Boaters are being reminded to steer clear of whales and their calves as the majestic giants make their annual journey south to cooler waters.
The Department of Environment and Conservation says whale sightings off Perth and Rottnest Island are expected to increase over the next few months as migrating whales return from WA's far north and head towards feeding areas in Antarctic waters.
Senior marine wildlife officer Doug Coughran said humpback whales could be seen as they returned from northern waters until December, while southern right whales that calve off the south coast could be seen as they move further south and travel closer to land, using sheltered waters to rest and feed their young.
Mr Coughran said boats should keep 100m from a whale for the safety of both themselves and the whale.
He said a fully grown humpback whale could weight up to 45,000kg.
"If a whale approaches your vessel, either place your motor in neutral or move slowly away from the animal, at a speed of less than five knots," Mr Coughran said.
"People who get up close on surfboards and boats are at greater risk, as whales weigh thousands of kilograms and may react violently, which can result in serious injury or death.
"If boats and surfers keep their distance, we can all get a view of these amazing creatures as they pass through our waters."
For more information visit http://www.dec.wa.gov.au/content/view/6400/2364 .