Ecologists from Down Under are keeping a wary eye on ocean waters as an "aggressive" fish migrates south from Papua New Guinea toward the Aussie mainland. What makes Anabas testudineus, or the climbing perch, so frightening that one scientist tells the Guardian it would be a "major disaster" for native fish, turtles, and birds? Well, predators who swallow the perch are in trouble: The fish simply swells up inside them until their throats are blocked and they choke or starve. And the climbing perch is no ordinary fish: It uses its sharp spines to crawl across dry land (check out the video shown here) and can breathe air—it has lungs in addition to gills, and Ecology Asia explains that it gulps down air and holds it in a "labyrinth organ." The freshwater fish can live for almost a week out of the water and apparently survive in salt water, as well as hide out in the mud of creek beds for six-month stretches.
The fish, a native resident of Southeast Asia, first moved southward to Indonesia and Papua New Guinea and now has been seen on Australia's two most northern outposts, the Guardian notes. Nathan Waltham, a researcher at James Cook University, doesn't think the perch can actually swim the entire way to the mainland, but he fears they'll find their way via the bottom of fishing boats "or as discarded live-bait fish." Fellow scientists in Papua New Guinea have already found some of the perch's victims (barramundi, catfish, and birds that tried to devour them), a worrisome discovery for Australia's ecological watchdogs. "When they populate an area they're not commonly found in, they can disrupt the balance of that habitat," Waltham says, per the Guardian. The fish are being closely watched, and fishermen are being alerted to keep a lookout as well. (Maybe we could sic this toxic snail on them.)