U.S. Customs and Border Patrol agents have been questioning Canadian fishermen in disputed territorial waters around Machias Island about possible illegal immigration, according to Canadian media reports.
But this summer that camaraderie has been threatened, Canadian fishermen claim, as officers with the U.S. Border Patrol have started to wade into the area, pull up aside their vessels and ask about their citizenship.
The area in question is around Machias Seal Island, an 8-hectare (20-acre) rock island at the Maine-New Brunswick border.
"Canada continues to investigate these incidents that occurred in Canadian waters, including through engaging with USA agencies involved in the matter", she said.
"We have enjoyed a respectful and cordial relationship with our USA counterparts".
The U.S. Border Patrol, which is part of U.S. Customs and Border Protection, declined to comment and referred all inquiries to the U.S. State Department, which did not respond to a request for an interview.
"Houlton Sector Border Patrol has conducted operations in the past in this area and will continue to conduct operations in the waters off the Coast of ME in jurisdictional waters of the United States", Stephanie Malin wrote in an email.
"Canada's sovereignty over the area is long-standing and has a strong foundation in worldwide law", the post said.
Laurence Cook, a spokesman for a Canadian fishermen's association, told Canadian media that at least 10 vessels were intercepted in the last two weeks alone near the Manchias Seal Island, just off the coast of ME and the Canadian province of New Brunswick. Any vessel operator that does not slow down and stop when ordered by Border Patrol agents can be criminally charged, Malin said.
The agency couldn't say how numerous vessels stopped were fishing.
Federal law gives Border Patrol the authority to stop, search and examine any vehicle entering the USA including those in a maritime environment, Malin said.
Unlike Canada, the United States does not help maintain the island but still believes that it is their property.
According to the local fisherman's association, both American and Canadian fleets have fished the 277-square-mile overlap "for years" - even if the relationship between individual lobstermen is said to be "strained".
Visitors head to Machias Seal Island on Friday, June 24, 2016.
"I honestly do not know what's going on", he said, adding that a directive to patrol the area may be linked to a broader culture change with the election of U.S. President Donald Trump.
Indeed, it's not for nothing the area is called the grey zone - gray zone to the Americans. The agency's authority extends to the borders of the US, including the area around Machias Seal Island claimed by the USA and Canada, she added.
Tiny Machias Seal Island itself is no geopolitical trophy, though it is a unique home to scores of puffins. Their counterparts in Canada mostly stayed off in the distance, setting cages during the winter around the coast of New Brunswick, Nova Scotia and Newfoundland.
Tensions are ratcheting up on the border - but not that border, the other one.
"Typical American bullies", Cook wrote in the June 25 post, asserting that the Canadian vessels were rightly fishing in Canadian water.
He has argued that Canada and the USA should submit the disagreement to arbitration at the world court.