The conservation group Sea Shepherd has ended its summer campaign against the Japanese whaling fleet in the Southern Ocean.

Sea Shepherd captain Paul Watson says they've decided to withdraw in the face of increasingly violent tactics from the Japanese whalers, including ramming.

"They're escalating their aggression and we're outnumbered", he said. "We just don't have the manoeuvrability or the speed that they do."

The Sea Shepherd ship 'Steve Irwin' is expected to dock in Hobart in about 10 days.

A spokesman for the Japanese Institute for Cetacean Research Glenn Inwood says the protesters departure will bring a welcome end to the violence.

Mr Inwood the whale hunt will continue for the rest of summer.