Black Abalone

Black abalone belong to a group of plant-eating marine snails that were once common in California. They once numbered in the millions along the California coast but are now endangered.

Before the time of commercial fisheries, native people along California’s coast ate abalone for thousands of years. Large groups of abalone shells indicating human settlement, or “middens,” date back 7,400 years. Abalone shells were also traded along routes starting in southern California and reaching east of the Mississippi River.

Black abalone continue to live in rocky intertidal and subtidal reefs along the California and Baja California coast. They are “broadcast spawners,” releasing eggs and sperm into the water by the millions when environmental conditions are right. Their strong, muscular “foot” allows them to attach to rocks and other hard surfaces while their oval-shaped shells protect them from predators. Although fishing for black abalone has been illegal in California since 1993, the high price of abalone meat makes them a target of poachers. This species has experienced major declines in abundance throughout the Southern California coast because of historical overfishing and—more recently—mass mortalities associated with a disease known as withering syndrome.

NOAA Fisheries is dedicated to conserving and restoring black abalone. Our scientists use innovative techniques to study, protect, and restore their population. We also work with our partners to ensure that regulations and management plans are in place to reduce poaching and increase the wild abalone population.

The black abalone is a marine snail with one large, oval-shaped shell and a muscular foot used to move and to attach to rocks. The blackish-blue shell has five to nine open holes (respiratory pores) used to breathe, remove waste, and reproduce. It also has a black-colored epipodium, an extension of the foot with tentacles used to sense the surrounding environment.

Abalone are slow-moving bottom dwellers. They attach to rocks and other hard surfaces using their muscular foot and when disturbed, they become difficult or impossible to remove. An abalone can also use its foot to move across surfaces. Black abalone are generally found in rock crevices.

Adults eat different types of algae. They can catch kelp drifting along the seabed or attached to rocks. Black abalone feed on giant kelp and feather boa kelp in southern California (south of Point Conception) habitats, and bull kelp in central and northern California habitats.

Black abalone live on rocky substrates in intertidal and shallow subtidal reefs (to about 18 feet deep) along the coast. They typically occur in habitats with complex surfaces and deep crevices that provide shelter for juveniles and adults. Because they occur in coastal habitats, black abalone can withstand extreme variations in temperature, salinity, moisture, and wave action. Black abalone range from about Point Arena, California, to Bahia Tortugas and Isla Guadalupe, Mexico. They are rarely found north of San Francisco and south of Punta Eugenia. In the mid-1900s, black abalone abundances were highest south of Monterey, particularly at the Channel Islands off southern California. Beginning in the 1980s, the spread of withering syndrome caused mass mortalities, leading to dramatic declines in black abalone throughout the southern portion of the range. Today, populations in southern California remain at low densities, with signs of natural recruitment and increasing numbers at a few sites. The status of the species in Mexico remains largely unknown, but is also depleted compared to historical levels due to overfishing and disease.

Black abalone are estimated to live up to about 30 years. Adults become sexually mature in the wild when they reach about 1.5 to 2 inches in shell length.

Abalone reproduce by broadcast spawning—releasing their eggs and sperm into the water. The eggs hatch after only one day if fertilized, but large amounts of sperm are needed to fertilize an egg. This means fertilization succeeds more often when groups of adult male and female abalone are close to each other when they spawn. Fertilized eggs hatch into larvae, which later grow into adults.

Overfishing

Due to their unique mating habits, abalone can be depleted by intense fishing that targets groups of animals.

A commercial abalone fishery opened in California in the early 1970s, peaked in the mid-1970s, and closed in the 1990s. The fishery used size limits and seasons to reduce the number of abalone caught. Even with these protections, the fishery greatly decreased the abalone populations and has had long-term effects on their recovery.

Illegal harvest (poaching) of black abalone continues to be a problem, particularly along remote stretches of the central California coast where numbers of black abalone are relatively high. Illegal harvest reduces black abalone abundance in the wild, further reducing the ability of populations to reproduce and sustain themselves over the long-term.

Disease

Withering syndrome is the primary threat to black abalone. The disease is a common and fatal infection that affects the digestive organs of abalone. The pathogen that causes it is currently present in the coastal oceans of California. Although all wild black abalone are likely infected, full manifestation of the disease appears to be more prevalent in the southern portion of the black abalone range (south of Point Conception, California) where water temperatures are relatively warmer. Die-offs associated with the disease are associated with sea surface warming events (e.g., El Niño events, thermal discharges). The disease’s northward progression poses a continuing threat to the remaining healthy populations; however, the impacts may be reduced due to the potential for black abalone to develop genetically-based disease resistance, as well as the existence of a phage that infects the pathogen and improves the survival of abalone.

Other abalone diseases have emerged over the past several decades in abalone populations outside of California (e.g., herpes virus, vibriosis, sabellidosis). To date, no outbreaks of these diseases have been observed in wild black abalone populations. However, black abalone may be susceptible to these diseases. Strict regulations and monitoring are needed whenever animals are imported and/or transported between facilities, to minimize the potential for introducing these diseases to wild abalone populations.  

Low Densities and Reproductive Rates

One female abalone can release millions of eggs at a time—but unless the eggs come in contact with sperm from spawning males, they cannot be fertilized. At some locations, black abalone have declined to such low densities that the remaining animals are far from potential mates. In these cases, spawning in the wild is unlikely or happening at low levels, making natural recovery of severely-reduced populations a slow process.

Spills and Spill Response Activities

Black abalone live in shallow coastal habitats that are vulnerable to chemical spills, such as oil spills. Spills and spill response activities could affect black abalone populations by directly killing or injuring animals and harming their habitat. The impacts may vary widely, depending on the type and amount of material involved, the location, local environmental conditions, and the status of black abalone populations within the spill area. We cannot predict where or when spills may occur, but can minimize the risks to abalone and their habitat through careful planning and coordination on spill response activities.