A small blenny of the shallow surge zone, holding position on bare rock in moving water.
To about 8 cm. Very elongate, with a short blunt head and a rounded overhanging snout. There is a deep notch in the dorsal fin, a simple tentacle over the front nostril, a multi-tipped tentacle over the eye, and a wrinkled lower lip. Olive above and white on the lower sides, with a row of square to rectangular black blotches along the middle of the side, white spots and flecks, and thin brown bars on the face.
The other small eastern Pacific rock and tide-pool blennies are separated by that deep dorsal notch and the wrinkled lower lip.
It lives on intertidal rocky reef and in tide pools, almost always in the top two metres, and it eats detritus and the microscopic algae growing on rock. It can breathe air for a while and will come out of the water. It lays sticky eggs on the bottom and the larvae drift.
The name needs a note. Barnaclebill blenny is properly the name of a different eastern Pacific fish, which lives in empty barnacle shells and is not recorded from Revillagigedo. This species is normally called the rock blenny or the notchfin blenny, and this site now uses rock blenny.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.