An effort to save one of the world’s most endangered species, a miniature porpoise that lives in the Sea of Cortez, is slated to begin Friday, using some of the biggest brains in marine biology, binoculars and four aging female dolphins.

The creature in question is the vaquita, which has seen its population shrink from a few hundred a decade ago to fewer than 30 in recent months. The dramatic, last-ditch rescue bid is the first operation of its type aimed at a marine animal, though similar efforts were made to save the California condor when its numbers dwindled to 22 in the 1980s and the American bison a century earlier.

Though the methods will be unusual — involving dolphins trained by the U.S. Navy and a mass relocation of what’s left of the vaquita — the stakes are serious.

“We’re really at a turning point at the utilization of ocean resources,” said Dave Bader, director of education at the Aquarium of the Pacific in Long Beach and one of dozens of people expected to go to the Sea of Cortez.

The vaquita is on the road to oblivion by mistake. Nobody — not the Mexican fishermen who accidentally kill them, nor the Chinese and Chinese-American consumers who like to eat the bladders of totoaba, a fish that’s about the same size as the vaquita and lives in the same sea — wants to wipe out vaquita.

But because totoaba bladders are prized as a delicacy in certain Chinese soups, and sometimes viewed as a medicine, the fishermen in Mexico have turned from simple spear fishing to gill net fishing as a way to capture as many totoaba as possible. The money is so good — dehydrated totoaba bladder can fetch $8,500 per kilogram — that a recent program by the Mexican government in which fishermen were paid to stop catching totoaba didn’t end the practice.

Whatever the motivation, the rise of gill net fishing for totoaba has done two things: It has reduced the totoaba population, and it has virtually wiped out the vaquita, which tend to get caught up in the same nets.

Numbers have never been in the vaquita’s favor. When the animal was identified as its own species, in 1958, the population was pegged at about 3,000, all living in the northern Sea of Cortez, eating small fish and squid. But a drop-off began in the late 1990s and really kicked in about three years ago, when the numbers fell from 97 in 2014 to 60 in 2015 and an estimated 30 at the end of last year.

“This is the most critically endangered marine mammal in the world, if not the most critically endangered animal in the world,” Bader said.

The dolphins expected to help save the vaquita aren’t members of a rare species, but they’re unusual all the same.

They’re part of a team of trained dolphins used by the Navy and others on humanitarian missions around the world and, sometimes, to find underwater mines. The team is headquartered in San Diego, but must be prepared to deploy to any spot around the world in 72 hours, said Jim Fallin, spokesman for the Space and Naval Warfare Systems Center Pacific, which handle the dolphins for the Navy.

The four dolphins were hand-picked for the vaquita mission.

Each is a female and somewhat aged, in their 30s and 40s (dolphins in captivity typically live 25 to 45 years.) And they’ve been trained to recognize the so-called “echo signature” used by the vaquita (and other aquatic mammals) to communicate. When the dolphins hear a vaquita, Fallin said, they’ll alert their human handlers by touching a panel with their noses. After that, the humans will try to capture the vaquita in a net.

The dolphins are already in the Sea of Cortez, living in underwater pens after being flown into the research area last week. While flying, the dolphin were kept in small, tent-like mats that held water and kept them comfortable, Fallin said.

When the mission begins, on Friday, they’ll work in shifts of up to three hours. The effort could last about a month.

Fallin said the four dolphin were chosen for “their gentle demeanor” and “distinct behavioral acumen.”

“They’re very responsive to our requests to do these kinds of searches,” he said.

It’s unclear if the vaquita will be as responsive. The creatures are shy and tend to live alone or in pairs; they surface for only a few seconds at a time, and they’re scared by loud noises like motor boats, Bader said.

Other than that, not much is known about them.

For example, vaquita have never been held captive before so nobody knows how they’ll respond to the second part of the mission — keeping them in saltwater pools in San Felipe, until they make more baby vaquitas and conditions in the Sea of Cortez improve for their long-term survival.

The process could take years.

The experts are hoping to catch up to 12 vaquita.

“We are, right now, planning to have them in our care for as long as is needed to ensure that the home they go back to is safe for them,” said Cynthia Smith, the executive director of the U.S. National Marine Mammal Foundation and general program manager of the rescue effort.

“If the animals cannot accept care by humans, if they are not able to adapt to our care, we will put them back. We do not ultimately want to cause them harm.”

One thing working for the vaquita, experts say, is the cute factor.

The smallest cetacean (whales, etc.), the vaquita measures five feet long in adulthood and weighs 100 pounds at full maturity. Known as the “panda of the sea” its eyes are encircled by black rings. Celebrities, such as Leonardo DiCaprio and Mexican investment mogul Carlos Slim, have taken up the cause of saving the vaquita.

“We like cute, cuddly and fuzzy on the endangered species list for sure,” Bader said. “But we also show a capacity to understand there are lots (of species) that need saving.

“There are a number of invertebrates, but it’s perhaps more difficult to get the public engaged around a ‘Save the Snails’ campaign than it is a ‘Save the Whales’ campaign.”

The mission is expected to begin Friday at sunrise.