Add to the list: pufferfish and drugged eels

The list of issues with Chinese imports gets more bizarre all the time:

China rejects U.S. warning on toothpaste

...A slew of Chinese exports have recently been banned or turned away by U.S. inspectors including, wheat gluten tainted with the chemical melamine that has been blamed for dog and cat deaths in North America, monkfish that turned out to be toxic pufferfish, drug-laced frozen eel, and juice made with unsafe color additives...

So what was the drug in the eel?