The black abalone occurs from Pt. Arena (northern California) to Cabo San Lucas (Baja California Sur), but this species is rare north of San Francisco and south of Punta Eugenia (Figure 1).^1,2 Black abalone appear to tolerate water temperatures ranging between 7-24°C (45-75°F).³

Black abalone occur throughout the longitudinal extent of the MBNMS.

Abalone live in areas with rocky reef because they require hard substrate for attachment. Black abalone live on coastal rocks from the high intertidal zone out to 6 m depth, though they are most abundant intertidally¹. Black abalone are often found in a clumped distribution in preferred microhabitats. Smaller individuals (<90 mm) tend to stay within the protective confines of crevices, under rocks, and in boulder fields.^4,5,6 This cryptic behavior probably helps smaller individuals hide from predators such as sea stars, crabs, and shorebirds. Individuals larger than 90 mm often occupy more exposed rocks and surge channels in areas where sea otters are absent, but are restricted to cracks and crevices where sea otters are present.^1,4,7,8 Black abalone larvae settle into areas characterized by bare rock and crustose coralline red algae.⁹ In areas where the density of large adult black abalone (or other grazers) has declined drastically, formerly suitable settlement habitat can become overgrown with encrusting sessile invertebrates (e.g. tube worms and tube snails) and may prevent settlement of black abalone larvae.^10,11

Based on information gathered from aerial surveys of coastal habitat types and field surveys of black abalone in central California, we estimated that approximately 6-12% of the coastline in the MBNMS is suitable habitat for black abalone.^2,12

On October 27, 2011 NOAA's Fisheries Service filed with the Federal Register a final rule⁴³ that identifies black abalone critical habitat along the California coast. In January 2009⁴², black abalone was listed as endangered under the Endangered Species Act, and the Act requires critical habitat be designated, to the maximum extent prudent and determinable, whenever a species is listed for protection. Once areas are designated as critical habitat, federal projects or permits and projects with federal funding are required to ensure their actions do not adversely modify the animal's habitat. Designating critical habitat does not affect citizens engaged in activities on private land that do not involve a federal agency.

A tagging study at Diablo Cove (San Luis Obispo Co.) found that activity patterns of black abalone tended to be size-related.⁴ Small abalone (< 40 mm) moved about actively, but only within crevices. Intermediate-sized abalone (55-75 mm) tended to be the most active, although much of this movement occurred within the shelter of cracks and crevices. This study did not find evidence of diel movement patterns or homing behavior. However, intermediate-sized black abalone appeared to prefer certain locations as stopping-over points; intermediate-sized abalone were almost always present at these locations, but not usually the same individuals. Large abalone (>100 mm) were sedentary with some individuals remaining in the same spot for up to 12 years. Large black abalone were often seen in very open, exposed locations.

Like many sedentary marine invertebrates, the black abalone relies on planktonic larvae for dispersal. However, the relatively short larval period (4-15 days) for this species may limit dispersal distance.¹³ Analysis of the genetic structure of black abalone populations on the central California coast indicates that these populations are composed predominantly of individuals that were spawned locally.¹⁴ Patterns in recruitment of juveniles to central coastal populations provide additional evidence that black abalone larvae do not tend to travel very far along the coast and, therefore, populations are relatively closed.¹⁵

Same as above

Historically, sea otters and Native Americans were two primary sources of mortality for large black abalone. However, over-hunting of sea otters and the elimination or relocation of native-American coastal settlements in the 1700s and 1800s allowed black abalone populations to increase dramatically.^3,16 Harvesting of abalone from dense intertidal beds in central and southern California and Baja California began in the mid-1800s by Chinese immigrants.^3,17 By 1879, annual catches exceeded 4 million pounds.³ However, this source of mortality was eliminated in the early 1900s by ordinances preventing commercial harvesting of abalone in waters less than 20 feet deep.³ Again, black abalone populations began to expand, reaching densities of over 60 abalone/m² in some locations in southern California.¹⁰

