Brett Bermingham and Chris Considine were fishing for bluefin tuna on Tuesday with three other crews when they saw the whales about 60 kilometres south of Warrnambool.

A smaller whale, estimated at eight metres, twice grabbed a tuna which had been hooked by Mr Considine. It then released the tuna as the men headed away, fearing for their lives.

Yesterday they showed off their mauled 30-kilogram catch - with numerous teeth marks - as they recalled the incident.

"We were 15 minutes into the fight with a tuna we hooked when we saw a killer whale heading towards us," Mr Considine said.

"We moved the boat out of its path and it disappeared, then it grabbed our tuna.

"It came within three metres of our boat. When we had almost run out of line we decided to chase it a bit and it let go. Then we saw three other killer whales - they were huge.

"Our boat is six metres, they would have been 12 to 14 metres long.

"We were reeling in as quickly as we could when our fish was grabbed again.

"I think it was the same whale. It let go again, we threw the tuna onboard and took off."

The men travel regularly to the shelf along with hundreds of other anglers lured by the hope of catching big game fish.

"There are so many fish, whales and dolphins out there," Mr Bermingham said.

Mr Considine said Warrnambool was missing out on a fishing-driven bonanza because of poor launching facilities.