Animal Diversity Web

Geographic Range

The red abalone ranges from southern Oregon to Baja California.

• Biogeographic Regions
• pacific ocean
  • native

Habitat

Red abalone are found in intertidal areas attached to rocks from 20-100 feet. The depth changes from one area to another depending on environmental factors. In the southern parts of California, it has been found deeper than fifty or sixty feet. Farther north, closer to southern Oregon, it can be found from the low tide zone out to about fifty feet. It prefers water from forty-five to about 60 degrees Fahrenheit.

• Habitat Regions
• temperate
• tropical

• Aquatic Biomes
• benthic
• coastal

• Other Habitat Features
• intertidal or littoral

Physical Description

The red abalone is a primitive, snail-like, univalve creature with myopic eyes on the end of retractable stalks, long jet-black tentacles, a large cupped mouth, and a black epipodeum which occasionally has alternating gray stripes.The outside of the large, thick shell is a dull brick red and a faint spiral that can be seen on one end. It is an asymmetrical oval in shape, broad and not very convex. The abalone breathes and discharges wastes through a row of holes on one side of the shell. There are typically 3-5 holes which fill up and are replaced by new holes as the abalone ages. The red abalone is the largest of all the abalone species.

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

Reproduction

The sexes are separate. The gonads of the females are green and those of the male, yellowish. Spawning takes place in from the middle of February through the first weeks of April. Males eject sperm and females eject eggs ( over 2 million in one spawning season) through the water. In 10 days, the free-swimming larva, called veligers, settle to the bottom and, within 2 months, develop into small sized adults. By the age of 1 year, an abalone is about 1 inch long, and within 4 years it reaches sexual maturity, at about 5 inches in length.

Behavior

The abalone lives a sedentary lifestyle, remaining in the same general area all its life.

It moves around by shuffling forward on its massive muscular foot, which has a surface area usually equal to the shell diameter. It is thus a very powerful huge suction cup with considerable surface adhesion. Because of this foot, the abalone has a remarkable way of protecting itself and becoming nearly invulnerable to its predators, which are mainly rock crabs, octopus, bottom-feeding fish, and the sea otter. Using its foot, it can both propel forward at a considerable speed, and cling firmly to a rock.

• Key Behaviors
• motile
• sedentary

Food Habits

A strict vegetarian feeding primarily on sessile macro-algae, kelp and plankton. In the southern part of its geographical ranges, they consume mainly giant kelp, and in the northern ranges, bull kelp. Abalones are able to detect food only at close proximities. Once food is detected, the abalone carefully glides slowly along, feeling its way, until it reaches the alga. It then raises its foot and comes down on the plant, trapping it beneath its body. It then consumes the alga, using its small rasplike teeth and extruding tongue, which often measures one-third of the animal's total body length. If interfered with while feeding, the abalone instantly clamps down, pulling its shell over its soft body. In this position it is difficult for most predators to remove the abalone from its substrate.

• Primary Diet
• herbivore
  • algivore
• planktivore

• Plant Foods
• algae
• macroalgae
• phytoplankton

Economic Importance for Humans: Positive

Abalone is commercially valuable for is edible foot, which is considered a delicacy and marketed fresh, dried, powdered, or frozen in fillets and steaks. The bulk of the crop goes to restaurants all over the world. About 2,800 metric tons or approx. 80, 000 individuals are taken in annually. The abalone shell, with its iridescent greens, blues, pinks and copper colors is used as a source of mother-of-pearl for art, and it is also found in many common decorative items such as buttons, ornaments, and trinkets.

Conservation Status

In the recent past, the abalone has been over-fished and exploited by fisheries, and by commercial and sport divers. As a result, abalone populations have been drastically reduced. California has passed many strict regulations in order to keep the abalone population flourishing. These laws include protecting abalone smaller than 8 inches in diameter, prohibiting the canning of abalone, and also prohibiting the shipment of fresh or frozen meat out of state.

• IUCN Red List [Link]

  Not Evaluated

Other Comments

An abalone's eyes can detect only vague contrasts between light and dark. Its nervous system does not contain a brain. It instead it uses a nerve center with nerve chords leading to ganglia, which control the animal's movements. As a result of their sedentary lifestyle, abalones can easily become covered with marine growths and serve as refuges for other small creatures. The large, flat shell may support a modest community of algae, sponges, barnacles, bryozoan, and hydroids. As many as 90 species of small living gastropods have been found living on the shells.

Contributors

Candice Middlebrook (author), University of Michigan-Ann Arbor.

References

Abbott, R. 1954. American seashells. New York: Van Nostrand Co., Inc..

Bevans, M. 1961. The Book of Sea Shells. New York: Doubleday and Company.

Halstead, B. 1988. Poisonous and Venomous Marine Animals of the World. Princeton, NJ: The Darwin Press.

Howorth, P. 1978. The Abalone Book. Happy Camp, California: Naturegraph Publishers Inc..

Morris, P. 1966. A Field Guide to Shells. Cambridge: Riverside Press.

Tucker, R. 1986. Seashells of North America: A Guide to Field Identification. New York: Western Publishing Company, Golden Press.