The brown, yellow-spotted eel peering out of a rock crack with its mouth opening and closing is one of the reef sights snorkelers and divers remember most in Cabo. It isn’t threatening you: it’s breathing.
A slender, laterally flattened eel with a pointed snout and both nostrils ending in distinct tubes. It is usually brown covered with dark-edged yellow spots, which become more numerous as it grows; some individuals are yellowish brown to almost white with darker brown mottling. Look for a black spot at the rear corner of the mouth with a white patch just in front of it on the lower jaw, and a rather faint black area around the small gill opening.
The jewel moray lives only in the tropical eastern Pacific, from the Gulf of California to Islas Lobos de Afuera in northern Peru, including the Galápagos. It stays on rocky and coral bottoms close to shore, usually between 1 and 25 m deep. Museum collections hold dozens of specimens from the tip of the peninsula, from the rocky shore of Bahía San Lucas and El Tule to Cabo Real, Los Frailes and Pulmo reef, collected from the 1950s to 2015.
By day it stays tucked into crevices with only its head showing; at night it comes out to hunt crabs, shrimps and small fishes. Like other morays it relies little on suction: it seizes prey with long, slender, conical teeth and swallows it with the help of a second set of jaws in its throat. It is a permanent resident of the reefs where it lives.
In a moray of the same genus, Muraena retifera, researchers filmed a second set of jaws launching forward from the throat into the mouth to grab struggling prey and drag it toward the gut. In one eel they traveled 3.5 cm, more than the length of its head.
Source ↗The jewel moray opens and closes its mouth constantly, and that movement is what keeps water flowing over its gills. It can look like a warning, but FishBase notes it is breathing, not a threat.
Source ↗The species was described in 1842 from specimens brought back by HMS Beagle. Its type locality is Santa María (Floreana) Island in the Galápagos, not Cabo’s Santa María bay.
Source ↗Its dark-edged yellow spots become more numerous as the eel grows, and some individuals are pale yellowish to almost white with brown mottling instead.
Source ↗In Egypt’s Red Sea, roving coral groupers shake their heads in front of giant morays to recruit them for a hunt; hunting together, the groupers caught about five times more prey per hour. That was a different moray species, and it hasn’t been documented for the jewel moray.
Source ↗Scripps Institution of Oceanography holds a jewel moray collected in March 1959 in the San Lucas submarine canyon, off the beach at Land’s End, at about 28 m, a little deeper than the usual 25 m given for the species.
Source ↗Jewel morays are resident around Los Cabos all year and are not a fishing target; people meet them while snorkeling and diving over rocky reefs. Museum specimens come from inside Bahía San Lucas, where Pelican Rock and the submarine canyon are, from El Tule and Cabo Real along the Corridor, and from Los Frailes and Cabo Pulmo on the East Cape. Look into cracks and under ledges by day; you will usually see just the head and the opening and closing mouth.
Morays aren’t aggressive, but they bite when a hand goes into their hole or near their head, and the teeth hold and tear. Don’t touch the reef or reach into crevices, don’t hand-feed them and keep your fingers away from the face. Medical case reports describe severe hand and forearm wounds and a real risk of serious bacterial infection, so clean any bite well and get it checked by a doctor. If one is hooked by accident on a reef, cut the line close to the mouth rather than handling it.
| Mexico (NOM-059) | Not listed in NOM-059-SEMARNAT-2010 (2019 update) |
|---|---|
| Cabo Pulmo National Park | Protected since 1995 (7,111 ha); extracting coral and other biogenic material is prohibited |
| Cabo San Lucas | Flora and fauna protection area; a submarine refuge since 1973, recategorized in 2000 |
| IUCN Red List | Least Concern (assessed 2007, published 2010) |
The Argus moray (Muraena argus) grows to about 110 cm, has rows of large yellow-brown blotches plus many small white spots, an intense black spot over the gill opening and no white patch before the black spot at the corner of the mouth. The hourglass moray (M. clepsydra) is covered in irregular cream spots and has a large, ringed black spot around the gill opening, at least 2.5 times the size of the eye.
Not aggressive, but it bites if you put a hand in its hole or near its head. Don’t touch, feed or corner it, and get any bite checked by a doctor because of the infection risk.
It’s breathing. Morays open and close the mouth to move water over the gills; it is not a threat display.
On shallow rocky reefs: inside Bahía San Lucas, along the coves of the Corridor and at Cabo Pulmo. Look into crevices and under ledges during the day.
Top illustration: Top Anglers. Photos: iNaturalist contributors, credited on each photo.
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