applying what has been learned thus far on cultured tang to other hard-to-raise reef fish popular with aquarium hobbyists.

By a wide margin, yellow tang have long been the most commonly captured aquarium fish in Hawaii waters.

In 2016, the last full year before a Hawaii Supreme Court ruling led to lower catches, nearly 335,000 yellow tang were reported caught in local waters, according to state data. Most were shipped out of state.

Kole, or goldenring surgeonfish, were the next most commonly caught fish that year, numbering about 49,000.

Over the past decade, yellow tang have made up more than 70 percent of the total aquarium catch in Hawaii, according to state data. Despite such numbers, the state says the fishery is sustainable.

Biota, which specializes in raising and selling cultured fish, is helping underwrite the cost of the tang research at Waimanalo. In exchange, the company gets the fish produced by the team, typically a batch a month.

The researchers have shared their breeding knowledge with others trying to raise saltwater aquarium fish, and that already has paid dividends.

After a visit to the Waimanalo facility in 2016, a University of Florida researcher returned home and applied the same basic techniques used with the yellow tang to raise blue tang. It worked.

While the vast majority of saltwater aquarium fish still are taken from the wild, environmentalists and others hope that successful ventures like the one in Waimanalo will gradually lessen the demand for wild-caught species, helping especially the ones that are being overfished.

“It’s huge,” Rene Umberger, executive director of For the Fishes, a nonprofit dedicated to protecting coral reef wildlife, said of the potential impact of the Waimanalo breeding venture.

By lessening pressure on the wild-caught ones, populations in the open areas likely would rise.

Some, however, say growing more aqua-cultured tang likely would have little impact on the health of Hawaii reefs.

“I think most aquariasts would prefer cultured yellow tang, but I don’t think it will greatly affect reef health one way or another,” said Alan Friedlander, chief scientist for the National Geographic Society’s Pristine Seas, a project that helps protect the last wild places in the world’s oceans. “Hawaii’s reefs are in decline because of overfishing, pollution and coastal development. If people want to see healthier reefs, then these are the areas that need to be addressed.”

Raising aquarium fish in captivity is not a new practice.

Almost all freshwater aquarium fish are bred, and clownfish, the saltwater species that was the star of the 2003 computer-animated film “Finding Nemo,” have been cultured for decades. Most clownfish sold in pet stores are captive- bred.

But they are different from yellow tangs in that their larvae are much larger and not so picky in what they eat, contributing to survival rates topping 80 percent, Callan said.

The process of breeding clownfish has become so refined that consumers can place orders picking from an array of designer colors, patterns and body characteristics.

The larvae of most reef fish, however, are like those of the yellow tang: tiny and challenging to raise in captivity, especially because the live food they eat is harder to grow.

To get the process just right, Callan’s team had to experiment with many variables. It took years, for instance, to get a robust population of females that would consistently produce high-quality eggs.

In those early years the larvae didn’t survive beyond a few weeks.

Among other things, the Waimanalo researchers had to tinker with how to grow the algae needed as food to raise zooplankton, tiny marine animals. The babies produced by the zooplankton become food for the tang larvae, but Callan and his colleagues had to adjust the menu ingredients numerous times to satisfy their temperamental wards.

The larvae initially develop into transparentlike fish and don’t turn yellow for about two months, when they are about the size of a quarter. It takes about a year for them to become adults, and they don’t start spawning until they are about 2 — likely a year or two earlier than in the wild.

Before the first juvenile tangs were produced in captivity, the obstacles seemed so insurmountable that many scientists were skeptical that it could be done.

But now that Callan and his team are beyond that hurdle, they’re focusing on the next one. If they are successful in producing juveniles from the initial batch of cultured tang, those would be the first second-generation ones bred at the Waimanalo facility, advancing the process in another significant way.

“There’s still work to be done to make this commercially feasible,” he said.