The researchers say that the marine mammals—whose name means "little cow" in Spanish—are accidentally drowning in the gill nets local fishers deploy for fish and shrimp. A mere 97 vaquitas remain.
Vaquitas are shy creatures, and rarely seen, except when they're pulled to the surface—dead—in nets. They've been known to science only since 1958, when three skulls were found on a beach. At the time, it was thought that they numbered in the low thousands. Scientists and fishers alike say the animals, with their pretty facial markings ("they look like they're wearing lipstick and mascara," one scientist said) and sleek bodies, are endearing.
There's danger now that the porpoises will become the second cetacean (the first was the baiji, or Chinese river dolphin) to succumb to human pressures, most likely disappearing forever by 2018.
"It's a complete disappointment for everybody, because we've all been working hard to turn this around, and the [Mexican] government has addressed this from the highest level possible," said Lorenzo Rojas-Bracho, a cetacean conservation specialist at Mexico's Commission of Natural Protected Areas and a member of the team.
Indeed, the Mexican government established a presidential commission on vaquita conservation in 2012, when scientists estimated the porpoise's population at 200.
To stem the vaquitas' decline, in 2005 Mexico created a refuge for them, banned all commercial fishing in the refuge's waters, beefed up enforcement, and invested more than $30 million (U.S.) to compensate fishers and encourage them to switch to other fishing methods.
It also established the international scientific team to monitor the porpoise's population, reproductive rates, and habitat. Its members hail from such august conservation bodies as the International Union for Conservation of Nature, the International Whaling Commission, the U.S. Marine Mammal Commission, and Norway's Institute of Marine Research.
All were optimistic then. "We thought we were going to see the vaquitas' numbers increasing by 4 percent a year," said Barbara Taylor, a marine biologist with the Southwest Fisheries Science Center in San Diego, California, and a member of the team. "Instead, they've had a catastrophic decline of 18.5 percent per year."
Chinese Demand—But Not for Vaquitas
That decline, Rojas-Bracho said, is "all due to illegal fishing that is out of control."
In the past three years, illegal gillnetting for the totoaba, a critically endangered fish that can grow to more than six feet long (1.8 meters) and 300 pounds (136 kilograms), has surged. Unfortunately, the porpoise and the similarly sized totoaba live in the same parts of the gulf.
The totoaba's swim bladder, highly prized as a traditional health food and medicine in China, can fetch thousands of dollars. Few fishers can resist the temptation.
"It's like trying to control traffic while someone's throwing money from the Empire State Building," said Rojas-Bracho, who learned of the extent of this illegal take from several fishers who are also on the presidential commission.
The team estimates that about 435 miles (700 kilometers) of legal nets are in the water every day during the fishing season, from mid-September to mid-June. "And that's not counting the illegal nets for the totoaba," Taylor says.
Because of the vaquita's timid nature (a sighting at 300 feet [90 meters] is considered close), scientists can't make visual counts of the animals. They rely instead on an array of special acoustic devices, deployed every year before the fishing season begins (they too are easily tangled in the nets), to record the sounds of the animals as they forage in the murky waters they favor. From these sounds, the researchers are able to estimate the vaquitas' numbers.
Because the animal's population is so low, the team says there is only one solution: Ban all gillnetting in the gulf's upper regions, including the waters surrounding the vaquitas' refuge. The ban must be strictly applied, even to the legal shrimp and fin fish fishery, and enforced with more police patrols on sea and land.
"It's a hard choice," Taylor acknowledges. Such a ban will hurt all the fishers, including those who aren't engaged in the illegal fishery. But, she said, if Mexico doesn't do that, it "will lose the vaquita."
Rojas-Bracho said that Mexico, China, and the United States governments also need to work together to control—if not end—the trade in totoaba swim bladders. The dried bladders are often smuggled across the U.S. border before ending up in the Chinese marketplace.
There is a modicum of hope. Even at only 97 animals (25 of them believed to be females of reproductive age), the species can still be saved, Taylor believes. "Most marine mammals, including other cetaceans, that have been taken down through hunting have come back, so it's not too late. But if nothing is done, they can also go extinct rapidly, as happened with the baiji. They can be gone before you know it."
The commission will meet again at the end of August to discuss what to do next to save the vaquita.
Virginia Morell is the author of four acclaimed books, including Animal Wise: The Thoughts and Emotions of Our Fellow Creatures.