MEXICO CITY (AP) — Mexican authorities have arrested two Chinese men for illegal trading in totoaba, a species linked to the near-extinction of the porpoise-like vaquita marina.

The totoaba is a large, endangered fish whose swim bladder is prized by chefs in China. The bladders can fetch tens of thousands of dollars.

Fishermen using gill nets to illegally catch totoaba in the Sea of Cortez are blamed for unintentionally sweeping up vaquitas.

Experts believe there now are fewer than 100 surviving vaquitas, which live only in the Sea of Cortez, also known as the Gulf of California.

The environmental prosecutors’ office said Tuesday three Mexicans were arrested with four totoabas and three bladders.

The Chinese men were found in a vehicle with three dried bladders.