Authorities said a 47-year-old Taunton man has died in a boating accident on the Taunton River. The Bristol district attorney’s office said Monday that Manuel Pinheiro was struck in the head Sunday when the boat he was riding in struck a tree in the river. Anthony Rose, 46, of Taunton pleaded not guilty Monday to drunken boating homicide and negligent operation of a boat. Prosecutors said Rose was drunk and speeding at the time of the accident Sunday afternoon. Prosecutors said Rose then drove his boat ashore near East Water Street in Taunton, where police and emergency services responded. Pinheiro was taken to Morton Memorial Hospital, where he was pronounced dead.