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The swellshark is able to swallow large amounts of water and swell its body to twice its normal size; hence its name.
  • Size

    3.3 feet (1 m)
  • Diet

    Small fishes and crustaceans
  • Range

    Pacific from central California to the Gulf of California and Southern Mexico
  • Habitat

    Rocky, algae-covered bottom areas in kelp beds

Physical Characteristics

  • Coloration is red-brown or yellow-brown with large dark blotches or saddles and small white or yellow spots.
  • Stout body with a flat broad head. Snout is short and the mouth is very large, extending behind the large oval-shaped eyes.
  • Has 55-60 small teeth in both the upper and lower jaw.
  • Maximum length of 3.3 feet (1 m).

Animal Fact

By gulping water, swellsharks can inflate to twice their size

Diet / Feeding

  • Diet consists of small fishes and crustaceans.
  • Ambush predator. Remains motionless on the bottom with its mouth open waiting for prey to wander in.

Range / Habitat

  • Occurs in the Pacific from central California to the Gulf of California and Southern Mexico. It has also been reported off the coast of Central Chile.
  • Found in warm waters on the continental shelf at depths to 1500 feet (457 m). Most commonly found at depths of 16-121 feet (5-37 m).
  • Typically occupies rocky, algae-covered bottom areas in kelp beds.

Reproduction & Growth

  • Oviparous. Female lays brown and black rectangular egg cases that have bottom-attaching tendrils. Eggs are laid in pairs and hatch in seven to 10 months depending on water temperature. Pups emerge at lengths of about 6 inches (15 cm).

Conservation Status

  • “Least Concern” on the IUCN Red List.

Additional Information

  • Primarily a solitary bottom fish, but can be found in aggregations while resting, sometimes piled on top of one another.
  • A nocturnal feeder spending daylight hours in caves and crevices.
  • Often found among the by-catch in commercial fishing nets and traps. Of no commercial interest.
  • Name derives from its ability to swallow large amounts of water and swell its body to twice its normal size, thereby appearing larger when threatened by a potential predator. Swelling also makes it difficult to dislodge the fish from a crevice or hole.


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