Eighteen specimens of the pipefish Microphis retzii were collected from several rivers on Iriomote and Ishigaki Islands (Yaeyama Islands, Ryukyu Islands, Japan) from 1990 to 2019. The records from Iriomote Island, including variously sized specimens plus brooding males over multiple years, suggest established settlement of the species. The records from Ishigaki Island, being the first specimen-based records of the species from that locality, are suggestive of a new settlement. Accordingly, M. retzii should be treated as a Japanese resident species, rather than one subject to abortive migration, making them eligible for evaluation of red lists in Japan.
