By RUDI HEMPE/ecoRI News contributor
NARRAGANSETT, R.I. — The water was cascading into the Blount Aquaculture Lab at the University of Rhode Island Bay Campus at a rapid pace and Terence Bradley wasn’t a bit worried that his latest research project was being inundated with close to 20,000 gallons of seawater.
That’s because the water was filling a huge tank that he, his graduate students and a research partner assembled in the laboratory as the first step in a project to breed bluefin tuna in tank captivity. If they succeed, it would be the first such operation in the country.
Bluefin tuna are an endangered species whose numbers in the world’s oceans are being depleted by the voracious market for such delicacies as sushi. The Atlantic bluefin tuna fishery is in danger, as are the fisheries for other types of giant tuna in the Pacific and the Mediterranean.
In fact, the market for tuna is so great that tuna “ranching” operations have sprung up around the world. Entrepreneurs capture wild tuna and place them in huge pens to fatten them up. Out of fear that the market will collapse unless steps are taken to increase the species, some ranching operations are now entering into aquaculture to try to breed the fish.
But breeding bluefin tuna is a difficult task requiring precise conditions and timing. That’s why Bradley, a professor in URI’s Department of Fisheries, Animal and Veterinary Science, and Peter Mottur, a fisheries graduate (1991) and president of a Newport-based firm called Green Fins, are partnering in this project. They are starting off using the smaller, less demanding — so far as breeding is concerned — yellowfin tuna.
Bradley and Mottur plan to soon be off the North Carolina coast in Mottur’s 35-foot research vessel in quest of several 10- to 15-pound yellowfin tuna that they will bring to the Blount Lab tank. There they hope to see the fish spawn under controlled conditions.
The plan is to get the methodology down so they can proceed with the next step — build a bigger tank with bluefin tuna as tenants. The project is being funded by Green Fins, which signed on as a research partner with URI in January and has committed about $700,000 to this project.
With this funding, they ordered the tank from an aquaculture tank-building company. The tank arrived in 8-foot sections that had to be bolted together with joints sealed with ample layers of fiberglass.
“We used 800 stainless steel bolts and wore out 36 drill bits,” Bradley said.
To make room for the 20-foot diameter tank that stands 8 feet high — the biggest at URI — they prepared a bed of pea gravel on the concrete floor and surrounded that with concrete blocks. PVC piping, some as large as 4 inches in diameter, had to be rigged up to bring in salt water and filter it. URI already had the pumps needed for the project. The water will be heated to 23 degrees Celsius using an energy-saving heat exchanger. That temperature is deemed ideal for spawning yellowfin.
One unique thing about the tank was that the room where it was installed had a support beam holding up part of the roof. The beam had to stay, so the tank was built around it. The beam, encased in fiberglass, stands in the middle of the tank. Actually, that will be a bonus, Bradley said, as it will force the fish to swim in a circular fashion rather than swimming across the tank and potentially colliding with the tank walls.
Vertical black stripes painted on the tank walls also give a visual reference for the fish.
The yellowfin will be fed frozen squid, shrimp, herring and mackerel. Mahi larvae will be used to feed the tuna larvae.
The rearing of yellowfin tuna should give the researchers the opportunity to get the bugs out of the procedure of breeding fish under controlled conditions, Bradley said, and the experience will be valuable for the next phase — building a bigger tank and stocking it with a few bluefin tuna in the 150- to 300-pound range. The challenges will be to get the fish to spawn at the right time, to get the larvae to survive and then to get the juvenile fish to survive to a weight of about 100 grams. The fish could then be sold to firms that want to produce larger fish or be released into the wild.
The tank needed for the bluefin project will be more than double the size of the present one — 50 feet wide and 15 feet high. There’s no room for something that size at the Blount Lab, so another site, nearby it is hoped, will be obtained.
The graduate students involved in the project are Taylor Voorhees, Donald Bacoat and Tori Spence.