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Conservation Status:  Safe for Now

AquaticCalifornia Moray

Gymnothorax mordax Bony Fishes

Aquarium of the Pacific - Online Learning Center - Species Print Sheet

California Moray
Not so intimidating when its mouth is closed | Used with permission of Ken Kurtis, Reef Seekers Dive Co.
California Moray
Not so intimidating when its mouth is closed | Used with permission of Ken Kurtis, Reef Seekers Dive Co.

Species Overview

Despite its snake-like appearance and lack of fins or scales, the California moray is a fish. They may have a frightening appearance; however, they are actually very timid fish. They have a keen sense of smell and poor eyesight. California moray have a second set of jaws inside their throat that spring forward to help them swallow. Small, pointed teeth are easily visible inside their mouth as their jaws open and close so they can breathe.

Species In-Depth | Print full entry

At the Aquarium

Our California moray eels live in one habitat with fish and in another with spiny lobster,

Geographic Distribution

Eastern Pacific Ocean from to Point Conception, California, south to Magdalena Bay, Baja California with the highest population densities in southern California, especially the southern Channel Islands.


California moray inhabit rocky areas to a depth of 40 m (130 ft),; however, they are most commonly found in waters from tide pools (juveniles) to a depth of about 30 m (65 ft). They usually stay between rocks and in crevices, emerge gin at night to hunt.

Physical Characteristics

California moray have a long snake-like body, small eyes, prominent teeth, tube nostrils, and a tapered tail. Round, uncovered gill openings are visible on either side of the head behind the jaw muscles. They do not have gill covers, scales, or pectoral fins. The skin is tough, leathery, and covered with mucus. Their sharp teeth face backward. Skin coloration ranges from dark or light brown to green and i3 is often mottled


to 5 feet 1.5 m (5 ft)

Diet and Feeding

Nocturnal feeders and ambush predators, they prey on small fishes, crustaceans, and octopus. These eels use their strong sense of smell to seek out and ambush prey. Taste and touch are also important senses in their hunt for food. Their lower jaw is covered with taste bud-like structures used for sensing food. When food is tasted, the mouth immediately acts as a grabber.


Spawning is believed to occur only in warm waters off Baja California. It is believed that the temperature of California coastal waters is too cold for reproduction to occur. Eggs and sperm are broadcast spawned and fertilization is external. Larvae may drift as plankton for as long as a year before settling to the bottom of tidepools where the young eels spend some time


California moray tend to be shy and timid, hiding from sudden movement. They spend the day in their cave or crevice with only parts or their entire head showing, emerging when tempted by the smell of food or curiosity.
California moray have a mutualistic relationship with the red rock shrimp (Lysmata californica). Almost every moray crevice contains red rock shrimp. The eels allow the shrimp to clean off dead skin and parasites, and to clean their teeth and mouths of bits of food. The eels in turn, protect the shrimp from other predators but at times, they do eat the shrimp.


The horseshoe crab has 10 “eyes” or light sensing organs scattered about its body from its head to and including its tail. It has one set of compound eyes like those of a fly, one set of simple, rudimentary eyes, and multiple photoreceptors on its telson. In spite of all these “eyes”, the crab’s vision is poor! Only movement is detected in the daylight and perhaps a blurry image by the compound eyes. At sundown, signals from the tail plus other factors give the crab improved night vision.


to about 19 years


Numbers of horseshoe crabs are declining. These crabs have many predators, migratory birds, some species of sharks, loggerhead sea turtles, and sea gulls but their most serious predator is humans. Since the mid 1800’s large numbers of horseshoe crabs have been caught to be used for bait in the eel and conch fisheries, cattle feed, and fertilizers. The decline of horseshoe crabs on the Atlantic coast has led to state and federal regulations on their harvest. Delaware regulations require that that the crabs be hand captured and returned to the area in which they were caught. Also crabs may only be harvested for LAL. Harvesting for use as eel bait or fertilizer is prohibited. Other states bordering Delaware Bay have not instituted similar restrictions. Regulating harvesting continues to be a controversial issue among fisheries, environmentalists, the pharmaceutical industry and state regulators responsible for natural resources. Impacts of climate change may affect horseshoe crabs—loss of spewing areas due to sea level rise and ocean acidification’s affecting shell development. Horseshoe crabs have adapted to environmental changes for millions of years. Will they have time to adapt to climate change? Predators other humans include some species of sharks, loggerhead sea turtles, sea gulls and migrating shorebirds. At the same time horseshoe crabs are spawning, huge flocks if shorebirds pause se in their migration from South America to northern breeding grounds as distant as the Arctic to feast on crab eggs.

Amazing Facts

Horseshoe crabs are often referred to as living fossils. There is some debate about whether calling these crabs should be called living fossils because of lack of anthropological evidence. The remains are usually preserving the structure of the hard body parts and horseshoe crabs closely resemble the fossilized structures found in rock – many of them over several hundred million years. In that way, they appear to be living specimens of long dead, fossilized species. However, that is not to say they have not evolved at all since there is no evidence that changes may have occurred in the soft tissue and biochemical mechanisms that cannot be studied in typical fossils. I suspect that very close attention to detail could even show minor changes to the exoskeleton of the horseshoe crab.

Horseshoe crabs live in ocean waters teeming with bacteria. Although they have no immune system, when injured, they are able to ward off infections due to a substance produced by the amebocytes in their blood that causes clotting of the wound. Scientists extracted this substance and develop a reagent called Limulus Amebocyte Lysate (LAL) for use in testing intravenous medicines, vaccines, and medical devices used in the treatment of humans and other mammals. The US Food and Drug Administration (FDA) now requires the use of the LAL test instead of the previous more time-consuming, less sensitive test that used rabbits to detect contamination.