A man has admitted to smuggling thousands of dollars’ worth of dried sea cucumbers into the U.S. from Mexico, according to federal officials.

On Thursday, Cheng Zhuo Liu, 50, of Chula Vista, Calif. appeared in federal court in San Diego. Liu pleaded guilty to smuggling 100 pounds of the endangered species on Oct. 3, 2013 by hiding them in his Hyundai’s spare tire area, according to U.S. Attorney Laura Duffy.

That amount of sea cucumbers has a market value of between $5,000 and $10,000.

The marine animals are protected under the Convention on International Trade in Endangered Species, so those who import them into the U.S. need a permit.

Duffy said Liu admitted he didn’t have any permits.

A black market has grown around the illegal sea cucumber trade in Asia, where Duffy said a pound might sell for $300.

Liu agreed to forfeit the sea cucumber seized. He faces a maxiumum sentence of five years in prison and a $20,000 fine on June 9.

Dried sea cucumber is used in Chinese cuisine as hoi sam, as well as for medicinal purposes.

Smuggling the animals has become a problem in Indonesia, Japan, Sri Lanka and Mexico. In the Caribbean Sea off the Yucatan Peninsula, illegal harvesting has decimated the sea cucumber populations. Rival gangs have clashed for control of the harvest, according to the U.S. Attorney.

Sea cucumbers have long, leathery bodies and are found on the ocean flood worldwide. The species Liu had is typically found in the Pacific Coast of Mexico, Central and South America, the Biodiversity Heritage Library says.