Biologists at the Academy of Natural Sciences have been studying the snakehead's impact on the other fish in the ponds.
"The normal native fish are not used to it. It's an excellent predator. It breathes air, so it doesn't need a lot of oxygen," said Richard Horwitz.
Adult snakeheads use their strong jaws and sharp teeth to catch, and hold tight, to their prey.
They can survive in areas low in oxygen, and can even come back to life after being frozen!
Even more unsettling, some snakehead species can walk for short distances.
"There was a lot of worry that these things were going to walk out of a pond and walk into the next one," said Horwitz.
Thankfully, the ponds in FDR Park seem to be doing very well. The species hasn't spread into neighboring waterways, like the Schuylkill River.
The snakehead population hasn't grown as fast as scientists feared, and other varieties of fish are still thriving.
"We've been catching more bass down here since the snakeheads have been here than before. That tells me they're not hurting the fish," said David Mannino of South Philadelphia.
Fishermen told us they do not have a problem with the snakeheads. In fact, they say it kind of enhances their fishing experience.
"They give you a good fight," said Randy Pizzo of South Philadelphia.
Fishermen at the pond are happy with the snakehead fish, but biologists at the academy still caution other fish varieties may be on the decline because of the snakehead.
"There's some indication that some of the small eels and other fish are much less common than they were before," said Horwitz.
For now, the impact of the snakehead on FDR Park is still unclear.
