The terrifying moment a pod of orcas descended on a vulnerable blue whale that had unwittingly entered their vicious hunting ground has been captured on camera.

Jemma Sharp, owner of Whale Watch Western Australia observed the struggle from only a few metres away and said the moment was bittersweet.

The family-owned business run whale-watching tours along Australia’s west coast, and had 40 customers on board with front row seats to the bloody battle.

Over five pods of orca worked together to exhaust the blue whale until it took it’s final breath

Tour operators and 40 whale watchers had front row seats to the three hour struggle

Ms Sharp explained the blue whale was simply in the wrong place at the wrong time, inadvertently entering the hunting and breeding ground of the orca.

Blue, humpback and minke whales swimming north from the Artic become exposed to pods of hungry orca when they enter Bremer Bay.

‘It’s a tricky situation, there’s no way around and they can’t get through’, she said.

Adult blue whales usually have the knowledge and experience to keep their distance from the territorial whales while entering the passage.

On this particular day, Ms Sharp said five pods of orca, numbering 75 individuals gathered in the water after the blue whale was spotted.

The other orca can be seen ‘surging’ towards the blue whale, leaping in and out of the water exposing a large percentage of their bodies.

Over a three hour period the orca worked together to exhaust the blue whale, trapping the animal on it’s side so it couldn’t breathe through it’s blowhole.

Ms Sharp said she could see this method wasn’t working because the blue whale was too strong, so matriarch ‘Queen’ began to bite the whale’s tail as a distraction.

The orca were seen ‘surging’ in and out of the water as they descended on the blue whale

‘All the family put their body weight on the whale so he couldn’t fight back, we saw the moment he took his last breath and then didn’t see him again’, Ms Sharp said.

While it was a heartbreaking moment, Ms Sharp said from a research perspective it was a privilege to follow the hunt through to the end.

‘It was a meaningful moment for the animals to be fed, it was nice to see all the birds and sharks and pilot whales receive a vital meal’, she said.

As for the whale watchers on board, Ms Sharp said they were able to have compassion for both the orca and the blue whale.

‘They were completely blown away but had the capacity to appreciate the importance of what they were witnessing.’