Moray Eel

Moray eels make up the family Muraenidae, containing more than 200 species of elongated, scaleless predatory fish found on coral reefs and rocky coastlines in tropical and subtropical seas worldwide. Unlike true eels of other families, morays lack pectoral and pelvic fins entirely, relying on serpentine body movement for locomotion. They are apex ambush predators within reef ecosystems, and some species are known to form cooperative hunting partnerships with groupers, in which the two species work together to flush prey from crevices. The green moray, a large Atlantic species often used as a representative example, is commonly encountered by divers on Caribbean and western Atlantic reefs.

Moray eels are identified by their snake-like shape and lack of typical fish fins.

• Body: elongated, scaleless, muscular, with a continuous dorsal-tail-anal fin margin
• Paired fins: pectoral and pelvic fins entirely absent
• Head: large with protruding jaws and sharp recurved teeth; a second, retractable set of pharyngeal jaws is a unique family trait
• Skin: thick, mucus-coated, often appearing uniformly green, brown, or patterned with spots or bands depending on species
• Gills: reduced to small round openings rather than typical gill covers

Behavioral note: the repeated mouth-opening seen at rest is a breathing action, not aggression.

Moray eels inhabit crevices, rocky overhangs, and rubble zones on coral reefs and rocky coastlines throughout tropical and subtropical seas worldwide, from shallow reef flats down to about 50 meters. Some species also tolerate brackish conditions near river mouths and estuaries. They spend the majority of daylight hours concealed within a chosen den, with only the head visible, and depend on structurally complex reef habitat for both shelter and ambush hunting opportunities. Their global distribution spans the Atlantic, Indian, and Pacific Oceans, with different species specializing in particular reef, rubble, or rocky-shore environments.

Moray eels are primarily nocturnal ambush predators, remaining hidden within reef crevices during the day with only the head exposed, and emerging to actively hunt at night. Their characteristic repeated mouth-opening is a respiratory action that pumps water over the gills rather than a threat display. They rely heavily on a strong sense of smell to locate prey such as fish, crustaceans, and octopus, striking with a rapid lunge and powerful bite aided by the unique pharyngeal jaw that helps draw prey into the throat. Some species are known to hunt cooperatively with groupers, flushing prey from crevices that the grouper cannot reach. Moray eels are largely solitary and territorial, defending a preferred den site, and secrete a protective mucus layer over their skin.