A 'megapod' of more than 100 humpback whales were seen feeding off the coast of Australia last week as they migrate to Antarctica.

The group of whales were filmed by a local tour group operator as they worked together to feed on a large school of bait fish at Bermagui on the Sapphire Coast region of New South Wales.

From about September, humpback whales return to Antarctica from the warmer northern waters, where they raise their young.

"Last year, this exact same week, we had a mass aggregation of humpback whales," tour group operator Simon Miller said.

"So, what that is, is where you get a mega-pod and it's where you've got more than 20 whales at the time feeding on a particular area. And this is something that was first witnessed last year.

"We've been witnessing whales feeding on the south coast for maybe like, 18, 19 years... but we've never witnessed them feeding in such huge aggregations before," Mr Miller said.