Black Abalone Withering Towards Extinction
Disease-Resistant Population Found on San Nicolas Island
August 15, 2007
Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334
Sea Grant Trainee Tal Ben-Horin prepares a black abalone for spawning in the wet lab at UC Santa Barbara. Photo: Hunter Lenihan.
California’s native black abalone are in jeopardy of withering into extinction. Once the most abundant large marine mollusk on the rocky intertidal coast, the species is now a candidate for protection under the federal Endangered Species Act.
Because black abalone populations have continued to dwindle despite the closure of the black abalone fishery in 1993, efforts to prevent the species’ extinction are becoming incredibly high-tech, as evidenced by ongoing California Sea Grant projects.
Shellfish biologists Carolyn Friedman and Hunter Steven Roberts, both of the University of Washington, Seattle, are trying to understand the genetic basis of resistance to a chronic, progressive wasting disease that has become the bane of abalone recovery efforts, both in hatcheries and the wild. The disease, withering syndrome, killed up to 99% of black abalone populations in parts of Southern and Central California in the 1980s and 1990s and was part of the reason for closing all commercial abalone fisheries.
Fish with “popeye” – swelling of the eye due to pressure build up in the brain. Credit: John Buchanan.
Friedman and Glenn VanBlaricom, a marine biologist with the University of Washington and the U.S. Geological Survey, have collected black abalone on San Nicolas Island in the Santa Barbara Channel that appear more resistant to withering syndrome than populations from the mainland coast of Central California. These resistant animals are the descendants of the one percent of the island’s black abalone population that survived successive epidemics of the disease.
Going, going, gone–Three pictures from the same location on Santa Cruz Island in 1986 (top), 1988 (center) and 1999 clearly show the dramatic loss of black abalone populations that has occurred throughout California, due to overexploitation and the deadly withering syndrome disease.Photos courtesy Brian Tissot, Washington State University, Vancouver
Because withering syndrome is so lethal and appears to be spreading northward as coastal temperatures warm, the scientists have suggested breeding disease-resistant specimens for out planting in the wild in Southern California. With this as an end goal, Friedman and colleagues are in the process of identifying immune-related genes and conducting an initial assessment of differences in gene expression between newly recruited black abalone from San Nicolas Island and those from Carmel.
Meanwhile, California Sea Grant biologist Hunter Lenihan is developing captive rearing techniques for black abalone in anticipation of out-planting experiments in Southern California.
“We have everything up and going,” Lenihan said. “We have a sophisticated spawning system in place. We just can’t get the males to spawn yet.”
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