Population Monitoring of the Endangered White Abalone

The white abalone (Haliotis sorenseni, above) was listed as an endangered species effective June 28, 2001.

An important issue of concern for southern California is that the white abalone may be close to biological extinction. The National Marine Fisheries Service (NMFS) Office of Protected Species received a petition to list white abalone as an endangered species on an emergency basis and designate critical habitat under the Endangered Species Act (ESA). The short, intense fishery for white abalone lasted 9 years. Although the fishery is now closed, the market price ($85.00/lb) is a strong incentive for poaching. According to a status review by Alistair Hobday and Mia Tegner1, an estimate of the total abundance of white abalone in California and Mexico is around 1,600 animals. This is less than 0.1% of the estimated pre-exploitation population size. This reduction has occurred in the last 30 years.

1Hobday, A and Tegner, M. (2000) Status Review of White Abalone, Haliotis sorenseni, throughout its range in California and Mexico. 90 pp.


White abalone was added to the NMFS list of candidate species on July 14, 1997 (62 FR 37560). NMFS initiated a status review of the species in August 1998. A petition from the Center for Biological Diversity was received April 29, 1999, and a second petition from the Marine Conservation Biology Institute was received on May 15, 1999. A 90-day finding that the petitioned action may be warranted was published on September 24, 1999 (64 FR 21725). Based on the preliminary status review by Hobday and Tegner (1999), NMFS's Southwest Regional Office determined a necessary listing under the ESA for this species. The status review concluded that the white abalone was in danger of extinction because densities found at the Northern Channel Islands (Davis et al. 1997) were below the threshold of successful fertilization.

New estimates of white abalone abundance

With the aid of scientists from the Seafloor Mapping Lab at California State University, Monterey Bay (CSUMB) scientists at the Southwest Fisheries Science Center (SWFSC) used the latest technology to map and quantify white abalone habitat. Using a remotely operated underwater vehicle (ROV) , members of the Benthic Resources (ROV) Program at the SWFSC then surveyed white abalone abundance at Tanner Bank, Cortes Bank, and San Clemente Island to obtain the latest estimates of the status of white abalone2. The amount of available habitat was determined to be much greater than previously thought, so total numbers of white abalone are likely higher than previously thought. Although this piece of information would seem to provide hope for recovery, actual densities (20 white abalone/ha, at best) are not high enough to allow for reproduction. At present densities the probability of reproduction in the wild is believed to be close to zero because a male and female must be within a few meters to spawn successfully.

2Butler JL, Neuman M, Pinkard D, Kvitek R and Cochrane G (2006) The use of multibeam sonar mapping techniques to refine population estimates of the endangered white abalone (Haliotis sorenseni). Fish.Bull. 104:521–532

Ongoing and Future Research

So what is the fate of the endangered white abalone? As abundance estimates are lower and the probability of successful reproduction in the wild is slim, it seems that other measures must be initiated to increase the chance of survival of this species. Scientists at the SWFSC will continue to survey wild populations to monitor their status, but the next logical step is to raise white abalone in captivity. If a captive breeding program proves successful there may bean opportunity to augment wild populations. Many issues arise when considering the introduction of captive-bred animals into the wild, but for white abalone this may be our only hope.

The National Park Service and others produced an 8 minute video entitled Race to Save the White Abalone. For more information, contact Channel Islands National Park, 1901 Spinnaker Drive, Ventura, CA 93001. Streaming video versions are available by clicking on the link above.

One of eight abalone species in California, white abalone is critically endangered.  Find out what scientists are doing to bring back this iconic sea snail in Southern California.