Mexico City - A new report on Mexico's endangered vaquita marina porpoise says authorities may have to consider trapping some of the few remaining specimens to try to breed them in captivity or semi-captivity.

The vaquita is the world's smallest porpoise, and only around 60 remain in the Gulf of California, the only place in the world they live.

The report by the International Commission for the Recovery of the Vaquita says off site - "ex situ" - conservation should be considered. That could mean putting the dolphins in breeding pens, either in coastal waters or elsewhere.

Some experts oppose that, saying efforts to capture them could kill the few vaquitas left. The Commission, known by its initials in Spanish as CIRVA, acknowledged the risks involved. Nobody has ever kept vaquitas in captivity, much less bred them.

"While recognizing the risks and complexities of such an approach, the International Commission for the Recovery of the Vaquita concluded that fieldwork to determine the feasibility of ex situ conservation actions for the vaquita is warranted," according to the report. "CIRVA agreed unanimously that capture of all remaining vaquitas is not a viable conservation strategy for vaquitas, which must, first and foremost, be protected in their wild habitat."

Omar Vidal, the head of the Mexico office of the World Wildlife Fund, the WWF, said that "capturing vaquitas to breed them would be far too risky and is not a viable option. With only around 60 vaquitas left, we simply cannot gamble with killing some while experimenting. Every single vaquita counts! I see no other way to save this porpoise than by focusing all efforts and resources in eliminating its accidental deaths in fishing activities."

Both sides agree that Mexico's current efforts haven't worked, and that the species is in a death spiral. Since the latest population estimates were made in December, at least three more dead vaquitas have been found, all killed by nets.

"The species is racing toward extinction," the commission wrote. "Even under optimistic scenarios about reproductive and survival rates, a catch of only three animals per year will likely result in a continued decline."

The vaquitas are threatened primarily by gillnet fishing for the totoaba fish, another endangered species in the area that is hunted for its swim bladder, considered a delicacy in China.

In April 2015, Mexican authorities announced a $70 million plan to ban gillnet fishing in about half of the upper Gulf. The plan promised to compensate fisherman for not using gillnets and offered them alternative, safer nets.

However that has not been effective for reasons ranging from the very high payoff - a totoaba bladder can sell for $5,000 in the United States and double that in Asia - to inefficiency in the compensation program. Some say criminal gangs may be involved in the illicit trade.

The commission said the Mexican government must enforce rules against gillnets, or ban all fishing in the upper Gulf, also known as the Sea of Cortez.