Ryan Photographic - Muraenidae - Moray eels

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Family Muraenidae

Fishbase lists 200 species of moray in 15 genera. They are widely distributed, being found in all oceans outside of the polar and sub-polar regions. One species lives in freshwater and many more can be encountered in brackish water. Highest diversity is found in the tropics. They range in size from the diminutive (11.5 cm) Snyder's moray (Anarchias leucurus) to the giant moray (Gymnothorax javanicus) which can reach 3m and 30 kg (I doubt this figure - these morays are so thick that a 3m specimen has to weigh more than 30 kg).

Morays have often been depicted in the popular literature as vicious and dangerous. Part of this reputation stems from the fact that a moray has to open and close its mouth to force water over the gills - this is misinterpreted by the non-biologist as threatening behavior. However they are big, powerful fish with lots of teeth and people do get bitten by them. A friend of mine was bitten in the finger while we were diving in the Sea of Cortez near Loreto. The eel must have mistaken his ungloved hand as a potential meal as it rushed out, bit and withdrew. Dave's finger bled profusely and he had to abort the dive - it probably should have had stitches but he went on the next dive anyway.

Morays have a set of pharyngeal teeth. Biologists have known about these ever since the advent of modern taxonomy. They were considered vestigial, that is present but not of much use. That was until a graduate student in California filmed slow motion footage of morays feeding. She observed these pharyngeal teeth being extruded into the jaw where they held food. I have seen (and photographed) a moray capture an angelfish which was far too big for the moray to ingest. At the time I thought it was misguided. Later, I thought that the pharyngeal teeth were probably tearing chunks out of the prey and allowing it to feed on smaller pieces. But the discoverer of this mechanism reports in a letter to Nature that the jaws help manipulate prey, which, together with extreme jaw elasticity, allow it to swallow large prey. Unfortunately the eel in the photograph retreated into the reef and I was unable to see the prey swallowed. Feeding eels can be a dangerous activity - here is video footage of a diver having his thumb bitten off by a large moray (ignore the banal references to "shark infested" water and please come back to my site).

It has recently been discovered that at least tw fish species, humphead wrasse and coral grouper, actively recruit a moray to help them in hunting.

While all morays are carnivores they don't all feed on fish. Some such as the snowflake moray and the zebra moray eat hard shelled crustaceans and possess crushing, rather than holding teeth.

Large eels may be ciguatoxic - that is they concentrate toxins from the fish they eat. These prey species pick up the toxins from a dinoflagellate which adheres to the algae and coral on which they feed. The toxin is unaffected by cooking. It is believed, but not yet scientifically demonstrated, that some morays may produce venom.