Fisheries Minister Gordon Hill has urged abalone fishers to observe bag and size limits this weekend, and warns there will be increased policing of the licence rules.
Mr Hill said the expected fine weather should attract a large number of people to Perth's metropolitan abalone reefs and already depleted stocks could suffer further if bag and size limits were not adhered to.
"The combination of calm weather conditions and low tides expected on Saturday morning, will expose many of the prime abalone reefs along the Marmion-Hillary's coastline," he said.
"Abalone catches have been good so far this year, but most of the legal-size animals appear to have been cropped off many areas of the reef top.
"I am advised by the Fisheries Department that there is a large proportion of undersized abalone in these areas.
"I am very concerned at reports that people are still exceeding the 20 per bag limit and also taking undersized animals.
"Despite efforts by Fisheries officers, some people are ignoring the rules - a situation which is putting abalone stocks at risk."