The spotted lanternfly may be Pennsylvania’s most infamous invasive species, but other pests can be just as annoying. Just ask Kyle Van Why, a federal wildlife disease biologist who tracked and captured a group of six feral pigs crossing the Delaware River into New York last year.

“Luckily, we were able to track these pigs through cameras and rumors from nearby landowners and remove them,” he said of his most elusive targets. “But it was a group that for about a year had moved between Pennsylvania and New York swimming the Delaware River.”

A plethora of foreign flora and fauna across Pennsylvania spread like wildfire and feed on native ecosystems, damaging all that lay in their wake, but experts say some of the most concerning are those that are introduced to nature intentionally by humans, wild boars and flathead catfish being two of them.

“A lot of our invasive species are just taking off, and some of those things you’ll never get rid of,” said Pennsylvania State University’s wildlife ecology and conservation research professor, Julian D. Avery. “We’re trying to think more about how we educate consumers in such a way that we can maybe head off future invasions by steering people to more sustainable choices.”

Experts say the good and bad news is that many of these species were only introduced to Pennsylvania ecosystems by humans, so future invasions can be thwarted by having a well-informed populace.

For starters, don’t release animals into the wild.

Wild boar in Pennsylvania

Let’s start with a prolific species that invaded Pennsylvania with the aid of humans: feral pigs.

According to the Pennsylvania Game Commission, these wild hogs (the descriptors are interchangeable) are enormous in size and spread, weighing as much as a refrigerator and producing litters of eight to 12 piglets. They’re the descendants of domestic pigs, Eurasian wild boars, and European and Asian hogs initially brought in by Europeans during colonization as a food source in the 1500s.

Feral swine throughout the U.S. today are pigs — the same ones you see on farms — who, over time, escaped captivity or were intentionally released by humans for sport hunting (which is illegal in Pennsylvania) or other reasons, like people who release their pet potbellied pigs into nature thinking they are “doing the right thing” after their pet grows too big for them, said Van Why.

In Pennsylvania, feral swine are primarily isolated to the southcentral part of the state in Franklin County, about three hours from Philadelphia, according to the state’s Department of Agriculture. (Philadelphia and its suburbs don’t see too many wild hogs.) Over the past decade-plus, the USDA has isolated the breeding population of feral swine from as many as 1,000 pigs across nine counties to now likely less than 100 animals in one to three counties, said Van Why.

“As far as a population, it is hard to say because we keep having small flair-ups of released or escaped pigs that we are dealing with,” he said. “It is really tough to put a number down because one small group with a few sows can quickly become 20 if there is a boar among them. The goal is to prevent this from occurring, so the sooner we hear about animals on the landscape, the sooner we can investigate and remove them.”

Pigs are not native to the U.S., where if left unchecked in the wild — made easier with very few natural predators — they can wreak havoc on wild plants and vegetation, crops, and farmland. They also eat many of the same foods native wildlife rely on, leaving less food for them, said Van Why. They can also carry diseases that endanger wildlife, livestock, and, in turn, humans.

The USDA’s Wildlife Services are the primary agency tasked with tracking, removing, and testing feral swine for disease in Pennsylvania. All feral swine sightings should be reported to the regional Game Commission office by calling 833-742-4868.

Flathead catfish in Pennsylvania

Anglers, a.k.a. fishermen, who introduced flathead catfish to Pennsylvania waterways prize this fish for its big size and good eating, but the invasive species does more harm than good.

“It’s eating native species and recreational species of fish. The problem is that people also love the sport of fishing for these giant things,” Avery said. “There’s this tension between a lot of the public knowing it’s a bad thing, but also people that would be happy to move it around and introduce it in other places because they like the thrill of fishing for it.”

Native to the Mississippi River basin, which the Ohio River drainage in western Pennsylvania is a part of, these gargantuan fish were introduced for sport fishing in Pennsylvania waters like the Delaware, Schuylkill, and Susquehanna rivers in the late ‘90s to early 2000s, according to Sean Hartzell, an aquatic invasive species biologist with Pennsylvania Fish and Boat Commission (PFBC).

“It’s an interesting case with the flathead catfish because it is actually native to part of the state, so we can say that they’re Steelers fans, but maybe not Eagles fans,” Hartzell said.

Since the introduction of these catfish to more eastern parts of Pennsylvania, they can now be found throughout the Philadelphia region. According to the U.S. Geological Survey, there are a couple dozen of these catfish along the Schuylkill River near Philly, and more than 100 along the Susquehanna River from Harrisburg to the Maryland border.

They’re some of the biggest fish to catch in Pennsylvania because they can grow up to three feet in size and weigh a whopping 60 pounds. The record for the largest flathead catfish caught in the state was just broken in May by a Franklin County fisherman, weighing in at 66 lbs. and 4 feet long. In Philadelphia, Roxborough’s Jonathan Pierce caught a 56-pounder in the Schuylkill River in 2020.

These whiskered (which are actually barbels, a sensory organ common in fish) monsters eat native fish, including other catfish, creating devastating effects on the ecosystem. In Georgia’s Altamaha River, flatheads reduced the population of a single fish species by 80%, according to the federal Sea Grant research program at Penn State University. “One of my colleagues described them as a giant aquatic vacuum cleaner just sucking up any smaller fish they can,” Hartzell said.

Researchers at Penn State and the PFBC are publishing years of data collected on the fish that will shed light on its effects on Pennsylvania ecosystems that flatheads aren’t native to, like the Delaware, Schuylkill, and Susquehanna rivers.

“We’ve been finding that they consume the fish that folks like to fish for, like smallmouth bass, rock bass, and sunfish,” Hartzell said of the research.

It’s up to everyday anglers to fish these giants out of our waters. Hartzell said if you catch a flathead, do your best to bring it home, eat it, or use it to fertilize your garden. You won’t be in trouble if you can’t get it home and release it after catching it. But, if you catch that flathead catfish and relocate it to another body of water, you can be fined.