After protection in the early 1900s, the remnant sea otter population in central California began to slowly expand its size and range. The reestablishment of the sea otter population along the central California coast in the early 1960s coincided with a substantial reduction in density of abalone in that region.⁷ As of 2004, approximately 2,490 sea otters occur between Half Moon Bay in the north and Gaviota in the south.¹⁸ Abalone stocks within the sea otters established range are too low for profitable commercial fisheries.⁶ Though sea otter predation can maintain black abalone populations at low abundance, some individuals find refuge from predation in deep crevices and exposed intertidal areas.^7,19

Harvest of black abalone resumed in 1968. Most of the harvest occurred in southern California and the Channel Islands, which was outside the range of the sea otter. Annual landings peaked in 1973 in the commercial fishery and 1981 in the recreational fishery.¹³ Rogers-Bennett and colleagues used landings data from the commercial and recreational fishery to estimate the baseline abundance of black abalone in California to be 3.54 million animals.¹⁷ However, this estimate was made using only data from southern California in the 1970s and 1980s, where population densities had not been depressed by sea otter predation. Therefore, this may be an over-estimate of the baseline population size given the re-establishment of sea otters in a large portion of the geographic range of the black abalone.

By the mid-1980's, due to over-harvesting along the southern California coast, black abalone were found primarily on offshore islands and inaccessible sections of the coast north of Santa Barbara. Then in the mid- and late-1980s, black abalone on the Channel Islands suffered massive local die-offs (generally >90% losses).^10,20,21 A fatal wasting disease called ‘withering syndrome’ (WS) was identified as the cause of these local die-offs (see “Threats” section below for more information about WS). WS was first noticed in 1985 at Santa Cruz and Anacapa Islands and by 1992 WS-related die-offs had occurred throughout the Channel Islands.^10,20 Prior to 1992, the only mainland site where a WS-related die-off had been observed was in Diablo Cove, the site of the discharge for PG&E’s Diablo Canyon Power Plant.²² Then a massive die-off began at a mainland site, Government Point, near Point Conception in 1992 (Figure 2).²³ Subsequent monitoring of sites along the central California coast detected a pattern of die-offs suggesting that withering syndrome was progressing northward up the coast, but not at a steady rate (Figure 2).^11,15,23 Mortalities from WS may have occurred along the mainland coast of southern California, but were not detected because of very low black abalone population sizes due to over-harvesting.¹⁵

Most black abalone populations in southern and central California that have experienced dramatic population declines (due to harvesting, WS or a combination of both) are experiencing very little or no recruitment of new individuals - even when recruitment is occurring in healthy populations only tens of kilometers away (Figure 2).^11,15,24 Miner and colleagues found almost no recruitment of juveniles at sites where adult density was less than one individual/m².¹⁰ Above this threshold density, recruitment levels varied considerably (even within sites) and were not related to adult density, suggesting that factors other than adult density (e.g. local current patterns) determined recruitment levels. Potential causes of low (or no) recruitment at sites with low adult density include: 1) local adult densities were too low for successful fertilization; 2) limited dispersal ability of larval abalone limited supply of larvae from healthy adjacent populations; 3) suitable larval settlement habitat was overgrown in the absence of adult abalone; and 4) newly recruited juvenile abalone were killed by WS before they could be observed and counted by researchers.¹¹ Currently, the extent to which each of these causes is negatively impacting recruitment levels is not known, but it appears that the recovery of local populations will be dependent on increasing the local density of adults.^11,15 CDFG estimated a minimum viable population size (size below which a population is at risk of recruitment failure) for all abalone species of 2000 abalone/ha or 0.2/m².¹³ This estimate was based on red abalone and may not accurately reflect the densities needed for successful fertilization and recruitment in black abalone populations.

A survey of black abalone populations at several sites in northern Baja California (between Punta Baja and the California border) in February 2005 found a different relationship between adult density and recruitment.²⁵ Recruits were observed at several sites where adult densities were not very high. Based on these observations, it appears that recruitment is occurring in Baja California populations at adult densities below those needed for successful recruitment in California populations.

