The banded killifish was assigned a status of special concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) due to biogeographical isolation and limitation of potential for range expansion. In the United States, states Ohio and Illinois list the western subspecies as endangered and threatened, respectively, due to range expansion of the eastern subspecies which has been documented to hybridize wherever the ranges of the subspecies overlap. As such, Ohio also classifies "F. d. diaphanus" as an injurious aquatic invasive species. Intergrades occur in the Saint Lawrence and Lake Erie drainages where the ranges of the two subspecies naturally come in contact.