This spring has seen a huge increase in the snakehead population swimming in the upper Chesapeake Bay, and the Susquehanna River in particular.
It was already well established that the invasive species could be found in every river flowing into the bay, as well as the bay itself, following their initial discovery in a Crofton, Maryland, pond near the Patuxent River, and later in the Potomac River.
“We are definitely seeing more reproductively active populations near that upper bay,” said Joe Love, a program manager with the Maryland Department of Natural Resources Freshwater Fisheries Program. He cited several rivers around Baltimore, as well as the Chester River on the Eastern Shore.
“We have seen more snakeheads in the fish lifts at Conowingo this year than in prior years — much more,” added Love. “In fact, 80 times more.”
Those fish lifts were installed so migratory fish could move up the Susquehanna past the dam that sits on the Maryland-Pennsylvania line. In 2017, there was one snakehead trying to pass through those fish lifts. This year, there have been 81 caught in those lifts. Love said that’s because there’s been a huge surge in the snakehead population in the lower Susquehanna.
The dam at Conowingo provides some deterrent to the snakehead’s effort to go north into Pennsylvania and New York, as do other smaller dams upstream along the Susquehanna.
According to a statement from Maryland’s Department of Natural Resources, those dams “may also slow the spread of snakeheads in the Susquehanna River to Pennsylvania to New York,” but it said nothing about being able to completely stop the spread into other states.
For now, scientists can only pay attention to how fast their populations grow and what they eat along the way. Anglers have been catching more and more of them in the Blackwater refuge area of Dorchester County, where the impact on other species is already being noticed.
“They consume a pretty wide variety of prey items,” said Love. “Fishes, amphibians, crayfish, crawfish.”
And he said that scientists have been documenting “some significant loss in relative abundance of sunfishes and perch because of the introductions of snakeheads” in the Blackwater River.
The impact they’ll have on the upper bay is going to depend on how the population grows there.
“It’s going to depend on how big the populations get and what kind of resources are in those rivers” feeding into the upper bay, said Love. “It’s likely that snakeheads will pose a threat to fishes and crayfishes in areas where they co-occur with them, and it’s likely that those impacts will be magnified when those populations get bigger.”
But, there is some solace to be taken by the fact that more and more anglers are hooking them on the end of their lines.
“One thing we are hoping is that anglers will be catching them, and when they do catch them, they’ll harvest them, which will help minimize their numbers and minimize their impacts on other natural resources in those areas,” Love said.