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Japan's Kindai Uni. changes sturgeons' sexes to female, could lead to cheaper caviar

A pair of young Siberian sturgeon are seen in this image provided by Kindai University.

OSAKA -- A batch of artificially incubated sturgeon which were fed female hormones have all become females, potentially paving the way for cheaper caviar production, Kindai University announced on Dec. 9.

Caviar made from cured sturgeon eggs are an expensive delicacy. Their price is exacerbated by the protracted time it takes to confirm which fish are male or female. If the Osaka Prefecture-based university's techniques can be put to widespread practical use, it may lead to the price of caviar coming down.

Producers run up high costs from work associated with identifying the sex of a sturgeon. They must wait until the fish are around 3 years old, and then open a section of their stomachs one by one to confirm the color and shape of their reproductive glands. The fish then have to be stitched back up and returned to the water. Raising the fish for the three years before their sex can be identified also causes a significant outlay.

According to Kindai University Aquaculture Research Institute associate professor Toshinao Ineno, four months after their artificial incubation, 150 juvenile Siberian sturgeon were given feed mixed with the hormone estradiol for around six months. After that, they were reared on regular feed, and when 45 of the fish were chosen at random to be inspected, all of them were found to have egg cells.

The next step is to see if the remaining fish produce eggs for caviar once they turn 5 years old.

The institute started researching sturgeon in 1995, and began selling its own brand of "Kindai Caviar" from 2008. It continues to take part in initiatives to improve the quality of caviar and the efficiency of its production.

Next, the institute aims to change all of a batch of sturgeons' sexes to female by using plant-derived phytoestrogen. Ineno said, "We want to have a workable version of this process as early as five years from now."

(Japanese original by Takeshi Nemoto, Osaka Science & Environment News Department)

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