Swell Shark, Cephaloscyllium ventriosum

Swell Shark, Cephaloscyllium vertriosum, Albino. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, June 2012. Length: 60 cm (2 feet 0 inches).

Swell Shark, Cephaloscyllium vertriosum. Fish caught from coastal waters off La Jolla Diego, California, November 2013. Length: 64 cm (2 feet 1 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Swell Shark, Cephaloscyllium vertriosum. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, May 2009. Length: 66 cm (2 feet 2 inches).

Swell Shark, Cephaloscyllium vertriosum. Fish caught off the Gordo I Bank, Baja California Sur, January 2022. Length: 66 cm (2 feet 2 inches). Catch and photograph courtesy of James Rosenwald, Saint Croix, Minnesota.

Swell Shark, Cephaloscyllium vertriosum. Fish caught from coastal waters off Loreto, Baja California Sur, June 2024. Length: 69 cm (2 feet 3 inches).

The Swell Shark, Cephaloscyllium ventriosum, is a member of the Cat Shark or Scyliorhinidae Family, and is known in Mexico as pejegato globo. They are named for their ability to double their body size by ingesting water as a tactic to avoid predation when threatened. They accomplish this feat by bending their body into a U-shape and grabbing their tail in their mouth allowing them to swallow water. Globally, there are seven species in the genus Cephaloscyllium, of which two are found in Mexican waters, both in the Pacific Ocean.

The Swell Shark has a stout cylindrical body that tapers at both ends. They have elongated, catlike eyes situated high on the sides of their head, which give them their common name and allows for easy identification. They vary in color with a mix of yellow and brown blotches, saddles, and white spots over a dark brown background. They are white ventrally and their undersides are also spotted. Their fins are all of a uniform tan coloration. Their head is flat and broad with a rounded short snout and a very large mouth that opens at the front and extends past the oval-shaped eyes. Each jaw has 55 to 60 small teeth. They have very small gill slits. They have 2 small dorsal fins, the first being well back on the body and originating over the pelvic fins, and the second being smaller and originating over the anal fin. Males have short stout claspers.

The Swell Sharks is a small sluggish benthic species found from the intertidal zone to the continental shelf and upper slopes preferring rocky algae-covered bottoms for shelter. They are found at depths up to 591 m (1,500 feet), however, are more common at depths of less than 37 m (120 feet). They reach a maximum of 1.0 m (3 feet 3 inches) in length. They are small elusive fish that spend their days hiding in caves and rocky crevices well camouflaged from their surroundings. They emerge at night to feed and lie in wait over sandy bottoms as ambush predators consuming small reef fish, benthic crustaceans, and mollusks. They are preyed upon by various large sharks and marine mammals including seals and sea lions. They are typically a solitary species but will form aggregations at times with some individuals piling on top of each other to rest. Reproduction is oviparous with females laying one or two egg cases (Mermaid’s Purses) that are 1 to 2 inches by 3 to 5 inches in size. Females attach the egg cases to rocks where they remain for 9 to 12 with the embryo being fed only by the egg yolk. The pups emerge as miniature adults that are 15 cm (5.9 inches) in length. Their populations are not well documented as they are abundant in some locations and absent from others.

The Swell Shark is a resident of all Mexican waters of the Pacific with the exception that they are absent from the northern 20% of the Sea of Cortez.

The Swell Shark cannot be confused with any other species due to its body profile.

From a conservation perspective the Swell Shark is currently considered to be of Least Concern with stable widely distributed populations. They are targeted by spear fishermen on a limited basis and are also of minor interest to recreational fishermen. They can also be an accidental by-catch in crab traps, gillnets, and trawl nets but are generally well-protected due to their rocky habitat. They have no commercial value as they are not consumed by humans due to the poor quality of their flesh. They are considered harmless and will only attack humans if provoked. They can be found in large public aquariums being able to survive in captivity for extended periods of time.