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The short answer is that abalone are sea snails valued as a seafood delicacy. The worldwide demand for abalone is great enough that commercial fisheries world-wide continuously struggle to manage their local abalone populations and their long term viability. Northern California is unique in that there has been a moratorium on commercial harvesting in effect for more than 50 years. The result is the densest population of abalone in the world that is legally open only to recreational harvesters. Coupled with the fact that the predominate species in northern California, the Red Abalone, happens to be the lagest of abalone and it's easy to understand the legendary reputation of northern California's fishery.
The term "abalone" originated in California and is the most widely recognized common name in use world-wide. Other names for abalone that are recognized in specific localities include:
pauas (New Zealand)
perlemoens
(South Africa)
ormers (British Channel Islands)
awabi
(Japan)
mutton-fish (Australia)
silieux (France)
jeon-bok (Korea)
orejas de mar (Mexico)
Other names I've encountered (but can't locate geographically), include ormeaux, zee-oor, seeohren, orecchia marina, orelhas, and tokobushi.
In terms of taxonomical classifications, abalone are members of the Mollusca phylum classed as Gastropoda and assigned to the family Haliotidae and genus Haliotis. What all that boils down to is that abalone are distantly related to clams, scallops, octopus, and squid with closer ties still to sea slugs and garden snails (yum...). Like garden snails, they have one shell that has a distinct spiral structure. This spiral shell is flattened and elongated in shape in abalone. It's the shape and look of an empty shell that suggests the "sea ears" genus name (Haliotis) given to abalone. The shell is prized for its iridescent inner layer that is more commonly known as "mother-of-pearl". Aside from its shell, the major anatomical components of an abalone include the characteristically large foot of a gastropod, the epipodium and its associated sensory organs, the mantle that is a defining characteristic for mollusks,and a disportionately large gonad.
The foot is shaped like a flatten mushroom turned upside down. The stem connects to the inside of the shell while the rest of the foot fills the entire opening. The result is a muscular foot with a proportionally large surface area. Abalone prefer rocky substrates in locations that can be subject to a lot of surge and wave action. The foot is used to generate the suction power needed for clamping to rocky surfaces. The outer edge of the foot is what is referred to as the epipodium. Bearing short tentacles, the is an extension of the foot and serves as a sensory organ. The characteristics of the epipodium are the most reliable indicators in determining the abalone species.
At the thin edge of an abalone shell is where you'll find the abalone's head (with eyes on eye stalks), a mouth, and a pair of long tentacles. The internal organs of an abalone are arranged under the shell and around the column connecting the foot to the shell. The largest organ is crescent or comma shaped and approximately half the length of the animal. This is a combined gonad/digestive system and its color can tell you the sex of the animal: a green or grey gonad indicates the more common female while a cream colored gonad identifies the males (it's within this organ that abalone pearls can sometimes be found).
The mantle is a thin, tough membrane that secures the internal organs within the protective shell while separating them from the external environment. At the same time, it's the mantle that creates the shell of the abalone: continuous mucus secretions by the mantle lay down layer upon layer of calcium carbonate and, in the process, slowly build the shell in thickness and overall size.
Three species of abalone can be found in the waters off northern California with the red abalone (Haliotis rufenscens) being the most common of them. Red abalone can be recognized by its black tentacles, black area around the foot, and 3 to 4 open pores that are slightly elevated above the outer surface of the shell. Red abalone have a smooth epipodium, scalloped along the edge, that is usually black in color. It is fairly common, though, to encounter individual red abalone with a vertically banded epipodium colored in grays and creams (almost as common are the erroneous rumors that these banded examples are red and green abalone cross breeds). Red abalone have the distinction of being the largest species in the world. The shell of an adult red abalone averages 6" to 8" in diameter with 9" being fairly common and trophy hunters looking for examples larger than 10" in diameter (the general store at Stewarts Point has an impressive display of trophy sized abalone worth a stop to see). The world record for this species is an astounding 12 1/3".
Also fairly common in northern California waters is the flat abalone (Haliotis walallensis). These guys like deeper water and, as a result, will most often been seen while on SCUBA. At first glance, they can be easily mistaken as juvenile red abalone but, on closer examination, you'll find yourself wondering. The most distinctive difference between the two species is that the flat abalone has a lacy epipodium that is a mottled yellow or green in color. Knowing that difference, flat abalone can be easily distinguished in good lighting. Other telltale indications are their small size (usually under 4") and the fact that they are often out in the open on a bare rock surface.
The third species found in northern California is the black abalone (Haliotis cracherodii) and it is exceedingly rare. A few examples have been discovered near Gualala in one very small area. The shell of a black abalone is either black or very dark blue with 5 - 9 pores that are flush with the shell surface. The epipodium and tentacles are black and smooth. Should you encounter an example, leave it alone. At the time of this writing, there is a total ban on harvesting of black abalone. Even if a ban is not in effect, the rarity of Black Abalone off northern California combined with its reputation as being exceptionally tough to chew (which says something for an abalone) suggests simply leaving it alone.
An excellent source for additional scientific information on abalone can be found at the University of California's CaliSphere web page on California Abalones.
Last Modified: August 12, 2006
