These bad-news fish are known for their voracious appetite, their ability to crawl - or wriggle - across land and - most important - the fact that they shouldn't be found in Philadelphia. After all, their native watering holes are in Asia. They starting showing up in the MidAtlantic region in 2004, at FDR Park in South Philly, the Potomac, and Chicago - in spots connected to major waterways. Now they have been found in the John Heinz National Wildlife Refuge at Tinicum.
Also on Philly.com: