FaunaHub

Moray Eel (family Muraenidae)

FishReef predatorEel

Giant moray (Gymnothorax javanicus) emerging from a reef crevice in the Red Sea.

Giant moray (Gymnothorax javanicus), Red Sea.

Image: Diego Delso, CC BY-SA 4.0, via Wikimedia Commons.

Overview

Moray eels (family Muraenidae) are elongated, snake-like predatory fish of reefs and rocky shores, with hundreds of species across warm and temperate seas. They are usually seen with the head poking from a crevice and the mouth opening and closing — which looks menacing but is mainly how they pump water over their gills to breathe. The animal shown here is the giant moray (Gymnothorax javanicus), one of the largest species.

Morays have a remarkable feeding adaptation: a second set of jaws in the throat that can move forward to grab prey and pull it back to be swallowed.

Conservation note: most moray eels are widespread and not of high concern, though some are affected by reef degradation and fishing. Verify a particular species' status at iucnredlist.org.

Habitat & Range

Moray eels live mainly on coral and rocky reefs in tropical and temperate seas, sheltering by day in holes, crevices, and ledges. Different species occupy different depths and habitats, from shallow lagoons to deeper reef slopes; a few live in brackish or fresh water.

Diet

Morays are carnivores that hunt mostly at night, preying on fish, crustaceans, and cephalopods such as octopuses. They rely heavily on a keen sense of smell to find prey in the dark and in tight spaces. Their hidden second jaws (pharyngeal jaws) help them grip and swallow prey in confined crevices where they cannot create strong suction.

Behavior

Morays are generally solitary and territorial, returning to favoured shelters. The constant mouth movement that exposes their teeth is mostly respiration, not threat. Some morays are known to hunt cooperatively with groupers, which flush prey from cover that the eel can reach inside the reef. They are most active after dark.

Human Interaction & Conservation

Moray eels are a favourite sight for reef divers. They are not aggressive toward people, but they will bite defensively if cornered or if hands are put into crevices, and large species deserve respectful distance. Like some other reef fish, large morays can occasionally carry the natural toxin ciguatera, a food-safety matter to check locally. For current status, consult authoritative sources.

More photos of the moray eel

Giant moray eel showing its open mouth and sharp teeth.

Giant moray (Gymnothorax javanicus).

Image: Diego Delso, CC BY-SA 4.0, via Wikimedia Commons.

Frequently Asked Questions — Moray Eel

Why do moray eels open and close their mouths?
It looks threatening, but the constant mouth movement is mainly how morays breathe — pumping water over their gills. Because they often sit in tight crevices, this rhythmic gaping is simply respiration rather than a sign of aggression.
Do moray eels really have two sets of jaws?
Yes. In addition to their outer jaws, morays have a second set of jaws in the throat (pharyngeal jaws) that can shoot forward to grab prey and drag it back to be swallowed. This is an unusual adaptation that helps them feed in confined reef crevices.
Are moray eels dangerous?
Morays are not aggressive toward people and generally keep to their shelters. They can bite defensively if cornered or if a hand is pushed into a crevice, so divers are advised not to reach into holes or feed them. Treated with normal respect, they pose little risk.
What do moray eels eat?
Morays are carnivores that hunt mainly at night for fish, crustaceans, and cephalopods such as octopuses, using a strong sense of smell. Some hunt cooperatively with groupers, which drive prey out of cover.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.