A harmful algae bloom in Discovery Bay that caused a shellfish closure in April has dissipated, officials with Jefferson County Public Health announced Friday.

Shellfish samples that were taken in the bay have been found to have safe levels of the marine biotoxin that causes paralytic shellfish poisoning, so the ban on recreational harvesting has been changed to limit only the collection of butter and varnish clams.

Other species of shellfish can now be harvested, the department said.

The harvesting of butter and varnish clams from Discovery Bay is still prohibited, as those shellfish species retain biotoxins longer than other species.

Michael Dawson, water quality manager for Jefferson County Public Health, said shellfish samples were taken between Monday, May 31 and Tuesday, June 1.

Blue mussels, Pacific oysters and geoduck were all below the action level of 80 micrograms per 100 grams of shellfish tissue, Dawson noted. 

"This represents a decline over several weeks of monitoring," he added. "No other biotoxins were present."

Signs have been posted at public access points on Discovery Bay noting the shellfish advisory change made by the Washington State Department of Health .

Health officials also said the red-orange bloom of algae that has been visible in Dabob Bay is not dangerous to shellfish, as it is not a toxin producer.

According to Jefferson County Public Health, Washington SeaGrant has confirmed that the bloom was caused by the marine phytoplankton Noctiluca scintillans.

More information is available at the Washington Recreational Shellfish Facebook page at www.facebook.com/WAshellfishsafety. 

To find out which areas are safe to harvest shellfish in Washington, check the map at www.doh.wa.gov/ShellfishSafety.htm or call the Biotoxin Hotline at 1-800-562-5632. 

For the latest information on regulations and seasons, visit the Fish and Wildlife website at wdfw.wa.gov/fishing or call the Shellfish Rule Change Hotline at 1-866-880-5431.