MEXICO CITY (AP) — Environmental groups called Thursday for an international ban on trade in a range of Mexican seafood and wildlife, seeking to force Mexico to do more to save the vaquita marina porpoise, the world’s most endangered marine mammal.

The United States already has an embargo on imports of shrimp from the upper Gulf of California. Also known as the Sea of Cortez, the body of water is the only place where the vaquita lives, and as few as 10 remain.

The Natural Resources Defense Council, the Center for Biological Diversity and two other groups said in an open letter that Mexico has failed to enforce a ban on fishermen using gill nets, which trap vaquitas. The nets are set to catch totoaba, an endangered fish whose swim bladder is considered a delicacy in China and is worth thousands of dollars.

“Only the strongest international pressure will force Mexico to get lethal fishing nets out of the water before these little porpoises disappear forever,” wrote Sarah Uhlemann, international program director at the Center for Biological Diversity.

There was no immediate comment from Mexico’s government.

In March, a government body raised criticism by announcing it would consider several proposals that would almost certainly harm the vaquita. The government has not announced whether those proposals will be accepted.

The Mexican inter-agency group said it is considering lifting endangered-species protection on the totoaba. Opening up legal fishing of totoaba would probably increase the deaths of vaquitas, but would provide a windfall for some fishermen in Mexico.

The group also said it is considering reducing the protection area for the vaquita, which would open up more areas to gill nets used for totoaba and other species. The nets trap and drown vaquitas.

The group also revived an old, discredited theory that blames the vaquitas’ decline on the lack of water flows from the U.S. through the Colorado River, which starts in the United States and empties into the Gulf of California.

The Colorado River theory posited that a decline of fresh water from the river due to U.S. usage had increased salinity in the upper Gulf, somehow affecting the vaquita.

Last week, the International Union for Conservation of Nature published a letter disputing that argument, saying that “the scientific community widely accepts that unsustainable mortality in gillnets (set for shrimp, totoaba and other finfish) is the cause of the vaquita’s rapid decline … There is no reason to seek an alternative explanation for the vaquita’s unprecedented decline.”

Mexico’s Environment Department has said the drop in the number of vaquitas and the area where they have been seen in recent years justifies reducing the protection zone, which currently covers most of the upper gulf. The zone starts around the Colorado River delta and extends south past the fishing town of San Felipe and near Puerto Penasco.

But such a move is also an admission the tiny porpoise may never return to the entire historic range of its habitat.

The appointment of the Brazilian army’s former chief health officer as the new army commander is an effort by President Jair Bolsonaro to heal a rift created by his firing of the defense minister and the subsequent removal of the top generals of all three military branches, analysts said Thursday.

Gen. Paulo Sérgio Nogueira, responsible for the army’s human resources, was appointed army chief Wednesday following the hasty departure of the leaders of Brazil’s army, navy and air force. The three men were forced out a day after Bolsonaro summarily fired retired army Gen. Fernando Azevedo e Silva as defense minister.

There has been little transparency around this week’s events, as neither the president nor the Defense Ministry explained what caused the change in leadership. Military and political experts said the unexpected firings, which some described as a “bomb,” were partly the result of the commanders’ reluctance to serve Bolsonaro’s political interests.

The reshuffle generated a deep — if brief — crisis within the military. Never since the return of democracy in 1985 had a president fired all the leaders of the military’s three branches, analysts said. The move caused uneasiness and great uncertainty as to the future of Brazil’s armed forces as the far-right president struggles with declining popularity and COVID-19 batters the country.

But the tapping of Nogueira as army chief was widely seen as an attempt by the president to ease tensions.

“The choice was to lower the tone,” said Juliano Cortinhas, who coordinates the research and study group on international security at the University of Brasilia.

Inside the military, Nogueira has a reputation of being a conscientious, reliable officer. He is also the man behind the military’s pandemic contingency plan, based on social distancing.

In a rare interview with Correio Braziliense on March 28, Nogueira praised the results of the measures he implemented to limit the spread of the coronavirus among military personnel and said he was preparing for a third wave of infections.

“The figures are relatively good in comparison with the population in general because of the prevention we have,” Nogueira said. “If this improved in Brazil, the number of people infected would probably be smaller.”

The lengthy interview was said by experts and the media to have greatly displeased Bolsonaro, who has strongly opposed the imposition by states and localities of strict health measures for the pandemic, arguing their economic damage will be more harmful than illnesses.

Brazil is currently battling with a fierce resurgence in coronavirus cases. The country reported a new daily high of nearly 4,000 deaths Wednesday, raising the toll for March above 66,000 deaths. That is more than double the number of deaths reported last July, which had been Brazil’s worst month in the pandemic.

“We have to be ready in Brazil. We can’t waver,” Nogueira said in the interview. “We have to work, improve the structure of our hospitals, have more beds, human resources so we can react if there’s a stronger wave.”

In the list of possible candidate for the army’s top post, he was among the oldest serving generals on active duty, which preserves military traditions and hierarchy.

For Cortinhas, the University of Brasilia professor, the changes in the military will not alter profoundly their relationship with Bolsonaro, at least in the short term.

“There was a name change, the game goes on,” he said. “The military continues to make a very important part of the Bolsonaro government.”

Other experts, however, said the crisis revealed a split in the ranks.

Eduardo Munhoz Svartman, president of the Brazilian Association for Defense Studies, stressed the distinction between active-duty members of the military — a contingent of about 300,000 men and women — and retired members.

Those who have entered the Bolsonaro government, including the new defense minister, former Gen. Walter Braga Netto, are usually retired military members and support the president.

But among active-duty military personnel, “there is a part that doesn’t want the armed forces to be used as a tool by the president,” said Svartman, who also teaches at the Federal University of Rio Grande do Sul. “There is growing internal polarization.”

Some active-duty generals are also eager to distance themselves from Bolsonaro’s handling of the pandemic. Most of Brazil’s 320,000 deaths occurred under the watch of active-duty Gen. Eduardo Pazuello, who was the federal health minister from May until last month. Pazuello is being investigated by a federal court for his handling of the collapse of the public health care system in the Amazonian city of Manaus.

While tensions have waned, João Roberto Martins Filho, a military expert, said things might never be the same between Bolsonaro and active-duty generals because of the removal of the three commanders.

“He crossed a dangerous line, and lost,” Martins Filho said. “This left a scar.”