An invasive river monster has become a big problem for native wildlife in parts of the US and Canda. The flathead catfish is set to become an apex predator as it eats its way through America, having been detected as far as Canada.

The flathead catfish (Pylodictis olivaris) really is a river monster, with the heaviest on record clocking 55.79 kilograms (123 pounds) at over 1.55 meters (5 feet) long. As mostly nocturnal hunters, they feed at night and go in search of live prey – but as they travel further from their native waters, they’re munching on all kinds of living things that conservations would rather they didn’t.

The Mississippi and Gulf drainages are their native waters, but since the 1950s, they’ve been introduced by anglers across the western US, making their way into systems that drain along the Atlantic Coast. In 2023, The Office of Governor Wes Moore (Maryland) announced that Moore was calling on the federal government to declare the expanding population of invasive fish species — including flathead catfish —to be “an ongoing commercial fishery disaster in the Maryland waters of the Chesapeake Bay”.

Why? Because they just eat so damn much.

“They are going to be one of the apex predators around every system once they establish those populations,” The Telegraph of Macon reports Georgia Department of Natural Resources Wildlife Resources Division biologist Joel Fleming told McClatchy News. “If they can fit it in their mouth, they’re going to eat it.”

One of the drivers for their ongoing spread is the fecundity of some of the females who – depending on their size – can on average lay 100,000 eggs at a time. Those eggs will be protected by the male until they hatch just over a week later, and the offspring will begin eating their first live fish once they reach around 10 centimeters (4 inches) in length.

As the catfish grows so too does its appetite, and they can go on munching their way through native wildlife for around 30 years. Their potential to cause harm to native ecosystems has meant that wildlife officials now encourage anglers to report any flathead catfish they catch, and – crucially – not release them back into the wild.

As for what to do with the invasive river monsters caught? Provided the water is clean, they are an excellent food source, and the invasivore diet is a delicious way out of a crisis.