Bremer Canyon turns on orca feast

Scientists have recorded weeks of frenetic marine activity at WA's Bremer Canyon as hundreds of different creatures made their annual pilgrimage to the Southern Ocean hotspot.

Killer whales, sperm whales, blue sharks, long-finned pilot whales, manta rays and, for the first time, a great white shark were among the vast array of species spotted in the lively patch 70km off Bremer Bay.

But the canyon's future as a haven for marine life is uncertain because the Federal Government could again release the area for petroleum exploration.

About 1200 people went to Bremer Bay this year for expeditions to see the phenomenon, which happens for only a few weeks each year.

Marine wildlife consultant Bec Wellard said they saw more killer whale calves this year and data collected could help scientists unlock the mystery of where orcas gave birth.

"On one day we saw five calves," the Curtin University PhD student said. "We're not sure where they are being born but one was only a few weeks old and I wouldn't imagine it would have swum too far.

"They are possibly born in the Antarctic, further east or west. This is still a frontier of science."

The Federal Department of Industry said two exploration permits over the Bremer Canyon area were cancelled in September because work conditions were not met but could be open for bidding as re-release areas.

There have been calls for the canyon to get marine park protection to make sure this spectacular display of nature continues.

The marine hotspot was found by Esperance filmmaker David Riggs while investigating the disappearance of a tagged great white shark in the area.

Tagging data showed the 3m shark vanished after suddenly diving hundreds of metres to the ocean floor and its tag washed up at Bremer Bay a few weeks later.

Mr Riggs believes killer whales might have attacked the shark in an area with a nutrient-rich upwelling from the ocean floor that attracts marine life.

"The main thing for me now is what else is attracted to this situation," he said.

"We can see there are killer whales, but what else is there? Where are the great whites? It's such a rich food source."

This year Mr Riggs saw a 5m great white he believed was pregnant basking on the surface about 2km from where killer whales were massing.