The swim bladder of an endangered fish caught only in Mexico nets tens of thousands of dollars on China’s black markets, with traffickers from both countries feeding the illegal trade.

The giant fish, a species of drum called totoaba, is banned from international trade but commonly poached off the Gulf of California, according to a report by the Elephant Action League (EAL), a nonprofit wildlife crime watchdog.

Three criminals in Mexico are said to be behind the trade in totoaba, prized in Asia for its gas-filled sac, or swim bladder. They fund the poachers in the fishing villages of San Felipe and Santa Clara, and then move the raw fish bladders to cities like Tijuana and Mexicali. There Chinese traders manage the drying, consolidation and eventual smuggling of the fish parts to southern China.

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The dried swim bladder, or maw, can fetch a price of between $20,000 and $80,000 per kilogram on the black market. Demand for maw stems from its use as an opulent business or wedding gift in China, as well as its value as an investment. Used as an ingredient in soup, the swim bladders have supposed medicinal benefits and are considered a delicacy.

An operation last December by Chinese customs officials led to the seizure of 444 kilograms of dried totoaba maw, said to be worth about $26 million – evidence of how surprisingly large and lucrative this illegal wildlife trade is.

InSight Crime Analysis

Though it’s unlikely any of Mexico’s dominant criminal groups are involved in the totoaba trade, individual drug runners have found ways to cash in.

According to the EAL report, the three criminals behind the totoaba trade have all at one time been connected to drug trafficking.

One trafficker paid off the Tijuana Cartel to move the swim bladders through areas under the group’s control, EAL reported.

Last year, authorities arrested a Sinaloa Cartel operative who also allegedly trafficked both drugs and totoaba. His links to the criminal group facilitated the transit of the swim bladders to Asia, El Universal reported.

Both Mexican and Chinese criminals have convened in Mexico around the trafficking of totoaba.

The Chinese traders, though not known to be from organized crime groups, are said to be involved in the export of other illegal seafood products, according to the EAL investigation. One trader is known as an “Elder Chinese,” a member of a group of businessmen who run both “legal and illegal enterprises,” according to the report.

SEE ALSO: How China Fuels Wildlife Trafficking in Latin America

Totoaba is not the only protected wildlife product that fuels organized crime in Latin America. The poaching of jaguars and pumas for export to China is a lucrative business in Bolivia, where a raw skin is worth several times the average monthly wage. Fins from a single shark can earn fishermen in Peru or Ecuador as much as $100. A kilogram of shark fin sells for $700 in Asia.

While Mexican and Chinese wildlife officials have been fighting the totoaba trade for more than half a decade, seizures only seem to get larger.

Until overfishing collapses totoaba populations, their bladders will be prized by wealthy Chinese consumers willing to pay high prices, and the trade will continue to provide opportunities for Chinese and Mexican criminal networks alike.