Mexico’s foreign relations secretary, Marcelo Ebrard, said incidents of fishing by Mexican boats in U.S. waters were mistakes, saying it can be difficult to locate the dividing line between the two countries’ territorial waters.

“Sometimes it is hard to determine the exact line. It's not something intentional,” Ebrard said.

But critics say it seems more likely that Mexican boats are going where the fish are, rather than making the same navigational error over and over again. The U.S. Coast Guard has apprehended many repeat offenders, with some Mexican fishermen being caught in U.S. waters over 20 times since 2014.