JAPANESE scientists are claiming vindication for their controversial lethal research whaling with a discovery that Antarctic minke whales are fast growing thinner.

The minkes had lost an average of 306 kilograms, or 9 per cent of their body weight, during the 18-year research program, says work published in the journal Polar Biology .

A likely explanation was a decline in the main food source, krill, caused by pressure from competitors, said the study led by Kenji Konishi, of the Institute of Cetacean Research in Tokyo.

The institute said killing whales was the only way to accurately measure parameters such as body weight or blubber thickness. In June, Japan's chief whaling negotiator, Joji Morishita, told a seminar in Chile there was evidence that something was happening. "Not only to cetaceans, but all other species are going through some change in distribution, and this might have something to do with planet change."

In the past 12 months, Japan has killed 695 whales in the Antarctic and North Pacific, out of a research quota of 1315, the institute's figures show.

Andrew Darby with Guardian News & Media