The walls in the basement of a building in Brooklyn’s Chinatown were whitewashed, and boxes of cleaning supplies were stacked on the red tile floor. But beneath the disinfectant smell, the unmistakable odor of fish lingered as the flimsiest calling card of a former tenant.

That tenant, Yong Hao Wu, sold fish until October for his Howei Trading Company out of this shop on Eighth Avenue in Sunset Park. Mr. Wu is now out of business and under arrest because the authorities have accused him of illegally importing thousands of live snakehead fish.

In China, the snakehead is a sweet, meaty staple harvested in farms, and when boiled into soup, it is reputed to possess remarkable healing properties. But once outside of its natural river habitats in China, Korea and Russia, it is a rapidly reproducing predator with such a voracious appetite it can wipe out entire schools of fish and destroy an ecosystem.

That the snakehead has been illegal to import into the United States since 2002 when it was found in a pond in Maryland has not diminished its demand — and perhaps has only fueled it. The fish, which has also been illegal to possess in New York State, has been sold in other markets like Boston and is also available through the Internet, officials with the United States Fish and Wildlife Service said.