Here's a great article regarding tuna.
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OHSHIMA, JAPAN—With a snap of its jaws, a
meter-long bluefin tuna grabs a fish tossed
into its circular enclosure and darts away in
murky Kushimoto Bay. “They’re excellent
swimmers,” says Yoshifumi Sawada, a fisheries
biologist at Kinki University’s Ohshima
Experiment Station, as he shovels fish into
the water. The note of pride in his voice is
understandable: The bluefins in the pen are
the product of a 30-year effort to rear secondgeneration
captive tuna—something no other
group in the world has accomplished. It’s “a
magnificent achievement,” says Daniel
Pauly, a fisheries biologist at the University
of British Columbia, Vancouver.
The feat could hold vital significance for
one of the ocean’s keystone predators. In
recent decades, the bluefin tuna’s succulent
belly meat has become the favorite of sushi
and sashimi aficionados, driving the price
sky high. Tunas auctioned at Tokyo’s Tsukiji
fish market routinely fetch tens of thousands
of dollars; in 2001, a prize 202-kilogram
specimen sold for an astounding ¥20.2 million,
or roughly $1000 per kilogram.
To satiate rising demand, dozens of tuna
farms have sprung up off Japan’s coasts.
Each year, Japanese fishers capture 300,000
to 400,000 young bluefins from the open
ocean and fatten them in pens before shipping
them off to wholesalers. But removing
juveniles from the wild has only increased
pressure on the heavily fished species, leaving
some populations on the brink of collapse
The bluefin’s eccentricities have contributed
to its downfall. “The bluefin tuna has
habits that are completely wrong for species
survival,” says Gary Sakagawa, a fisheries
biologist at the U.S. National Oceanic and
Atmospheric Administration’s Southwest
Fisheries Science Center in San Diego, California.
For instance, young
tuna congregate in coastal
areas in spring and summer as
they feed on schooling fish,
making them easy prey for
fishers, Sakagawa says.
The researchers at Kindai,
as the university is known
locally, hope their breakthrough
will give wild tuna a
reprieve. “We want to supply
all of the farmed bluefin tuna
harvested in Japan,” says
Sawada. They have a long way
to go. This year, Sawada says
they hope to sell up to 20,000
juveniles to fish farms, a small fraction of
what’s needed. “This technology will take a
while to have a positive impact on the conservation
of tuna,” says Pauly.
Kindai’s tuna program started in 1970,
when “it seemed Japanese were eating up all
the world’s tuna,” says university trustee
Hidemi Kumai, a fisheries biologist who led
the Kindai research for years. Concerned that
the country would be blamed for depleting
wild tuna stocks, Japan’s Fisheries Agency
funded three groups, including one at Kindai,
to try raising bluefin tuna from eggs.
As a private university with campuses
scattered across a rugged peninsula that juts
into the Pacific Ocean southeast of Osaka,
Kindai emphasizes “practical studies”
attuned to the needs of local agricultural and
fishing communities, Kumai says. Kindai
had already succeeded in raising yellowtail,
sea bream, sole, and other fish from eggs.
The university sells fry to farmers and harvests
mature fish for the market, then sinks
the proceeds into research.
The know-how gleaned from farming
other fish, however, didn’t readily transfer to
bluefins. “Tuna have many unique characteristics
that make culturing them difficult,”
says Sawada. For starters, bluefin tuna, one
of the larger oceanic predators, are simply
much bigger than other farmed fish. A halfcentury
ago, before overfishing started to
take its toll, 4-meter-long tuna tipping the
scales at half a ton were common. These
days, mature bluefins can exceed 2 meters in
length and weigh 250 kilograms.
When it comes to captive breeding, more
than size matters. Tuna, unlike most pelagic
f ish, are warm-blooded. And like some
sharks, they must move continuously to
force water over their gills; otherwise, they
suffocate. “They swim all day, all through
their lives,” Sawada says.
Bluefins are built for both
speed and endurance: They
can accelerate as quickly as a
sports car, and they crisscross
the Atlantic several times a
year. For these reasons, tunas
require pens much bigger
than those used for other captive
It took the Kindai group
4 years to learn how to keep
penned tuna alive longer than
a few months. Then it took
another 5 years, until 1979, to
get them to spawn. That was a
world first, Kumai says, but his team couldn’t
keep the spawned fish alive. Then, for more
than a decade, they couldn’t get captive tuna
to spawn at all.
