Aquaculture Ahi: The Holy Grail of Fish Farming

October 2, 2013

Robert Duerr,

Ahi, also known as yellowfin tuna and bigeye tuna, have suffered from overfishing and are becoming harder and harder to catch in the wild. That’s why farm-raised ahi are so coveted, but the prize has proved elusive. Others are trying and Kraul has worked on the project himself since 2005.

“Replacing or supplementing wild catch with hatchery-raised tuna makes sense, but this is technically difficult with current technology,” says Kraul, who has 35 fish-hatchery tanks on a half-acre of land leased at the Natural Energy Laboratory of Hawaiiat Keahole Point in Kona.

“We have made progress in the capture and spawning of tuna to provide eggs for culture. … The major obstacle to successful hatchery production now is survival of young tuna larvae.”

Tuna farming has been tried elsewhere since the 1970s. It took Japan’s Kinki University 32 years and $50 million to successfully artificially inseminate and farm-raise a type of bluefin tuna that is called Kendai tuna. Today, Kendai remains a rare and expensive treat for sushi lovers, and is especially favored because it contains less mercury than wild-caught bluefin tuna.

Kraul says he began fish farming in the 1970s, raising mullet at Oahu’s Oceanic Institute. He went on his own when a friend gave him eggs from a Potter’s angelfish. Today, his company, Pacific Planktonics, is focused on raising reef fish, food fish and fish feed.

Pacific Planktonics has a worldwide reputation in the specialty niche of raising live phytoplankton and zooplankton for fish feed. These are the microscopic plants and animals that the larvae of ocean swimming fish need to survive.

The National Oceanographic and Atmospheric Administration reports that the worldwide production of wild fish for food has essentially stagnated since the mid-1980s. In the same period, NOAA says, aquaculture production has grown at an average annual rate of 8.3 percent, making it the fastest growing type of food production in the world. Asia is the world’s biggest supplier of farmed fish, with more than 90 percent of the world’s output. Meanwhile, the U.S. imports 91 percent of its seafood at an annual cost of $10.4 billion.

Hawaii has a long tradition of fish farming. The late William Kikuchi, an anthropologist on Kauai and an expert on fishponds, said Hawaiians began fish farming about a thousand years ago and that farm fish were once a major source of food in Hawaii, especially during famines.

Kraul believes the world’s love for tuna and increased fish pressure makes it a strong candidate for fish farming. Kraul says that, in the 1980s, the National Marine Fisheries Service in Hawaii successfully raised low-cost skipjack tuna, also locally known as aku. However, Kraul says, no one has raised ahi in Hawaii before.

In the quest to farm ahi, Kraul competes with tuna institutes in Japan, Australia, Panama, Indonesia and Spain that all have spawning tuna broodstock in tanks. A publicly traded Australian company, Clean Seas Tuna, is working closely with Kinki University on raising southern bluefin tuna.

Kraul believes ahi have a competitive advantage over bluefin tuna because they reproduce at a smaller size. Ahi lay eggs at 33 pounds, while bluefin need to weigh hundreds of pounds to breed.

Ahi broodstock needs smaller cages, so startup costs are lower, too. Kraul has two ahi broodstock named “Biggie” and “Silver” that each weigh about 80 pounds.

“My yellowfin tuna spawned July 21,” he says, “and I raised a few babies to test some research hypotheses. I hope to do another batch in early September.”

If his larval feeding methods work, it will be a groundbreaking bridge from ahi larvae to fingerling, which Kraul calls his biggest challenge.

Kraul believes Pacific Planktonics has “the resources that may improve tuna-hatchery culture, based on the current hypothesis that nutritional deficiency may be the problem.” Kraul hopes successful results will help tuna aquaculture expand to commercial scale in Hawaii.

“Many have failed,” says Kraul, “so most seek the fish with the best profit potential, i.e., high price: moi, kahala, maybe tuna. I think Hawaii can compete.”

In fact, he says, Hawaii is already a leader within the United States in aquaculture research and development.
“Hawaii has a really conducive government climate for aquaculture. The general public likes fish, saving fish and wants more fish to eat. It would be great to have a local supply.”

Kraul’s work is endorsed by Bill Spencer, co-founder of Hawaii Oceanic Technology Inc. and president of the Hawaii Venture Capital Association. Spencer has the only U.S. company dedicated to tuna farming, and in 2009 Spencer began working with Kraul to supply the hatchery that would validate Oceanspheres, his patented 200-foot-diameter, open-ocean tuna-cage system that will be first deployed off Kona.

“We have been working with Syd as his commercial partner for several years now,” Spencer says. He calls Kraul’s efforts a “real breakthrough.”

“He has raised more species from egg than probably any scientist. … He is a gem. He is the most capable person to succeed at the larval rearing of ahi. Our collaboration has already resulted in some important breakthroughs that demonstrate that spawning ahi in captivity and raising the spawn from egg to plate is an achievable goal.”

Another expert that agrees about tuna farming’s bright future is Kevin Hopkins, director of the Pacific Aquaculture and Coastal Resource Center affiliated with UH-Hilo.

“I think tuna farming will be important for the Big Island,” he says, but notes the challenges. “The problem is that (tuna) grow nicely in tanks in the hatchery but, after the larvae, it can be an expensive proposition. You need an economy of scale.”

Hopkins remains upbeat.

“I’ve known Syd Kraul for many, many years. I’ve done projects with him and had a graduate student work with him on tuna. Syd’s work is a good problem. Like many of us he operates on a shoestring budget and does remarkably well for what he does.”

We Love Fish

A UH report says Hawaii’s residents eat 37 pounds of fish a year on average, more than double what the average American eats, which is about 16 pounds a year. That means the average Hawaii resident eats about 11.4 ounces of fish a week.

The report, published last year by UH’s School of Ocean and Earth Science and Technology, looked at the 10 years from 2000 to 2009 to come up with its estimate of local fish consumption.

When both recreational and commercial fishermen were included, the local supply accounted for 51 percent of the fish eaten, the report found. Foreign sources – mostly from Taiwan, Japan, New Zealand, the Philippines and the Marshall Islands – accounted for 44 percent of the fish Hawaii eats and non-Hawaii U.S. sources accounted for 5 percent. The favorites?

Different species of fresh tuna, including ahi and aku, are the No. 1 choice of Hawaii consumers, followed by salmon. The top species that are caught by noncommercial fishermen are ahi and mahimahi.