Rhinogobius brunneus collected from Hachijo-jima island: first specimen-based records of the genus Rhinogobius (Teleostei: Gobiidae) in the Izu Islands, Tokyo Metropolis, Japan

Abstract

From August 2019 to August 2025, 56 specimens (19.3–61.0 mm in standard length) of the amphidromous gobiid fish Rhinogobius brunneus (Temminck and Schlegel, 1845) were collected from Hachijo-jima island, the Izu Islands, Tokyo Metropolis, Japan. No gobies of the genus Rhinogobius have previously been recorded in the Izu Islands except for a photographic record of R. brunneus from Hachijo-jima island. Therefore, the present specimens represent the first verifiable records of Rhinogobius in the region. The occurrence of this species, which adapted to small rivers, reflects the freshwater environment of the Izu Islands, characterized by numerous steep, small rivers.