California’s annual quarantine on sport-harveted ocean mussels ended at midnight Oct. 31, the California Department of Health (CDPH) announced.

A sampling of mussels confirmed that shellfish-borne paralytic shellfish poisoning (PSP) toxins, as well as domoic acid, remained at safe or undetectable levels — with the exception of the northern Channel Islands region (which includes Anacapa, Santa Cruz, Santa Rosa and San Miguel islands).

Though the ban was lifted in most areas, CDPH said the quarantine on sport-harvesting of mussels, other shellfish, fish and the viscera of crustaceans will remain in effect for the Channel Islands area.

According to the CDPH website, the annual mussels quarantine is issued each year for the California coastline typically from May through October.  Commercially harvested shellfish are excluded from the quarantine because additional steps are taken to assure shellfish entering the marketplace are free of toxins and safe for consumers.  

Paralytic shellfish poisoning (PSP) is a poisoning that affects the nervous system.  Mussels and other bivalve shellfish feed on certain marine plankton that can have naturally occurring concentrated levels of PSP toxins.

Other types of bivalve shellfish poisoning, like Domoic Acid Poisoning (DAP), sometimes referred to as Amnesic Shellfish Poisoning (ASP), have been linked to natural food sources for filter-feeding animals.  

According to the CDPH, no known cases of human DAP poisoning have been reported in California this season, but DAP has been linked to several poisonings of marine mammals along the Pacific Coast and may have caused several mild cases of human poisoning in Washington state.

CDPH issues warnings or quarantines for shellfish after the animals test positive for PSP or DAP.  Local health departments, various state and federal agencies, and others manage the monitoring program.  The CDPH also provides a Shellfish Information Line (800-553-4133) that consumers can call in order to receive updated information about shellfish poisoning.