The defendants are accused of importing totoaba swim bladders, used in traditional Chinese medicine.
Authorities in China are prosecuting 11 people for smuggling $119m (£90m) worth of fish swim bladders from Mexico.
They are accused of bringing in 20,000 swim bladders from totoaba fish from the Gulf of California in Mexico and selling them in China.
Swim bladders enable totoaba to maintain their buoyancy in the water.
They are used in traditional medicines in China and can fetch up to £15,000 on the black market.
