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World’s most endangered marine mammal down to 30 individuals

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The vaquita, a small porpoise found only in Mexico’s Gulf of California, now faces extinction, scientists say in a report published today. Only about 30 individuals remain, according to an acoustic survey that counted the animals’ clicking noises last summer. The report dashes hopes that naval patrols and Mexico’s emergency gillnet ban, authorized in May 2015, would halt the vaquita’s precipitous decline. The numbers also add new urgency to a controversial plan to capture some of the remaining animals for a captive breeding program, scientists say.

“The situation is completely out of control,” says Lorenzo Rojas-Bracho, a cetacean expert at the National Institute of Ecology and Climate Change in Ensenada, Mexico, and member of the International Committee for the Recovery of the Vaquita, an international advisory group to the Mexican government. “Of course, there’s a risk in capturing the vaquitas. But it’s clear now that they will be killed [in gillnets] anyway.”

A 2015 survey estimated the vaquitas at about 60 individuals. They’re dying out because they get trapped in illegal gillnets, many set to catch another endangered species, the totoaba fish. The fish’s swim bladder commands extraordinarily high prices (sold for as much as $100,000 on the black market, according to a report last year from the Environment Investigation Agency) in China and some other Asian markets, where it is erroneously thought to help with a range of ailments from liver disease to arthritis. The demand has so far proved impossible to control, says Rojas-Bracho, adding that criminal organizations now control the totoaba fishery.

Efforts to develop alternative gillnets that the vaquitas could escape (as exist now for sea turtles) have also failed, largely because of opposition from and sabotage by suspected totoaba fishers, Rojas-Bracho says. And the 2016 agreement between Mexican President Peña Nieto and former U.S. President Barack Obama to permanently ban gillnets throughout the vaquitas’ range has not changed local fishers’ behavior so far.

Vaquitas are shy and rarely seen, but they make clicking noises while hunting. To track their numbers, scientists deployed a grid of 46 click detectors for 60 days throughout the animals’ range in the summer of 2016, using the same sites they’d monitored in 2015. The team also added detectors at 47 new sites in areas where vaquitas spend most of their time. In the 46 standard sites, the number of recorded vaquita clicks per day dropped by 44% from 2015 to 2016, indicating a 49% decline in the cetaceans’ population. The clicks recorded at the additional sites did not alter this grim statistic, or the final conclusion: Vaquitas will be extinct in a few years.

<p>Vaquita numbers have plunged precipitously in the past few years.</p>

Vaquita numbers have plunged precipitously in the past few years.

Comité Internacional para la Recuperación de la Vaquita, adapted by J. You/Science

In a last-ditch effort to save the species, the scientists will attempt to capture an unspecified number of vaquitas in October. Hoping to avoid frightening the porpoises, the recovery team plans to use bottlenose dolphins from the U.S. Navy Marine Mammal Program to spot them in the gulf’s dark waters. The vaquitas are familiar with dolphins, which also inhabit the gulf.

Although details remain to be worked out, the naval trainers say through a spokesperson that they will use standard operant conditioning techniques (think clicker-trainer with your dog) to teach the dolphins to locate the vaquitas. The training will teach the dolphins to use their sonar to seek out “air-filled lungs.” After a dolphin identifies a target, it will learn to touch a plate on the side of the boat to alert its handler, and then swim in the direction of the animal and leap in the air. The dolphins have already completed a successful test run, locating harbor porpoises, which are about the same size as vaquitas, in San Francisco Bay.

In the real event, after a dolphin spots a vaquita, members of the recovery team will head toward the porpoise in a small boat, equipped to bring the animal on board. “We have no idea of how they will react,” says Jonas Teilmann, a cetacean biologist at Aarhus University in Denmark, who helped develop methods for working with harbor porpoises, another species that scientists had difficulty keeping alive when captured because they often stopped breathing. “Based on our work with harbor porpoises, we know we must watch their blowhole, and monitor their heart rate.” When porpoises dive, Teilmann explains, the water pressure on their breastbone, which is softer than ours, tells them to stop breathing so that they do not drown. Unfortunately, when removed from the water and placed on a hard surface, the cetaceans also experience this pressure through gravity—a sensation they’ve never felt before—and often automatically stop breathing. Teilmann’s team discovered that putting the porpoise on a stack of thick baby changing pads somehow removes that pressure, and the cetaceans  begin breathing normally again.

Rojas-Bracho and the team wish that they could begin the capture and breeding program sooner. Unfortunately, the legal curvina fishing season is to open shortly. Between 600 and 1000 permits may be given, says Rojas-Bracho, who calls the action “madness,” particularly because it is not yet clear whether the gillnet ban will continue to be enforced. Illegal totoaba nets remain a danger, too. Indeed, already this year, a fisherman showed Rojas-Bracho a photo of another dead vaquita in a gillnet. “If there were 30 at the end of last summer, there are probably fewer now,” he says.

“We wish we could leave them in the wild,” Teilmann adds. “But right now there’s no other way to stop their extinction.”

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