Posts Tagged bluefin tuna

Nov 21 2014

Surrogate sushi: Japan biotech for bluefin tuna

AP Business Writer

TATEYAMA, Japan (AP) – Of all the overfished fish in the seas, luscious, fatty bluefin tuna are among the most threatened. Marine scientist Goro Yamazaki, who is known in this seaside community as “Young Mr. Fish,” is working to ensure the species survives.

Yamazaki is fine-tuning a technology to use mackerel surrogates to spawn the bluefin, a process he hopes will enable fisheries to raise the huge, torpedo-shaped fish more quickly and at lower cost than conventional aquaculture. The aim: to relieve pressure on wild fish stocks while preserving vital genetic diversity.

Yamazaki, 48, grew up south of Tokyo in the ancient Buddhist capital of Kamakura, fishing and swimming at nearby beaches. His inspiration hit 15 years ago while he was out at sea during graduate studies at the Tokyo University of Marine Science and Technology, and a school of bluefin tuna streaked by.

“They swam just under the boat, and they were shining metallic blue. A beautiful animal,” Yamazaki said. “Before that, tuna was just an ingredient in sushi or sashimi, but that experience changed bluefin tuna into a wild animal to me.”

An animal, that like so many other species, is endangered due to soaring consumption and aggressive modern harvesting methods that have transformed the bluefin, also known as “honmaguro” and “kuromaguro,” from a delicacy into a commonly available, if pricey, option at any sushi bar.

This month, experts in charge of managing Atlantic bluefin met in Italy and raised the quota for catches of Atlantic bluefin tuna by 20 percent over three years. Stocks have recovered somewhat after a severe decline over the past two decades as fishermen harvested more to meet soaring demand, especially in Japan.

But virtually in tandem with that, the International Union for Conservation of Nature put Pacific bluefin tuna on its “Red List,” designating it as a species threatened by extinction.

About a quarter of all tuna are consumed by the Japanese, according to the United Nations Food and Agricultural Organization. They gobble up most – between 60 percent and 80 percent – of all bluefin. Rosy, fatty “chu-toro” from the upper part of bluefin bellies, is especially prized for sushi and sashimi.

Out at his seaside lab in Tateyama, on the far northern rim of Tokyo Bay, Yamazaki and other researchers are hoping their latest attempt to get mackerel to spawn bluefin will prove a success. An earlier attempt failed due to what he thinks was a problem with the water temperature.

Yamazaki’s technique involves extracting reproductive stem cells from the discarded guts of tuna shipped by cold delivery from fish farms and inserting them into mackerel fry so tiny they are barely visible.

The baby fish are put in an anesthetic solution and then transferred by dropper onto a slide under the microscope. Researcher Ryosuke Yazawa deftly inserts a minute glass needle into one’s body cavity to demonstrate.

Under the right conditions, the tuna stem cells migrate into the ovaries and testes of the mackerel. The team is now waiting to see if the mackerel, when mature, will spawn tuna, and if the tuna will survive. Following that, they could be released into the sea or farmed.

The research team has already succeeded in using surrogate technology to produce tiger puffer fish, the poisonous “fugu” used in sashimi and hotpot, using smaller grass puffer fish. It has produced trout spawned by salmon. Companies that import rare and tropical fish also are interested in the technology.

The method could help reduce pressure on wild populations, Yamazaki hopes, and also help ensure the greater genetic diversity needed to preserve various species.

Though he started out working in the field of genetic modification, Yamazaki emphasizes that his techniques involve only surrogate reproduction, not GM.

The main “tricks,” as he calls them, are using baby fish as future surrogates, because their immature immune systems will not reject the tuna cells, and relying on the natural tendency of the reproductive stem cells to mature and produce viable offspring. To simplify matters, the lab is using triploid, or sterile hybrid fish commonly bred at fish farms, that will not develop eggs or sperm of their own species.

Yamazaki expects his research to be useful for commercial purposes. Though researchers elsewhere have succeeded in breeding tuna in captivity, the process is costly and survival rates are low. Mackerel, less than a foot long when caught, are much easier to handle and keep in land-based tanks than tuna, which can grow to nearly the size of a small car and require far more food per fish. The mackerel also mature more quickly and spawn more frequently, if they are well fed and kept at the right temperature.