Based on the timing of onset of WS-related mass mortality events, the WS pathogen appeared to have been moving north up the California coast since the mid-1990s (Figure 2).^15,23 Recently, the WS pathogen was positively identified in all black abalone populations that were sampled in the MBNMS.²⁶ Though all populations in the MBNMS have the pathogen, not all the populations show signs of WS. Abalone with WS were first observed near the Sanctuary’s southern boundary at Rancho Marino in 2002 and Piedras Blancas in 2003 (Figure 2 ).^2,11 Two signs of WS-related mass-mortality events - declining abundance of all size classes and little or no recruitment of juveniles - have been observed at these two sites since mid-2003. However, the rate of decline has been much slower at Rancho Marino and Piedras Blancas than was observed at sites further south, such as Boathouse and Cayucos, where catastrophic declines occurred over 12-18 months (Figure 2).^2,11,15

All remaining healthy populations of black abalone in California occur in the MBNMS. Though most black abalone populations in the MBNMS appear to be healthy, some black abalone with symptoms resembling WS were recently observed at four sites throughout the MBNMS; at San Simeon and Point Sierra Nevada (southern MBNMS sites) in 2004 and Carmel Point (central MBNMS site) and Pebble Beach (northern MBNMS site) in 2005 (Figure 2).² WS has not been confirmed at these sites and other causes of starvation, such as temporary burial or decreased food supply, can cause abalone to have a withered appearance. However, soon after the appearance of withered abalone at each site, a decrease in abundance was also observed. Continued monitoring is needed to determine if the recent decreases in abundance are due to WS, and if they signal the beginning of a declining trend. It is important to note that the emergence of WS at four sites scattered throughout the geographic range of the MBNMS would signal a significant change in the pattern of spread of this disease from a predictable northward expansion to a more random and unpredictable pattern.²

Withering syndrome: WS is caused by the bacteria Candidatus Xenohaliotis californiensis, which attacks the lining of the digestive track and obstructs the production of digestive enzymes.³¹ Abalone with WS cannot properly digest their food and appear to use the protein in the foot muscle as an energy source. External symptoms of WS include reduced body mass, atrophy of the foot muscle (Figure 3), inability to strongly adhere to rocks, and lethargy.^10,20 Abalone that are not strongly attached to rocks are easily dislodged and battered by waves or eaten by predators and scavengers. Abalone not eaten by predators presumably die of starvation. WS occurs in abalone of all sizes.^5,10 Experiments indicate that transmission of the bacteria does not require direct contact between infected and uninfected individuals, but rather transmission can occur via the water column.³² For reasons not yet well understood, some abalone can be exposed to WS without developing the disease. It is not known whether these individuals are resistant to the disease, and if so, if the resistance can be passed-down to offspring.³³

Elevated water temperature: Elevated water temperature increases the rate of mortality of black abalone with WS both in the laboratory and in the field.^5,21,22,34 The first mainland abalone population to experience a WS-related mass mortality event was located in Diablo Cove, the site of the thermal discharge for PG&E’s Diablo Canyon Power Plant.²² Thermal pollution, global warming, and other human-induced increases in water temperature would be expected to accelerate the rate of mortality in abalone populations with WS. Natural increases in water temperature also have been linked to increased rates of mortality. In central California massive die-offs of black abalone have occurred during El Niño and non-El Niño years, but the rate of mortality was found to be significantly faster during El Niño events (~24 months) compared to non-El Niño years (~41 months).¹⁵

Predation: Sea otters are a primary source of mortality to adult black abalone. Where sea otters occur, abalone are restricted to deep crevices and cryptic habitats inaccessible to sea otters.⁸ However, crowding in crevices may still allow black abalone to reach the elevated local densities necessary for successful reproduction. Other predators of black abalone include sea stars, fishes, octopus, and crabs.^1,35

Loss of habitat: Coastal development and pollution can remove or damage suitable habitat for abalone. Settlement habitat for larval abalone appears to be maintained by adult abalone and other grazers (such as sea urchins and limpets). In areas with reduced population sizes of grazers, many formerly suitable settlement habitats may be overgrown leading to declining recruitment rates.¹¹

Food limitation: Black abalone predominately eat bull kelp and giant kelp. El Niño events can cause mortality of large kelps and this decrease in food availability could stress abalone populations. Food limitation may be especially stressful in populations that are already suffering from disease or other threats.¹³ Red and purple sea urchins utilize the same food and living space as juvenile and adult black abalone.¹³ Increases in the size of urchin populations could lead to increased competition and suppress abalone growth and reproduction (but grazing by urchins may also help to maintain the crustose coralline habitat necessary for abalone recruitment). In the event of food limitation, sea urchins tend to outcompete abalone and can reduce algal resources to a level below that necessary to maintain abalone.¹³

Illegal take: The extent of illegal removal of abalone in central California for personal consumption or commercial sale is unknown.¹³ The accessibility of black abalone during low tides makes this species vulnerable to take by seaside visitors who are not aware of the legal protections for this species. In addition, abalone that are pried from rocks, and later replaced, often die if the animal is not given sufficient time to re-attach to the substrate or if the foot has been cut or injured (abalone blood does not clot).

