Mexico defended its fishermen Tuesday after the United States government banned Mexican fishing vessels from U.S. ports on the Gulf of Mexico because of poaching, saying the incursions were accidental.

The U.S. government says Mexico has not done enough to prevent its boats from illegally fishing for red snapper in U.S. waters in the Gulf.

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.

Starting Monday, Mexican fishing boats in the Gulf are "prohibited from entering U.S. ports, will be denied port access and services,” the National Oceanic and Atmospheric Administration wrote in a ruling in early January.

Mexico's Agriculture and Fisheries departments said Monday they are holding informational chats with fishermen on Mexico's northern Gulf coast near the border to bring their attention to the poaching issue.

"It is important to note the willingness the fishermen have shown toward carrying out this type of measure,” the departments said in a statement.

Mexico, however, has a poor record of enforcing fishery limits or safeguards, critics say. Small Mexican boats frequently use prohibited long lines or nets to haul in snapper in U.S. waters. Such nets and lines can indiscriminately trap marine life.

The environmental group Oceana Mexico said in a statement in January that "Mexico has yet to implement fully" its environmental commitments to implement sustainable fishing practices as required by the U.S.-Mexico Canada free trade pact.

Environmentalists say Mexico’s attitude on the Gulf fishing dispute mirrors its lack of effort to stop gill net fishing in the Sea of Cortez, or Gulf of California, that has driven the vaquita marina porpoise to the brink of extinction.