Fire Department spokesman Kyle Moore tells KOMO Radio the fire was aboard a decommissioned National Oceanic and Atmospheric Administration ship moored near the NOAA office in the Sandpoint area of Seattle.
He says the fire was in a storage compartment below the main deck that holds netting and other materials. Workers were welding in the compartment last week.
Moore says firefighters managed to starve the fire of oxygen by pumping in carbon dioxide into the storage compartment.
He says hazardous materials on board were not threatened and there's little smoke.
The NOAA website says the 215-foot Miller Freeman was decommissioned at the end of March. It was used for fisheries research and was based at Newport, Ore.
Firefighters worked for two-and-a-half hours to completely extinguish the flames. The ship is set to be scrapped, leaving the damage estimate at $100.