TOKYO -- Achieving a complete farming cycle for Pacific bluefin tuna remains a difficult, costly endeavor. Feed One, a leading Japanese fodder supplier, might be able to help.
It has a new feed for the fry of the favorite sushi ingredient.
The Yokohama company says the feed, Ambrosia, developed specifically for Pacific bluefin tuna fry, could alleviate the complete farming cycle's weak link -- raising fertilized eggs of farmed parents into adults and repeating the process.
The company is set to sell the scallop-derived feed to seafood companies, universities and local governments trying to develop full-circle farming of Pacific bluefin tuna.
So far, the only company that has successfully completed a Pacific bluefin farming cycle is Maruha Nichiro, which started to commercially ship the fish in 2015. The company's tuna are sold at major supermarket chains as sashimi cuts and in other forms.
Feed One and Kyokuyo jointly operate a Pacific bluefin tuna farm in Sukumo bay, in the western Japanese region of Shikoku. The goal is to achieve a complete cycle and ship farmed fish under the Tunagu brand in November.
In nature, bluefin tuna fry feed on plankton, which Ambrosia was designed to replace. In a Pacific bluefin farming cycle, it takes about three years from hatching to shipment of adults. In the initial four months, 99% of the fry die off. The company believes Ambrosia can raise the 1% survival rate by several times.
Ambrosia uses an extract from black scallop guts, called uro, which are usually discarded. When Feed One tested a sample from a Hokkaido industrial research center, Pacific bluefin fry responded eagerly.
The company then tested various other ingredients, including yeast extract and fish meal, until it was satisfied that it had hit on a winning recipe. The feed was formed into granules to enhance digestion, and repeatedly tested on fry immediately after hatching, which only takes place once a year.
Developing Ambrosia was not easy. Pacific bluefin fry are extremely discriminating about what they eat, compared to salmon, yellowtail or sea bream, partly because they eat live, moving objects, such as plankton. Furthermore, fish fry cannot efficiently absorb nourishment from feed as their digestive systems are undeveloped. This presented an additional challenge for developers trying to come up with fodder that fry could and would eat.
Atsushi Akimoto, head of Feed One's aquatic research department, said fish farming still has a long way to go. Cost efficiency is a key issue. Akimoto's team is "consuming 15kg of fish to grow a tuna just 1kg," he said.
This is the opportunity Ambrosia hopes to seize. The fodder is potentially the first viable artificial feed for Pacific bluefin, and Feed One expects it to go a long way in making farmed tuna more viable.
The company plans to pitch the product to companies and universities that are developing technologies for a complete aquaculture cycle.
The cost-saving impact Ambrosia could have on Pacific bluefin farming has yet to be fully analyzed. Akimoto admits the new feed still needs to be improved; fry fed with it were found to grow at a slower pace than those fed with live feed.
"We need to continue our research so it can make the fish grow faster and bigger," he said.
Seafood consumption is exploding in China and other emerging countries. Meanwhile, the Pacific bluefin tuna population is thought to be around one-10th what it was in 1961.
With the fish having grown scarce, excessive catching of their fry has come under close global scrutiny. And there are moves to adjust the Pacific bluefin catch.
At an international conference held from late August to early September in Busan, South Korea, a new regulatory framework was agreed upon that will allow flexible fishing quotas determined by fish populations.
In early August, Japan's Fisheries Agency notified domestic fishermen of a policy to reduce quotas for Pacific bluefin juveniles -- what fry grow into.