A Japanese fleet will set sail Sunday on its largest whaling program yet in the South Pacific and break the moratorium set on hunting the famed humpback whale in 1963, the Fisheries Agency said Saturday.

Four ships led by the 8,044-ton Nisshin Maru will leave the port of Shimonoseki on Sunday morning, the agency said. Two observation boats left northern Japan on Wednesday.

The fleet has orders to kill up to 50 humpbacks — the first known large-scale hunt for the whales since the moratorium put them under international protection.