Tokyo ? Humpback whales are in the cross-hairs again.

Japan’s whaling fleet will leave port shortly for the South Pacific with orders to kill up to 50 humpbacks – the first known large-scale hunt for the whales since a 1963 moratorium put them under international protection.

The Fisheries Agency has refused to release the fleet’s departure date. But the lead whaling ship’s operator, Kyodo Senpaku Ltd., said the fleet could set sail from the southern city of Shimonoseki this weekend.

The ships, led by the 8,030-ton Nisshin Maru, will embark on their largest scientific whale hunt in the South Pacific.

Besides humpbacks, they will take up to 935 Antarctic minke whales and up to 50 fin whales.

But it is Tokyo’s plans to hunt the humpback – a favorite among whale-watchers for its distinctive knobby head, intelligence and out-of-the-water acrobatics – that has triggered condemnation from environmentalists.

“These whales don’t have to die,” said Junichi Sato, a Greenpeace spokesman. “Humpbacks are very sensitive and live in close-knit pods. So even one death can be extremely damaging.”