, Gloucester, MA

September 4, 2013

Cove-based study eyes 'juvenile' bluefin tuna

By Sean Horgan
Staff Writer

---- — Next week, weather permitting, scientists from the University of Massachusetts’ Gloucester-based marine research center will head motor out to sea from Cape Cod in search of bluefin tuna.

They won’t be looking for the giant bluefin or the babies. They’ll be searching for the juvenile bluefins. For those juveniles, swimming in their middle schools, tagging season is about to begin.

The project, being coordinated by researchers and scientists at UMass’ Large Pelagics Research Center based in Gloucester’s Hodgkins Cove, will use the latest in electronic pop-up satellite tags to help develop enough data about these teenage tuna to potentially answer questions about migratory patterns, swimming depth, growth rate, breeding and the mixing of tuna from the western and eastern fishing grounds.

“We see this project having extraordinary value in terms of providing long-term data that could help us better understand these fish,” said Molly Lutcavage, the director and research professor at the local UMass facility. “It’s immensely important.”

The project is valuable on several fronts. While it is chiefly a data-gathering scientific enterprise, it also is a prime — and still rare — example of the scientific community and commercial fishermen working together.

“We have long-standing working relationships with a variety of captains and they’ve been invaluable,” Lutcavage said. “They helped develop the methods for landing and handling the fish. Throughout our history, we have a continuing record of working with the fishermen.”

The plan calls for the UMass scientists to leave Chatham on the Tammy Rose, captained by Eric Stewart at 4 a.m. Tuesday, with an expected return around 3 p.m. that day. The same schedule would apply for the following two days, as well.

The tagging process works like this: The tuna, generally 44-46 inches, is captured by rod and reel and brought aboard the boat. As soon as the fish hits the deck, the blur of activity ensues.

“The crew handles the fish, brings it aboard through the tuna door,” Lutcavage said. “We put it on a nice padded vinyl matt. We quickly cover the tuna’s eyes with a wet cloth so they don’t get stimulated and will calm down.”

The tuna gets a quick once-over to determine its general health. The mate who brought it on board is charged with getting the hook out. Then the UMass scientists go to work.

“There’s usually at least two of us,” Lutcavage said. “One of us measures the fish to get the data and (project manager) Emily (Chandler), who is a geneticist, will make sure we get a fin clip to see which side of the ocean it came from.”

Then comes the tagging, with one of the scientists applying the satellite tag with a “tagging stick” near the rear dorsal fin.

The fish then is returned to the water. So how long does all of this take?

“About a minute,” Lutcavage said. “The tag then trails behind the fish, collecting and storing the data,”

The tags, which go for $4,000 each, are a bit of a modern marvel. They are really a sea-going computer, about 13.5 inches long including their built-in antennae. The body of the tag contains sensors to measure water temperature, pressure, the computer, an argos radio transmitter and the battery.

When the tag releases from the fish, either because the fish has died and drifted to the sea bed, simply comes loose or reaches its programmed deadline, it floats to the surface and uploads all of its data to a receiver on one of NOAA’s satellites.

That data is collected off the receiver on the satellite by the French company CLS and returned to the UMass scientists. For this project, the UMass scientists have 55 satellite tags at their disposal, with a total value of $220,000.

The reality is that there will be a whole lot of waiting in between the tagging and the information gathering.

“Some (tags) pop up early and some fish get recaptured early,” Chandler said. “But for the most part, it’s sit and wait while we do our other work.”

Sean Horgan may be contacted at 978-283-7000 x3464, or Follow him on Twitter at @SeanGDT