It is considered that, since these foreign species have high productive ability, they are negatively affecting the eco-system in that area and, in fact, some of the native species such as killifish and field gudgeon have disappeared due to the changes in predation in the environment.
これらは繁殖力が強く、生態系に悪影響を与えているとされ、事実、メダカやタモロコなど、いくつかの在来種が補食関係の変化により姿を消している。