Japan's whaling fleet is set to return to port tomorrow after killing little more than half its intended catch in the Antarctic due to harassment by activists, officials said.

The 8,044-tonne Nisshin Maru mother ship is scheduled to dock in Tokyo on Tuesday morning, ending a five-month voyage, while the five other fleet vessels will dock at various ports in the capital and western Japan.

Japan, which says whaling is part of its culture, had aimed to kill 850 minke whales and 50 fin whales on its annual hunt. It dropped an original plan to kill up to 50 humpbacks after coming under international pressure.

But the total catch for the year came to 551 minke whales with no fin whales "as a series of offshore protests prevented the fleet from achieving its initial goal," said Shigeki Takaya, a fishery agency official.

The Sea Shepherd Conservation Society - whose militant protest ship was involved in a series of high-seas clashes with the Japanese fleet - has said its campaign saved 500 whales.