The whale, believed to be an adult female humpback measuring 43 feet (13 metres) in length, was found Wednesday on the ship's so-called "bulbous bow," the section of the vessel's leading tip that goes through the water, said Julie Speegle, spokeswoman for the National Oceanic and Atmospheric Administration in Juneau.
The whale is believed to have become attached to the bow overnight before being discovered Wednesday morning.
Officials from the U.S. Coast Guard and NOAA's National Marine Fisheries Service briefly detained the ship, the Sapphire Princess, in an area south of Juneau to open an investigation and remove the whale's body. The ship was allowed to proceed in the afternoon.