Japan's whaling fleet has returned from the Antarctic ocean with their smallest catch in years, blaming anti-whaling group Sea Shepherd for interfering in their operations.

The ships had returned to port with only 507 whales, just over half the number they set out to catch, the BBC reported.

That included 506 minke whales and one fin whale.

The BBC reported the whalers were angry at Sea Shepherd's "violent interference" in the hunt.

Clashes between the two sides lasted 31 days at sea.

Hamilton Sea Shepherd activist Peter Bethune is awaiting trial in Japan after boarding the Shonan Maru II on February 15.

He was attempting to carry out a citizen's arrest on the ship's captain and present a bill for Sea Shepherd's ship, the Ady Gil, which sank following a January collision with the Shonan Maru II.

He was arrested when the ship returned to port on March 12 and charged with trespass. Japanese authorities later added charges of assault, illegal possession of a knife, destruction of property and obstruction of business.

Assault and business obstruction charges carry prison terms of up to 15 years or a fine up to 500,000 yen ($7260). Trespassing could bring a prison term of up to three years or a fine up to 100,000 yen.

Mr Bethune will be sentenced next month, having admitted some of the lesser charges.

Japan's annual whale hunt is allowed by the International Whaling Commission as a scientific programme, although the whale meat is sold for eating.

An international moratorium was imposed on commercial whaling in 1986.

Meanwhile, the Norwegian government has set a commercial whaling quota of 1286 whales.

The International Whaling Commission (IWC) will meet in June to consider a proposal to allow Norway, Japan and Iceland to commercially hunt whales in exchange for a reduction in the number of animals killed.

- NZPA