Farming the ocean for tuna

PLENTY OF FISH: University of Rhode Island aquaculture professor Terry Bradley on the boat Miss Amy Lynn. Bradley is the scientific force behind Greenfins LLC. / COURTESY TERRY BRADLEY
PLENTY OF FISH: University of Rhode Island aquaculture professor Terry Bradley on the boat Miss Amy Lynn. Bradley is the scientific force behind Greenfins LLC. / COURTESY TERRY BRADLEY

On a modified lobster boat docked at the University of Rhode Island’s Narragansett Bay campus, aquaculture professor Terry Bradley is getting ready for a fishing trip to catch some yellowfin tuna.
Bradley grew up on fishing boats, but isn’t looking for a trophy or big score on the Japanese sushi market. Instead he hopes to bring a few more tuna back to URI’s tanks to spawn in a project intended to protect wild fish stocks from growing global demand for seafood.
Bradley is the scientific force behind Greenfins, an academic-commercial partnership designed to solve long-standing aquaculture challenges while creating a lucrative local tuna-nursery business.
“Right now aquaculture represents 50 percent of all seafood, and demand continues to increase, particularly with health-conscious consumers,” Bradley said on a phone call from the docks. “Because the demand for tuna is so strong, we believe it can command a premium price.”
Greenfins was formed a year and a half ago when URI graduate and serial entrepreneur Peter Mottur discovered Bradley’s aquaculture research and approached him with funding to expand it into a commercial enterprise.
The venture settled on yellowfin tuna, which are smaller and more plentiful than the bluefin tuna that fetch the highest sushi prices and are the focus of Japanese farming efforts, but more valuable than the species, such as albacore, usually found in cans.
The company is still likely years away from generating revenue from tuna sales, but Mottur said the potential market and potential positive environmental impacts made it a compelling investment.
“One of the big problems with tuna ranching – usually in the Mediterranean, Australia and Mexico – is they use these giant seine nets to catch tuna and then drag them back to pens, a lot of time before the fish can sexually mature,” Mottur said. “Eventually when you do it at that scale, it takes a toll. The U.S. is good about enforcement, but these other countries aren’t, and it’s a global fishery, so commercial guys here are seeing stocks go down.” If Greenfins can successfully breed tuna in tanks, harvesting wild schools of the fish may not be necessary or profitable.
Mottur said in addition to selling tuna to ranches and seafood operations, Greenfins hopes to one day release some farmed fish into the ocean to bolster the wild population.
To get to that point, Greenfins needs to overcome some technical challenges. Unlike salmon or tilapia, getting large, fast-swimming tuna to successfully reproduce is difficult, as is keeping the tiny larval-stage tuna alive during their first few weeks of existence.
The baby tuna won’t eat regular fishmeal or any manmade feed and have to be sustained on a diet of living plankton-like organisms called rotifers, which the farm produces.
“It is very difficult to raise the larvae, because they are so small and they have to get live feed,” Bradley said. “The larval stage is the critical issue, and once we get that solved, things could really take off.”
In addition to working on the feed problem, Greenfins needs a bigger tank to hold its growing brood of fish.
The current tank holds 20,000 gallons of water, but Greenfins is building a new 100,000-gallon tank expected to be ready for use in October.
Greenfins’ plan is to grow tuna to a size where they can be sold to a larger fish farm that would continue to grow them before harvesting and selling them into the market.
What to feed farmed fish, especially once they reach adulthood, has been one of the biggest challenges of aquaculture and one of the reasons many have considered it worse for the environment than catching wild fish.
Traditionally, to grow fish like salmon and tuna in captivity, farmers have fed them meal made out of processed smaller fish. As a result, aquaculture operations often remove more wild fish from the ocean than they would if they caught the tuna or salmon wild. As fish farming operations have become more sophisticated, the amount of wild fish going into fishmeal has gone down, from 50 percent to less than 10 percent for salmon, and Bradley said one of the goals of the project is to reduce it for tuna, possibly moving toward an all-plant-based feed.
On the other side of the piscine metabolic system, Greenfins intends to help fix another environmental concern with fish farming: the waste that dense pens of fish deposit in the water while being fattened up.
Greenfins consciously decided to focus on land-based aquaculture, both because it provides better control of the aquatic growing environment than marine pens, and because tank wastewater can be treated.
Although Mottur studied marine sciences at URI as an undergraduate, his career has so far taken him to businesses in information technology.
Since getting involved in Greenfins, he said he has found some similarities between fish farming and IT.
Mottur said he has one additional investment partner in Greenfins, but declined to say how much he has put into the business or plans to in the future. So far he has funded all the capital equipment while URI has provided the campus space and intellectual talent.
Greenfins hopes to perfect a repeatable breeding process with good survival rates in the next year and then start scaling it toward commercial production.
Ultimately, Mottur said tuna aquaculture has the kind of market potential to foster a large industry with URI a nexus bringing the techniques used around the world together.
“There are a lot of people working on great things here and abroad, and what we are looking to do is use URI as a center of excellence in research to pull it all together,” Mottur said. “If we can bring these great minds together and collaborate, we can make an egg to fork, or, with sushi, an egg to chopsticks solution.” •

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