Gymnothorax mordaxCalifornia moray

Geographic Range

Distribution ranges from Magdalena Bay, Baja, California, north to Point Conception (Bushing 2000). The population density of the Gymnothorax mordax is greater in southern California with the highest densities in Southern Channel Islands, and Catalina (R.E.E.F. 2000).


Inhabits cracks and crevices within rocky reefs in the subtidal zone to 40m (UCLA), but is usually found at 0.6-20m (Eschmeyer 1983).

  • Aquatic Biomes
  • reef

Physical Description

Gymnothorax mordax has a snake-like body, with no scales or lateral line (Eschmeyer 1983). Coloration is light or dark brown, to green, often mottled. Lack of pectoral and pelvic fins distinguishes it from all other eel-like fishes. The California Moray has numerous canine-type teeth that are translucent in the juvenile. A round gill opening is present, however respiration requires the moray to constantly open and close its mouth to push oxygenated water over their gills. A full grown adult can reach up to 152cm or 5ft (UCLA 2000).


Gymnothorax mordax reproduces by external fertilization. Eggs hatch into a specialized planktonic larva called a leptocehalus that eventually settle to the bottom. Juvenile morays can be found in tidal pools, but upon maturation seek deeper water. Very little is know about the leptocephali and juvenile stages of their life cycle, because most specimens found are probably over thiry years old (Eschmeyer 1983). It is hypothesized that the morays off the coast of southern California do not reproduce because the water is too cold. Instead the ocean currents bring the leptocehalali north from Baja California, which then settled out of the upper water column to mature in southern California. The life span of the California moray is speculated to be thirty years or more (UCLA 2000).


Gymnothorax mordax has a mutualistic relationship with the red rock shrimp, *Lysmata claifornica*. The red rock shrimp clean the moray of dead skin and parasites; in return the moray provides the shrimp with protection by allowing the shrimp to coinhabit the moray's crevice (PBS 2000).

Communication and Perception

Food Habits

Nocturnal predator on small reef fishes, octopi, shrimp, crabs, lobster, and sea urchins (Bushing 2000). Gymnothorax mordax uses its well developed sense of smell to hunt their prey (PBS 2000).

Economic Importance for Humans: Positive

The California moray is popular aesthetic fish among the diving community. Unlike some other eels, Gymnothorax mordax is not poisonous to humans and, therefore, can be eaten (Eschmeyer 1983).

Economic Importance for Humans: Negative

California moray eels usually won't leave their crevices to attack divers, unless they are aggravated by divers prodding, spearing, or capturing them. Since they do have numerous razor sharp teeth they can inflict serious lacerations on a diver if they do bite (Eschmeyer 1983).

Conservation Status


William Fink (editor), University of Michigan-Ann Arbor.

Rosie Clarke (author), University of Michigan-Ann Arbor.


Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.


uses touch to communicate


Bushing, W., July 16, 2000. "Catalina Island Conservancy" (On-line). Accessed October 21, 2000 at

Eschmeyer, W., H., Hammann, H.. 1983. A Field Guide to Pacific Coast Fishes of North America. Boston, USA: Houghton Mifflin Company.

PBS, "California Moray" (On-line). Accessed October 24, 2000 at

Reef Environmental Education Foundation, April 4, 2000. "Distribution report of Califonia Moray (Gymnothorax mordax) for California Moray (Gymnothorax mordax )" (On-line). Accessed October 24, 2000 at

UCLA, "California Moray" (On-line). Accessed October 24, 2000 at