The native biodiversity of Japan is currently being threatened by alien fishes, such as the bluegill, leading to the strict prohibitions of all activities that are capable of introducing the species into the wild. Now, a team of researchers at Tokyo University of Marine Science and Technology released a study outlining a recent instance of the illegal release of the bluegill fish approximately 10 years after the prohibitions were introduced.

The study began back in June 2015 when undergraduate student and co-author of the study Akinori Teramura posted two photographs of the invasive bluegill fish, along with two young goldfish that also do not belong in local fauna, on Twitter, claiming he found them in an outdoor public pool in Yokohama, Japan. After witnessing this post, Yusuke Miyazaki, lead author of the current study, decided to release a report on the information.

Public pools are typically closed during the colder seasons and it is during this period that native aquatic insect species make their way into them. However, in this case, the pool was isolated from natural waters since its creation, leading the team to believe that the alien fishes were likely released from an aquarium or from a local shop, an activity that is also illegal.

"Our report demonstrates an example of web data mining in the discipline of Citizen Science," the authors said. "Web data mining has been rapidly developing over recent years, and its potential continues to expand."

"Community awareness of this issue needs to be improved, and widespread reporting of cases such as this one will help," they concluded.

The findings were published in the Feb. 26 issue of ZooKeys.