Japanese whaling fleets set sail Monday to hunt whales commercially for the first time in 31 years, a day after Tokyo formally left the International Whaling Commission.

As an IWC member, Japan halted commercial whaling in 1988. But it continued hunting whales for what it claims were research purposes, a practice criticized internationally as a cover for commercial whaling.

On Monday morning the Nisshin Maru, a whale factory ship belonging to Kyodo Senpaku Co., and two other whalers left the port of Shimonoseki, Yamaguchi Prefecture, to conduct offshore whaling of minke, sei and Bryde's whales.