Photo/Illutration The Dotonborigawa river in Osaka’s Minami district (Asahi Shimbun file photo)

OSAKA--Endangered Japanese eels are thriving in a seemingly unlikely spot, the Dotonborigawa river that runs through the city’s busy Minami entertainment district.

Eels were caught there for the first time as part of academic studies during a November survey led by Osaka Prefecture’s Research Institute of Environment, Agriculture and Fisheries.

Yoshihiko Yamamoto, a senior researcher at the institute’s biodiversity center, said the finding shows that an ecosystem has been established that allows Japanese eels, which prey on earthworms, crayfish and other creatures, to live in the river.

“Many people do not even know that fish swim in the Dotonborigawa,” he said. “The discovery offers an opportunity for people to understand that a variety of living organisms are linked with each other in nearby areas.”

The Japanese eel is listed in the Endangered Class IB category on the Environment Ministry’s red list, meaning it is at high risk of becoming extinct in the wild in the near future.

The species also falls into the Endangered Class II division in Osaka Prefecture’s red list.

Japanese eels have been found in other waterways in Osaka Prefecture, according to the research institute.

They had long been thought to inhabit the Dotonborigawa river as well, but no firm evidence existed.

In November, researchers from the institute and elsewhere set up longline and other traps in the river, capturing 11 eels measuring between 30 and 60 centimeters long. A 60-cm eel is “slightly larger than those grilled,” the institute said.

Researchers concluded that they are Japanese eels based on morphological characteristics and other features.

Some of the eels that were caught are on display through April 7 at a special exhibition themed on “endangered species that exist in nearby areas” at the institute’s biodiversity center in Neyagawa, Osaka Prefecture.

A Japanese eel caught in the Dotonborigawa river (Provided by Osaka Prefecture’s Research Institute of Environment, Agriculture and Fisheries)