Rotlachs
Prior to 1940, the main species of fish in Lake Tazawa included the indigenous "kunimasu" ("Oncorhynchus nerka kawamurae"), Sockeye salmon, Japanese dace (genus "Tribolodon"), Japanese trout, char, carp, catfish and eel. However, after the acidic content of the lake changed in 1940, the only surviving fish is the dace, while most of the other species, including the "kunimasu", are thought to have gone extinct.