Blackiston's Fish-Owl is one of the largest owl in the world, which wing-span reaches to 190cm The total population of them is only about 140 in Japan. All of them lives in Hokkaido and about half of them live in Shiretoko peninsula.

　Blackiston's Fish-Owl live in fish rich pristine rivers, as their main diet is fish. A pair of Fish-Owl need about 5000 fishes/year to rise up one chick. Only one family can live in each river, but the number of pristine river is limited. Their average reproduction rate is 0.5 chicks/year. In case of the pair of Fish-Owl observatory, it is about 1 chick/year, due to the effect of appropriate feeding. As a Fish-Owl lives about 30 years, these reproduction rates are not low numbers. But good habitats are already saturated and there is no place left, where young birds set-up new territories. Reconstruction of river environment is an very important key to recover the population