Outer surface of shell of red abalone, viewed from the anterior end. The coin is 23 mm (almost 1 inch) across

The red abalone, Haliotis rufescens, is a species of very large edible sea snail, a marine gastropod mollusk in the family Haliotidae, the abalones, ormer shells or paua.

Red abalone is the largest,^[1] and most common abalone found in the northern part of the state of California, and it is the only species of abalone still legally harvested (on a restricted basis) there.

Distribution

The red abalone can be found along the west coast of North America, from Oregon to Baja California, and Mexico.

Habitat

Red abalone live in rocky areas with kelp. They primarily feed on bull kelp and giant kelp. They are found from the intertidal zone to water of 100 foot depth.

Shell description

The red abalone's shell length can reach a maximum of 31 cm, making it the largest species of abalone in the world.

The shell is large, thick, and dome-shaped. It is usually a brick red color externally. Typically the shell has three or four oval holes or respiratory pores. These holes collectively make up what is known as the selenizone which form as the shell grows. The inside of the shell is strongly iridescent and has a large central muscle.

External anatomy of the soft parts

Below the shell the black epipodium and tentacles can be seen. The underside of the foot is a yellowish white in color.

Diseases

Red abalones are subject to a chronic, progressive and lethal disease: the Withering Syndrome or abalone wasting disease. This disease has had a poorly understood impact on the species overall, but populations still seem low.

Human use

Red abalone has been used since prehistoric times—red abalone shells have been found in Channel Island archaeological sites dated to nearly 12,000 years old. Red abalone middens—refuse deposits where red abalone shells are a major constituent—are abundant in archaeological sites of the Northern Channel Islands dated between about 7500 and 3500 years ago. The Native American Chumash peoples also harvested this species along the Central California coast in the pre-contact era.^[2] The Chumash and other California Indians also used red abalone shells to make a variety of fishhooks, beads, ornaments, and other artifacts.

Diseases of Abalone in California

ventral view of the shell of Red abalone.

In the 1980s an employee of the California Department of Fish & Game privately farming abalone in California imported abalone, H midae, from South Africa and failed to quarantine the foreign species. This introduced a parasite of the shell called sabellid worms, known as Terrabrassabella heterouncinata which escaped into the ocean at Cuyucos, Ca where an abalone farm had long been established and was introduced into the wild at many other sites but became established in wild populations only at Cuyucos. Shortly after another disease of abalone which proved to be devastating to wild populations as well as farmed abalone appeared on Santa Cruz Is. and was subsequently spread to the other Channel Islands and there to the mainland of California. This disease was known as Withering Syndrome because the abalones starved to death even when food was plentiful because the parasite infested the digestive tract and prevented digestion and absorption of kelp, the abalone's primary food source. Coincidently, the disease first appeared a few years after H midae were imported into California near Smugglers Cove on Santa Cruz Is. adjacent to the area where an abalone farm at Port Hueneme, Ca. harvested the seaweed used at their farm, and was found to spread from there to the other islands.^[3] Withering Syndrome was introduced to Northern California by abalone farmers and by California Dept. of Fish & Game employees who planted abalone infected by Withering Syndrome into wild places North of Point Conception where the disease had not been successful at spreading naturally due to the colder waters North of Pt. Conception ^[4]

At first the pathologist for the CA Dept. of Fish & Game claimed that the disease which caused Withering Syndrome was caused by parasites of the abalone's nephridia, but were unable to prove this using established protocols for transmission and infection. Withering Syndrome, over fishing, and habitat loss has been responsible for the listing of abalone, black abalone and white abalone, as an Endangered Species and the U.S. Fish & Wildlife will begin a program to reintroduce abalone but the disease Withering Syndrome has struck all the abalone farms at one time or another in California and has been spread to Iceland and Ireland by the export of infected California Red Abalone, H rufescens. Abalone exported to Israel before H midae were imported to California were not reported to have Withering Syndrome. Black abalone, red abalone, green abalone, white abalone, and two other species of abalone have virtually disappeared from Southern California because of Withering Syndrome while the Northern California populations have remained more numerous because of the colder waters. Green abalone and white abalone are not common to Northern California, whereas they were once numerous in Southern California, and black abalone may become extinct in the near future.

Farming

Because of the destruction of most wild populations of abalone, abalone farming has become a booming business. Unlike some aquaculture, growing abalone has little environmental impact because they eat fast-growing kelp, which regrows quickly upon harvest.

Wild harvest

In 1916, documentation of the modern California fishery began.^[5] Fishing for these abalone populations peaked in the 1950s and 1960s but was followed by a decline in all five species (red, green, pink, white, and black abalones) of the fishery.^[5] Prior to this point, the fishery seemed sustainable with the increase in species that could be fished and the expansion of fishing areas.^[6] The California Fish and Game Commission ended fishing for abalone in 1997 though additional factors that were involved in the depletion of the fisheries included disease, recovery of the sea otter population.^[5]

In Northern California, however, commercial fishing was only legal for three years during World War II.^[7] As a result, a recreational fishery still exists in northern California. Because scuba diving to harvest abalone is banned, the fishery consists of shore pickers searching the rocks at low tide, and free divers using breath-hold diving to search for them. This essentially creates a reserve for the abalone in the water below thirty feet, where few divers are skilled enough to go. Currently, the minimum legal size is 7 inches, and three specimens may be taken per day. There is also a yearly legal limit of 24 abalone per person.

References