This is a fairly common fish in the Bahamas and Caribbean, but it is rarely captured for the trade. First it's common name is an arrow blenny and that first photo is of one "cocked" to strike at a piece of food. Second they are tiny, the books say it gets an inch long but I have never collected one an inch long, most are around 1/2 to 3/4 of an inch. I have kept them a few times and they are very cryptic, which maybe another reason they are not in the hobby, they are very hard to see, they fit through most collecting nets and they are not usually in the same locations that most of the tropicals that we target for collection live. They tend to like to drift off the bottom in hidden places like overhangs and caves and rarely sit in a hole, making them hard to even locate unless you are looking for them specifically.
EDIT: I didn't see Luiz's post, if you haven't found too many it is because you are not looking in the correct places, they are usually not near the bottom but up in the water column, and they tend to like the shadows of overhangs and crevices. They rarely sit in a hole and unlike most other blennies they are not bottom dwellers. When I had them in a tank they never went into a hole until the lights went out, if they were frightened instead of a hole they went up to an overhang in the tank and swam around under the upper parts of the rockwork.
. Sweet fish.
