Taxonomy & Related Groups comparison

Eel vs Moray Eel: Key Differences Explained

The short answer

Every moray is an eel, but most eels are not morays. True eels form the order Anguilliformes, several hundred species sharing a ribbon-shaped body and a transparent leaf-like larva called a leptocephalus. Morays are one family inside that order, Muraenidae, recognisable by the absence of pectoral fins, a small round gill pore instead of a slit, thick scaleless skin heavy with mucus, and a second set of jaws in the throat that helps draw prey backwards.

The main difference

Eel names the order Anguilliformes; morays are one family within it, set apart by round gill pores, absent pectoral fins and pharyngeal jaws in the throat.

Moray is the eel most people picture, so it quietly stands in for the whole order, and the word eel is simultaneously attached to several fishes that are not eels at all — which makes this pair as much about naming as about anatomy.

At a glance

Comparison of Eel and Moray Eel across 7 dimensions, with an interpretation of each difference.
What differs	Eel	Moray Eel	What it means
Rank	Order Anguilliformes — several hundred species across roughly fifteen to twenty families	Family Muraenidae — around 200 species within that order	The relationship is containment: every moray is an anguilliform, but freshwater eels, congers and snake eels are not morays.
Pectoral fins	Present in many families, including freshwater eels and congers	Absent in adults, leaving a smooth flank behind the head	The missing pectorals are one of the quickest ways to place an eel in the moray family from a photograph.
Gill opening	A slit-shaped opening in most families, sometimes with a visible flap	A small round pore behind the head, often no bigger than a coin	The circular pore, combined with constant mouth-gaping to move water, is a moray signature.Repeated mouth opening is respiration, not display, and is often misread as threatening behaviour.
Throat jaws	Pharyngeal elements present as in most bony fishes, without the moray's extreme mobility	Highly mobile pharyngeal jaws that can move forward into the mouth and draw prey back	This mechanism suits a predator that cannot create strong suction inside a narrow reef crevice.
Habitat and migration	Includes catadromous freshwater eels that grow in rivers and spawn far out at sea, plus deep-sea and burrowing families	Almost entirely marine, in reef and rocky crevices, with a small number in brackish or fresh water	The order's life histories are far more varied than the crevice-dwelling reef image morays supply.
Skin and scales	Minute scales embedded in the skin in Anguilla, absent in several other families	Scaleless, with a thick mucus layer that also lines the crevices the fish occupies	The heavy mucus coat suits an animal squeezing through abrasive coral and rock.
Size range	From small burrowing species barely a hand long to congers exceeding two metres	Roughly 20 cm in the smallest species to around 3 m in the giant moray, with slimmer species longer still	Both spans are wide, so length alone will not tell you whether an eel is a moray.Maximum lengths for the largest morays and congers rest on limited records and are frequently overstated.

Rank: EelOrder Anguilliformes — several hundred species across roughly fifteen to twenty families
Moray EelFamily Muraenidae — around 200 species within that order
The relationship is containment: every moray is an anguilliform, but freshwater eels, congers and snake eels are not morays.
Pectoral fins: EelPresent in many families, including freshwater eels and congers
Moray EelAbsent in adults, leaving a smooth flank behind the head
The missing pectorals are one of the quickest ways to place an eel in the moray family from a photograph.
Gill opening: EelA slit-shaped opening in most families, sometimes with a visible flap
Moray EelA small round pore behind the head, often no bigger than a coin
The circular pore, combined with constant mouth-gaping to move water, is a moray signature.Repeated mouth opening is respiration, not display, and is often misread as threatening behaviour.
Throat jaws: EelPharyngeal elements present as in most bony fishes, without the moray's extreme mobility
Moray EelHighly mobile pharyngeal jaws that can move forward into the mouth and draw prey back
This mechanism suits a predator that cannot create strong suction inside a narrow reef crevice.
Habitat and migration: EelIncludes catadromous freshwater eels that grow in rivers and spawn far out at sea, plus deep-sea and burrowing families
Moray EelAlmost entirely marine, in reef and rocky crevices, with a small number in brackish or fresh water
The order's life histories are far more varied than the crevice-dwelling reef image morays supply.
Skin and scales: EelMinute scales embedded in the skin in Anguilla, absent in several other families
Moray EelScaleless, with a thick mucus layer that also lines the crevices the fish occupies
The heavy mucus coat suits an animal squeezing through abrasive coral and rock.
Size range: EelFrom small burrowing species barely a hand long to congers exceeding two metres
Moray EelRoughly 20 cm in the smallest species to around 3 m in the giant moray, with slimmer species longer still
Both spans are wide, so length alone will not tell you whether an eel is a moray.Maximum lengths for the largest morays and congers rest on limited records and are frequently overstated.

