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Moray Eel Newsletter

That's a Moray

The underwater world has many beautiful sights and, diving along a reef, you can spot innumerable fascinating forms of life. There are some reef creatures that simply make divers stop in their tracks, snap out of their general reverie and focus on them. None does this better than the moray eel.

Unlike any other creature on the reef, it is usually concealed in a crevice with little more than its large head protruding, flexing its jaw and seeming to stare out at you with an expression of alarm. What a magnificent creature!

Moray Eel Fact Sheet

Family name: Muraenidae
Order name: Anguilliformes
Common name: Moray eels
Scientific name: Muraena

Distinguishing Features

Morays come in a variety of shapes and sizes, from 25 cm ribbon eels to a full 4m of giant moray. Speckles, stripes, freckles and tattoos, are all terms used to describe their patterns and they appear in colours including black, white, blue, green, brown and yellow.

Despite their differences, there are many common features among the different species. There is a dorsal fin which runs the length of the body. They don't have pectoral and pelvic fins, lending them a snake-like appearance. Teeth for tearing, not chewing line their wide mouths. They have a secondary set of teeth called 'pharyngeal jaws' that are thrust forward to grab prey and drag it down into their digestive system. If this reminds you of the film 'Alien' then it is with good reason as this feature of moray eels was the inspiration for that feature of the alien.

There are over 100 species of moray, including the giant moray eel (Gymnothorax javanicus), the Ribbon eel (Rhinomuraena quaesita), the snowflake moray (Echidna nebulosa), the zebra moray (Gymnomuraena zebra), the Fimbriated moray (Gymnothorax fimbriatus), the honeycomb (Muraena melanotis) and the white-eyed moray (Siderea thyrsoidea).

Behaviour

An unusually excessive amount of mucous covering their skin allows them to swim quickly all over the reef without hurting themselves. The mucous also strengthens the burrows of those eels that live in sand. The mucous does not ward off parasites however, so cleaner shrimps and wrasses can often be seen busily grooming the moray.

Some of their reputation as scary creatures comes from the fact that they continuously open and close their jaws showing their sharp teeth. Rather than a display of aggression, this is done to waft water over their small gills to facilitate respiration. Nothing more.

Feeding Habits

Morays hunt at night using their sense of smell as their main tool. Unsurprisingly dead and rotting flesh is of particular interest to morays. As carnivores their diet includes other fish, crustaceans, cephalopods and molluscs. When preying they often lurk in holes in the reef, launching themselves forward when the prey is close enough. Their lighting fast attack and powerful bite are impressive.

No consideration of the attacking potential of a moray would be complete without watching this amazing video.

Reproduction

Another fascinating feature of the moray eel is gender-identity. Studies have shown hermaphroditism. This is sometimes synchronous (functional testes and ovaries at the same time) and can reproduce with either sex. Others are sequential meaning they begin life male and then become female.

Coitus involves 2 or 3 morays wrapping their long slender, smooth bodies together and simultaneously releasing sperm and eggs. They do not hang around to discuss their feelings afterwards or make plans for family life. Intercourse marks the beginning and end of the morays' relationship.

Life Cycle

Hatched eggs float in the open ocean for about 8 months as leptocephalus larvae, after which they swim down as elvers to begin life on the reef. The life expectancy of a moray depends on species, with some being 6 years and some as much as 36 years.

Predation

Moray eels eat moray eels. So too do sharks, barracuda, large groupers and homosapiens. They in fact have relatively few predators and they are all big and cannot fit into the safety of reef fissures the way moray eels can.

Distribution and Habitat

Tropical and temperate seas are home to morays who are found in shallow water in habitats like reefs, rocks and estuaries.

Ecological Considerations

Habitat destruction is probably the moray eel's biggest concern. As reefs die and waters are polluted, they have fewer places to live. Although they are fished and eaten by humans in small quantities, their toxicity is enough to prevent them becoming favourites on the menu. They harbour ciguatoxin, the main toxin of the deadly ciguatera which kills humans, apparently including King Henry I of England.