'On the figures reported to the International Whaling Commission (IWC) that shouldn't have happened.' Franklin said it had been surmised that more whales had been taken by the Soviets than were reported, but it was not until the late 1990s that the data confirmed it.

'The Russians took about 25,000 whales in the years from 1959 to 1961, of which only a fraction were officially reported to the IWC,' he said.

'Our study has now linked the reported catches and the data recording the illegal catches with the breeding areas in Antarctica, confirming suspicions that these illegal catches on top of earlier whaling did lead to the collapse of these populations.

'It's been established that only around 150 humpback whales survived out of those Pacific and east Australian populations, from what we believe to have been pre-whaling numbers of between 45,000 and 65,000 whales.'

These findings were presented to the International Whaling Commission meeting in Portugal earlier this year, said a Southern Cross release.