Black Abalone Withering Towards Extinction, Scientists Say

"Starting in the late 80s, it just eliminated them very quickly in southern California and has worked its way up the coast," he said.

The syndrome is caused by a bacterium. It gets into the digestive tract, causing the mollusks to shrivel, said Melissa Neuman. Neuman is the abalone recovery coordinator for the National Marine Fisheries Service in Long Beach, California.

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"By the time we see the foot withering, it's too late," she said. Within a few months, the disease can wipe out more than 90 percent of a population.

And it's nearly impossible for black abalone to recover when their populations are so obliterated, Tissot said.

The species reproduces through a process known as broadcast fertilization: males release their sperm and females their eggs into the water column where they come together. Babies then latch onto cracks and crevices in the rocks where they develop.

Normally, the sheer abundance of sperm and eggs means a new generation will arise. "But when mortality happens and densities are low, they are not close enough for that to happen," Tissot said.

Monitoring, Hoping

According to Tissot's research, the bacterium that causes withering syndrome can survive in cold water but the disease only takes hold when the ocean temperature rises above 65 degrees Fahrenheit (18 degrees Celsius).

For example, during the El Niño events of 1993 to 1994 and 1997 to 1998, researchers observed withering syndrome creep up the coast towards Big Sur, California. El Niño is a periodic warming of the Pacific Ocean that influences weather patterns around the world.

Melissa Miner is a marine biologist at the University of California, Santa Cruz, who monitors the effect of withering syndrome on black abalone. She said healthy populations remain north of San Luis Obispo, California, but the future is uncertain.

"The thing we're worried about is the disease is present in populations all the way up to San Francisco," she said.

Miner and her colleagues hope that the colder waters in the north will prevent the disease from taking hold, but the possibility of another strong El Niño and the gradual ocean warming due to the Earth's changing climate are cause for concern.

According to Tissot, another hope is that some populations will develop immunity to withering syndrome, "but we've never seen that."

Meanwhile, Neuman and her colleagues with the National Marine Fisheries Service are conducting a status review of black abalone to determine if the mollusks warrant a designation as either threatened or endangered under the U.S. Endangered Species Act.

The review should be completed by mid 2006. "We're trying to be proactive," she said.

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