Researchers in Japan use soybean compound to make catfish 100% female

The Mainichi -- May 27
SHINGU, Wakayama -- A team of researchers in Japan has succeeded in making catfish all female with a compound found in soybeans -- a development that promises to increase the production efficiency of this and other species whose females are more valuable than males in the food market.

The team, from Kindai University's Aquaculture Research Institute and based at the institute's Shingu Station in Shingu, Wakayama Prefecture, used isoflavone -- a compound found in soybeans similar in effect to female hormones -- to create the all-female groups of catfish. The feat is a Japan first, according to the university.

As female catfish grow faster than males, "by making them all female, production efficiency will rise," commented team leader and aquaculture science associate professor Toshinao Ineno. "This can be applied to other farm-raised fish whose females are more valuable."

According to Ineno, in catfish cultivation, which has been attracting attention as an alternative to increasingly scant eel, females grow to shipping weight -- at least 600 grams -- in six to 10 months after hatching. Males, which grow more slowly, are often discarded. Though it has been known that administering female hormone turns male catfish into females, this method is banned for fish for human consumption. So Ineno came up with the idea of using soybean isoflavone, which is sold commercially as a dietary supplement.