24 January 2020

Third update: Swan and Canning algal bloom warning remains in place

The Department of Health is reminding recreational water users that the toxic Alexandrium algal bloom warning for the Swan and Canning river systems remain in place.

This reminder comes ahead of the Australia Day long weekend, a peak period for recreational use of these waterways.

Fish, crabs or shellfish collected from within the following waterways should not be consumed due to the potentially toxic Alexandrium algae:

  • the Swan River – from Pelican Point to the South of Perth Yacht Club and upstream to Tonkin Highway Bridge (this includes the commonly known areas of Matilda Bay, Perth Waters, Elizabeth Quay, Barrack Street Jetty, Claisebrook Cove, Maylands Yacht Club, Ascot Waters and Riverside Gardens)
  • the Canning River – from the South of Perth Yacht Club and upstream to Kent Street Weir (this includes commonly known areas of Canning Bridge, Mt Henry Bridge, Salter Point, Shelley Bridge, Riverton Bridge, Castledare).

The ingestion of toxins produced by this microscopic species of algae can produce a type of poisoning known as paralytic shellfish poisoning (PSP). Cooking will not destroy these toxins.

People who consume wild shellfish, crabs or fish collected from the affected area of the Swan and Canning rivers may experience symptoms including:

  • tingling or numbness of the lips
  • prickliness of the fingertips and toes
  • nausea or vomiting
  • impaired balance
  • dizziness
  • slurred speech
  • double vision
  • weakness
  • difficulty in swallowing or breathing
  • loss of fluids and diarrhoea.

In severe cases PSP may cause muscular paralysis in people who consume affected shellfish, crabs or fish. Shellfish includes oysters, mussels, clams, pipis, scallops, cockles and razor clams.

Anyone who has consumed shellfish, crabs or fish collected from the affected area of the Swan River and experiences any of these symptoms should seek urgent medical attention, particularly if they have difficulty breathing.

They should also retain uneaten portions of mussels or other shellfish to help determine a likely cause of any symptoms.

As a general rule people should avoid eating recreationally collected shellfish in rivers, estuaries or other waterways where there is an increased likelihood of contaminant or nutrient inputs that could lead to increased microscopic algae growth.

Farmed shellfish purchased in supermarkets and other commercial outlets in WA are not affected because there is a strict quality assurance program to ensure they are safe for human consumption.

Other recreational activities including swimming, skiing and boating in the Swan and Canning rivers are not affected by this microalgae species, but as a general rule swimming should be avoided in areas of discoloured water.

Health warning signs advising against crabbing, shellfish collection and fishing have been erected at key locations including bridges, jetties, boat ramps and popular accessible foreshore areas within the affected region.

The Department of Biodiversity, Conservation and Attractions (DBCA) will continue to the situation and provide information to the Department of Health.

Read detailed FAQs on the Alexandrium algal bloom and paralytic shellfish poisoning (external site). A map detailing affected waterways can be viewed on the DBCA website.


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