Japan has conducted extensive illegal whaling across the globe for over a decade, according to new research that finds the International Whaling Commission (IWC) has failed to properly manage the hunting of whales.

The new study, published in the journal Royal Society Open Science, expands earlier research that determined Japan regularly engaged in illegal killing of sperm whales in the North Pacific during the 1960s. The latest investigation finds Japan for at least 12 years also falsified data for catches of sperm whales south of the equator, with the impact likely still being felt today.

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"Sperm whales were devastated by the catches -- 400,000 in the Southern Hemisphere, 315,000 in the North Pacific, and that doesn't include the huge number taken before 1900," Phillip Clapham, who co-authored the paper with his wife Yulia Ivashchenko, told Discovery News.

"We don't know the impact of these catches on this long-lived, very social animal," continued Clapham, who is the leader of the Cetacean Assessment and Ecology Program at the Alaska Fisheries Science Center's National Marine Mammal Laboratory. "They are difficult to study because they range so widely in habitats far offshore. But the catches must have caused massive disruption to the population and the tight-knit social system of the species."

A key method of controlling whale populations involves body length, which relates to their age and likely breeding status, particularly for females. The IWC previously set a minimum legal catch length of 38 feet.

For the study, the researchers compared whale length data from catches Japan reported to the IWC with data for the same period from the Soviet Yuri Dolgorukiy factory feet during 1960–1975.

The Soviets and other countries also conducted illegal whaling, but Ivashchenko, also at the National Marine Mammal Laboratory, managed to find formerly secret Soviet whaling industry reports in Russian archives.

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"The data used in this particular paper were collected by Dmitry Tormosov, who hid 57,000 individual catch records (i.e., forms filled out on the deck of the factory ship) in his potato cellar in Kaliningrad for 30 years until after the Cold War," Clapham said. "We've seen the original data."

Prior to the 1972 implementation of the International Observer Scheme (IOS), which required that an independent inspector be aboard whaling ships, the Soviet fleet was documented as having killed 5,536 female sperm whales, of which only 153 were at or above the minimum legal length. During the same period, Japan killed 5,799 female sperm whales and reported 98.5 percent were of legal size.

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