The fisheries agency said activists had stepped up attacks on whaling ships
Japan's annual Antarctic whale-hunting season has fallen short of its target catch because of disruptions by anti-whaling activists, officials say.
Japan's Fisheries Agency said its fleet had killed 679 Minke whales out of a planned 935, and just one Fin whale, despite a target of 50.
It partly blamed the disruptions on the Sea Shepherd Conservation Society, a US-based environmental group.
Protesters had escalated their attacks on Japanese ships, the agency said.
The Fisheries Agency said 16 days of hunting were lost due to bad weather and confrontations at sea between activists and the six-ship whaling fleet.
It added that several hunting ships were damaged in collisions or by chemicals thrown by the protesters.
Japan abandoned commercial whaling in 1986 after agreeing to a global moratorium.
But its fleet continues to hunt whales in the name of scientific research, which is allowed under international rules.
Whale meat not used for study is sold for consumption in Japan - which critics say is the real reason for the hunt. The meat can be found in supermarkets and restaurants across the country.
Many people in Japan regard whaling as a cherished cultural tradition, says the BBC's Roland Buerk in Tokyo.
Generations of children have been given whale meat for their school lunches, our correspondent says.
Consumption of whale meat is now low, but attempts have been made to increase its popularity by marketing whale curry and whale burgers, he adds.