Oil spill: Oil impacts are not well known, but black abalone mortality has been shown after an oil spill.³⁶

No threats are unique to the MBNMS

In 2004, the black abalone was added to the National Marine Fisheries Service’s “Species of Special Concern” list.⁴¹ In 2005, NMFS funded a status review of black abalone in California and the draft report is scheduled for release at the end of 2006.³⁸ If the status report finds that black abalone qualify for listing under the Endangered Species Act (ESA), then NMFS would become the primary agency responsible for management and recovery of this species (a state agency is currently the primary management agency - see “State” section below). The sea otter, an important abalone predator, is protected under both the Marine Mammal Protection Act (MMPA) and the ESA and managed by the U.S. Fish and Wildlife Service. A management conflict may arise between protecting remnant black abalone populations at central California sites and recovering the endangered sea otter population that feeds on them.

The California Fish and Game Commission (Commission) has management authority over abalone species occurring in state waters and the California Department of Fish and Game (CDFG) administers and enforces the regulations adopted by the Commission. The depleted condition of black abalone resources, due to the combined impacts of overfishing and withering syndrome, led the Commission to impose a moratorium on commercial and recreational fishing of black abalone in 1993. In 1997, the Thompson bill (Assembly Bill 663) created a moratorium on taking, possessing, or landing abalone for commercial or recreational purposes in ocean waters south of San Francisco, including all offshore islands. This bill also mandated the creation of an Abalone Recovery and Management Plan (ARMP) and that the Commission manages abalone stocks in a manner consistent with the ARMP (FGC §5520 and §5522). The purpose of the ARMP is to provide a cohesive framework to direct recovery efforts and to manage existing and future fisheries. The Commission adopted the ARMP in December 2005.¹³ The ARMP Recovery Plan for black abalone outlines the following recovery tasks (“key sites” are identified in ARMP Table 6.6):

• Assessing Recovery: Sites in central and southern California will be surveyed to determine current population levels. Sites will be surveyed periodically to assess changes in abundance over time.
• Culturing Programs: Develop a culture program for black abalone to provide stock for out-planting and to answer questions regarding the effects of, and resistance to, WS.
• Out-planting Feasibility Study: The out-planting of adult or larval abalone involved new techniques that must be evaluated before applying them on a larger scale. Locations for out-planting must be well protected from poaching.
• Aggregation/Translocation Feasibility Studies: In localized areas, remaining abalone populations may be too dispersed for effective reproduction to occur. The number and density of abalone that are needed for facilitating reproduction needs to be determined. Translocation would be used to re-introduce animals to areas once populated by a high abundance of abalone. Evaluation of donor and receiving populations (both genetic and disease testing) must be made before a translocation is conducted.
• Aggregation or Translocation: If feasible, these recovery techniques will be used at the appropriate key locations
• Out-planting: If feasible, black abalone will be out-planted at the appropriate key locations
• Genetics: A genetics study will be completed to estimate genetic diversity and to determine if sub-populations exist.
• Resistance to WS: Central California black abalone populations will be evaluated for WS resistance.
  

CDFG is coordinating with researchers at a number of academic institutions to accomplish the recovery tasks outlined in the ARMP (Contacts: Ian Taniguchi and Peter Haaker, CDFG – Los Alamitos). The following research projects are currently underway:

