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Researchers successfully crossbreed fish species

They hope to be able to breed endangered species in common fish.

By ASSOCIATED PRESS
Published September 14, 2007

WASHINGTON - Papa salmon plus mama salmon equals ... baby trout?

Japanese researchers put a new spin on surrogate parenting as they engineered one fish species to produce another, in a quest to preserve endangered fish.

Idaho scientists begin the next big step next month, trying to produce a type of salmon highly endangered in that state - the sockeye - this time using more plentiful trout as surrogate parents.

The new method is "one of the best things that has happened in a long time in bringing something new into conservation biology," said University of Idaho zoology professor Joseph Cloud, who is leading the U.S. government-funded sockeye project.

The Tokyo University inventors dubbed their method "surrogate broodstocking." They injected newly hatched but sterile Asian masu salmon with sperm-growing cells from rainbow trout - and watched the salmon grow up to produce trout.

The striking success, published in today's edition of the journal Science, is capturing the attention of conservation specialists, who say new techniques are badly needed. Captive breeding of endangered fish is difficult, and attempts to freeze fish eggs for posterity so far have failed.

"They showed nicely that ... they produced the fish they were shooting for," said John Waldman, a fisheries biologist at Queens College in New York.

"Future work should look to expand this approach to other fishes in need of conservation, in particular, the sturgeons and paddlefish," he added. "We have a lot of species of fish around the world that are really in danger of becoming extinct."

The Japanese researchers' ultimate goal: Boost the rapidly dwindling population of bluefin tuna, a species prized in a country famed for its tuna appetite.

"We need to rescue them somehow," said Goro Yoshizaki, a Tokyo University marine scientist who is leading the research.

The experiments, funded by a Japanese research institute, used still fairly plentiful species to develop the technique. Now comes Idaho's attempt to prove whether the method is really useful in trying to produce the endangered sockeye salmon.

In January, Yoshizaki helped University of Idaho scientists collect and freeze immature sperm tissue from young sockeye salmon being raised at a state-run hatchery. Next month, he will be back to help Cloud thaw the tissue and implant it into sterile rainbow trout.

In Japan, Yoshizaki is focused on bluefin tuna, noting that standard "marine ranching" techniques are difficult for tuna that can reach man-size.

He has begun experiments into how to produce baby tuna from mackerel, which are nearly a thousand times smaller than adult tuna. If it works, "we can save space, cost and labor," he predicted in an e-mail interview.

[Last modified September 13, 2007, 23:44:34]