Updated September 11, 2017 13:00:30

Photo: Fremantle Sea Rescue spent hours on Saturday unsuccessfully trying to free the whale from ropes. (Supplied: Fremantle Sea Rescue)

An operation has resumed this morning to rescue a humpback whale caught in a cray pot rope off the coast of Western Australia.

Authorities were alerted to the plight of the eight-metre whale after a call from a member of the public about 11am on Sunday.

Fremantle Sea Rescue skipper Josh Gammon-Carson said the whale was trapped in what appeared to be a cray pot or octopus pot rope.

"It was swimming around in circles and looked in distress," Mr Gammon-Carson said.

"It had a rope wrapped around its body in front of its fin and another one through its mouth."

For more than seven hours, 13 officers from Parks and Wildlife and the Fremantle Sea Rescue were on the water, "trying different techniques to try and slow down the whale to cut free the ropes".

Rescuers followed the humpback whale to Trigg, but the rescue was suspended just before 6:00pm due to fading light.

The whale has not been spotted today.

Parks and Wildlife senior marine officer John Edwards said it was important they found the whale.

"The animal's in that 8-10 metre range, so it has still got a lot of growing to do, and the rope won't grow with it," Mr Edwards said.

"So unless it parts and falls off or we're able to get to it and cut it off, the long-term prognosis for the animal is not as good as we'd hope."

Whales are commonly known to migrate along the coast of WA in September travelling towards Antarctica for summer.

"This time of year is fantastic for whale watching, but unfortunately we do get incidents like this," Mr Gammon-Carson said.

The skipper said it was important other people on the water were cautious around the animals and gave the emergency vessels space to help them.

"Have a look at the whales, but do remain clear. It is against the law to drive a boat within 100 metres of a whale," he said.

"If you do see a whale in distress contact Fremantle Sea Rescue or the Department of Parks and Wildlife directly, we can assist."

Photo: Sea Rescue officers said the whale had a rope wrapped around its body and one in its mouth. (Supplied: Fremantle Sea Rescue)

Topics: mammals---whales, marine-biology, sea-transport, animal-welfare, fremantle-6160, trigg-6029

First posted September 11, 2017 08:23:18