Test of Snakehead Poison Starts
U.S. Officials Seek Ban on Imports, Interstate Transport

The poison seems to be working so far. However, they're canny. It's possible that they're just faking. You've seen fifties horror movies, haven't you? The scientists think they've found a way to defeat the creature, and it seems to work... until it comes back, more powerful than ever. Then you have to bring in the Army or Gamera or somebody to defeat it.