This is a Juvenile of Polydactylus sp. It's a fish of Family Polynemidae . Polynemidae species is rare fish at Scuba Diving. It inhabits the sandy bottom, sand, mud bottom of the bay. Sometimes entering the brackish water. and It's often observed around the beach. But, probably, they are doing "abortive migration" at Japanese sea. Because, Adult is not a lot in Japan. Juvenile of Polydactylus TL:50mm Juvenile of Polydactylus TL:50mm Meristic Characters - D Ⅷ-Ⅰ,13; A Ⅲ, 12; P 1 13 +6; P 2 Ⅰ, 5; (This picture) I could not getting the specimen of this species. In Japan so far, Polynemidae is known only 4 species from 2 genera of Eleutheronema and Polydactylus . I did think that it's Polydactylus sexfilis of these four from”Meristic Characters”, but there was a difference in the number of pectoral fine . Since the measurement of the pectoral fin is such from the image, it might not be accu...