BEIJING, Sept. 14 (Xinhuanet) -- Searching for a method to preserve endangered fish, Japanese scientists have engineered one fish species to produce another.

The Tokyo University inventors named their procedure "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.

Their success story, published in Friday's edition of the journal Science, is captivating conservation specialists, who say new techniques are sorely 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."

Idaho state scientists begin the next big step next month, attempting to produce a sockeye salmon, which is highly endangered in that state. They will use 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 Japanese researchers' ultimate goal is to 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.

(Agencies)