A bumper salmon season is on the cards for WA, according to the state's peak angling body, with an early start likely because of cooler ocean currents along the west coast.

If the season goes as expected, it would follow on from two other exceptional years, where the sheer volume of salmon saw swimmers in Perth and Rockingham ducking to avoid leaping schools of fish.

Recfishwest spokesman Tim Grose said salmon have already been spotted along the south coast near Esperance and Albany.

"We've seen already through social media there are some schools starting to form and move," Mr Grose said.

"Less warm water pushing down from the north and more of that cool water coming in from the south means we're seeing fish start their run early, so the time is now for fishers to get their gear ready."

Mr Grose said the best place to catch salmon was from the beach, and Recfishwest would be distributing a map detailing the top fishing locations.

"Albany's Cheynes Beach on the South Coast and Injidup Beach, Hamelin Bay and Bunker Bay in the South West are excellent and safe spots to go south of Perth," he said.

Changing weather helps fish

Oceanographers say the early salmon run is not surprising, with a change in weather systems bringing cooler ocean currents to the west coast in recent years.

UWA Professor of Coastal Oceanography Charitha Pattiaratchi said the usual summer pattern was for high pressure systems to linger in the Bight, bringing easterly winds and hot weather.

It will be the third consecutive bumper salmon system, if the forecasts are accurate. ( ABC News )

But he said these high pressure systems have been failing to stay put, pushing southerly winds over the ocean and cooling it down.

"For the last maybe three or four years we've seen a similar pattern," Mr Pattiaratchi said.

"2016 was the warmest year on record globally, and during that time there were only three places in the world where it was cooler — the northern Atlantic off Greenland, in the South Atlantic and in Australia's south west.

"The same pattern was there in 2017 also, but it was not as cool as the year before."

Mr Pattiaratchi said the southerly winds had also been pushing water offshore, bringing cold water to the surface — a process known as upwelling.

He said water rising from the ocean floor contained more nutrients, which meant more food for fish, explaining an increase in numbers.

"We all like the colder and milder weather, but from an ocean point of view, it increases the productivity, particularly in terms of fish," he said.