The morphology of the miniature gobies Pandaka trimaculata and P. lidwilli on Okinawa Island was described and their habitats were investigated. Postflexion larvae, juveniles and adults of the two species could usually be identified by body depth, in addition to the pigment pattern on the first dorsal fin of adults and juveniles, formerly the only known distinguishing characteristics. Postflexion larvae could also be identified by the arrangement of ventral melanophores on the tail. Postflexion larvae of the two species (6－7 mm in standard length[1]SL), collected by small seine net from the Teima Stream estuary at high tide and the surf zone of a beach near the estuary, from April to November, 1999, had almost full fin ray complements, there being no earlier stage larvae present. The occurrence of the two Pandaka species was investigated at 21 sampling stations along the Teima Stream from February to March and in July, 2006. Fishes at various developmental stages (6－14 mm SL), from postflexion larvae to adults, were collected from stations set in shallow shores, and in small creeks and tide pools within the estuary. Therefore, it is suggested that the larvae arrived at the beach and estuary after spending most of their larval stages at sea, subsequently settling into adult habitats in the estuary where they became pigmented and completed their adult transformation. Pandaka trimaculata occurred in various habitats, being broadly distributed from the middle to upper reaches of the estuary. By contrast, P. lidwilli was restricted to stations in the middle reaches of the estuary, the preferred habitat always consisting of soft muddy substrate close to mangroves.
