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Home › Sea Life Facts › Marine Species › Vertebrates › Moray Eel

Interesting Facts about Moray Eels

[Phylum: Chordata] [Class: Actinopterygii] [Order: Anguilliformes] [Family: Muraenidae]

There are more than two hundred recognised species of morays in the family Muraenidae (meaning eels). Most are found in marine ecosystems, with the exclusion of a few freshwater morays (e.g. Gymnothorax polyuranodon).

Yet, one of the lesser-known facts about moray eels is the way they capture their favourite prey (slow-moving reef fish) using a second set of "alien-like" jaws (called pharyngeal jaws).

Moray Eels Habitat and Geographical Range

Most of the tropical and subtropical seas around the world contain ideal habitats for morays, especially:

• Eastern and Western Atlantic Ocean
• The Red Sea
• Indo-Pacific region (e.g. the Great Barrier Reef, Indonesia, Thailand, and the Philippines)
• Eastern Pacific (e.g. Central and South America)
• The Gulf of Mexico (including parts of the Caribbean Sea)

The vast majority of moray eel types tend to live solitary lives and can be quite territorial. As a result, they like to hide in coral reef formations, among rocky crevices, and underneath continental slopes, shelves, and ledges.

Moray Eel Characteristics and Behaviour

Despite their snake-like appearance, moray eels are in fact fish. Even so, very few species have "typical" fish fins (e.g. pectoral and pelvic fins).

As a consequence of that, these physical characteristics accentuate their laterally compressed, serpentine (eel-like) body shape.

Instead, almost all moray eel species have a long dorsal fin that runs continuously from the head to the caudal and anal fin.

Pro Tip: Another page contains a breakdown of moray eel anatomy with further details about the function of their key body parts.

Moray Eels Size and Weight

So, how big are moray eels? In actual fact, the size and weight varies depending on the species, with an average length around one (1) metre (3 feet).

By body mass, the world's biggest moray eel is the giant moray (Gymnothorax javanicus). But, the slender giant moray (Strophidon sathete) is the longest, measuring up to four (4) metres long and weighing up to twenty seven (27) kilograms (60 pounds).

The smallest is Snyder's moray (Anarchias leucurus), which only measures about eleven (11) centimetres long (4 inches).

But wait - there's more:

Even though it's best not to touch a moray eel, the skin is smooth, scaleless, and covered in a thick, slimy mucus that often contains toxins - known as ciguatoxins.

The body colouration varies between the different types of moray eel. For example, some have solid colours, and others have stripes or spots that create extra camouflage among rocky outcrops.

On the whole, the moray eel genus has small 'inefficient' eyes, a wide jaw, and a snout with tubular nostrils. It's a fish that relies on an acute sense of smell to identify prey.

Interesting Fact: Besides the sharp, backward-pointing teeth, the secondary jaw is a unique feature among the moray eel classification (scientific name Muraenidae). After the initial bite, they use the pharyngeal jaw to grab prey and pull it into the throat - without needing to generate suction.

What Do Moray Eels Eat?

Morays are typical bottom-dwellers that tend to be rather inactive during the daylight hours. But, they become a lot more active at night time when they start to hunt.

They are predatory carnivores that have large intimidating teeth used for tearing and grasping their prey - which may include carrion (the decaying flesh of dead sea life).

Moray eels feed on small fishes, octopuses, squid, cuttlefish, and marine worms.

Even so, snowflake and zebra morays possess blunt crushing molars that are best suited for targeting marine crustaceans, such as crabs, shrimps, lobsters, and even red lionfish.

How Do Morays Eat Their Prey?

Most fish use a process known as "negative pressure suction feeding" to swallow their food. But, moray eels tend to struggle with this feeding action because their head is too narrow.

Instead, they launch the second jawline of pharyngeal teeth from the back of the throat into their prey. Doing so immobilises the victim and makes it easier to transport the food inwards for digestion. No other animals use this behavioural trait of capture and restraint.

Morays are Cooperative Hunters

Research suggests that roving coral groupers (Plectropomus pessuliferus) will shake their heads to "recruit" giant morays to help them hunt.

Why?

The theory is that the practice of "cooperative hunting" allows some morays to flush out victims from crevices and niches that are inaccessible to groupers.

Interesting Fact: Morays frequently open and close their mouths. Even though it may look threatening, it's part of their respiratory system as they pump water over the gills to breathe.

Moray Eel Species List

How Do Moray Eels Reproduce?

It's fair to say that moray eel reproduction has rarely been observed. Even though accurate information is limited, scientists understand that they spawn infrequently - and deep in the ocean during the darkness.

Because most moray species are dioecious, sexual reproduction involves males and females. Through a process of external fertilisation, they release their eggs and sperm into the water column.

Here's the thing:

In the wild, spawning occurs in open water away from their normal habitat. Female moray eels can release several thousand eggs in one single event.

During the larval stage, fertilised eggs will hatch into transparent, slim headed, ribbon-like larvae. The larvae drift with the ocean currents for up to twelve (12) months, feeding on planktonic organisms and other types of detritus, until they develop into juvenile eels and settle into a suitable reef or benthic habitat.

Threats and Predators of Moray Eels

The IUCN Red List of Threatened Species assessed most of the moray eel species (Muraenidae) in 2019 and they specified them as being of "Least Concern" (LC). Having an average lifespan of more than ten (10) years is one of the reasons why.

Even so, these efficient mid-level predators are not totally immune to predation. For example, some of the ocean wildlife that preys on moray eels include:

• Barracudas
• Groupers
• Reef sharks
• Sea snakes
• Other moray species (yes they are cannibalistic fish)

Nonetheless, some contributing factors for diminishing populations in a few vulnerable regions include coral reef destruction and degradation, bycatch, marine garbage pollution, and warming seas.

Interaction with Humans

Generally, morays are not aggressive to humans (e.g. scuba divers and snorkelers) unless they feel threatened. But, large moray eels can inflict a serious bite if you provoke them or disturb them by accident.

Even though scuba diving with fish can be an exciting experience, hand-feeding marine species has its associated risks.

Put another way:

In the past, morays have bitten aquarium keepers during feeding and recreational scuba divers - mostly due to the moray's poor vision and their robust feeding response.

Moray Eels and the Aquarium Trade

Anyone who enjoys keeping big fish as pets will know that some of the moray species are popular with aquarium hobbyists. Morays kept in captivity tend to be hardy and disease resistant.

As a consequence of that, some of the popular morays kept in large aquariums include the goldentail moray, the snowflake moray, and the zebra moray.

Pro Tip: Even though some species are eaten by humans in some countries, they can cause ciguatera poisoning due to toxin accumulation.

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