Not all experts favor such high-tech solutions for the bluefin.

Amanda Nickson, director of global tuna conservation for The Pew Charitable Trusts, said the partial recovery of Atlantic bluefin stocks shows that enforcement of catch limits, backed by threats of trade bans, can work.

Earlier this year, the multi-nation fisheries body that monitors most of the Pacific Ocean recommended limiting the catch of juvenile bluefin tuna to half the average level of 2002-2004. Scientists found that stocks of the species had dwindled to less than 4 percent of their original size. It also found that most fish caught were juveniles less than 3 years old, before they reach reproductive maturity.

The group set a 10-year target of rebuilding the population to 8 percent of its original size.

“As long as you don’t take too many, those populations can rebuild and rebuild fairly effectively,” she said.

Perhaps so, said Yamazaki, but over the centuries, humans have repeatedly over consumed resources, sometimes past the point of no return.

“Japanese people eat tuna from all over the world. We have to do something. That is the motivation for my research.”

5903779_G(AP Photo/Tokyo University of Marine Science and Technology, Goro Yamazaki)

5903780_G(AP Photo/Elaine Kurtenbach)

5903781_G(AP Photo/Elaine Kurtenbach)

5903782_G(AP Photo/Shizuo Kambayashi, File). FILE – In this Jan. 5, 2014 file photo, people watch a bluefin tuna laid in front of a sushi restaurant near Tsukiji fish market after the year’s celebratory first auction in Tokyo.

5903783_G(AP Photo/Elaine Kurtenbach)

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Nov 6 2014

Countries increase protections for overfished Pacific bluefin tuna

During a meeting of the Inter-American Tropical Tuna Commission (IATTC) this week, the United States, Mexico and Japan developed a joint proposal to reduce the catch limit of Pacific bluefin tuna in the eastern Pacific Ocean (EPO) in 2015 and 2016. IATTC member nations adopted the proposal by consensus, taking a critical step in rebuilding the population of this overfished species.

“With this agreement we will see reduced impacts on juvenile bluefin, which will contribute to rebuilding goals,” said Barry Thom, U.S. Commissioner to the IATTC. “We can only achieve rebuilding of this important species by working together across the entire range of the species and by reducing both juvenile and adult catch.”

 Bluefin tuna. NOAA photo. 

Pacific bluefin spawn in the western Pacific Ocean near Japan, and a portion of the population typically migrates to the EPO off of Mexico and the United States for a few years before returning west to spawn. The species is considered overfished and has declined to historic lows, with an estimated 3 to 5 percent of its historic spawning biomass remaining.

Approximately 80 percent of the fishing impacts on Pacific bluefin occur in the western and central Pacific Ocean (WCPO), with the remaining 20 percent occurring in the EPO. Japan’s fisheries account for the majority of the catch in the WCPO, while Mexico’s fisheries account for the majority of the catch in the EPO. Given the greater fishing impacts in the WCPO, reductions in the WCPO catch across all age classes will be critical in allowing the species to rebuild.

The Western and Central Pacific Fisheries Commission, which manages fisheries in the WCPO, is expected to adopt additional Pacific bluefin catch reductions at its annual meeting this December.

The staff of the IATTC recommended a 20 to 45 percent reduction in Pacific bluefin catches in the EPO.  This week’s agreement by IATTC member countries limits the Pacific bluefin catch in the EPO to no more than 6,600 metric tons in 2015 and 2016 combined, for an effective annual catch of 3,300 metric tons. That represents a roughly 43 percent reduction below the average catch from 2010 to 2012, which matches the IATTC staff scientific recommendations.

“These reductions are not only in line with the conservation advice, but they’re also balanced reductions reflecting where the majority of the fishing impacts occur,” Thom said. “All nations need to do their part in rebuilding this stock and this agreement is a big part of making that happen.”

The agreement also calls for member countries to reduce the catch of bluefin tuna by sportfishing vessels by a proportion similar to the reductions in the commercial catch.

