About 75 whales have died after beaching themselves, while another 50 are still alive on the beach and a further 25 are in the shallows.
The whales were spotted by a commercial fisherman at 6am on Friday about one kilometre north of the Hamelin Bay boat ramp, near Augusta.
Parks and Wildlife Service staff and vets will assess the health of the surviving animals, then return them to deeper water.
"The strength of the animals and the windy and possibly wet weather conditions will affect when and where we attempt to move them out to sea," incident controller Jeremy Chick said.
"The main objectives are to ensure the safety of staff and volunteers, as well as (ensuring) the whales' greatest chance of survival."
The Department of Primary Industries and Regional Development has issued a shark advice and warns people to avoid the area."It is possible the dead and dying animals will act as an attractant, which could lead to sharks coming close into shore along this stretch of coast," the department warns.
"While it's not uncommon for sharks to be present off the WA coast throughout the year, people should exercise additional caution until the stranding incident is resolved."
All beaches between Hamelin Bay and Boranup have been closed.
WA's largest mass stranding involved 320 long-finned pilot whales in Dunsborough in 1996.
Nine short-finned pilot whales were found dead at Albany's Ledge Point in November 1984, while 38 became stranded in April 1991 at Sandy Point, north of Broome.
SHORT-FINNED PILOT WHALES ARE:
- Closely related to long-finned pilot whales but have shorter flippers with less of an elbow
- Brownish-grey to black, with a pinkish-grey anchor shape on the undersides
- Have a bulbous forehead but the flippers are less than 18 per cent of the body length
- About 4m long for females and 5.5m for males
- Inhabitants of tropical and sub-tropical waters
