Six ships left a port in northern Japan on Monday for a whale hunt in an offshore research program that critics have denounced as a cover for commercial whaling.
The fleet departed Ishinomaki, Miyagi Prefecture, to intercept up to 60 minke whales thought to be located within a 48- to 80-km area offshore, the Fisheries Agency said.
The ships will return by the end of May, and the catch will be used to study what whales eat, the agency claimed.
The International Whaling Commission banned commercial whaling in 1986 to protect the endangered mammals but approved limited hunts for research a year later.
Japan's expedition purportedly will collect data to study the impact of the mammal's feeding on fish stocks. The Fisheries Agency will report its findings to the IWC.
Annually, Japan kills about 400 minke whales in the Antarctic and another 210 whales -- 100 minke whales, 50 Bryde's whales, 50 sei whales and 10 sperm whales -- in the Northwestern Pacific.