Red Abalone
Haliotis rufescens

 

Physical Description

  • The red abalone’s shell length can reach a maximum of 12 inches.
  • The shell is large, thick, and dome-shaped. It is usually a brick red color externally, typically with algae growing on it.
  • Typically the shell has three or four raised oval holes (called respiratory pores), that are used for breathing, excreting waste, and reproduction.
  • The shape of the shell is determined by the crevice or crack the abalone grew up in.
  • The shell interior is famously iridescent.
  • The body of the animal (the foot and the tentacles) is black, and the underside is yellowish.

Range

  • Sunset Bay, Oregon to Baja California, Mexico.

Habitat

  • Live in rocky areas with kelp.
  • Found at subtidal depths to about 180 feet.

Reproduction

  • Usually reach maturity at 5 inches, females may reach maturity as small as 1.5 inches and males as small as 3.3 inches.
  • Reproduce by broadcast spawning, where release sperm and eggs into the water.
  • A young female just releases a few thousand eggs, a large adult can release up to 6 million eggs.
  • In Northern California spawning is from April to July, in Southern California it is year-round.
  • When one abalone starts to spawn, it usually triggers others to start in the area.

Diet

  • Adults feed on the kelp species that grow in their home range, including giant kelp, feather boa kelp, and bull kelp.
  • Juveniles eat coralline algae, bacteria, and diatoms.

Predators

  • Sea otters and humans.
  • Humans have been harvesting red abalone for approximately 12,000 years.

Interesting Facts

  • It is the largest species of abalone in the world.
  • It is the only species of abalone still legally harvested in California, and only by recreational divers and rock pickers, and only north of San Francisco Bay. 
  • Their population has mainly declined due to overfishing and withering syndrome.
  • Abalone were eaten by native people along California’s coasts for thousands of years, and abalones shells are often found in large piles called middens at their settlement sites.

Sources: UC Santa Cruz; Aquarium of the Pacific; Evolution, distribution and systematics of Haliotidae, p. 3–18; World Register of Marine Species

Photo: Dave Rudie

NOAA’s Southwest Fisheries Science Center here in La Jolla is researching abalone and how to help them recover.