United States Fish and Wildlife Service (USFWS) agents recently nabbed an alleged smuggler in Calexico, California with more that $3.6 million worth of fish swim bladders. The bladders were taken illegally from the endangered Totoaba macdonaldi, a fish protected in both Mexico and the United States.

Customs and Border Protection officials first caught the alleged bladder bandit, named Song Shen Zhen, as he attempted to cross the border with a bag containing 27 swim bladders. The officials let Zhen go, but the USFWS tailed him to his hideout, where they found 214 more bladders, plus a processing operation, ledgers and evidence of overseas shipping.

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In China, cooks make a soup from fish swim bladders that supposedly boosts fertility and improves circulation and skin health. The bladder from Totoaba macdonaldi is prized because of its high collagen content. A single bladder can fetch $5,000 on the U.S. black market, plus another $10,000 when resold in Asia, according to the USFWS.

“Many species, including Totoaba, are teetering on the brink of extinction due to poaching to supply the illegal wildlife trade. While we may never know how many Totoaba bladders were harvested illegally, such disregard for the protections that were put in place to benefit this endangered species could have a disastrous effect on the fish population,” said USFWS Deputy Chief Edward Grace in a press release.

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Six-foot, 220 pound Totoaba were once common in the Gulf of Mexico. However, the fish depend on the Colorado River delta to spawn, but as the river has been siphoned off for drinking water and agriculture, the Totoaba‘s breeding grounds have degraded. On top of that, overfishing and pollution have also taken their toll. The International Union for the Conservation of Nature lists Totoaba macdonaldi as critically endangered.

IMAGE: Fish swim bladders (Algirdas, Wikimedia Commons)