Tracking the mighty, mysterious Bluefin Tuna. Living on Earth’s Jeff Young tags along on a tuna tagging expedition. Science is slowly unlocking the secrets of the Atlantic Bluefin, a highly evolved swimming machine that’s highly coveted for the sushi market. After decades of overfishing and an oil spill in its spawning grounds, there are now signs of hope that the Bluefin can bounce back. Photo: High-tech tags let scientists follow the tuna’s wide-ranging migration. Dr. Molly Lutcavage says not all the big Bluefin go to the Gulf of Mexico. Maybe they have a secret spawning ground? (Photo: Paul Murray Courtesy of Large Pelagics Research Center)
YOUNG: Scientists at the International Union for the Conservation of Nature recently published gloomy assessment of the world’s tuna. Five of the eight tuna species are now in the “threatened” or “near threatened” categories on the IUCN’s Red List. All Bluefin Tuna, the All Bluefin Tuna, the report warns, are “susceptible to collapse under continued excessive fishing.” The U.S. government last month named the Atlantic Bluefin a “species of concern.” It’s been overfished on both sides of the ocean for decades. And last year’s Gulf oil spill struck spawning grounds just as eggs and larvae were in the water. But on a recent fishing trip I learned that some scientists tracking the Atlantic Bluefin are starting to see a few hopeful signs that this amazing animal can make a comeback.
[WATER SOUNDS, BOAT ENGINE]
YOUNG: We push off from Chatham, Massachusetts on Cape Cod at 4 a.m.,Normal hours for Capt. Eric Stewart. Stewart is 47. He’s been fishing here since he was a teenager. How big are tuna to him? For his 20th wedding anniversary, Stewart got a new wedding band engraved with Bluefin Tuna. Not what Mrs. Stewart had in mind.
STEWART: (Laughs) Well, she said I’m not gonna have a bluefin ring! And so that was the end of the discussion. Then all of a sudden she says, “I think that’s a great idea.” I said, “oh great, well what are you gonna get?” She says, “Oh don’t worry, don’t worry.” So uh needless to say my new tuna ring cost me a little bit more than I thought it was going to! But I got my wish.
YOUNG: (Laughs) Stewart’s surrounded by reminders of what’s on the line with his charter fishing business. This boat, the Tammy Rose, is named for his wife. His first mate is his son, Corey. If he can’t fish, they’re all sunk. Mere talk of the Bluefin as an endangered species hurt business.
STEWART: It was frustrating for me and it impacted tackle sales and impacted charters. And you know, it’s given Bluefin like this bad mark when there is nothing farther from the truth.
YOUNG: Away from the microphone Stewart tells me some of his fishing colleagues were not happy with him making this trip. Bad news about the Bluefin comes from three types of people, scientists, environmentalists and reporters — and Stewart has all three on this outing, organized by the Pew Environment Group. But he thinks it’s important for fishermen tell their story.
STEWART: We’re out here every day. The number of fish that I’ve seen in the last five or six years clearly shows that the population is growing, not declining.
[WATER AND SOUND OF TROLLING BOAT]
YOUNG: About six miles off of the Cape, Humpback Whales breach, sending spray into the dawn light.
YOUNG: Stewart follows the whales. Where they feed, so do Bluefin.
STEWART: See all the birds and everything up here now? So this is really looking good.
YOUNG: Corey sets the seven trolling lures at staggered lengths behind the boat. And we wait.
[TROLLING MOTOR, RADIO CHATTER]
YOUNG: Then, a powerful swirl at one of the middle rigs.
[REELS SPINNING LOUDLY]
STEWART: Big fish. Here we go! Gotta clear the other lines guys! Big fish!
YOUNG: The reel dumps line. The deck is chaos as the fish crosses lines.
STEWART: Get the other squid rig in the boat! Get the squid rig in the boat! Right there in the short corner! Someone get that squid rig in the boat! This is a big fish guys, this is not a little fish.
YOUNG: Reporter Lisa Densmore straps into a harness and takes the rod and reel.
STEWART (SHOUTING): What do you think Lisa? Is this worth waking up at 4 o’clock in the morning for or what? (Laughs) Come on!
YOUNG: You got a guess on this fish here?
STEWART: You know what, he made a really strong run…He’s possuming us! There he goes.
YOUNG: Possuming, what’s that?
STEWART: He’s just gonna trying to reverse directions. Playin’ possum. Uh, this fish could be 58 inches. He made a huge run. But you just can’t tell. You really can’t tell till he comes up.
YOUNG: Stewart maneuvers the boat as his son coaches Densmore back and forth on the deck — a move called the tuna tango. After some 25 minutes the big Bluefin shows a flash of color near the surface. Stewart’s early guess at its size was way off. This thing’s as big as me.
STEWART/YOUNG: There he is! Oh, wow there he is, wow!
YOUNG: Up close, a Bluefin is a marvel; a bullet of pure, hydrodynamic muscle. They’re among the few fish that regulate their body temperature. Warm muscles move them faster and farther than just about anything in the water. One tuna tagged on this side of the ocean was caught just 53 days later on the other side, in Norway. Andre Boustany watches this one fight. He’s a Duke University marine biologist who's tagged about 500 fish in his study of Bluefin.