The United States is also considering steps to sharply reduce recreational bluefin catches from a limit of 10 fish per person per day, with possession allowance of 30 fish per multi-day trip, to a limit of two fish per person per day, with a possession limit of six fish total. The U.S. recreational catch limits are expected to be adopted by the Pacific Fisheries Management Council in November and to be effective for the 2015 fishing season.


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Sep 17 2014

Bluefin Tuna Are Showing Up in the Arctic—and That’s Not Good News

When you throw a net into the ocean, you never know what you’ll pull out.

That was the case for researchers cruising the freezing Arctic waters off Greenland in August 2012 in search of mackerel to see if there were enough of the fish to support a commercial fishery. In one haul, three endangered bluefin tuna, each weighing roughly 220 pounds, were pulled onto the ship’s deck amid six metric tons of mackerel.

“It was a bit surprising,” said Brian MacKenzie, a marine ecologist at the National Institute for Aquatic Resources at the Technical University of Denmark. The research ship was sailing in the Denmark Strait, between Greenland and Iceland, where water temperatures have historically been too cold for bluefin tuna.

More bluefin tuna have been caught off eastern Greenland since then. From June to the end of August of this year, Greenland fishing vessels caught 21 tuna—in addition to 65,000 metric tons of mackerel, according to Greenland Today.

The ever warmer Arctic waters could have profound impacts on how fisheries and food webs are managed and conserved in the future as tropical and Mediterranean species migrate into what were once colder waters.

With Arctic waters warming and attracting bluefin tuna, Iceland and Norway in 2014 implemented commercial quotas for the prized fish. “It’s small, only 30 [metric] tons each,” said MacKenzie. “But it indicates that the distribution is really changing.”

“Climate change is really challenging political and diplomatic relationships,” said Nick Dulvy, a professor of marine biodiversity and conservation at Simon Fraser University, in Burnaby, British Columbia. “Species names will change, and if your quotas are tied to a species name, that’s a problem for the fishery,”

In 2009, after mackerel had spread to the coastlines of Iceland and the Faroe Islands, Iceland set itself a mackerel quota of 112,000 metric tons. That angered the European Union, and conservationists worried that stocks of the humble fish would suffer.

MacKenzie and his colleagues analyzed the water temperatures east of Greenland using satellite imagery, oceanographic buoys, and measurements from ships. They found warm water had spread from the southeast Atlantic toward eastern Greenland. August temperatures in 2010 and 2012 were warmer than any other time since 1870. They recently published their findings in the journal Global Change Biology.

In fact, between 1985 and 1994 and 2007 and 2012, waters with temperatures greater than 11 degrees Celsius in the Denmark Strait and Irminger Sea has increased by 278,000 square miles—an area larger than Texas. “It’s only in the past two to three years that we can see that the temperatures of the waters east of Greenland have gotten above 10 degrees Celsius in the summer time,” MacKenzie said.

Not only can bluefin tuna tolerate warming Arctic waters more easily, their prey can too.

Mackerel have been increasing their reach since the mid-2000s, according to MacKenzie, moving from the European continental shelf out toward the Faroe Islands and on to Iceland.

The oily fish is a preferred sustenance for tuna, which usually only search for prey in waters where the minimum surface temperature is above 11 degrees Celsius, said MacKenzie. That the tuna were brought in with a load of mackerel in 2012 suggests there was a school of tuna hunting the smaller fish, he said.

Finding bluefin tuna off Greenland is more evidence that climate change is shuffling the species swimming about the world’s oceans. Fish generally found in warmer waters are being spotted in regions formerly filled by cold-tolerant species, or are expanding their range. Mackerel have moved into the waters south of Iceland, and anchovy now swim the North Sea.

“Around Denmark, we’re seeing species that 15 to 20 years ago would have been extremely rare, such as anchovy and red mullet,” said MacKenzie.

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Aug 1 2014

Farming The Bluefin Tuna, Tiger Of The Ocean, Is Not Without A Price

Dan Charles  |  July 30, 2014


Yonathan Zohar, Jorge Gomezjurado and Odi Zmora check on bluefin tuna larvae in tanks at the University of Maryland Baltimore County’s Institute of Marine and Environmental Technology. (Courtesy of Yonathan Zohar)


In a windowless laboratory in downtown Baltimore, some tiny, translucent fish larvae are swimming about in glass-walled tanks.

