Temporal range: 70 –0Ma
|Red abalone, Haliotis rufescens|
Red abalone is the largest, 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.
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 soft parts
Below the edge of the shell, the black epipodium and tentacles can be seen. The underside of the foot is yellowish white in color.
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.
History of 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. The Chumash and other California Indians also used red abalone shells to make a variety of fishhooks, beads, ornaments, and other artifacts.
History of diseases
In the 1980s, an employee of the California Department of Fish & Game, who was privately farming abalone in California, imported some Haliotis midae abalone from South Africa, and failed to quarantine the individuals of this foreign species. This introduced a parasite of the shell, a species of sabellid polychaete worm Terebrassabella heterouncinata. This species escaped into the ocean at Cayucos, California, where an abalone farm had long been established. It was also introduced into the wild at many other sites. Fortunately, Scientists at the University of California, Santa Barbara, with the staff of the Abalone Farm, California Department of Fish and Game biologists, and teams of volunteers, many from the University of California, Santa Barbara and Cuesta College in San Luis Obispo were successful in eradicating the pest population.
Shortly after this, another disease of abalone (which proved to be devastating to wild populations as well as farmed abalone) appeared on Santa Cruz Island, and was subsequently spread to the other Channel Islands, and from there to the mainland of California. This disease was known as "Withering Syndrome" because the abalones starved to death even when food was plentiful. This was because the parasite infested the digestive tract of the abalones and prevented digestion and absorption of kelp, the abalone's primary food source.
Coincidentally, Withering Syndrome first appeared a few years after H. midae were imported into California, near Smugglers Cove on Santa Cruz Island, adjacent to the area where seaweed was harvested for an abalone farm at Port Hueneme, California. Withering Syndrome was found to spread from there to the other islands.
Withering Syndrome was accidentally introduced to Northern California not only by abalone farmers but also by the 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.
At first the pathologist for the California Dept. of Fish & Game claimed that the disease which caused Withering Syndrome was caused by parasites of the abalone's nephridia, but scientists 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 black abalone and white abalone as Endangered Species. The U.S. Fish & Wildlife will begin a program to reintroduce abalone. Withering Syndrome has struck all the abalone farms in California at one time or another, and has also 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 now not common in Northern California, whereas they were once numerous in Southern California, and black abalone may become extinct in the near future.
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 the abalone eat fast-growing kelp, which regrows quickly upon harvest.
In 1916, documentation of the modern California fishery began. 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. Prior to this point, the fishery seemed sustainable with the increase in species that could be fished and the expansion of fishing areas. 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.
In Northern California, however, commercial fishing was only legal for three years during World War II. 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 an annual legal limit of 18 abalone per person and 9 per county.
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- Red Abalone University of California, Santa Barbara
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- "Marine Protected Areas in Central California and Potential Benefits to Selected Species: Abalone". California Department of Fish and Game. Retrieved 2012-05-07.
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- Gastropods.com: Haliotis (Haliotis) rufescens
- California Fish and Game Abalone Information
- Abalone Recovery and Management Plan
- Calif. aquafarmers cash in on demand for abalone
- Abalone Informational Brochure: You Hold Their Future In Your Hands
- "The Abalone Song," radio episode featuring lyrics by George Sterling and others from California Legacy Project.
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