Facing similar difficulties, the two competing
research groups gave up, and Kumai
worried that Kindai’s program would get the
ax. At one point, he confessed to Kindai’spresident that his team had “no results
despite spending a lot of money.” “The president
said to me, ‘You have to take the long
view when considering living creatures,’ ”
Kumai recalls. With such encouragement,
he says, the group resolved to “succeed in
this project at any cost.” (The price of success
is hard to quantify, he says, as the Fisheries
Laboratory, with an annual budget of
about $25 million, doesn’t itemize expenses
by project.) Finally, in 1994 their captive
tunas spawned again.
Through sheer persistence, the team has
gained a trove of information about tuna biology.
Postmortems on dead juveniles revealed
that many fish were snapping their necks by
swimming into the walls of the square enclosures.
Such injuries tapered off after fish
passed their 80th day. In juvenile tuna, the tail
f in, used for propulsion, develops more
quickly than the pectoral and abdominal fins,
which adults use to steer and brake, Kumai
says. “The only thing [juvenile] tuna can do is
dash straight ahead,” he says. To reduce the
number of deadly collisions, the researchers
switched to circular enclosures.
After numerous other tweaks to rearing
techniques, the Kindai team eventually bred
mature fish. Six fish spawned in 1995, and
16 from the class of 1996 survived to adulthood.
Those fish spawned in 2002, and
Kindai is now rearing the third generation.
“We’ve completed the life cycle,” Kumai
says. That, says Sakagawa, “gives us some
idea what may be going on in nature.” The
Kindai group has identified behavioral triggers
for spawning and clarified that the time
of first spawn is more closely related to size
than age. The group acknowledges that they
still have a lot to learn. Kumai figures they
get mature fish from only about 1% of eggs,
compared with 60% for sea bream.
The Kindai group now hopes to develop
an attractive product. They are selectively
breeding tuna for fast growth, disease resistance,
and higher-quality meat, Sawada says.
The group does not plan to genetically engineer
tuna out of concerns about unforeseen
consequences if fish were to escape into the
wild. But they are introducing the use of
molecular markers, small DNA fragments
that identify desirable traits, says Yasuo
Agawa, a molecular biologist who cut his
teeth on Drosophila and recently joined the
Kindai team. Pauly, however, worries that
the feed requirements of scaled-up tuna
farming could harm wild stocks of feed fish,
many of which are a staple for people in
That might be avoided if the Kindai
group’s most ambitious plan succeeds: to
transform their captives into vegetarians.
Sawada says they intend to gradually substitute
plant protein for fish feed, in part to
improve the program’s sustainability. Pauly,
for one, is skeptical. “This is where these
plans veer off into science fiction,” he says.
He notes that despite decades of trying, the
Norwegian salmon industry has not weaned
farmed salmon off a fish diet.
It is unclear what impact the landmark
breeding success might have on wild tuna
stocks. Sakagawa worries that replacing fish
caught for farms with juveniles raised from
eggs might simply expand the market, as
happened when Australian fisheries started
pen-rearing captured Southern Pacif ic
bluefins. He says he appreciates Kindai’s
contributions to understanding tuna reproductive
biology. However, Sakagawa says, “I
don’t think it’s a solution for conservation of
Toward that end, Japan’s Fisheries
Research Agency is working to raise tuna
from eggs for release. To have an impact on
natural populations, a restocking effort
would have to be massive—and “many issues
need to be solved before [we can] start to
release tuna,” says agency official Kazumasa
Ikuta. But as the Kindai team has demonstrated
in their decades-long effort to breed
tuna, patience is a virtue.
Sounds like propoganda to keep the media at bay and allow Japan to literally take every tuna they can out of the water. Rather than growing fish to breed in their pens, they should be concentrating on getting a higher percentage of that 1% of eggs to maturity. Rather than trying to raise 300,00-400,000 fish annually to maturity for spawning and marketing, it seems a whole lot smarter and feesable to capture 5,000 spawning females near spawning, fertilize and grow their eggs, hatch millions of fry, and grow them to a size capable of fending for themselves in the wild. If they could raise huge numbers of tunas to the 20 pounds plus size for live wild release, they may actually be able to help restock the population which they have destroyed. Raising bluefins from eggs to giant size is impractical and stupid when you consider the amount of supply of bluefin needed to accomodate their tastes and the expense to raise each fish. Each fish alone would eat thousands of pounds of food.