The National Marine Fisheries Service announced Tuesday that the marine mollusk has been listed as endangered.
The black abalone was once common in tide pools all along the California coast. But overharvesting, a devastating disease and possibly changes in the ocean environment associated with climate change have caused 90 percent reductions throughout most of its range.
“The plight of the black abalone speaks volumes about the way we treat our oceans,” said Brendan Cummings, ocean program director for the Center for Biological Diversity, which petitioned to have the abalone listed.
San Luis Obispo County has been on the frontline of black abalone conservation since 1988, when the disease — withering syndrome — gained its first foothold on the mainland in the warm waters of the Diablo Canyon nuclear power plant’s cooling water discharge cove.
Withering syndrome originated in the Channel Islands. It is considered the primary threat to the abalone.
Black abalone have been wiped out in many of the beaches in Southern California and the Channel Islands where the mollusk was historically the most numerous. The agency estimates that there is a 96 percent chance that black abalone will be extinct within the next 30 years.
When the petition to have the black abalone listed was accepted in April 2007, withering syndrome had made its way to the San Luis Obispo/Monterey county line. Since then, it has been detected as far north as the Farallon Islands near San Francisco, said Melissa Neuman, a fisheries biologist for the National Oceanic and Atmospheric Administration.
The disease is a bacterial infection that prevents the abalone from absorbing nutrients, causing the soft tissue to wither away. Beaches newly infected with the disease are littered with empty abalone shells.
Black abalone is one of about a half-dozen Pacific abalone species. It was the most familiar to beach-goers because it’s the largest tide pool species and the only abalone exposed by low tides.
Harvesting of any kind of abalone is prohibited south of San Francisco. In Northern California, free divers still harvest red abalone, which are also raised commercially at The Abalone Farm near Cayucos.
Despite the listing, there is some reason for optimism, Neuman said. Some populations in the Channel Islands are clinging to survival.
This indicates that these populations are either developing a resistance to the disease or environmental conditions are buffering them from the sickness. The disease is most virulent in warmer water, and the colder temperatures along the abalone’s northern range may slow the spread.
Poaching and climate change are also considered threats to black abalone. Poachers target black abalone at low tide.
Climate change affects abalone in two ways, Cummings said. Warmer ocean temperatures promote the spread of withering syndrome and cause acidification of the ocean, which impairs the ability of abalone to form their protective shells.
Now that the abalone has been added to the endangered species list, the National Marine Fisheries Service will declare critical habitat for the animal and develop a recovery plan.
David Sneed can be reached at 781-7930.