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."

Sperm whale podGabriel Barathieu, Wikimedia Commons

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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This unrealistic distribution, together with the fact that Japanese fleets were supposedly able to catch 37 times the number of legal-sized females as the Soviet fleet, indicates the catch data was extensively by Japan, according to the researchers.

Even the IOS was often ineffective.

Clapham said that, in theory, having an inspector of a different nationality on a factory ship ruled out cheating. "But we know from Soviet biologists that it didn't entirely; inspectors couldn't be on the processing deck 24 hours a day, and they were sometimes intentionally distracted with 'celebrations' by officers who took them to drink in their cabin when something illegal was about to come aboard."

He added that whaling nations today maintain that the system of inspection proposed, should commercial whaling resume, is adequate.

"Yet it's clear from genetic analysis of what's being sold in the Japanese market that there's stuff there that you can't account for through the whaling we know about," he said. "Much of this is likely local bycatch by fishermen (it is legal in Japan to kill a whale in a net). But Japan and the other whaling countries have adamantly refused to accept a truly independent, third-party monitoring system that includes every step from the catch to the market."

Another problem concerns assessments of current whale populations, which take into account past catch data. If the data are significantly false, as the scientists have just determined, then the assessments themselves will be inaccurate.

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C. Scott Baker, associate director of Oregon State University's Marine Mammal Institute and a professor in the Department of Fisheries and Wildlife, told Discovery News that the new study presents "compelling evidence that the Japanese commercial whaling fleet was engaged in widespread falsification of records prior to the introduction of international observers in 1972."

Vendors sell whale meat at the Tsukiji fish market in Tokyo, 2008. Stefan Powell, Wikimedia Commons

"Their careful analysis confirms that the reported lengths of the sperm whales in the Japanese records were intentionally falsified to cover up the killing of females below the legal length set by the IWC," Baker added. "The impact of this illegal hunting of undersized females is unknown and can only be determined once the records are corrected and assessed by the IWC."

Baker said it's ironic Soviet whaling records were used to demonstrate the implausibility of sperm whale lengths documented in the Japanese records, given how much illegal whaling the Russians did over the years.

Several Soviet scientists who were aboard the factory ships at the time, however, have since corrected past data. Japanese scientists have come forward as well, but, Baker said, "to my knowledge, none have come forward with the true records from the fleets operating in national waters."

He concluded, "It is critical that Japan's ongoing scientific whaling, and any future commercial whaling, must have a robust system of observation and inspection, including onboard observers, vessel location beacons and DNA testing of market samples to confirm catches."