Four whaling vessels left a port in Miyagi Prefecture on Thursday to take part in the last of what the government calls a scientific research program before the country's exit from the International Whaling Commission at the end of June.

The ships, which left the port of Ayukawa, will join four other vessels from different areas of Japan on the mission to catch up to 80 minke whales in April and May off Miyagi and Aomori prefectures to gather data on the whale population, including approximate ages.

They will also look at the stomach content of the animals with a view toward improving management of marine resources. The data will be used as a reference for commercial whaling, which Japan plans to resume in its exclusive economic zone for the first time in 31 years starting in July.