Not to contradict what you have posted, but the information I have read from a gentleman by the name of Terry Ruff, he is in the Customs and Border Protection office in Port Huron, Michigan. Fishing vessels that do not touch Canadian land have free egress, are treated as not leaving the U.S. water. However if a vessel anchors in Canadian water, ties up to another vessel at a Canadian port or otherwise docks in Canada must report upon return. Also any vessel over 31' in length must report also.
US Department of Homeland Security
US Customs and Border Protection
2321 Pine Grove Avenue
Port Huron, MI 48060
I'm sure he won't mind being contacted if there are any further questions. Hopefully this will help.