American Oyster MSX Restricted Areas

 

The Maine Department of Marine Resources Rule Chapter 24.10(4)(F) restricts the movement of American oysters (Crassostrea virginica) in the Damariscotta River, Quahog Bay, and Upper Sheepscot River Estuary due to the detection of the protozoan parasite MSX (Haplosporidium nelsoni). The locations of the MSX restricted areas are available as a layer on DMR’s aquaculture webmap, which is linked below. This restriction does not prohibit harvest but does restrict the introduction of oysters from this area to other water bodies within the state, including for wet storage. Based on our current knowledge, MSX is limited in its distribution within Maine. No hatcheries operating in Maine have tested positive for MSX to date.

 

MSX is specific only to American and Pacific oysters; it is not known to affect other marine species. Furthermore, it is not a human health concern. However, MSX caused heavy oyster mortalities in the Damariscotta River in 2010 and was detected in the Upper Sheepscot River Estuary (Marsh River) in 2013 and in Quahog Bay in 2020. While MSX related mortalities are relatively new to Maine, the parasite has been present throughout southern New England and the Mid-Atlantic states for decades. It was first discovered in Delaware Bay in 1957 and then Chesapeake Bay two years later.

 

As a reminder, product from out-of-state or from restricted areas within Maine (i.e. the Damariscotta and Sheepscot Rivers, and Quahog Bay) may not be re-submerged, wet stored or placed in flow through systems elsewhere in the state without a permit from DMR. Resubmergence, wet storage and/or storage in a flow through system of oysters from out of state or from an area restricted due to the detection of shellfish pathogens may cause the spread of those pathogens. LPA sites are not eligible for transfer permits.

 

Additional Resources:

 

 

  • Please direct questions about MSX, including the permitting process to DMR’s Pathology Program at: Pathology.DMR@maine.gov