The 31-metre Viking Storm collided with the 12-metre Maverick on Friday, about 48 kilometres off the northwest coast of Washington state, outside U.S. territorial waters, sending the smaller boat to the bottom.
Three of the four people aboard the Seattle-registered Maverick were not hurt and were pulled from the frigid water by the crew of the Viking Storm.
An extensive air and water search ended Saturday without spotting any trace of the fourth man, 32-year-old Kelly Dickerson.
No one aboard the Vancouver-registered Viking Storm was injured and the vessel suffered only minor scrapes and a dent to its bow.
A U.S. Coast Guard spokesman says that agency is conducting an investigation, while a release from the Transportation Safety Board notes a Canadian team will also try to determine what caused the collision.