9/17/11
The sudden death of thousands of red abalone and other invertebrates along the Sonoma County Coast over the past few weeks has prompted state wildlife officials to propose an indefinite ban on abalone fishing while biologists search for a cause.
The California Fish and Game Commission passed an emergency order Thursday to close the only abalone fishery in the state after continued reports of dead mollusks along the shoreline and in the water in Bodega Bay, Russian Gulch, Fort Ross, Timber Cove and Salt Point State Park.
California Department of Fish and Game officials said the mass die-off was caused by an unusual and virulent red tide.
"It is an unprecedented event," said Ian Taniguchi, the senior marine biologist for fish and game. "It's definitely going to affect the fishery. It is such a significant event that it may change how we manage the overall abalone fishery in the future."
Taniguchi said the red tide, which is a large bloom of phytoplankton, suddenly appeared late last month. Abalone divers reported a dark reddish brown tide and very low visibility. On Aug. 27, huge numbers of dead abalone, urchins, starfish and gumboot chitons, an oval shaped mollusk, were strewn all over the beaches, he said.
The carnage continued at a startling pace. Tom Jahng, 39, who was diving in the Fort Ross and Timber Cove areas on Sept. 5, said he encountered the rotting carcasses of hundreds of abalone and other mollusks on the beach and lying underwater.
"In the shallows, within the first quarter-mile of diving, there was just dead abalone and sea urchin everywhere," said Jahng, 39, of Los Angeles, who grew up in the Bay Area and often dives along the pristine Sonoma coast, which is normally teeming with colorful urchins and sea life. "I was heartbroken. I was devastated. It was a graveyard."
Taniguchi said the deadly bloom spread from Bodega Bay all the way to Anchor Bay, in southern Mendocino County, but the hardest hit area was at Fort Ross. A team of biologist divers from the department estimated that 30 percent of the red abalone at Fort Ross had died. At Timber Cove, 25 percent were dead. Some 12 percent of the abalone at Salt Point died too, according to the survey.
Marine scientists up and down the coast are trying to figure out what caused the tide and why it is so deadly. One possibility is that the phytoplankton was so plentiful that it sucked all the oxygen out of the water, suffocating invertebrates. The other theory is that this particular plankton species is emitting biotoxins that are essentially poisoning sea life.
"We haven't figured out for sure yet, but we are leaning more toward toxic poisoning," Taniguchi said.
The makeup of this particular tide is of particular interest to biologists, who took samples and found that the most abundant organism in the killer bloom was an algal species called Gonyaulax spinifera. This particular spore creates a biotoxin called Yessotoxin, which was found in low levels in the dead abalone, Taniguchi said.
"We have never seen this species off our coast in California as far as we know, at least not in a large algal bloom like this one," said Taniguchi, adding that the species was also found in blooms this summer in Washington state. "There is not much known about this particular biotoxin, but it appears to affect invertebrates."
