Maine DMR Issues Precautionary Closure for ASP

Lamoine—The Maine Department of Marine Resources has precautionarily closed a stretch of the downeast coast to harvesting of four shellfish species due to test results and experience with an emerging biotoxin, domoic acid, in recent years.

The closure, implemented September 7, 2018, prohibits harvesting of clams, mussels, oysters and carnivorous snails between the southern tip of Petit Manan and the southern tip of Pond Point on Great Wass Island. The Department of Marine Resources Public Health Bureau tests coastal shellfish areas for biotoxins weekly, from March through October, or later when testing indicates the continued presence of biotoxins. Testing includes sampling of water to determine the species and concentration of marine algae known as phytoplankton which produce biotoxins.

For most types of phytoplankton, when routine water sampling detects cell concentrations (in terms of numbers of cells per liter of water) that are known to produce toxins, sampling of shellfish begins. When shellfish samples are shown to have toxins in concentrations specified by the National Shellfish Sanitation Program (NSSP), areas are closed to shellfish harvesting.

The current precautionary closure is due to water and shellfish sampling that indicated the presence of domoic acid, the biotoxin that causes Amnesic Shellfish Poisoning (ASP). While toxin levels in shellfish sampled in the impacted area fall below the NSSP threshold for closures, Maine DMR has determined that Pseudo-nitzschia, the marine algae which produces domoic acid, causes shellfish to become toxic more quickly than other species of phytoplankton.

The use of precautionary closures for ASP is designed to prevent the need for recalls of product which can be impacted by the rapidly toxifying species of phytoplankton if harvested between initial and follow up shellfish sampling.