Japan's whaling fleet left on Tuesday for the Antarctic for a three-month, scaled-down hunt, the Japanese government said.
The announcement comes despite protests from opponents who say Tokyo has not proven that whales need to be killed for research.
Japan says lethal sampling is indispensable to obtain data on the maturing ages of whales.
The expedition will be the first since the International Court of Justice ruled last year that the hunts were not truly scientific, forcing Tokyo to revise its Antarctic whaling plans.