MEXICO CITY >> The U.S. Trade Representative’s Office filed the first environmental complaint against Mexico Thursday for failing to protect the critically endangered vaquita marina, the world’s smallest porpoise.

The office said it had asked for “environment consultations” with Mexico, the first such case it has filed under the U.S.-Mexico-Canada free trade pact. Consultations are the first step in the dispute resolution process under the trade agreement, which entered into force in 2020. If not resolved, it could eventually lead to trade sanctions.

Mexico’s government has largely abandoned attempts to enforce a fishing-free zone around an area where the last few vaquitas are believed to live. Nets set illegally for another fish, the totoaba, drown vaquitas.

U.S. Trade Representative Katherine Tai said that “USTR is committed to protecting the environment and is requesting this consultation to ensure Mexico lives up to its USMCA environment commitments,” adding “We look forward to working with Mexico to address these issues.”

Sarah Uhlemann, international program director at the Center for Biological Diversity, said “this is a big move that could save these little porpoises from extinction.”

“Illegal fishing is out of control in Mexican waters, and the vaquita is paying the highest possible price,” Uhlemann said in a statement. “We’re glad the U.S. government is taking Mexico to task for violating its environmental obligations and threatening the vaquita’s existence.”

Mexico’s Economy Department said after the complaint was announced Thursday that “The Mexican government reaffirms its commitment to the proper implementation of the USMCA and the responsibilities it has within it.”

It was the second stinging rebuke in less than a week for Mexico, which has done a poor job controlling the environmental practices of its fishing boats.

On Monday, Mexican fishing boats in the Gulf of Mexico were “prohibited from entering U.S. ports, will be denied port access and services,” the National Oceanic and Atmospheric Administration said, in response to years of Mexican boats illegally poaching red snapper 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.

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.

But the plight of the vaquita marina — of which perhaps as few as 10 survive in the Gulf of California — that has made Mexico look the worst.

For example, Mexican authorities allowed the environmentalist group Sea Shepherd to return to the Gulf, also known as the Sea of Cortez, to help in conservation efforts, but no longer allows the group to remove illegal gill nets.

It was the latest instance in which the Mexican government appeared to give more weight to sovereignty and fishing concerns than to protecting the species.

For years, Mexico has relied on Sea Shepherd boats to remove most of the illegal nets that trap and drown vaquitas, while doing relatively little to combat violent attacks by poachers on the environmentalists’ ships. The group estimates it has removed about 1,000 of the long, heavy nets over the last six years.

But the environmentalists were forced to leave the Gulf in January 2021 after a New Year’s Eve attack in which fishermen rammed a Sea Shepherd vessel with their boat; one of the fishermen later reportedly died of injuries sustained in that attack.

Since then, the job of locating and removing nets has been largely left to Mexico’s navy, which has done little to stop fishermen setting nets to catch totoaba, a fish whose swim bladder is a delicacy in China and sells for thousands of dollars per pound (kilogram).

President Andrés Manuel López Obrador has expressed his dislike of foreign interference, and his desire to balance the interests of fishermen and endangered species.

“We don’t need foreigners telling us what to do or placing sanction on our country’s fishermen,” López Obrador said in June. He insisted that “we can reach an agreement that seeks an equilibrium between fishing and productive activities, and taking care of species.”

That attitude appeared to be behind the government’s decision in July to abandon the policy of maintaining a fishing-free zone around the small area holding the last remaining vaquitas.

The measure announced replaces the fishing-free “zero tolerance” zone in the upper Gulf with a sliding scale of punishments if more than 60 fishing boats are seen in the area on multiple occasions.