A fugitive anti-whaling activist known for confronting Japanese whaling vessels off Antarctica is due to testify about his actions in a U.S. court Wednesday.

Paul Watson, founder of the Oregon-based Sea Shepherd Conservation Society, is expected to take the witness stand in a contempt of court hearing in Seattle.

The Japanese whalers argue that the organization 10 times violated an order barring its vessels from attacking or coming within 500 yards of the whaling ships. They've asked the 9th U.S. Circuit Court of Appeals to impose fines of $100,000 for each violation, though they suggested the court waive those fines as long as the protesters stop confronting their ships.

The case is part of a long-running fight between the protesters and Japan's whaling fleet, which kills up to 1,000 whales a year, as allowed by the International Whaling Commission.

Japan is permitted to hunt the animals as long as they are killed for research and not commercial purposes, but whale meat not used for study is sold as food in Japan. Critics say that's the real reason for the hunts.

For several years, Sea Shepherd operated anti-whaling campaigns in the Southern Ocean. Activists aboard its vessels would hurl acid and smoke bombs at the whalers and drag ropes in the water to damage their propellers.