Secret illegal Soviet whaling, during the years from 1947 to 1973, led to the decimation of some populations of humpback whales in the Pacific, according to a new study by collaborating marine researchers.
Wally Franklin, a PhD student with Southern Cross University's Whale Research Centre and co-director of The Oceania Project, was one of the contributors to the study, which was presented to the International Whaling Commission meeting held in Portugal earlier this year.
Mr Franklin said while it had been known for some years that almost 100,000 whales had been killed secretly by the Soviet whaling fleet in the southern hemisphere, it had not been clear how this had impacted on the current humpback whale population.
"It was always a mystery why the population of humpback whales off the east coast of Australia and in the Pacific region suddenly collapsed in the early 1960s," Mr Franklin said.
"This new study has shown the link between the illegal catches during the late 1950s and early 1960s and the collapse of the Australian and Pacific populations."
During the 1950s the whaling stations at Tangalooma (in Queensland) and Byron Bay each had a quota of whales which they could usually get in a couple of days.
"By the early 1960s, all of a sudden they just couldn't find any whales to meet the quotas and basically the industry collapsed," Mr Franklin said. "On the figures reported to the International Whaling Commission (IWC) that shouldn't have happened."
Mr 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."
Mr Franklin said while the east Australian population was showing a steady rate of increase, the population that migrated past New Zealand to places such as Fiji had not.
"There were hundreds of whales reported off Fiji in the late 1940s and 50s, but the whales have not gone back and now there are virtually none," he said.
"We are seeing signs that some of the whales from the east Australian population may be now moving into the Pacific and we are hopeful this will eventually lead to a stronger recovery.
"We are conducting further studies to identify the whales in these locations."
Mr Franklin said with the ongoing threat of renewed 'scientific' whaling in the Southern Ocean it was imperative that there was a watertight system to ensure compliance with the international regulations, requiring independent observers.
As it did in the 1950s and 1960s, the International Whaling Commission relies on self-reporting of catches.
"We want to make sure that the illegal catches which led to the decimation of these whale populations cannot be repeated in the future," Mr Franklin said.