Monitoring Trends in Abundance, Recruitment, and Size-structure (Contacts: Pete Raimondi, UC Santa Cruz (PISCO/MARINe); Mary Elaine Dunaway, MMS (MARINe); Jack Engle, UC Santa Barbara (MARINe). Two research consortiums have been monitoring intertidal resources, including black abalone populations, in central and southern California. The Multi-Agency Rocky Intertidal Network (MARINe) monitors sites at the Channel Islands (San Miguel, Santa Rosa, Santa Cruz, Anacapa, Santa Barbara and Santa Catalina) and on the mainland in San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Orange and San Diego counties. The Partnership for the Interdisciplinary Study of Coastal Oceans (PISCO) monitors mainland sites in Monterey, Santa Cruz and San Mateo Counties. Abundance, size-structure and recruitment of black abalone are monitored twice a year – in the spring and fall – in fixed plots at each site. Site-wide timed searches are employed at locations where abalone numbers are too low to monitor within a limited area. The MARINe program is supported by 23 organizations including federal, state and local government agencies, universities, and private and volunteer organizations. Core funding for PISCO is from The David and Lucile Packard Foundation and the Gordon and Betty Moore Foundation.

Dynamics of Black Abalone Populations at San Nicolas Island, California (Principle Investigator: Glenn VanBlaricom, University of Washington). The purpose of this research is to identify and understand temporal trends in recruitment, survival, predation by sea otters, and mortality associated with withering syndrome disease, and to synthesize effects of those factors on abalone population size and structure. Data on abundance, size distribution, microhabitat distribution, and feeding activity are collected in permanent plots at each of nine intertidal study sites along shore at San Nicolas Island. Data collection began in September 1979 and will continue indefinitely. Collaborators: Carolyn S. Friedman, University of Washington. Funding sources: US Geological Survey and College of Ocean and Fishery Sciences, University of Washington.

An Assessment of the Impact of Withering Disease on the Genetic Structure of Black Abalone Populations: Implications for Recovery and Restoration (Principle Investigators: Peter Raimondi and Giacomo Bernardi, UC Santa Cruz; Steve Lonhart, MBNMS). The main objectives of this research are to compare the genetic structure of 1) healthy and diseased populations; and 2) populations before and after the disease hits. Study period: 7/1/05 - 7/1/06. Collaborators: California Fish and Game. Funding: the Packard Ocean Science and Technology Endowment.

Assessing Withering Syndrome Resistance in California Black Abalone: Implications for Conservation and Restoration (Principle Investigators: Hunter Lenihan, UC Santa Barbara; Carolyn Friedman and Glenn VanBlaricom, University Washington; Kevin Lafferty, USGS-WERC). The main objectives of this research are: 1) to assess if progeny of survivors of WS epidemics are more resistant to the disease than are progeny from non-disease-selected parents; and 2) to optimize spawning methods for black abalone. This research began in February 2006 and will continue through February 2008. Collaborators: Peter Haaker and Ian Taniguchi (CDFG) and Tom McCormick (CIMRI). Funding sources: California Sea Grant, UW, CDFG, and Abalone Farm Inc.

Population Viability Analysis for Black Abalone (Principle Investigator: Dan Goodman) The main objective of this research is to estimate current population size, optimum sustainable population levels, and extinction rates under different mortality levels. Both fishery-independent and dependent data, such as abundance over time, local temperature regimes, and habitat characterization and availability over as much of the range as possible, will be combined into one database. Quantitative techniques and methodologies for predicting future population status will be assessed. This project began in September 2005 and will continue through September 2006. Collaborators include Melissa Neuman (NMFS), Brian Tissot (Washington State University), and John Butler (NMFS). Funding Sources: NMFS, Protected Resources Division.

Shoreline Inventory of the black abalone in the MBNMS (Contact: Pete Raimondi, UC Santa Cruz). Long-term monitoring of black abalone populations in the MBNMS began at one site in the southern portion of the MBNMS in 1995 and additional sites have been added over time. Currently, 10 sites throughout the geographic extent of the MBNMS are monitored by either MARINe (3 sites in San Luis Obispo Co.) or PISCO (7 sites in Monterey, Santa Cruz and San Mateo Counties). Abundance, size-structure and recruitment are monitored twice a year – in the spring and fall – in fixed plots at each site. MARINe surveys in the MBNMS are funded by the Minerals Management Service and core funding for PISCO is from The David and Lucile Packard Foundation and the Gordon and Betty Moore Foundation. Funding from the MBNMS allowed PISCO to set up 7 additional monitoring sites in the MBNMS in 2004 and 2005.

