Cephaloscyllium ventriosumSwell shark

Geographic Range

Cephaloscyllium ventriosum (swell shark) is found in the eastern Pacific Ocean, ranging from Central California, in the Monterey Bay, to southern Mexico and central Chile (Compagno 1984). (Compagno, 1984)


Cephaloscyllium ventriosum is a benthic and epibenthic shark living in warm-temperate and subtropical continental waters. The depth range of this species varies from inshore to 457 m and is most common at depths of 5 to 37 m. Cephaloscyllium ventriosum is sometimes found in algal-covered bottom without kelp, but prefers rocky, algal-covered areas of kelp beds. This species is usually found motionless in rocky caves and crevices during the day, and swims slowly through bottom algae or in open water close to the bottom at night (Compagno 1984). (Compagno, 1984)

  • Other Habitat Features
  • caves
  • Range depth
    457 (high) m
    1499.34 (high) ft
  • Average depth
    5-37 m

Physical Description

Cephaloscyllium ventriosum is a large, strongly variegated catshark. Swell sharks are yellow-brown with many dark spots and occasional light spots on the body, fins, and underside of head and abdomen. Juveniles are usually lighter in color than mature adults ("MarineBio.org" 2005). The snout is very short and broadly rounded with nasal flaps reaching the mouth. This species has two dorsal fins, the second much smaller (Compagno 1984). The maximum size is at least 100 cm, with adult males ranging from 82 to 85 cm. The size at hatching is 14 to 15 cm (Compagno 1984). ("MarineBio.org", 2005; Compagno, 1984)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    100 (high) cm
    39.37 (high) in
  • Average length
    82 to 85 cm
  • Average basal metabolic rate
    44.3 cm3.O2/g/hr


Cephaloscyllium ventriosum is oviparous and lays eggs in large, greenish-amber egg-cases which hatch in 7.5 to 10 months depending on the water temperature. The young have a double row of enlarged toothlike projections down the back that aid the young in forcing their way out of the egg-cases (Compagno 1984). (Compagno, 1984)


There is little information available for the mating system of C. ventriosum.

There is little information about the reproductive cycle of C. ventriosum. (Bester, 2006)

  • Range gestation period
    7.5 to 12 months

Although there is not much detailed information on parental investment in this species, female individuals of C. ventriosum anchor the egg cases (usually two) in a rocky, algae-covered location for protection until the eggs hatch. Egg cases have twisted tendril-like extensions on each of their four corners, which catch on seaweed and rocks, helping to keep the egg case from drifting. The newborn pups feed on mollusks and crustaceans immediately, with no assistance from either parent. ("MarineBio.org", 2005; Bester, 2006)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female


There is no information available on the lifespan of C. ventriosum.


Although C. ventriosum is a solitary species, it is sometimes found in groups of several individuals while resting. Occasionally they are found piled atop one another (Compagno 1984; "MarineBio.org" 2005).

Cephaloscyllium ventriosum is usually inactive during the day, found in rocky caves and crevices, and becomes active at night to hunt ("MarineBio.org" 2005). ("MarineBio.org", 2005; Compagno, 1984)

Communication and Perception

There is little information available on how C. ventriosum communicates and perceives the environment. Sharks, in general, have keen chemical perception abilities and can sense electronic signals as well.

Food Habits

Cephaloscyllium ventriosum feeds on bony fishes, alive and dead, and crustaceans. Young feed on mollusks, crustaceans, and small fish. Swell sharks have large mouths and relatively small, sharp-pointed teeth that could handle large prey, but these sharks seem incapable of dashing after active prey (Compagno 1984).

It is thought that this species specializes in catching diurnal bony fishes that are relatively inactive and unresponsive at night. The nocturnal activity pattern of this slow and weak-swimming species aids in capture of prey (Compagno 1984). Swell sharks often are seen remaining motionless on sea floor, waiting for prey to wander by or be swept into their mouths by currents. They have also been known to enter lobster traps to eat lobsters (Bester, 2006). (Bester, 2006; Compagno, 1984)

  • Animal Foods
  • fish
  • carrion
  • mollusks
  • aquatic crustaceans


Cephaloscyllium ventriosum can take in water or air as a means of escaping from predators, giving it the common name "swell shark." It hides in rocky caves and crevices and swallows water to expand its stomach if attacked. This behavior ensures that it is tightly jammed into crevices and cannot be pulled out. If these sharks are threatened when out in the open, they grab their tail in their mouths, to form a U-shape and swell with water, making themselves difficult to grab or manipulate. Sphincter muscles at both ends of the stomach trap the water. Relaxation of these muscles releases the water, returning the stomach to normal size (Bright 2000). If taken out of water, this species can also gulp air, which makes it swell up like a balloon. When this air is released, a barking sound results (Bright 2000). Swell sharks are also cryptically colored. (Bright, 2000)

Swell sharks are preyed on by marine mammals, including sea lions, seals, and larger sharks. Developing swell shark embryos are sometimes eaten by marine snails, which bore through the egg casing. (Bester, 2006)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

There is little information available about the ecosystem role of C. ventriosum. They are both predators on fish, crustaceans, and mollusks, and are preyed on by larger predators.

Economic Importance for Humans: Positive

Cephaolscyllium ventriosum is not fished commercially, and although this species is ocassionally caught by sportfishers and divers, the flesh is probably not utilized (Compagno 1984). (Compagno, 1984)

Economic Importance for Humans: Negative

There are no known adverse effects of C. ventriosum on humans, as they only become aggressive when harassed. ("MarineBio.org", 2005; "MarineBio.org", 2005)

Conservation Status

Cephaloscyllium ventriosum are not commercially fished, but are often caught as bycatch in the lobster and crab fishing industries. Although this species is not currently threatened or endangered, bycatch poses a potential conservation risk due to slow reproduction and the small number of young produced each year.


Tanya Dewey (editor), Animal Diversity Web.

Meredith Grycki (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), 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


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

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.


an animal that mainly eats meat


flesh of dead animals.


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


uses electric signals to communicate


union of egg and spermatozoan


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


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.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


2005. "MarineBio.org" (On-line). Accessed October 18, 2005 at http://marinebio.org/species.asp?id=383.

Bester, C. 2006. "Biological Profiles: Swell Shark" (On-line). Florida Museum of Natural History, Ichthology Department. Accessed February 10, 2006 at http://www.flmnh.ufl.edu/fish/Gallery/Descript/SwellShark/SwellShark.html.

Bright, M. 2000. The private life of sharks : the truth behind the myth. Mechanicsburg, PA: Stackpole Books.

Compagno, L. 1984. FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2. Carcharhiniformes. Rome: Food and Agriculture Organization of the United Nations.