This is official site of Black Water Dive® produced by photographer Ryo Minemizu. Black Water Dive® is a kind of night diving. We are setting up underwater lights of high-color rendering on the sea bottom of night that while considering tides, times, places. The creature which appears is mainly juveniles and larvae. All is fascinating, and it's not to be seen at daytime or regular night diving. It will be your first experience. This site will introduce the state of the event and the creatures seen and also future of BWD schedules. *"BWD"stands for Black Water Dive®.*Black Water Dive® is a registered trademark of Ryo Minemizu.
ラベル ツバメコノシロ属の幼魚 の投稿を表示しています。 すべての投稿を表示
ラベル ツバメコノシロ属の幼魚 の投稿を表示しています。 すべての投稿を表示


Juvenile of Polydactylus sp.(Family:Polynemidae)

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
Juvenile of Polydactylus  TL:50mm
Juvenile of Polydactylus
Juvenile of Polydactylus   TL:50mm
Meristic Characters - D Ⅷ-Ⅰ,13; A Ⅲ, 12; P1 13+6; P2 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 accurate. It is very similar to the Polydactylus sexfilis, but perhaps It's a possibility other than known distribution and species. In recent years, the Polynemidae are known 8 genera 43 species in the world. Of these, have been known 21 species at the Polydactylus.
Polydactylus sexfilis (Valenciennes, 1831) - (Japanese name: Nanyo-agonashi)
D Ⅷ-Ⅰ,12-13; A Ⅲ, 11-12; P1 15-16+6; P2 Ⅰ, 5;
Related species; (in Japan)
Eleutheronema tetradactylum (Shaw, 1804)  - (Japanese name: Minami-konoshiro)
D Ⅷ-Ⅰ,13-15; A Ⅲ, 14-16; P1 17-19+4; P2 Ⅰ, 5;
Polydactylus plebeius (Broussonet, 1782) - (Japanese name: Tubame-konoshiro)
D Ⅷ-Ⅰ,12-13; A Ⅲ, 11-12; P1 15-18+5; P2 Ⅰ, 5;
Polydactylus sextarius (Bloch & Schneider, 1801) - (Japanese name: Kataguro-konoshiro)
D Ⅷ-Ⅰ,12-13; A Ⅲ, 11-13; P1 13-15+6; P2 Ⅰ, 5;

Pectoral filaments is very long and It reaches the anal fins.
Juvenile of Polydactylus
Pectoral filaments 6
Juvenile of Polydactylus
Pectoral soft rays does not branch

Motomura, H. 2004. Threadfins of the world. An annotated and illustrated catalogue of polynemid species known to date. Family Polynemidae. FAO Species Catalogue for Fishery Purposes. No. 3. Rome, FAO. 117 p., 151 figs, 6 pls.

Nakabo, T. (ed.), 2013. Fishes of Japan with pictorial keys to the species, third edition. Tokai University Press, Kanagawa, Pp, 2428. (in Japanese).
Family Polynemidae - Threadfins
Polydactylus sexfilis,  Sixfinger threadfin  : fisheries, aquaculture, gamefish, aquarium