A fisherman died Wednesday morning after he fell off his vessel into Portland Harbor, officials said.Officials said the 51-year-old fisherman fell into the water as the vessel was preparing to dock at the Portland Fish Pier just before 8:45 a.m.The crew from a U.S. Coast Guard ship that was docked on a nearby wharf witnessed the incident and launched a small rescue boat while other crew members ran to the scene and tried to help from the dock, officials said.The fisherman was pulled from the water by the rescue boat and taken to a nearby pier where paramedics tried to resuscitate him, officials said.He was transported to the Maine Medical Center and died a short time later.The man's body was taken to the Medical Examiner's Office in Augusta to determine his cause of death.The fisherman's name has not been released while officials notify next of kin.