Except for triplefins some other fish wear such dress, for example Lipophrys nigriceps blenny. The most distinctive mark to be seen with the naked eye — is the presence of the three dorsal fins every Tripterygion feature. That's, in fact, why all the triplefins have been entitled so.
At this shot one may see a short speckled fin almost on the back of fish's head, then comes an elongated semitransparent one, followed by the third, that last almost to the yellow rudder.