Mycotic Periostracal Sloughing of Mussels


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Mycotic periostracal sloughing of mussels, MPS.

Scientific name or taxonomic affiliation

Unidentified fungus.

Geographic distribution

A few locations on the coasts of Newfoundland and Prince Edward Island, Canada.

Host species

Mytilus edulis.

Impact on the host

Affected shells exhibit brown discolouration associated with sloughing of the periostracum. Mussel farmers and processors have expressed concern that MPS may affect marketability.

Diagnostic techniques

Gross Observations: Brown discolouration of the shell and possible evidence of sloughing of the periostracum.

Wet Mounts: Presence of fungal hyphae beneath the remaining periostracum of affected mussels.

Electron Microscopy: Fungal hyphae associated with the periostracum of affected mussels.

Methods of control

Concerns about the possibility of transferring MPS with mussel culture activities should be addressed through research efforts to understand the disease, identify the fungus involved, determine its current distribution and assess if the condition can be controlled or circumvented.


Moret, K., K. Williams, C. Couturier and J. Parsons. 1999. Newfoundland cultured mussel (Mytilus edulis) industry 1997 health survey. Bulletin of the Aquaculture Association of Canada 99-3: 35-37.

Citation Information

Bower, S.M. (2004): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Mycotic Periostracal Sloughing of Mussels.

Date last revised: June 2004
Comments to Susan Bower

Date modified: