Sneaky Snakeheads in the Susquehanna

Snakeheads Sneak in with Susquehanna Shad

Dr. James J. S. Johnson

Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints. For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ.   (Jude 1:3-4)

Keeping a balance, during times of sudden change, is a challenge(1)—even for spawning fish like American Shad (Alosa sapidissima), who now need a reopening of river pathways, or else the population’s normal life cycle is imperiled.(1),(2),(3)

SHAD released form hopper at Conowingo Dam (Will Parsons photo)

But when fish population’s movement restrictions are relaxed, as they recently were in Maryland, other risks arrive—like tares infiltrating a wheat-field.(4)

Thus, while solving one problem another problem arrives with a vengeance. This interactive imbalance resulted from two abrupt changes, summarized below.

American shad just couldn’t get a break this spring in their efforts to repopulate the Susquehanna River. The migratory fish got a late start on their spawning run up the Chesapeake Bay’s largest tributary because the fish lift at Conowingo Dam remained shut down for nearly six weeks out of concern for spreading COVID-19 among workers at the dam. Then, when the dam’s owner, Exelon [Corporation], finally figured out a way to run the fish elevator with reduced risk to the workforce, the facility shut down for the rest of the season after less than four days. The staff spotted some unwanted interlopers—northern snakeheads—hitching a ride over the dam with the shad. It marked the first time the invasive fish [introduced] from Asia had been seen in the Susquehanna above Conowingo [Maryland], which is just 10 miles upriver from the Chesapeake Bay.(2)

SHAD in hopper bucket lift at CONOWINGO DAM (Maryland) photo credit: Will Parson / Chesapeake Bay Program

So, to stop further invasion by snakeheads, the fish transit lifts were again stopped at the Conowingo Dam.(2)

As a first-level impact to the Chesapeake Bay watershed’s ecosystem, recent adjustments to American Shad movement restrictions—in reaction to pandemic politics—began to jeopardize the opportunities for American Shad to “be fruitful, multiply, and fill” their historic habitat in the Chesapeake Bay watershed.(5)

By this time in a typical year, the main fish lift at Conowingo Dam would be busy hoisting thousands of fish daily over the 94-foot high barrier, including a dwindling number of American shad and river herring, so they can swim up the Susquehanna River to spawn. But the lift has been idle so far this spring, another victim of the coronavirus pandemic. Exelon [Corporation], which owns the hydroelectric facility, suspended fish passage operations just before they were to start.(3)

To reproduce shad need to swim upstream during the spawning season. Why? Shad, like salmon and sturgeon, are anadromous—they begin live in freshwater streams but eventually swim downstream and live thereafter at sea (in this case, the Atlantic Ocean)—but they return to freshwater rivers and streams for reproductive spawning.(6)

Thus, if shad’s natural spawning runs are stymied by blocked pathways (or are otherwise defeated), the successful reproduction of that shad population is locally threatened.(2),(3),(6)

So how were the spawn-run shad blocked from swimming upstream, from the Chesapeake Bay into the Maryland part of the Susquehanna River, and further upstream into the Pennsylvania part of the Susquehanna River?

The Conowingo Dam, in Maryland, blocks the natural flow of the Susquehanna River. So, the spawn-run shad need to use fish transit “elevators” to bypass the hydroelectric power dam, but these elevators were stopped pursuant to Maryland governor Larry Hogan’s ultra vires shut-down decree.(2),(3), (7)

The hydro companies on the Susquehanna are taking precautions to ensure plant operators and essential maintenance staff stay healthy and safe…. There are fish passage facilities (fish-ways) at each of the four Hydroelectric Dams on the lower Susquehanna River. Conowingo, Holtwood and Safe Harbor Dams, the first three moving upriver, have fish lifts or elevators. …  Fish lifts work by using water currents to attract the migrating fish into a channel. Crowder gates close to crowd the fish over the hopper bucket, and the bucket is lifted vertically to the level of the reservoir upstream. The water and fish in the bucket are then dumped into an exit trough which leads the fish to the reservoir. All of the fish-ways were constructed with viewing windows where biologists count the migrating fish.(7)

Because Exelon executive interpreted Governor Hogan’s decree as declaring Exelon’s dam operations as “non-essential” activities—without factoring in federal Supremacy Clause applications of Exelon’s federal contract—Exelon suspended operation of the fish lifts, which prevented anadromous shad from completing their usual spring spawning run.(2),(3),(8)

Political pressure (under federal law) was exerted on Exelon, to resume operating the fish lifts, so that migrating shad could resume their spring spawning runs. Eventually, Exelon restarted fish transit elevator operation, allowing latecomer shad to access upstream for their spawning runs.(2),(3)

Now comes the second phase of this ecosystem’s politics-prompted imbalance.

In the American Shad’s migration-delayed process, an invasive predator—the Northern Snakehead (so-called because its exterior resembles the pattern of rattlesnake!)—“tailgated” through the dam-lift’s usual gatekeeping restrictions, and many Snakeheads evaded efforts to capture and remove them from access to upstream waters of the Susquehanna River.(3)

“We [i.e., Exelon staff] were directed by the resources agencies to discontinue operations due to the amount of northern snakeheads that were spotted,” Exelon spokesperson Deena O’Brien said. Only 485 American shad made it over Conowingo via the elevator before it got shut down. That’s barely 10% of the 4,787 lifted over the dam last year, which was itself an all-time low since the lift was installed in 1991. Lift operators spied a total of 35 snakeheads mixed in among other fish in the lift, according to the Pennsylvania Fish & Boat Commission. They managed to net and remove 14 of them, but 21 eluded capture and swam upriver once hoisted atop the dam.(2)

Snakehead fish are ray-finned, perch-like fish that are so vicious and destructive that in many jurisdictions it is often a punishable crime to facilitate snakehead fish introduction into lentic (standing, like pond-water) or lotic (moving, like streams and creeks) inland freshwaters.(9)

Northern snakeheads, which are native to parts of China, Russia and Korea, first showed up in the [Chesapeake] Bay watershed in 2002 when a pair [was] found in a pond between Baltimore and the District of Columbia. They have spread widely since, becoming established in the Potomac River and in rivers and creeks on Maryland’s Eastern Shore and all the way north to the head of the Bay. Biologists [including U.S. Fish & Wildlife Service biologists] … [are] worried that snakeheads, which eat other fish, could depress populations of other species. A survey of the Blackwater and Little Blackwater rivers on Maryland’s Shore — two places teeming with snakeheads — found a decline in fish of all types by more than 80% in a decade’s time. [emphasis added] … Snakeheads have been trying to get upriver past Conowingo since 2017. Last year, a total of 81 snakeheads were spotted trying to take the lift, but all were caught and removed.(2)

Snakehead fish are non-native apex predators, i.e., there is no normal predator “above” them in the riverine biome food chain. Snakeheads are destructively voracious eaters—eating other fish (like carp), amphibians (like frogs), mollusks, aquatic insects, and even small rodents!—snakeheads’ shiny teeth consume by aggressive thrust-feeding (thrusting jaws forward when seizing prey).(2),(10)

NORTHERN SNAKEHEAD, invasive fish that can breathe air and live outside of water for a little while, when traveling to reach a new body of water (photo credit: Will Parson / Chesapeake Bay Program)

Also, snakehead fish are resilient—they can breathe air, survive on land for up to four days (and wriggle ¼ of a mile on land, while seeking the water of a pond or drainage ditch); they routinely wreak monstrous havoc on otherwise balanced ecosystems—earning them the scary nickname “Fishzilla”.(10)

So, as the U.S. Fish & Wildlife Service, with others, tries to protect the populational security of the American Shad, in the Susquehanna River, there is now greater peril from the party-crashing “illegal alien” snakehead fish—an ecological nightmare known as “Fishzilla”.

Maybe the Conowingo Dam’s fish transit lift should never have been shut down in the first place. If the shad’s usual fish-way migration routine had never been interrupted, Exelon’s later gatekeeping mishap—which allowed the snakehead fish to infiltrate (like tares invading a wheat-field)—might have been avoided.

So snakeheads stealthily snuck in, shadowing spawning Susquehanna shad. In our fallen world, which will “groan” until when the Lord Jesus returns to fully redeem His creation, we face both ecological and political imbalances.(1),(4),(11)
Northern Snakehead fish (Channa argus) caught in Bushwood, Maryland (Chesapeake Bay Program)


  1. Johnson, J. J. S. 2020. Big-picture Balancing is Needed Even during Crisis. ICR News (May 1, 2020), posed at . See also Johnson, J. J. S. 2020. Balancing High Risks: Learning from Mountain Goats. Creation Science Update (April 23, 2020), posted at .
  2. Wheeler, T. B. 2020. Snakeheads Shut Down Late-starting Shad Lift at Conowingo Dam. Chesapeake Bay Journal (May 27, 2020; updated May 29, 2020), posted at .
  3. Wheeler, T. B. 2020. Shad Hatcheries, Fish Lifts Fall Victim to Coronavirus. Chesapeake Bay Journal (May 12, 2020), posted at .
  4. Matthew 13:24-30 (parable of wheat and tares).
  5. Genesis 1:20-22 (fish commanded to be fruitful, multiply and fill seas).
  6. Anadromous fish—like salmon and sturgeon—to reproductively spawn, return from the ocean, and swim upstream into freshwaters. Regarding Atlantic Salmon, see Johnson, J. J. S. 2020. Salmon Young Take the Plunge in May. Creation Science Update (May 13, 2020), posted at . Regarding Atlantic Sturgeon, see Johnson, J. J. S. 2015. Anadromous Fish ‘that Swam with Dinosaurs’ Neither Extinct Nor Extirpated. Creation Research Society Quarterly. 51(3):207-208.
  7. Pennsylvania Fish & Boat Commission (staff writer). 2020. Susquehanna River American Shad. Pennsylvania Fishes (accessed May 31, 2020), posted at .
  8. Political boundaries now matter—even to fish like shad. Most of the Susquehanna River flows through Pennsylvania. However, the lower part that flows through the Conowingo Dam is located in Maryland, so the dam operator company (Exelon Corporation) is subject to Maryland politics, including the recent shutdown edicts of Maryland’s governor Larry Hogan.
  9. For example, the Code of Virginia (at Section 18.2-313.2) criminalizes the introduction of snakehead fish into jurisdictional waters of Virginia.
  10. “It sounds like something out of a horror movie: An invasive, predatory fish that eats everything in sight, can breathe air and live on land. Officials say the fish, called the northern snakehead — or “fishzilla” — has been found in Georgia — and it’s bad news for native species.” (Quoting Petersen, B. 2019. WSB-TV Atlanta News (Oct 9, 2019), posted at .)
  11. Johnson, J. J. S. 2010. Misreading Earth’s Groanings: Why Evolutionists and Intelligent Design Proponents Fail Ecology 101. Acts & Facts. 39(8):8-9, posted at .

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