A derelict Japanese ship dislodged by last year’s massive tsunami is drifting toward Alaska, the Coast Guard said. The shrimping vessel was floating slowly northwest in the Gulf of Alaska about 125 miles west of the nearest point of land — Forrester Island outside the Dixon Entrance, a maritime transportation corridor separating U.S. and Canada jurisdictions. The ship is heading in the direction of the south-east Alaska town of Sitka 170 miles to the north, traveling at about one mile per hour, Coast Guard spokesman David Mosley said. “Our main concern is maritime traffic,” he said.