Swan River Trust Riverpark officers removed 160 dead fish from the Swan River at Fishmarket Reserve, Guildford during the weekend and today.
The fish were mainly black bream, of various ages.
The Trust has been monitoring elevated levels of Karlodinium veneficum in the mid to upper reaches of the Swan River between Rivervale and middle Swan Bridge since early March.
Karlodinium veneficum is a single cell microalgae found in most Western Australian waterways and typically increases in density between mid-summer and autumn.
Trust principal scientist Dr. Kerry Trayler said the Trust was looking at a range of factors that may have contributed to the fish deaths including low oxygen levels and the presence of Karlodinium veneficum.
“How Karlodinium affects the fish is not fully understood, but it is suspected their gills become damaged causing them difficulty in extracting oxygen from the water,” Dr. Trayler said.
Dr. Trayler said the Trust was undertaking tests to determine the cause of the deaths and would continue daily inspections in the Swan River.
Oxygen levels are variable in the area and as a precaution the Trust will switch on the Guildford Road Bridge oxygenation unit to increase oxygen levels in the river.
As a long-standing precaution, the Department of Health advises people not to eat wild shellfish from the Swan Canning Riverpark.
The Trust encourages the public to report dead or sluggish fish in the Swan Canning Riverpark, please contact the Trust on 9278 0900 or after hours 0419 192 845.
Media contact: Bridget Tombleson 9278 0953 or 0434 603 684.