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An expedition underway in the Gulf of California aims to get the most accurate count to date of the endangered vaquita — a small species of porpoise that has been nearly wiped out largely as a result of illegal fishing.

Elusive and isolated to one corner of the Gulf of California, the vaquita has long been difficult to spot. Now they are almost gone, with fewer than 100 believed to remain in the wild.

The survey to get an accurate count of the porpoises began on Sept. 26 and will continue through early December. Scientists from Mexico, Germany, the U.S. and United Kingdom are doing the counting aboard the R/V Ocean Starr.

Conservationists, researchers and the government of Mexico have mounted a full-on effort to save the vaquitas, which have been in decline at least since they were first identified by scientists in the 1950s.

They have been driven to the verge of extinction in part by fishermen intent on catching the also-endangered totoaba fish, which is prized in Asia for the supposed medicinal properties of its swim bladder, which aids the animal's flotation.

Chief expedition scientists Lorenzo Rojas of SEMARNAT and Barbara Taylor of NOAA Fisheries meet with Mexico's Minister and Deputy Minister of the Environment and Natural Resources, the Director of Fisheries and the Governor of Baja California aboard the R/V Ocean Starr on Oct. 1, 2015. Todd Pusser / NOAA Fisheries West Coast

“We’re at the last battle — which we’re hoping to win — for a patient that’s basically on the emergency table,” said Barbara Taylor, a National Oceanic and Atmospheric Administration researcher and one of the two chief scientists on the expedition. “It’s an absolutely stunningly beautiful species that’s only found in this tiny space in Mexico.”

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The vaquita lives only along the upper stretch of Mexico’s Baja peninsula. A report from the International Committee for the Recovery of the Vaquita in May found that the number of animals in the wild declined at an annual rate of 31 percent between 2011 and 2014, much faster than the previously projected decline rate of 18.5 percent.

“This porpoise probably has always had a relatively small population, but incidental mortality in gillnets over several decades have reduced the species to very low, critical numbers," said Omar Vidal, director general of the World Wildlife Fund-Mexico. “I believe that we are running the risk of losing the species, and this is certainly the last chance to save this unique Mexican porpoise."

The presence of shrimp fishermen was long thought to be the biggest threat to vaquitas, who get entangled in their gill nets and drown. In recent years, however, researchers say the rapid rate of decline has been driven by illegal trafficking in the totoaba fish.

In January, prosecutors in California’s Southern District brought charges against a 61-year-old furniture store owner who allegedly snuck 58 of the fish bladders into the U.S. from Mexico.

The totoaba bladders can go for between $1,400 and $4,000 in Mexico, according to an indictment, and yield 10 times that rate in Asia.

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In a separate case in 2014, Song Shen Zhen, 75, of Calexico, California was sentenced to one year in prison plus restitution of $120,500 after he was found with 241 totoaba swim bladders, worth as much as $3.6 million overseas, prosecutors said.

“There was money in the ocean,” said Lorenzo Rojas-Bracho, coordinator of marine mammal research and conservation at Mexico’s National Institute of Ecology and Climate Change and the ongoing expedition’s other chief scientist. He and Taylor are also both members of the International Committee for the Recovery of Vaquita, which was created by the Mexican government in 1996.

That economic opportunity led the Mexican government to step up policing of the Gulf waters where the remaining vaquitas live.

In April, Mexican President Enrique Peña Nieto declared a two-year emergency ban on gillnet fishing in the vaquita zone and directed the Mexican Navy to patrol for illegal fishing activity to give the vaquita a fighting chance.

On April 30, the country also announced a partnership with Sea Shepherd, the international marine conservation organization that is perhaps best known for its efforts to curtail Japanese whaling activity.

The survey team sailing in the Gulf of California has already reported vaquita sightings, including one that occurred during a visit to the vessel by a Mexican official.

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