Mexico City (AP) - Experts said Wednesday they have suspended a program to capture and enclose the few remaining vaquita porpoises in Mexico's Gulf of California, after the one they managed to catch died quickly in captivity.

Lorenzo Rojas, the lead scientist in the effort, described what may be the last close contact between humans and the world's smallest porpoise, of which less than 30 remain. Rojas said he doubts there will be enough of the elusive porpoises left next year to even make an attempt to capture any.

"She was adapting, but in a few seconds something triggered in her brain and she just started swimming faster, incredibly fast, like she wanted to fly away from where it was, with no perception of the space, inside where she was," Rojas said of the adult female captured over the weekend.

That vaquita had been taken to a floating pen on the sea where experts had hoped to protect her, but the animal began to act oddly in obvious stress. The only other vaquita captured, a calf, had also quickly shown signs of distress and was quickly released weeks ago.

The experts tried to do the same with the adult female, but it was too late.

"The vets decided it was time to release her. They pulled her out to sea and they put the animal facing the open ocean, and it started swimming, but it started swimming in a very random way … and the vets decided to bring her up on the boat again," said Rojas, chairman of the International Committee for the Recovery of the Vaquita. "They did CPR for three hours and tried to keep it alive."

The vaquita died about six hours after capture. An autopsy and test are being conducted to determine why it died.

But with so few vaquitas left, the ones remaining can't be put at risk, experts said.

"These tiny porpoises do not respond well to the stress of capture, and not a single additional vaquita should be deliberately put in danger in this way," the Animal Welfare Institute said.

Chillingly, initial results from the autopsy of the dead vaquita showed that she hadn't had a calf in two or three years. There may be so few left they are having difficulty finding breeding partners.

Mexico's environment minister, Rafael Pacchiano, tried to put the best face on things, saying the search effort had at least found vaquitas.

"We have seen several groups of vaquitas, including mothers with calves, so that is a good sign," Pacchiano tweeted. "Conservation of the vaquita will continue being a priority."