The Department of Health is warning people not to eat shellfish from the lower Swan and Canning River estuaries.
This area includes Blackwall Reach through to East Perth and Canning Bridge through to Salter Point.
The warning follows recent testing which has confirmed toxic microscopic algae at elevated levels.
These algae can produce a toxin which can be absorbed by filter feeding shellfish and ingestion of affected shellfish could result in diarrhetic shellfish poisoning (DSP).
Acting Environmental Health Executive Director, Jane Cook, said people should avoid eating wild shellfish collected recreationally.
"These algae are not visible to the naked eye and normal cooking processes will not destroy the toxins in the shellfish," Ms Cook said.
"Community members are advised to avoid eating wild shellfish including anything from rivers, estuaries or other waterways.
"Anything from a supermarket or other commercial outlet in WA will be okay, as there are strict quality-assurance programs in place to ensure safe consumption."
Shellfish includes oysters, mussels, clams, pipis, cockles and razor clams. They do not include crustaceans such as shrimp, prawns, or crabs.
Anyone who has recently eaten recreationally caught shellfish should monitor for potential symptoms of DSP including:
- nausea
- vomiting
- abdominal discomfort
- diarrhoea
- headaches
- chills.
Illness can last for up to three days. Anyone experiencing symptoms should seek medical attention.
The Department of Biodiversity, Conservation and Attractions regularly monitors and reports on algae levels in the Swan and Canning Rivers.
