A controversial, last-ditch plan to round up the last remaining vaquitas—a critically endangered porpoise found only in the Sea of Cortez—may get underway this spring with the aid of U.S. Navy-trained bottlenose dolphins. The vaquitas would be placed in a protected enclosure while efforts are made to get illegal fishing in the area under control.

The population of these small porpoises has reached the point where they face imminent extinction. A report by marine conservationists issued in May 2016 estimated that less than 60 vaquitas remain.

Their numbers have dropped dramatically in the last 20 years. There were 567 individuals in 1997, 245 in 2008 and just under 100 in 2014. The report puts a high probability on extinction within five years.

Vaquita refuge established in 2005 where gillnet fishing is prohibited.National Geographic

The Mexican government has been working with local fishermen to save the species. In 2005, Mexico established a refuge off San Felipe in the Gulf of California. Gillnet fishing was banned in the refuge. The government is spending $74 million to compensate fishermen and encourage them to use safer fishing methods.

For a time, it worked. Although the population continued to decline, it did so at a slower rate. Scientists hoped it would soon turn around and begin to recover.

But they didn't count on China.

The country's newly-minted millionaires stimulated a demand for dried fish bladders. Called fish maw, they are alleged to possess medicinal properties including the ability to increase fertility. The source of those fish bladders: the Mexican totoaba, a critically endangered fish found in the same waters as the vaquita.

Totoaba bladders are worth up to $5,000 per kilogram and can command as much as $100,000 on the black market in China, according to a 2016 report by the Environmental Investigation Agency. They can be found at retailers in major Chinese cities as well as online sites such as Alibaba. Poachers often take their boats out at night, and use gillnets under the cover of darkness to round up as many totoaba as they can. The vaquita are merely bycatch, caught up in the nets where they often drown or die from stress.

Fish maw wholesaler in Shantou, China (c) EIAEnvironmental Investigation Agency

Details of the plan to save the vaquita are still being worked out.

Plans may involve using dolphins from the Navy Marine Mammal Program, which has studied, trained and deployed these highly intelligent animals since the 1950s. Dolphins would be used to help locate vaquitas. They would then be coaxed into lightweight surface gillnets. It's never been done before with vaquitas, but harbor porpoises in Greenland have been captured safely in a similar manner.

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