We visited a small city, Ono. Here there is a stickleback conservation center called "Itoyo-no-Sato", which means "the hometown of the threespine stickleback" in Japanese. Ono has a lot of spring water-fed ponds. However, the number of stickleback habitats in this area has been decreasing, so the city constructed a reserve pond for conserving the endangered population and a facility by the pond for the education of local citizens. You can observe sticklebacks not only from the water surface but also under the water through the window of the facility.
The city of Ono also has a lot of nice places to visit, such as the "Ono Castle" and a sake brewery, which makes a sake brand named "Itoyo (threespine stickleback in Japanese)"!
Ono city travel information (English)
Please check the nice movie clip produced by Andrew Hendry: https://www.youtube.com/watch?v=EVSJ_U19xLE