The U.S. Fish and Wildlife Service reported the 25-foot whale carcass to NOAA after biologists working in the area found it about a mile from the Farrallon Islands with 1- to 2-foot slashes on its side.
It was not immediately clear whether the wounds were inflicted before or after the whale died.
Boaters are reminded of the presence of groups of humpback and gray whales known to swim in sanctuary waters, relatively close to the shoreline and directly through busy shipping lanes.
Boaters should avoid coming within 300 feet of the animals, cutting across a whale's path or making sudden speed or directional changes, according to NOAA.