How they are related

Anguilliformes, the true eels, is an order of ray-finned fishes distinguished by an elongate body, reduced or absent pelvic fins and a distinctive transparent leptocephalus larva. Muraenidae, the morays, is one family within it, alongside congers, snake eels, garden eels and deep-sea families. Several fishes called eels are not anguilliforms at all, including the electric eel, which belongs to the South American knifefishes and is not a true eel.

A note on naming: Eel in everyday use covers both the order Anguilliformes and several unrelated fishes named for their shape, including the electric eel, wolf-eel and sand eels. Only anguilliforms are true eels, and moray names a family rather than a species.

Telling them apart

Look behind the head. A moray has no pectoral fins and a small round gill pore, with a continuous fin running along the back into the tail. Freshwater eels and congers keep visible pectoral fins and a slit gill opening. Morays also tend to be more patterned, with spots, reticulations or bold colour, while congers and freshwater eels are more uniformly brown, grey or olive.

No pectoral fins, a round gill pore, patterned skin, head poking from a reef hole: moray. Visible pectoral fins, a slit gill opening, plain colour, often in fresh or brackish water: another kind of eel. And if the fish generates electricity, it is not an eel at all — the electric eel is a knifefish that acquired the name from its shape.

Habitat and distribution

The order spans habitats that have almost nothing in common. Freshwater eels of the genus Anguilla grow for years in rivers and estuaries before migrating far out to sea to spawn. Garden eels colonise sandy slopes in colonies of burrows. Deep-sea families live thousands of metres down. Morays occupy holes and crevices in coral and rocky reefs, mostly in tropical and warm temperate seas, and rarely leave that structure.

Diet and ecological role

Eels across the order are largely carnivorous, taking fish, crustaceans and invertebrates, with deep-sea species scavenging and burrowing species specialising on small prey in sediment. Morays hunt around reef structure, largely at night, taking fish, octopus and crustaceans, and their pharyngeal jaws address a specific problem: an animal wedged in a crevice cannot generate the suction most fish use to swallow, so prey has to be pulled inward mechanically.

Behaviour

Most morays sit with the head projecting from a hole, gaping rhythmically to ventilate the gills, and become active after dark. Freshwater eels behave nothing like this, undertaking one of the longest known fish migrations at the end of their lives. Some morays have been observed foraging alongside groupers on reefs, an association reported in field studies, in which the two species search complementary parts of the structure.

Senses and adaptations

Morays run heavily on smell, with prominent tubular anterior nostrils, which suits hunting at night in structure where vision is of limited use. The pharyngeal jaw mechanism is the family's most distinctive adaptation and was described in detail in comparative anatomy work on reef morays. Across the wider order, the leptocephalus larva is itself an adaptation, a transparent ribbon that drifts on ocean currents for months before transforming into a recognisable eel.

More on this topic: Animal senses and adaptations.

Lifespan and life stages

Life histories differ sharply within the order. Freshwater eels may spend a decade or more, sometimes far longer, growing in rivers before a single spawning migration at the end of life. Morays are thought to be relatively long-lived reef fishes, with published estimates for larger species running to a decade or more, though ageing reef eels is difficult and figures rest on limited samples rather than large studies.

People and these animals

The order matters commercially through the freshwater eels, which support major fisheries and aquaculture and whose populations have declined steeply in Europe, North America and East Asia. Morays are less important as food, and large individuals of some reef species are among the fishes associated with ciguatera, which leads some fisheries and communities to avoid them. Both groups are affected by habitat change — river barriers for eels, reef degradation for morays.

Conservation context

The most serious concerns in the order attach to the freshwater eels rather than the morays, with several Anguilla species assessed as threatened after long declines linked to river barriers, habitat loss, fishing pressure and changes in ocean conditions. Morays are generally less exploited, though reef degradation affects them indirectly. Assessments are revised as new data appear, so listings should be checked rather than assumed.

Several freshwater eel species carry serious threat assessments following long declines, while moray statuses are more varied and less studied. Check the current IUCN Red List entry for the species concerned.

