CRITTER: Meet the dangerous Ewa fang blenny

This 4-inch long, skinny fish has a huge smile on its face, and looks totally harmless. It swims in open water above the reef and wiggles back and forth like an earthworm crawls, and it is one of the most dangerous little fish in Hawai‘i. The way it feeds is truly amazing, and it is rarely ever eaten by larger fish.

The fang blenny has a jaw designed like that of a large predator shark, with two huge fangs on its upper jaw. It mimics another fish so it can get close to big fish of which it preys upon. You would think that a big fish would eat a small fish, but this is the other way around.

The fang blenny looks very similar to a cleaner wrasse. The cleaner wrasse is a larger fish friend because the wrasse eats parasites off of the bigger fish keeping it clean and healthy. The larger fish often will open its mouth and let the cleaner wrasse go inside and clean its teeth. The larger fish never eats the small cleaner wrasse because it keeps the bigger fish healthy.

The fang blenny looks and moves just like the cleaner wrasse, so a big fish will come by a cleaning station where the cleaner wrasse hangs out and expects to get cleaned, but just the opposite happens. The fang blenny mimicking the cleaner wrasse will zoom right up to the trusting larger fish and take a bite out of its scales, or even out of the larger fish’s open mouth.

The larger fish will dart away wondering what happened. Once the fang blenny has a chunk of the larger fish in its mouth, it goes back to its hole in the reef, backs in and rests while it finishes its fish dinner with a smile on its face.

You can see the fang blenny in action in my Koloa Landing Kaua‘i movie posted on my YouTube at Underwater2web.

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Terry Lilley is a marine biologist living in Hanalei and co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawai‘i go to www.reefguardianshawaii.org.