The on-going research projects summarized above address a number of the recovery tasks outlined for black abalone in the ARMP. Additional information is needed in the following areas:

• What are the causes of recruitment failure at sites where black abalone populations are at reduced densities? The following potential causes of low (or no) recruitment must be examined:
  • Local adult densities are too low for successful fertilization. The minimum density required for successful fertilization needs to be determined. The appropriateness of redistributing local adult abalone into aggregations above the minimum density needs to be assessed.
  • Limited larval supply either because locally produced larvae are not retained or larvae from adjacent populations are not arriving. The dispersal potential of larvae at different sites and under different current patterns needs to be determined. If larval supply is found to be low and the effort to culture black abalone in the lab is successful (see “Research” section above), then the feasibility of out-planting larvae should be assessed.
  • Suitable settlement habitat for larvae is lacking. Habitat requirements for black abalone settlement need to be determined. The availability of suitable habitat and the factors that lead to loss of this habitat should be identified.
  • New recruits are dying. The potential causes of recruit mortality – predation, food limitation, and disease - should be assessed. The persistence of WS in the environmental after a mass-mortality event and the susceptibility of new recruits to the disease should be determined.

• The remaining healthy black abalone populations in California occur in the MBNMS. A few of these populations (San Simeon, Point Sierra Nevada, Carmel Point, Pebble Beach) recently have shown signs of potential onset of disease and decline. Continued monitoring of all sites in the MNBMS (especially the 7 additional sites monitored by PISCO in 2004-2005) is critical to understanding the health of Sanctuary populations and for determining if and how WS is spreading to new populations in the Sanctuary.

• Support on-going efforts by state and federal management agencies to manage and restore the black abalone throughout its range.

• Minimize or eliminate sources of thermal pollution near black abalone populations. Raise public awareness of the potential negative impacts of global warming and rising sea surface temperature on black abalone populations.
• Prevent take of black abalone from rocky intertidal habitats of the MBNMS. Enforce existing regulations to reduce or prevent poaching for both recreational and commercial uses. Reduce injury to or removal of black abalone by visitors to rocky intertidal areas through education outreach materials and programs. Outreach efforts should encourage citizens to report poaching and other violations to the appropriate authorities (e.g., CDFG using the CalTIP program).⁴⁰
• Reduce damage to suitable abalone habitat from coastal development or pollution. Also reduce loss of food resources, such as kelp forests adjacent to or up current from black abalone populations.⁴⁰

9. Douros WJ (1985) Density, growth, reproduction and recruitment in an intertidal abalone: effects of intraspecific competition and prehistoric predation. University of California, Santa Barbara.

39. Geiger DL (2000) Distribution and biogeography of the Haliotidae (Gastropoda: Vetigastropoda) world-wide. Bollettino Malacologico 35: 57-120. http://www.vetigastropoda.com/ABMAP/text/index.html

40. Addressed in part by JMPR Wildlife Disturbance Issues – Tidepool Protection Action Plan. Joint Management Plan Review (JMPR). Proposed Action Plans. Draft report. Monterey Bay National Marine Sanctuary. http://sanctuaries.noaa.gov/jointplan/drafts/mb_mp.html

41. National Marine Fisheries Service (April 15, 2004) Endangered and Threatened Species; Establishment of Species of Concern List, Addition of Species to Species of Concern List, Description of Factors for Identifying Species of Concern, and Revision of Candidate Species List Under the Endangered Species Act. Federal Register 69(73): 19975-19979. http://www.epa.gov/fedrgstr/EPA-SPECIES/2004/April/Day-15/ e8593.htm

42. National Marine Fisheries Service (January 14, 2009) Endangered and Threatened Wildlife and Plants; Endangered Status for Black Abalone. Federal Register 74(9): 1937-1946. http://www.nmfs.noaa.gov/pr/pdfs/fr/fr74-1937.pdf

43. National Marine Fisheries Service (October 27, 2011) Endangered and Threatened Wildlife and Plants; Final Rulemaking to Designate Critical Habitat for Black Abalone. Federal Register 746(208): 66806-66844. http://www.nmfs.noaa.gov/pr/pdfs/fr/fr76-66806.pdf

Pete Ramondi, Melissa Miner, Christy Bell, Melissa Neuman, and Ian Taniguchi reviewed this document and provided helpful comments.