Abalones

Contributed by Dr. Bonnie Becker

Where found:  Under rocks and crevices in the low intertidal (although now they are rarely or more accurately never found in the intertidal. Historically, Green and Black Abalone were found in our tidepools in abundance. Now greens are extremely rare, and no Black Abalone has been reported in Cabrillo National Monument since monitoring began in 1990).

Interesting facts:

• Little needs to be said about the incredible commercial value of this limpet-like snail, for its shell and especially for its meat. It is now possible to raise an abalone to 1-2 years in a hatchery and transplant them to the wild.
• Once common in California waters, they are virtually gone from the intertidal. If a visitor or volunteer finds one, please remember where it is and notify a ranger, but please do not tell the public!
• The food of the red abalone influences the color of its shell. Since red algae are being eaten much of the time, the general hue of the shell is red or pinkish. Distinct bands in the shell reflect changes in diet.

Adaptations:  Besides man, abalones have a number of predators, including crabs, octopuses, fishes, sea otters, and sea stars. Abalones tend to live wedged in between rocks, held to the substrate by a large muscular foot. Once they have clamped down on the rock, it is impossible to remove them without a pinch bar. Although they tend to stay relatively still, they are capable of movement-especially when being attacked by a sea star.

Food:  Strictly vegetarian. Younger animals eat microalgae, older animals eat larger plants. They use their foot to capture loose plants as they drift by.

Life history:  Growth is highly variable. Red abalone reach 10 cm in about 3-6 years. Growth slows with age, so animals who are close to full size can be well over 20 years old. Maturity is reached within 4 years and fecundity is high (a few thousand the first season, millions in older individuals). Fertilization is external, with white sperm and green-gray eggs being released into the water. This can happen throughout the year but most often happens in the spring and summer.

Classification:
Phylum: Mollusca (Soft-bodied animals with external shells or modified internal shells)
Class:     Gastropoda (Snails, Limpets, Sea hares, Nudibranchs, etc.)
Subclass: Prosobranchia
Order:     Archaeogastropoda (Limpets, Abalones, Turbans)
Superfamily: Pleurotomariacea
Family:         HaliotidaeGenus and Species: There are 8 species of abalone on the Pacific Coast, distinguishable from the shapes and colors of their shells, and in some cases from the number of holes in the shell.

Last revised 24-Nov-17