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Ragfish: Icosteoidei

PHYSICAL CHARACTERISTICS, GEOGRAPHIC RANGE, HABITAT, DIET, BEHAVIOR AND REPRODUCTION, RAGFISH AND PEOPLE, CONSERVATION STATUS

Young ragfish have limp bodies. The body is broad from back to belly and narrow from side to side. It is smooth-skinned and scaleless, except along the lateral line, where the scales have small spines. The lateral (LAT-uhr-uhl) line is a series of pores and tiny tubes along each side of a fish's body and is used for sensing vibrations. The snout is blunt and looks like that of a calf. The dorsal (DOOR-suhl) fin that runs along the midline top of the body has one spine. The tail fin is rounded and fanlike. The pelvic fins, the pair that corresponds to the rear legs of four-footed animals, have one spine. All fins have tiny spines on the surface.

When ragfish become adults, the body lengthens and becomes less broad from back to belly, and a ridge develops along the midline of the belly. The lateral line spines, the spines on the fins, and the pelvic fins disappear. The color turns to solid dark brown over the entire body and fins. Ragfish have been reported to reach a length of about 7 feet (2.1 meters).

Ragfish live in the northern part of the Pacific Ocean.

Ragfish usually live offshore in deeper water.

Ragfish probably eat small fish, squid, octopuses, and jellyfish.

Ragfish have never been observed in their natural habitat. They probably live alone. Large ragfish sometimes are found stranded on the shore. Ragfish are ready to spawn when they are seven to nine years of age. The eggs probably are fertilized (FUR-teh-lyzed), or joined by sperm to start development, outside the female. The eggs and larvae drift in the water. Larvae (LAR-vee) are animals in an early stage that must change form before becoming adults.

Ragfish are not caught for food or sport.

WHAT'S IN A NAME?

The Latin name of the ragfish, Icosteus aenigmaticus, means "puzzling fish with yielding bones." Ragfish have cartilage rather than bones, so they are limp and raglike when out of the water.

Ragfish are not threatened or endangered.

Ragfish have never been observed in their natural habitat. (Illustration by Michelle Meneghini. Reproduced by permission.)

FOR MORE INFORMATION

Books:

Nelson, Joseph S. Fishes of the World. 3rd ed. New York: Wiley, 1994.

Web sites:

Nokkentved, N. S. "Unusual Deep-Water Fish Causes a Stir on Shore. The Olympian. http://www.theolympian.com/home/specialsections/Critters/20020806/26894.shtml (accessed on February 8, 2005.)

Additional topics

Animal Life ResourceFish and Other Cold-Blooded Vertebrates