Toxin halts shellfish harvest


High levels of a dangerous biotoxin produced by algal blooms has prompted a prohibition of recreationally harvested mussels, clams and scallops in Tomales Bay south of Nick’s Cove.

It is the first time the toxin, which typically closes non-commercial harvest during summer months, has appeared in winter in the inner and middle sections of the bay. In the mid-1990’s a winter algal bloom closed portions of the bay near Lawson’s Landing.

Hog Island Oyster Company and Tomales Bay Oyster Company must temporarily cease harvesting in the affected areas, instead taking stock from their leases in the outer bay.

The biotoxin causes paralytic shellfish poisoning, which in mild cases brings about tingling in the mouth and fingertips and in the most extreme cases causes paralysis and death. 

(Tod Friend, the owner of Tomales Bay Oyster Company, said he purposefully poisoned himself one time “just to see what the effect was.” He said he felt tingling in his eyebrows, lips and fingers.)

When the warning, which was issued Dec. 13, ceases, the shellfish cultivated in the affected areas will flush the toxins and the meat will be safe for consumption.

Gregg Langlois, a senior environmental scientist at the California Department of Public Health, said there is no understanding of what causes the algal blooms and therefore no means of predicting the events.

One small 10-acre mussel farm in Marshall, Cove Mussel Company, has halted harvesting completely because of the toxin, since all of its acreage is affected. Scott Zahl, the owner of Cove Mussel, said that winter rains normally put harvest on pause due to the influence of fecal coliform. 

But recent rains and the biotoxin closure is taking a toll on his bottom line.

“It’s kind of a serious impact at this point,” said Mr. Zahl, who harvests between 400 to 500 pounds of mussels a week, along with roughly 4,000 oysters, which he mostly sells to West Marin restaurants. 

But, Mr. Zahl added, “It’s farming, essentially. There’s always factors like this. You have good years and bad years.”


For up-to-date information on warnings, call the state health department’s shellfish hotline at (800) 553.4133.