Abstract
Two new freshwater species of the gobiid fish genus Rhinogobius, R. yaima and R. yonezawai, are described based on specimens from swift streams in the Ryukyu Islands, Japan. Rhinogobius yaima (16 specimens, 30.2–66.2 mm SL) is distinguished from all congeneric species by the following combination of features: 40–43 longitudinal scales; 10+16=26 vertebrae; head depressed, body and caudal peduncle elongate; first dorsal fin low in males, not extending posteriorly to second dorsal fin; fifth pelvic-fin segmented ray usually divided into five branches at its first (most proximal) segmenting point; pectoral-fin base and prepelvic area naked; belly with small cycloid scales except for a narrow area around ventral midline; a distinct orange oval spot on pectoral-fin base; two orange stripes on temporal region, reaching posteriorly to below origin of second dorsal fin; four vertical rows of orange dots on caudal fin in males; a pair of black blotches at caudal-fin base in females when alive or freshly collected. Rhinogobius yonezawai (17 specimens, 45.8–75.2 mm SL) differs from all congeners by the following combination of features: 35–39 longitudinal scales; 10+16=26 vertebrae; first dorsal fin in males high and falcate, non-filamentous, extending posteriorly to second dorsal-fin; fifth pelvic-fin segmented ray divided into four branches; pectoral-fin base and prepelvic area naked; belly with small cycloid scales except for a narrow area around ventral midline or around anterior half of ventral midline; a distinct black oval spot on pectoral-fin base; two orange stripes on temporal region, reaching posteriorly to below first dorsal fin; six to eight vertical red or orange lines on caudal fin in males; a black bifurcated blotch posteriorly at caudal-fin base in females when alive or freshly collected.
