By Madeline Palmer
Warning signs will be placed around a section of the Swan River to deter people from fishing, after authorities discovered elevated levels of potentially toxic microscopic algae.
- The area affected extends from the Old Swan Brewery to Garret Road Bridge
- If consumed, the toxins could produce food poisoning and muscular paralysis
- There are no health concerns about commercially-caught shellfish
The WA Department of Health is advising people not to eat fish, crabs or shellfish collected from waters extending from the Old Swan Brewery, Mounts Bay Road and upstream to the Garret Road Bridge.
It said this included the commonly known areas of Perth Waters, Elizabeth Quay, Barrack Street Jetty and Claisebrook Cove.
Cooking will not destroy toxins
Acting environmental health executive director Michael Lindsay said ingesting toxins produced by the detected microscopic algae, Alexandrium spp, could produce a type of food poisoning known as paralytic shellfish poisoning (PSP).
“These algae, which are not visible by the naked eye, can produce a toxin which could be absorbed by filter-feeding shellfish and potentially consumed by crabs, and finfish to a lesser extent,” Dr Lindsay said.
“It is important to note that cooking will not destroy these toxins.”
Symptoms of poisoning include 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 can cause muscular paralysis.
Dr Lindsay said anyone who experienced those symptoms after eating fish or shellfish from the river should seek urgent medical attention, particularly if they had respiratory distress.
“Do not discard uneaten portions of mussels or other shellfish as these may assist with determining a likely cause of any symptoms,” he said.
Shellfish includes oysters, mussels, clams, pipis, scallops, cockles and razor clams.
No concerns about commercially-caught shellfish
Dr Lindsay advised against eating shellfish collected recreationally, particularly in rivers and estuaries, as their safety could not be guaranteed.
He noted farmed shellfish purchased in supermarkets and other commercial outlets in WA were not affected as there was a strict quality-assurance program to ensure they were safe for human consumption.
Dr Lindsay said the recent rise in algae could be attributed to a combination of factors including the temperature, salinity levels, calm water conditions and limited rainfall.
He said other recreational activities including swimming, skiing and boating were not likely to be affected by this microalgae species, but as a general rule swimming should be avoided when the water was discoloured.
Not all WA waterways are monitored for algal blooms, and anyone who sees or suspects an algal bloom is urged to report it to their local government authority or to the Department of Water and Environmental Regulation’s ALGALWATCH.