MEXICO CITY — So few of Mexico’s vaquita porpoises remain that the international committee to protect the endangered species is preparing to catch and enclose as many as it can in a last-ditch effort to save them from extinction, experts said Thursday.

According to rough estimates, only about three dozen of the world’s smallest porpoise remain in the upper Gulf of California, the only place it lives. With population numbers falling by 40 percent annually, there could now be as few as eight breeding females left. The species has never been held successfully in captivity.

Fishermen lured by Chinese demand for a fish that swims in the same waters have apparently defeated Mexico’s efforts to protect the vaquita in its natural habitat.

Lorenzo Rojas-Bracho, chairman of the International Committee for the Recovery of the Vaquita, said an international team is being formed to launch the capture program in the spring.

‘‘It would involve locating them, capturing them, and putting them in some kind of protective area,’’ Rojas-Bracho said, adding that the current plan envisions putting them in a floating enclosure or pen in a protected bay.

Rojas-Bracho said the committee is establishing a group of experts in acoustic monitoring, porpoise capture, veterinary medicine, and other specialties to carry out the effort.

‘‘The team is the best that can be put together in the world. It is the ‘dream team,’ ’’ he said.

But catch-and-enclose is risky; the few remaining females could die during capture, dooming the species. Breeding in captivity has successfully saved species such as the California condor. But the vaquita has only been scientifically described since the 1950s and has never been bred or even held in captivity.

Associated Press