The last hope for helping the vaquita porpoise dodge extinction could be a project to capture some of the few that remain and breed them in semi-captivity, according to a group of international experts set up to monitor the species.

Other experts, however, say the plan could actually accelerate the demise of the snub-nosed resident of the Gulf of California that appears set to become the fifth marine mammal on record to go extinct.

The latest report released this week by the International Committee for the Recovery of the Vaquita, or CIRVA, a team set up by Mexican authorities to observe the vaquita population, argues that "ex-situ approaches" must be seriously considered. The CIRVA report accepts that the project carries with it major risks because the vaquita has never before been kept in captivity, but argues that there could be no other option left.

"Given the very small number of vaquitas and the ongoing threats they face, the option of ex-situ conservation must be openly evaluated," the report says. "If the vaquita goes extinct, the question will be asked: Was ex-situ conservation considered as an option and, if not, why not?"

An advance of its report, published last month, warned that the number of vaquitas left has fallen to a mere 60 in total. It did not specify the number of females in reproductive age.

The group blamed illegal fishing for the totoaba fish as the main cause of the porpoise's decline because the mammal gets caught in the nets used. The totoaba swim bladder is considered a delicacy in China, and fishing for it has continued despite a government ban imposed in the name of preventing the vaquita going extinct.

Now the group has revealed the results of a special workshop held last year in Holland and Denmark to explore possible strategies for breeding the vaquita in different types of enclosed pens.

But some close observers of the vaquita are frightened that trying to capture even a few specimens could prove to be the nail in the specie's coffin.

"With only around 60 vaquitas left, we simply cannot gamble with killing some while experimenting. Every single vaquita counts," Omar Vidal, the head of the Mexican office of the World Wildlife Fund, told the Associated Press. "Capturing vaquitas to breed them would be far too risky and is not a viable option."