Following Tuesday’s event, the department said they received public reports of erratic “pilchard type fish” who were seen leaping out of the water at Woodman Point.
DPIRD said it would also investigate this incident, and its aquatic diagnostics pathologists would test samples of the fish to determine the cause of the unusual behaviour.
Water samples will be sent to the Department of Water and Environment Regulation’s phytoplankton ecology unit.
On Friday morning officers also responded to reports of starfish deaths on Challenger Beach in Kwinana, where they discovered about 100 dead starfish.
Samples have also been collected for analysis.
DPIRD fisheries and agriculture resource management executive director Dr Rick Fletcher said people need to be aware of these events and be cautious when hitting the water this weekend.
“The key advice around any fish kill is that you do not touch the affected fish or the water in their vicinity, or collect any fish for samples or use the dead fish as bait,” he said.
“It’s also important not to consume any fish that have been caught in the area of the fish kill.
“Fisheries officers will continue to monitor the beaches in case of further fish deaths and any additional species that may be observed,” he said.
Any fish kills should be reported to FishWatch reporting line on 1800 815 507.