An investigation has exposed new details of the illegal trade in the totoaba fish’s swim bladder.

Totoaba swim bladders are used in traditional medicine and can fetch thousands of dollars per kilogram in Chinese markets.

Illegal fishing for totoaba is the primary reason vaquita porpoises are headed toward extinction.

Elephant Action League’s investigation has identified the people involved and the routes they use to smuggle the bladders to buyers in China.

A new investigation sheds light on an illegal trade that endangers the world’s smallest and most endangered cetacean species, the vaquita porpoise (Phocoena sinus). The report released July 7 by the wildlife crime investigation organization Elephant Action League (EAL) details what its investigators unearthed about cartels trading illegally in the totoaba fish’s swim bladders.

Vaquitas are a small porpoise found only in Mexico’s Gulf of California. Official estimates recently placed the population at 30 or less individuals, but advocacy groups maintained in early March of this year that there may be 12 or fewer left.

The animals are in great danger because they’re often caught in nets meant for totoaba (Totoaba macdonaldi), a large fish that is also endemic to this body of water. The swim bladders, called maws, are are used in traditional medicine and can fetch thousands of dollars per kilogram in Chinese markets: Maws are now more valuable than gold, and their trade is illegal, and shutting this trade down is seen as the only way to save the world’s remaining vaquitas.

Through its “Operation Fake Gold,” EAL says it has identified “totoaba cartels” that specialize in the poaching and trafficking of totoaba swim bladders out of Mexico. The supply chain starts in the fishing villages of San Felipe and Santa Clara where the totoaba are caught and the maws extracted. Maws are then smuggled out of the country by operations in cities like Tijuana and Mexicali.

This is a well known problem to law enforcement: over a span of just five days this past April, Mexican police arrested two men attempting to take hundreds of maw out of the country, according to reporting by the Mexico News Daily.

But EAL’s undercover investigation appears to have dug much deeper, finding that the totoaba cartels are led primarily by three Mexican nationals who fund the poachers and then sell the swim bladders to a group of Chinese traders and businessmen living in Mexico. It is these Chinese traders that facilitate the smuggling of totoaba maws to China.

“The team performed so well in Mexico under very difficult operational scenarios. I equally need to praise the work of our Asian undercover agents who performed very dangerous work, but whose identities must remain a secret and known to only a few,” said EAL’s Andrea Crosta of the investigation.

Smugglers transport totoaba maws to China primarily via air routes, avoiding direct flights and usually within checked bags, EAL found. The maws travel via hubs in Hong Kong, South Korea, Japan, and Taiwan, many times along routes used for drug trafficking, according to sources.

EAL notes that in addition to the public report, the group has prepared a Confidential Intelligence Brief (CIB) that has been shared with authorities in Mexico, China, and the U.S. The CIB contains a wealth of information including details on 40 persons of interest involved in totoaba trafficking.

Read all of Mongabay’s reporting on the vaquita issue here.

Banner image: A dead vaquita. Image courtesy of Elephant Action League.