Although there are additional species, the primary species in Southern California waters are the White, Red, Pink, Green, and Black Abalone. Whites, which at one time were common, are currently on the Federal endangered species list. They are generally found in depths greater than 70 to 80 feet. Reds, the species most closely associated with commercial fisheries of abalone, are typically found in shallower water than Whites, but seem to prefer the colder waters north from Point Conception to the Pacific Northwest. Two shallow water species which prefer warmer temperatures below Point Conception, Pinks and Greens, are well familiar to Southern California scuba divers who hunted abs prior to the current moratorium. Blacks are a shallow sub-tidal and inter-tidal species which used to be very common, but has disappeared dramatically from Southern California waters and tide pools.
Although all species of abalone were affected, Blacks were hit the hardest by Withering Foot Syndrome during the 1990s. This condition, which is a bacterial infection, is fatal to abalone and was a contributing factor to the extreme decline in populations. The abalone still left are possibly resistant to the disease, and their progeny will hopefully be the recipients of some form of genetic immunity.
According to catch data available dating back to before World War I, the huge numbers of abalone being taken during the 1930s through the 1960s were dropping off precipitously starting in the 1970s. Withering Foot Syndrome in the 1980s and 1990s was like the “straw on the camel’s back,” in terms of decimating populations that were already dramatically reduced due to commercial fishing and sport diving.
The precipitous decline in abalone populations is in one sense simply a reversal of factors which lead to abnormally high populations in the 19th and 20th centuries. Sea otters used to range along the entire California coast, and they fed voraciously on abalone. Abalone were forced to hide way back in crevices during the day, in order to avoid becoming “otter lunch.” Otter pups were preyed upon by eagles, ospreys, and other large raptors, with some kind of equilibrium in effect over thousands of years. When hunting nearly wiped out the otter in the first part of the 19th century, abalone populations soared, creating a “Garden of Eden” for humans to plunder in the 20th century.
It is difficult at this point to determine how the average number of abalone during the long period of equilibrium would compare to current numbers. But the White abalone is now on the endangered species list, and it has historically been relatively protected from otters by its deep habitat. And, at least in some areas, there would seem to be an abnormal absence of abalone altogether.
Abalone are broadcast spawners, and it is believed the females may be stimulated to release eggs into the water by the presence of sperm from nearby males. The optimal distance between male and female abalone, in terms of the highest ratio of successful fertilizations, is believed to be within about three feet. Perhaps due in part to this key to successful reproduction (as well as the presence of favored food sources), many abalone tend to “aggregate” together in groups. Unfortunately, what is good for the highest ratio of successful fertilization is also good for abalone hunters (otter or human); where there is one abalone, there are likely to be numerous others in the immediate area. An entire breeding aggregation could be wiped out, or significantly reduced, by a single boat load of commercial or sport divers (or, for that matter, a family of otters) taking abalone for food.
It takes at least five to seven years for abalone to reach sexual maturity, so as adult populations have dropped dramatically in particular areas, in some cases there simply weren’t enough sexually mature abalone left “aggregated” to spawn in the most efficient and successful manner. The Abalone Restoration Project is therefore studying the feasibility of artificially aggregating abalone organisms that are present, but appear to be relatively widely disbursed, such as has been observed at San Clemente Island.
The Abalone Recovery Project has been farming White abalone, the progeny of 12 specimens retrieved from the Farnsworth Bank area off Catalina Island, and is preparing to institute planting of juvenile organisms by the end of 2003. Most of the abalone farms are breeding Reds, and no readily available source of Pink or Green abs is currently on the horizon for transplanting to the shallow sub-tidal areas of Southern California where they used to flourish. Catalina Conservancy Divers had begun transplanting juvenile abalone at Catalina Island in the early 1990s, but Withering Foot Syndrome, and an infestation of a parasitic South African worm (now believed under control), caused a moratorium on transplanting which interrupted that project. The White abalone transplanting being done by the DF&G Abalone Recovery Project is therefore the only affirmative restoration likely to be ongoing within the next year.
In the long term, it is expected that even with transplanting from farms, and a continued moratorium on taking of abalone, the recovery of populations in Southern California waters, to a level even a fraction of the mid-20th century, is likely to take decades. The picture is complicated by the possible continued further migration of sea otters, a Federally protected species, south of Point Conception. If they continue a return to the Channel Islands and coastal areas south toward Mexico, the long term fate of abalone populations will be very uncertain for a long time to come.