Red Abalone

Posted on July 24, 2015 Updated on July 24, 2015

Red Abalone Shell

From April 1 through November with a month long break in July, the harvesting of Abalones is popular with locals and tourist alike. The search for abalone ranges from friendly foray to full scale abalone obsession for California divers.

The prized abalone is of course the Red Abalone. The classification in the animal kingdom, abalone belong to the phylum Mollusca, a group which includes clams, scallops, sea slugs, octopuses and squids.

Anatomy: The abalone shell is prized because of their inner, iridescent layer. The outside of the shell has a row of respiratory pores. The musculer foot has a strong suction power permitting the abalone to hold tightly to rocky surfaces. A column of shell muscle attaches the body to its shell. There is a mantle and epipodium that circles the foot which is a sensory structure and extension of the foot which bears tentacles.

The internal organs are arranged around the foot and under the shell. The crescent shaped gonad, is gray or green in females and creamed colored in males. It extends around the side opposite the pores and to the rear of the abalone. The abalone has a pair of eyes, a mouth and an enlarged pair of tentacles. Inside the mouth is a long, file-like tongue called the radula, which scrapes its food matter to a size that can be ingested.

The gill chamber is next to the mouth and under the respitory pores. The water is drawn from under the edge of the shell, and then flows over the gills and out the pores. Waste and reproductive products are carried out in the flow of water. Since an abalone has no obvious brain structure, the abalone is considered to be a primitive animal. However, it does have a heart on its left side and blood flows through the arteries, sinuses and veins, assisted by the surrounding tissues and muscles.

Reproduction: The sexes are seperate and can be distinguised in individuals as small as one inch when the gonads begin to develop. An 8 inch abalone may spawn 11 million eggs or more, while a male abalone can release trillions of sperm. The presence of eggs and sperm in the water may stimulate other abalone to spawn, thus increasing the chances of fertilization. When eggs hatch they are a microscopic, free living larvae. It drifts with the currents for about a week, then the abalone larvae settles to the bottom, and sheds its swimming hairs and begins to develop the adult shell form. The chance that an individual larvae will survive to adulthood is very very low. Fortunately abalone and most mollusks are prolific spawners but the mortality still exceeds 99%.

Food: Abalone eat marine algae. The adults can feed on loose peices drifting with the current. Abalones eat giant kelp, bull kelp, feather boa kelp and elk kelp are preferred, although most others may be eaten at other times. Abalone tend to stay in one location waiting for food to drift by. They can move daily, seasonally or when food becomes scarce for a long period. Juvenille abalone graze on coralline algae that grows on the rocks and diatoms and bacterial films. As they grow they increasingly rely on drifting algae.

Withering Syndrome: is a terminal phase of a bacterial infection. “Rickettsia-like Procaryote” (RLP) is a newly found bacterium. The RLP bacterium infects the digestive system of the abalone. When RLP sufficiently develops, the abalone slowly starves to death. Once abalone exhibit the visual signs of Withering Syndrome, they will expire within a few months.

In 1998, California Department of Fish & Game (CDFG) realized that they had been authorizing the transfer of RLP infected abalone from southern California to northern California aquaculture facilities. Inspection of abalone from California’s aquaculture facilities quickly confirmed RLP infested facilities from southern California up to the Oregon border. In August 1998, CDFG banned shipments of RLP infected abalone seed from southern California to facilities north of San Francisco.

What was an RLP free nursery facility in Crescent City has been infected with RLP and was pumping untreated effluent into the ocean. According to a letter dated February 8, 2000, circulated by the Director of the CDFG, the ban on shipment of RLP infected abalone north of San Francisco was re-imposed following the shipment of these 6400 RLP infected abalone.

Ground Zero: Northern California’s remaining abalone represents about 17% of the state’s original abundant resource. RLP has been found at Van Damme State Park. The Park is in the heart of the recreational abalone diving Mecca in Northern California. One of sixty abalone tested from Van Damme State Park has been found infected with RLP. The presence of RLP at Van Damme is believed to be the result of a single out-planting five years ago. Van Damme could be ground zero for a northern Withering Syndrome epidemic, which would totally decimate the northern California red abalone. The future survival of California’s last remaining abalone may well rest on sciences’s purging the RLP infestation, and on the public’s resolve to save this valuable resource.