I went to Okinawa located in the Japanese most south last month and visited at several rivers.
Okinawa area is subtropical zone.
I took a lot of pictures and video clips there.
Those were there crowdedly.
They come from the south by a Kuroshio Current.
The number of living in Okinawa may be increased by global warming.
They're Stiphodon.sp which started to be always checked in Okinawa from several years before.
Their scientific name is uncertain or unclear.
(17 May 2012)I add a postscript to the following.
16 May 2012 - 11:42am
Ken Maeda, a researcher in OIST’s Marine Genomics Unit,
has identified a new freshwater goby species on the islands of Okinawa and Iriomote.
The species, Stiphodon alcedo, is described in the latest issue of the journal Cybium.
"A new species of amphidromous goby, Stiphodon alcedo, from the Ryukyu Archipelago"
http://www.oist.jp/pressrelease/oist-re ... yu-streams
Two males are quarreling.
This is the male by which the married color shows full.
The same male by which the married color shows half.
Lower right one is big female.
Another male with basic color.
These aren't Stiphodon genus, but it's introduced here.
2 males are fighting.
Their female has a clear body.
The male changes the body color to appeal to the female.
But the female is not Sicyopus.
In fact, the male gets a wrong partner.
It is a female of Lentipes that he appeals.
Their female has a clear body too.
Therefore it is difficult to find them.
One male is surrounded by many females.
I am not used to English. Therefore,It is likely to sometimes misunderstand it.