California’s Endangered Black Abalone Face Unique Challenges

By Michele Roest

January 2022

One early foggy morning, Dr. Steve Lonhart, a research ecologist for Monterey Bay National Marine Sanctuary, was searching for endangered black abalone along the coast of Central California. He was in Big Sur, a roughly 90-mile stretch of sanctuary coastline often referred to as “the world’s most spectacular meeting of land and sea,” where the Pacific Ocean crashes into the rocky reefs, and steep cliffs tower above the sea. During the day, the drive along the Big Sur Highway is typically slow and packed with visiting tourists eager to snap photos of themselves along this majestic stretch of sanctuary coastline. On this particularly foggy morning, with a start at 3:00 a.m., the drive was an intense 90 minutes of winding in and out of seasonal watersheds and hugging the edge of 200-foot cliff drop-offs. Instead of tourists, only a few deer and a single skunk were seen along the road.

Searching for Survivors

Lonhart and his passenger, University of California at Santa Cruz (UCSC) doctoral student Wendy Bragg, were driving south to meet a third biologist, retired National Park Service scientist Dan Richards, who was waiting for them at a roadside pullout. They drove further south, finally reaching a locked gate leading to private property. Bragg had secured permission from the property owner to hike down a privately maintained trail that snaked back and forth across the cliffs to the rocky shore below.

Crashing waves boomed rhythmically, even though the ocean was still cloaked in darkness and fog. The beams of their headlamps attracted moths, which bounced off their faces as they prepared to walk across boulders and rocky reefs. They could smell the ocean, salty with a hint of decay. Seaweeds, ripped off the reef by waves and tossed onto shore, were decomposing, creating a unique smell familiar to the biologists.

Scrambling over slick rocks covered with algae, Lonhart peered under rocks with a waterproof flashlight, checking the deep cracks and crevices for black abalone. On the third attempt, his powerful light revealed a dark hemisphere of black, about the size of half a grapefruit: an endangered black abalone was at the back of a shallow crevice, almost completely hidden from view and partially buried by sand and cobble. Lonhart slowly and carefully removed as much of the loose material as he could, then used his tools to remove the stressed abalone before it could clamp down firmly to the rock. He worked with Bragg to place it on a sheet of hard plastic, which it quickly latched onto, and then into a damp mesh bag with its own tag number, carefully documenting where it had been collected and taking several photos. Then Lonhart and the others continued their search for more black abalone, survivors of a debris flow that buried nearly all of them alive.

a black abalone on a rocky shoreline
The blue-black color and oval shape indicate a black abalone, partially hidden by fallen rocks in the intertidal zone near Big Sur. Photo: Steve Lonhart/NOAA

An Iconic Coastal Species

The black abalone (Haliotis cracherodii) is one of several abalone species, a type of marine snail, that occurs in California coastal waters. Black abalone typically occur in rocky intertidal habitat, the area between high and low tides. Abalone use their large, strong muscular foot to crawl over and cling to rocks; this foot and the rest of the body are covered by a single shell, shaped like an upside-down bowl. Indigenous communities harvested black abalone and used the shells to make fish hooks or to trade with inland tribes. Abalone shell trade routes have been documented from Southern California to east of the Mississippi River.

Black abalone only occur along the western coast of North America, from just north of San Francisco in California to Bahia Tortugas and Isla Guadalupe in Baja Mexico. This species experienced major population declines caused by a lethal disease known as withering syndrome, which spread throughout its entire range. The black abalone was listed as endangered under the Endangered Species Act in 2009.

a person standing on a rocky shoreline hands an abalone over to another person wearing orange waders
UCSC doctoral student Wendy Bragg prepares to outplant a rescued abalone in a new location beyond the influence of the debris flows. Photo: Steve Lonhart/NOAA

Recent Impacts and Unique Challenges

The Big Sur coastline in Monterey Bay National Marine Sanctuary represents one of the largest healthy populations of black abalone. However, this population faces additional threats from landslides and rain-induced debris flows. The spectacular beauty of the coast, with steep mountains dropping into the sea, also poses danger—dirt and rocks from above are constantly flowing downward, into the intertidal zone below. In 2017, the massive Mud Creek Slide piled six million metric tons of rock and dirt onto the intertidal, adding 15 acres (653,400 square feet, or over 11 new football fields) of sediment to the existing coastline, smothering all life underneath. Thousands of endangered black abalone were killed within the impact zone.

In August 2020, Big Sur’s Dolan Fire burned out of control for more than four months, destroying 125,000 acres (over 5 million square feet) of forest and burning 20 miles of coastline. In January 2021, an extreme rain event called an atmospheric river, dropped 15 inches of rain in less than three days, washing tons of dirt, rocks, and trees off the Dolan Fire scar, burying much of the intertidal zone below.

a black abalone with a tiny ID tag on its shell
A rescued and tagged black abalone has been relocated to a safe intertidal habitat. Researchers will continue to follow the movements and survival of the rescued animals. Photo: Wendy Bragg/UCSC

Recovery Efforts Underway

After these recent disasters, Lonhart assisted researchers from UCSC to rescue and recover black abalone that were partially or completely buried at the margins of the debris flows, which had spread from the creek outlet to the shore along the coast. Some of the abalone were still alive and struggling to survive. Found individuals were brought to a lab where they were measured, tagged, and fed giant kelp, their preferred food. Returning survivors back to their original locations was risky. Due to the lack of vegetation that helps retain the soil in place, fire-scarred areas are vulnerable to debris flows for two to three years after the initial burn. The research team sought to identify suitable new intertidal habitat, safe from debris flows, that could support black abalone transplants. After several months in the lab, the recovered black abalone were marked and then delivered to their new location. Dedicated low tide surveys help track the movements and survival of the black abalone in their new homes over time.

Steve Lonhart
Dr. Steve Lonhart points to an area of the intertidal buried by debris from the January 2021 atmospheric river event, with several endangered black abalone buried under sediment. Photo: NOAA

“Monitoring endangered black abalone is exciting and important work,” says Lonhart. “We never quite know what to expect when we head down to the intertidal, since it is such a dynamic environment. This kind of monitoring allows us to track black abalone survival and better understand sediment movement that is still happening, months after the original debris flows.”

As difficult as species recovery and restoration challenges can be, the Central California coast population of black abalone have tremendous support in the dedicated researchers who study them. This collaboration with includes scientists of the Multi-Agency Rocky Intertidal Network (MARINe), National Marine Fisheries Service, NOAA Office of National Marine Sanctuaries, University of California at Santa Cruz, California Department of Fish & Wildlife, California Department of Transportation, Tenera Environmental Services, and the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO). Thanks in part to funding from the National Marine Sanctuary Foundation for this work.

Michele Roest is a program coordinator and community liaison for Monterey Bay National Marine Sanctuary.