BOUSTANY: In the past decade or so we’ve learned more about Bluefin Tuna than we did in, you know, maybe a hundred years before that. It’s just been an amazing flurry of scientific discovery in the last decade or so.
YOUNG: A tagged fish can reveal a wealth of data. A harvested fish can fetch a small fortune. In January, a giant Bluefin caught near Japan set a new record at auction: $396 thousand. For a single fish. If this fish is over 73 inches, it’s a keeper. Boustany’s not sure which way things will go.
BOUSTANY: I don’t know actually, what they’re gonna do, that’s a good question. (laughs) If it’s a legal commercial size then they’ll stick it with the harpoon. If it’s too small they’ll tag it with a conventional tag and let it go.
YOUNG: Will this Bluefin swim away with a tag or be sushi on someone’s table? We’ll get back to that. But let’s talk about just what we’re learning about Bluefin Tuna, and why there’s cautious optimism about its future.
LUTCAVAGE: There are signs we believe that Bluefin, if properly managed, and if taken good care of, can rebound much more quickly.
YOUNG: That’s Molly Lutcavage. She directs the Large Pelagics Research Center at the University of Massachusetts, Amherst. She says fishing quotas are finally cutting chronic overfishing in the Mediterranean Sea. She’s seeing more juvenile bluefin. And there’s the intriguing data from the high tech tag she uses, called a pop-up satellite tag. It’s a mini computer that tracks the fish’s location, depth, and water temperature for a year.
LUTCAVAGE: So the tag pops up to surface and then starts transmitting the log data to receivers’ onboard orbiting satellites. That recorded information is then relayed to the tagger, in this case me, via email.
YOUNG: That is so cool. This changes whole set of questions you can ask of your data.
LUTCAVAGE: Absolutely. We were among first people to use this pop-up technology. And of course the first year we used it, the tags came off the fish and the fish weren’t where they were supposed to be, which was in the Gulf of Mexico during the presumed spawning period. So it was first sort of volley back by the fish, saying, ‘hey, we’re not doing what you scientists think we’re doing.’
YOUNG: Lutcavage and her team have a couple of theories. The first is that Bluefin along the eastern U.S. coast are likely shifting farther north and east, in some cases out of U.S. waters. Second, and more controversial, is that Bluefin have other spawning grounds beyond the Gulf of Mexico, some spot the fish have kept secret.
LUTCAVAGE: From our tagging we’ve seen only about a third to half of the fish that we tag each year entering the Gulf of Mexico. What that suggests to us is either Bluefin don’t spawn every year or they’re spawning in these other locations. We think it’s highly unlikely that such a large number of adult Bluefin Tuna, that appear to leave their feeding areas in really good condition, would take a year off. It could happen, but if it does, it means that Bluefin Tuna are violating life history.
YOUNG: That idea’s hotly debated. But all the scientists I spoke to agree that while they’re still concerned about Atlantic Bluefin, the fish could be turning the corner. It all depends on strict enforcement of fishing quotas and stopping illegal fishing, especially in the Mediterranean. And that’s where another kind of tuna tagging might help. Lee Crocket of the Pew Environment Project says electronic catch documentation could track harvested fish much like grocers use bar codes to keep inventory.
CROCKETT: You would tag the fish with a wire tag that has a bar code that can be scanned into a computer system. And then, as that fish travels through the system, it’s accounted for in this database. So it’s something that, you know, we think would be important to be able to prevent illegal fishing and unreported fish, but it’s not there yet.
YOUNG: A few companies are using this system. Pew is pushing the international body that regulates tuna fishing to adopt it.
[BOAT SOUNDS, LIGHT ENGINE NOISE]
YOUNG: Meanwhile, back on the Tammy Rose, it’s the moment of truth for Captain Stewart and his big Bluefin.
STEWART: That’s a pretty big fish. I’d like to get a good look at him, though.
YOUNG: It’s 70 inches. Big — but not big enough to harvest. Stewart puts in the tag and then it’s back in the water with a little help. Stewart gently places the hook of a long handled gaff under the tuna’s pectoral fin. Cory Stewart explains.
CORY STEWART: He’s reviving him. He gets very tired. Just like if you work out you build up a lot of lactic acid. These fish do the same thing. So, big fish like this, you swim him for a little while, get oxygen back into his gills, back into his system, get lactic acid out of him. And then he starts kicking, he starts really swimming again, and you can release him and you know he’s gonna be okay.
STEWART: Alright, let’s let him go!
YOUNG: There he goes.
YOUNG: Stewart’s not too upset that this one that got away.
STEWART: It was 3 inches short. It’s a really nice fat healthy fish, too, which is good. Today’s all about trying to tag and release 'em. So actually in a lot of regards I’m really happy. (Laughs) What I’ve also learned from working with scientists is how little we really know. I mean, how little do we really know about a fish that can swim the ocean? We’ve really only just begun to scratch the surface on Bluefin Tuna. And they are an amazing, magnificent creature and certainly, almost like the king of the sea.
YOUNG: For the sake of the fish and the fishermen: Long live the king.
[Jorma Kaukonen “There’s A Bright Side Somewhere” from 2009 Blues Summit (Fur Peace Ranch Inc/The Orchard 2010).]
YOUNG: Just ahead – how the new virtual landscape of the internet could decide the fate of real-world environments. That’s coming up, on Living on Earth!
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