Recent tests have found high levels of algae that could produce shellfish poisoning, according to a Department of Health warning issued earlier this month.
�Eating contaminated shellfish may cause shellfish poisoning, with symptoms including nausea, vomiting, diarrhoea, dizziness, numbness, breathing difficulty or memory loss,� Department acting environmental health director Michael Lindsay said.
Shellfish include oysters, mussels, clams, pipis, scallops, cockles and razorclams.
They do not include crustaceans such as shrimp, prawns, crabs or lobsters.
Dr Lindsay said farmed shellfish purchased in WA supermarkets were not affected.