They are infant bluefin tuna. Scientists in this laboratory are trying to grasp what they call the holy grail of aquaculture: raising this powerful fish, so prized by sushi lovers, entirely in captivity. But the effort is fraught with challenges.

When I visited, I couldn’t see the larvae at first. They look incredibly fragile and helpless, just drifting in the tanks’ water currents. But they’re already gobbling up microscopic marine animals, which in turn are living on algae.

“It’s amazing. We cannot stop looking at them! We are here around the clock and we are looking at them, because it is so beautiful,” says Yonathan Zohar, the scientist in charge of this project.

It’s beautiful to Zohar because it’s so rare. Scientists are trying to raise bluefin tuna completely in captivity in only a few places around the world. Laboratories in Japan have led the effort. This experiment, at the University of Maryland Baltimore County’s Institute of Marine and Environmental Technology, is the first successful attempt in North America.

Scientists still have a long way to go to succeed. Most of the larvae have died, but hundreds have now survived for 10 days, “and we are counting every day,” says Zohar. “We want to be at 25 to 30 days. This is the bottleneck. The bottleneck is the first three to four weeks.”

If they make it that far, they’ll be juvenile fish and much more sturdy. Then, they’ll mainly need lots to eat.

Fully grown, the bluefin tuna is a tiger of the ocean: powerful and voracious, its flesh in high demand for sushi all around the world.

Journalist Paul Greenberg wrote about bluefin tuna in his book Four Fish. If you’re an angler, he says, catching one is an experience you don’t forget.

“When they come onboard, it’s like raw energy coming onto the boat. Their tail will [beat] like an outboard motor, just blazing with power and energy,” he says.

The fish can grow to 1,000 pounds. They can swim up to 45 miles per hour and cross entire oceans.

They’re also valuable. Demand for tuna has grown, especially in Japan, where people sometimes pay fantastic prices for the fish.

That demand has led to overfishing, and wild populations of tuna now are declining.

That’s why scientists like Zohar are trying to invent a new way to supply the world’s demand. They’re trying to invent bluefin tuna farming.

“The vision is to have huge tanks, land-based, in a facility like what you see here, having bluefin tuna that are spawning year-round, on demand, producing millions of eggs,” he says.

Those eggs would hatch and grow into a plentiful supply of tuna.

That brings us back to these precious larvae. Before there can be aquaculture, large quantities of these larvae have to survive. Here in the laboratory, the scientists are tinkering with lots of things — the lights above the tanks, the concentration of algae and water currents — to keep the fragile larvae from sinking toward the bottom of the tank.

“They tend to go down,” explains Zohar. “They have a heavy head. They go head down and tail up. If they hit their head on the bottom they are gone. They are not going to survive.”

Enough are surviving, at the moment, that Zohar thinks they’re getting close to overcoming this obstacle, too.

But that still leaves a final hurdle. The scientists will need to figure out how to satisfy the tuna’s amazing appetite without causing even more damage to the environment.

A tuna’s natural diet consists of other fish. Lots of other fish. Right now, there are tuna “ranches” that capture young tuna in the ocean and then fatten them up in big net-pens. According to Greenberg, those ranches feed their tuna about 15 pounds of fish such as sardines or mackerel for each additional pound of tuna that can be sold to consumers. That kind of tuna production is environmentally costly.

Zohar thinks that it will be possible to reduce this ratio or even create tuna feed that doesn’t rely heavily on other fish as an ingredient.

But Greenberg says the basic fact that they eat so much makes him wonder whether tuna farming is really the right way to go. It increases the population of a predator species that demands lots of food itself.

“Why would you domesticate a tiger when you could domesticate a cow,” he asks — or, even better, a chicken, which converts just 2 pounds of vegetarian feed into a pound of meat.

If farmed tuna really can reduce the demand for tuna caught in the wild, it would be worth doing. But it might do more good, he says, to eat a little lower on the marine food chain. We could eat more mussels or sardines. It would let more tuna roam free.


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