Rescuers are hopeful an entangled whale may have freed itself after a fishing net was found adrift with a gaping hole in the middle.

The discovery of the net was made by conservationist Andrew Stevenson, in waters off the south-west of the Island heading out to Challenger Banks - where the humpback whale was spotted by fishermen earlier this week.

Mr. Stevenson, who is filming a documentary on Bermuda's migratory humpback whales, said that when the net was laid out on the deck of the Sea Shepherd Conservation Society ship the Farley Mowat, it revealed a large hole the size of a whale's head.

He went out on Saturday looking for the whale in the 40ft catamaran 'The Windrush'. The Provincetown Center for Coastal Studies in the US advised him to take a windsurfing mast, duct tape and serrated knife among the equipment to help free the whale, but not to get in the water with it.

Mr. Stevenson said yesterday: "We found a large tangled-up green fishing net exactly where the whale had been seen earlier in the week. When we pulled it out on the deck there was a great big hole about the size of a whale's head. It looked like a massive harness or halter.

"We are hopeful that the whale has either struggled free or that it has backed up and the net has just come off the front of its head. We feel tremendously relieved."

The entangled whale was first spotted by fishermen on Tuesday, at Chubbs Head beacon. On Wednesday it was then seen near Argus Banks.

Fisheries wardens from the Department of Environmental Protection have spent four days searching for the whale in their offshore boat, The Sentinel.

John Edmunds, head fisheries warden, said: "We have made many patrols, and yesterday (Saturday), we went right round the Island but didn't find it, so we are all very optimistic the whale has now freed itself.

"We are confident, given that the net Mr. Stevenson found was similar to that seen by the fishermen. It's a big ocean out there and so looking for the whale was like looking for a needle in a haystack, but we are hopeful it has found its way free."

Mr. Stevenson is asking anyone who spots humpback whales off Bermuda to report their sightings to: 77-SPOUT-(777-7688) or to email: spout@logic.bm

He has also set up a website: whalesbermuda.com to encourage schools to get more involved with sightings and appreciation of these wonders of the deep.