Photo/Illutration Giant salamanders kept at a swimming pool of a closed elementary school in Nabari, Mie Prefecture, are seen on Nov. 30. (Satoru Ogawa)

NABARI, Mie Prefecture--A swimming pool at a shuttered elementary school here may be the last outpost for a species of giant salamander.

When the pool water was drained recently to replace it with freshwater, about 170 of more than 1-meter-long creatures could be seen wriggling around.

Typically lurking in riverbeds in valleys in western Japan, including mountainous parts of this city, giant salamanders are recognized by the central government as special natural treasures.

However, these ones are hybrids of indigenous species and counterparts imported from China, according to DNA analysis.

The latter were brought to Japan as pets or to be consumed as meat, but they found their way into the wild after being abandoned or for other reasons. They eventually mated with species endemic to Japan and spawned offspring.

Japanese giant salamanders are listed on the Environment Ministry's Red List for endangered species. In addition to their habitat being threatened over the years due to river works, the invasion of counterparts from China into their habitat has compounded their problems.

The Nabari municipal government thus decided to embark on a program to "segregate" hybrids to protect the native species. Those discovered in the city have their DNA examined and are placed in the pool if found to be a crossbreed.

While the nonnative species are not welcome in Japanese rivers, they also need to be protected because they are rare animals.

Crossbred varieties have also been found in Kyoto and Okayama.

A study by Kyoto University researchers showed that 90 percent of the giant salamanders inhabiting the Kamogawa river in Kyoto and its tributaries are the result of crossbreeding.

Kanto Nishikawa, associate professor of environmental studies at Kyoto University, called for a long-term plan to deal with the hybrids.

"Giant salamanders generally live more than 50 years," he said. "As there is only so much local officials can do to manage them, Japan needs to consider ways of handling the animals from a long-term perspective."

Nabari city officials encourage people to visit the pool to look at the rare species and also take them to schools to educate children.

Zenkichi Shimizu, head of the secretariat of the association of Japanese giant salamanders, who is involved in the survey of the endemic species, stressed the urgency of increasing awareness of the predicament facing Japanese giant salamanders.

“Giant salamanders bear the brunt of human activities,” he said. “We should alert local residents as to what is happening to nearby rivers.”