MEXICO CITY -- A gang of dozens of fishermen overturned inspectors’ trucks, burned or destroyed 15 vehicles and patrol boats, and beat three inspectors from the office for environmental protection in a town on Mexico’s Gulf of California.

The fishermen were angered by Mexico’s attempt to save the vaquita porpoise by banning some types of net fishing in the Gulf --also known as the Sea of Cortez -- where only about 30 of the elusive animals are believed to survive.

The office said Thursday the inspectors managed to escape after the attack on Wednesday, but that criminal charges were being filed. The attacks were directed against personnel and property of the office for environmental protection, the country’s fisheries council, and the commission for protected natural areas.

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Fishermen lured by Chinese demand for the swim bladder of a fish known as the totoaba, which inhabits the same waters as the vaquita, have decimated the porpoise population.

Vaquitas are caught in the same kind of nets that illegal totoaba fishermen use. Prices for a kilogram of totoaba swim bladders can reach thousands of dollars.

The fishermen in the town of Golfo de Santa Clara, in Sonora state, were apparently angered over a delay approving permits for corvina, another kind of fish whose legal season would normally begin around now.

But experts are worried that corvina boats could also illegally carry totoaba nets.

Mexico has announced that special permits would be needed for corvina fishermen, and inspectors said the fishermen had applied for those permits late.

Totoaba fishermen have mainly cut and run when confronted by Mexican Navy patrols in the past, but activists and environmentalists have warned that criminal gangs appear to be involved in the lucrative illegal trade and that threats have been mounting.

Experts and the Mexican government previously announced a plan to catch the few remaining vaquitas and enclose them in pens for protection and possible breeding.

Mexican authorities already banned gillnet fishing in the vaquitas’ habitat, but that has proved difficult to enforce.

A study done in November by an international committee of experts that used acoustic monitoring to survey the population of the porpoise. The results showed vaquita numbers had declined 90 percent over the last five years, and the study estimated that because numbers have dropped so fast there are probably less than 30 now.

It’s not easy to count them because their numbers are dwindling and the animals are notoriously elusive, “60 Minutes” correspondent Sharyn Alfonsi reported last year. That’s one reason why most people have never heard of vaquitas and fewer have seen one.

In May 2016, Alfonsi reported that fishermen were being compensated for their lost catch for two years -- the Mexican government was paying them $60 million not to fish.

The international committee found that illegal fishing continues, saying 31 illegal nets were pulled from the Gulf of California in October and November.

Experts acknowledge the catch-and-enclose plan is risky, because the few remaining females could die during capture, dooming the species.

Still, some experts say the capture program may be the vaquitas’ only hope. But others worry that fishermen may engage in a free-for-all once the endangered vaquita is removed and thus wipe out other species in the gulf.