* Machine-gun fire from cutter sinks abandoned vessel
* Blacked-out ship posed danger to North Pacific navigation
* Japanese owner did not want to salvage the vessel (Updates with sinking of "ghost ship")
By Yereth Rosen
ANCHORAGE, Alaska, April 5 (Reuters) - The U.S. Coast Guard, firing repeated machine-gun blasts from one of its cutters, on Thursday scuttled an abandoned Japanese "ghost ship" that had been washed out to sea near Alaska by last year's devastating tsunami.
The derelict fishing vessel Ryou-Un Maru, which posed a threat to other marine traffic, sank at about 6:15 p.m. local time (0215 GMT on Friday), nearly five hours after the Coast Guard first opened fire on the ship, Coast Guard Chief Petty Officer Kip Wadlow told Reuters.
"It's confirmed," he said. "The vessel has been sunk and is no longer a navigational hazard in the area."
The cutter crew sent the Ryou-Un Maru to the ocean floor with a series of blasts from a 25mm machine-gun, firing intermittently on the drifting vessel for about an hour, then pausing as the ship caught fire and listed in the sea. The barrage resumed after a two-hour break, and the boat was underwater about two hours later.
The ship's Japanese owner has said it had no plans to salvage the vessel, and Wadlow said it had been slated to be scrapped even before it was swept away by the tsunami.
The Ryou-Un Maru was among the 1.5 million tons of debris the Japanese government estimates was dragged out to sea by the immense tidal surge unleashed by last year's Fukushima earthquake, said Ben Sherman, a spokesman for the National Oceanic and Atmospheric Administration.
"This boat, in this case, we know was at a particular pier, and before the tsunami it was there and after the tsunami it wasn't," Sherman said.
Experts from NOAA and other agencies determined that sinking the ship was the best way to manage the potentially dangerous fuel on board, Sherman said. "They anticipate that it'll dissipate or evaporate very quickly," he said.
Although most of the tsunami debris expected to hit U.S. coastlines is predicted to arrive in 2013 or later, some items have already washed ashore. In Alaska, most of the marine debris identified as tsunami-related has been buoys and floats from oyster farms.
The Ryou-Un Maru, carrying up to 2,100 gallons of diesel fuel, was about 170 nautical miles southwest of the Alaskan town of Sitka and had been drifting toward busy navigational lanes used by cargo vessels plying the waters of the Great Circle route between North America and Asia, Wadlow said.
The Great Circle arcs from the U.S. West Coast to east Asia, passing through the Aleutian Islands.
The ship was initially spotted by Canadian officials in waters off the coast of British Columbia, Wadlow said. It drifted into U.S. waters on Saturday, and the U.S. Coast Guard began its close monitoring of the vessel.
The ship, nearly 200 feet (61 meters) in length, lacked any lighting, making it a dangerous obstacle at night, Wadlow said. (Editing by Alex Dobuzinskis, Cynthia Johnston, Lisa Shumaker and Paul Simao)