What they have in common

Both share the elongate, ribbon-like body plan and reduced fin set of the true eels.
Both pass through the transparent leptocephalus larval stage found across the order.
Both are carnivorous, taking fish, crustaceans and other invertebrates.
Both rely heavily on smell rather than vision when locating prey.

Key differences

Eel refers to an order of several hundred species; moray is one family of roughly 200 within it.
Morays lack pectoral fins, which many other eel families retain.
Morays have a small round gill pore, while most other eels have a slit-shaped opening.
Moray pharyngeal jaws are exceptionally mobile and pull prey backwards into the throat.
Freshwater eels migrate between rivers and the open ocean; morays stay with reef and rock structure.
Morays are scaleless with heavy mucus, whereas freshwater eels carry minute embedded scales.

Where people go wrong

Treating moray as a synonym for eel, when it is one family among many in the order.
Reading a moray's rhythmic gaping as aggression, when it is how the fish ventilates its gills.
Calling the electric eel an eel, when it is a South American knifefish in a different order.
Assuming all eels are marine, when freshwater eels grow in rivers and estuaries before migrating to sea.

Frequently asked questions

Are all eels morays?

No, the relationship runs one way. Morays are a single family, Muraenidae, inside the order Anguilliformes, which also contains freshwater eels, congers, snake eels, garden eels and various deep-sea families. So every moray is a true eel, but the great majority of eel species are not morays. The reef moray simply dominates the mental image because it is the most photographed member of the order.

Why does a moray keep opening and closing its mouth?

It is breathing, not threatening. Morays have small round gill pores rather than wide slits, so they pump water over the gills by opening and closing the mouth rhythmically. Because the head usually projects from a crevice while the body stays hidden, that constant gaping is the most visible thing about the fish and is very widely misread as aggression by divers and photographers.

Is an electric eel a true eel?

No. The electric eel belongs to the South American knifefishes, an entirely different order of freshwater fishes, and shares only body shape with true eels. Several other fishes carry the name misleadingly too, including the wolf-eel, which is a wolffish, and sand eels, which are sand lances. Body elongation has evolved many times in fishes, and common names have followed the shape rather than the ancestry.

What are pharyngeal jaws and why do morays need them?

They are a second set of jaws located in the throat. In morays these are unusually mobile and can move forward into the mouth to grip prey and draw it backwards. The reason appears to be spatial: a fish wedged into a narrow crevice cannot expand its mouth to create the suction most fishes use to swallow, so prey has to be transported mechanically instead of hydraulically.

Do freshwater eels and morays share the same larval stage?

Yes, and it is the order's most distinctive feature. Both pass through a leptocephalus stage — a flattened, almost fully transparent ribbon of a larva that drifts in ocean currents, sometimes for months, before transforming. It is so unlike the adult that leptocephali were originally described as separate animals. Even freshwater eels that spend most of life in rivers begin at sea in that form.

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Sources and methodology

How this comparison is built: FaunaHub comparisons are assembled from the sourced animal profiles behind them rather than written as standalone claims. Figures such as size, mass, and lifespan are typical ranges that vary by subspecies, population, region, sex, age, and — where relevant — whether an animal lives in the wild or under human care, so they are presented as ranges rather than fixed values. Where a common name covers a group rather than a single species, the page says so instead of implying a species-to-species match. Conservation status changes over time and should be confirmed against the current IUCN Red List. Dimensions that could not be supported from the underlying profiles are omitted rather than filled in.

What this page does not do: it does not rank the two animals, predict the outcome of a confrontation, or present either one as stronger, smarter, or better. It is not veterinary, medical, first-aid, handling, capture, hunting, or pest-control guidance. For an animal in your care, or any situation involving injury, contact a qualified veterinarian, your local wildlife authority, or emergency services.

Sources and further reading

Authoritative references used for general educational context. External links open in a new tab. These sources do not endorse FaunaHub.

UniversityAnimal Diversity Web — Anguilliformes (true eels) — University of Michigan order-level account
GovernmentNOAA Fisheries — Marine Life — U.S. government science agency for marine species and habitats
ReferenceEncyclopaedia Britannica — Animals reference — Editor-reviewed encyclopedia overview entries
ReferenceBritannica — Moray — Editor-reviewed encyclopedia entry
UniversityAnimal Diversity Web — University of Michigan Museum of Zoology — Peer-edited reference accounts for animal species
Wildlife referenceIUCN Red List of Threatened Species — Authoritative source for current conservation status
ReferenceWoRMS — World Register of Marine Species — Authoritative register of marine species names

Last updated: 2026-08-04