White Abalone (Haliotis sorenseni)
Status | Taxonomy | Species Description | Habitat | Distribution |
Population Trends | Threats | Conservation Efforts | Regulatory Overview |
Key Documents | More Info
Status
ESA Endangered - throughout its range (California and Mexico)
Taxonomy
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Archaeogastropoda
Family: Haliotidae
Genus: Haliotis
Species: sorenseni
Species Description
The white abalone is an herbivorous, marine, rocky benthic, broadcast spawning gastropod.
The shell is oval-shaped, very thin and deep. The bottom of its foot is orange, and the epipodium (a sensory structure and extension of the foot that bears tentacles) is a mottled orange tan. White abalone can grow to about 10 inches long (25 cm), but are usually 5-8 inches (13-20 cm).
As broadcast spawning gastropods, white abalone reproduce by releasing their eggs and sperm into the surrounding water. If fertilized, the eggs hatch after only one day, but high concentrations of sperm are required in order for an egg to be fertilized. Therefore, aggregations of adult male and female abalone are necessary for successful fertilization to occur.
Like many gastropods, white abalone have a complex life cycle involving larval stages. Fertilized eggs hatch into larvae; these larvae eventually metamorphose into the adult form and settle from the plankton to a hard substrate.
Habitat
White abalone are found in open low and high relief rock or boulder habitat that is interspersed with sand channels. Sand channels may be important for the movement and concentration of drift macroalgae, such as Laminaria farlowii, Agarum fimbriatum, and a variety of red algae, upon which white abalone are known to feed. White abalone are reported to be most abundant between 25-30 m (80-100 ft) depth, making them the deepest occurring abalone species in California.
Distribution
The historic range of white abalone extended from Point Conception, California, USA, to Punta Abreojos, Baja California, Mexico.
In the northern part of the California range, white abalone were reported as being more common along the mainland coast. However, in the middle portion of the California range, they were noted to occur more frequently at the offshore islands (especially San Clemente and Santa Catalina Islands). At the southern end of the range in Baja California, Mexico, white abalone were reported to occur more commonly along the mainland coast, but were also found at a number of islands including Isla Cedros and Isla Natividad.
It remains unknown whether this distribution pattern resulted because of lack of suitable habitat along the mainland coast in the middle portion of the range, or was due to overfishing in these more accessible mainland regions.
Since the mid-1990s, extremely low numbers of isolated survivors have been identified along the mainland coast in Santa Barbara County and at some of the offshore islands and banks in the middle portion of the range, indicating the current range of white abalone in California may be similar to what it was historically.
No recent information on current range is available for Baja California. The white abalone population in Mexico is thought to be depleted based on commercial fishery data, but the status of the species in Mexico remains largely unknown.
Population Trends
Surveys conducted in Southern California show that at least a 99% reduction in white abalone density has occurred between the 1970s and today. Once occurring in numbers as high as 1 per square meter of suitable habitat, recent surveys show that densities average 1 per hectare (10,000 square meters) in the Channel Islands off southern California. White abalone are frequently found alone, and thus have little chance for successful fertilization.
 Video: Race to Save the White Abalone NMFS Southwest Fisheries Science Center |
Threats
The most significant threat to white abalone is related to the long-term effects that overfishing has had on the species. Due to their life history characteristics as long-lived, slow moving bottom dwellers with external fertilization and variable recruitment rates, abalone are particularly susceptible to the pressures imposed by intense commercial and recreational fishing.
A short-lived commercial fishery began in the early 1970s, peaked mid-decade, and collapsed in the 1980s. The fishery was historically managed using size limits and seasons, but such methods failed because they did not account for density dependent reproduction and assumed regular successful settlement of the larvae. Overfishing reduced white abalone densities to such low levels that males and females were too far apart from one another to successfully reproduce.
The low densities of the animals in nature, resulting in repeated reproductive failure, make it unlikely that the species will recover on its own. Without human intervention, it was estimated that the remaining white abalone in the wild would disappear by 2010. Because current populations are only small fractions of former numbers, recovery of the species will be complicated by genetic drift, founder effects, and a loss of genetic diversity.
Abalones are also vulnerable to various bacterial and parasitic infections.
Conservation Efforts
Aside from NOAA's National Marine Fisheries Service (NMFS)' proactive conservation activities, there are numerous groups, both in the United States and internationally, doing work to gather more information and build programs to help save the white abalone. Some of these active groups include the Channel Islands National Park 
and the California Department of Fish and Game .
These groups assess abalone populations and conduct research into the basic biology, disease pathology, and ecology of abalones. A consortium of scientists, fishermen, conservation organizations, universities, federal and state agencies, and mariculturists in private enterprise has been formed to develop and execute a plan to restore white abalone populations.
The White Abalone Restoration Consortium developed a four-step restoration plan:
- locate surviving white abalone by surveying historical habitat;
- collect brood stock;
- breed and rear a new generation of juveniles and ultimately, brood stock; and
- reestablish refugia of self-sustaining brood stocks in the wild.
Federal, state, and private funds have recently supported white abalone submersible surveys and the establishment of an aquaculture facility specifically designed to breed white abalone in captivity and rear offspring to adulthood for outplanting to the wild.
Regulatory Overview
Prior to the listing of white abalone under the ESA, the State of California closed the white abalone fishery in 1996 and subsequently closed all abalone fisheries in central and southern California in 1997. Measures taken during the late 1970s and 1980s to regulate the abalone fishery included prohibiting fishing during a portion of the spawning season, bag limits for recreational fishermen, limited entry, and permit fees.
The white abalone was designated as a candidate for listing under the Endangered Species Act (ESA) in 1997 for the California region south to Baja California, Mexico. In August 1998, NMFS initiated a review of the biological status of white abalone.
A petition from the Center for Biological Diversity to list the white abalone as endangered and designate critical habitat was received on April 29, 1999, and a subsequent petition from the Marine Conservation Biology Institute was received on May 15, 1999. A finding [pdf] that the petitioned action was warranted was published in the Federal Register on September 24, 1999. NMFS completed its status review [pdf] of the species in March of 2000.
NMFS published a proposed rule [pdf] to list the white abalone as endangered on May 5, 2000. NMFS published a final rule [pdf] listing the white abalone as an endangered species on May 29, 2001. The white abalone is the only mollusk listed under the ESA by NMFS.
Key Documents
(All documents are in PDF format.)
| Title | Federal Register | Date |
|---|---|---|
| ESA Listing Rule | 66 FR 29046 | 05/29/2001 |
| Draft Recovery Plan | 71 FR 64512 | 11/02/2006 |
| Critical Habitat Designation Not Prudent | 66 FR 29046 | 05/29/2001 |
| Status Review | n/a | 05/20/2000 |
