The 8,145-ton mother ship Nisshin Maru and two whaling vessels, - the 747-ton Yushin Maru No.2 and the 742-ton Yushin Maru No.3, arrived at the port in Yamaguchi Prefecture on Friday. Opponents of the Japanese program say it's a cover for commercial whaling because the whales are sold for food.
Japan's Fisheries Agency described the expedition as "research for the objective of studying the ecological system in the Antarctic Sea", and said that three of the five ships returned to Shimonoseki port in western Japan Friday.
Officials said the whalers used parts of the whales to determine their age, nutrition, and reproductive conditions. She called the event "obscene cruelty".
Japan intends to cull 4,000 more whales over the next 12 years as part of its "research".
A handout photo from activist group Sea Shepherd allegedly shows a dead Antarctic mink whale on board the Japanese vessel Nisshin Maru in Antarctic waters in the Australian Whale Sanctuary on Jan 15, 2017.
Kitty Block, executive vice-president of Humane Society International, an animal protection group based in Washington D.C., said Japan is needlessly killing whales every year. The global moratorium on whaling has been in place since 1984.
Critics say it's a dying industry, but Japan's government has spent large amounts of tax money to sustain the whaling operations, saying it's a Japanese cultural tradition that must be preserved.