ZANESVILLE, Ohio -- As it cuts a squiggly track through the southeast Ohio hill country, the Muskingum River might seem like an unlikely battlefront in the war to keep Asian carp out of the Great Lakes, but the results of a recent study indicate these dreaded invaders could be present near there and pushing north toward a gateway to the Lake Erie watershed.
Multiple water samples taken from the Muskingum River last fall carried the environmental signature of bighead carp, an invasive species threatening the ecosystem of the Great Lakes. A report released Friday by the Nature Conservancy -- in conjunction with the Muskingum Watershed Conservancy District, the Ohio Department of Natural Resources, and researchers from Central Michigan University -- indicated 10 of the 222 samples from the river tested positive for bighead carp eDNA.
Asian carp have been established in the Ohio River for more than a decade, but these eDNA results indicate the fish could be present in the Muskingum some 80 miles north of where the Muskingum joins the Ohio at Marietta.
The Muskingum has a series of old dams and deteriorating locks, but if the genetic evidence is accurate, those have not provided a significant impediment to the carp moving up the river system.
"This information seems to indicate they have already gotten past the dams," said John Navarro of the Ohio Department of Natural Resources. "They've shown no tendency to slow down. They are barreling up these waterways."
The Asian carp fight has been going on for at least two decades and involves a cadre of state and federal agencies.
The term Asian carp refers to four invasive species that present various levels of threat to the waterways of the U.S. and the Great Lakes: bighead, silver, grass and black carp.
Bighead and silver carp were imported in the 1970s to help control algae in fish farms in Arkansas, and reached the Mississippi River system either by escaping those facilities during floods, or by accidental introduction. These two species have been surging across the watershed ever since, and are the most destructive. They are filter feeders that devour plankton, depleting the food sources for native fish. They thrive in nutrient rich waters, such as those offered by the Muskingum River or western Lake Erie, and are prolific breeders.
Grass carp consume aquatic vegetation and destroy habitats of native fishes, while black carp eat snails and mussels and are a threat to those species.
Bighead and silver carp now dominate large stretches of the Missouri, Mississippi and Illinois rivers, making up as much as 90 percent of the fish in places. Their primary access route to the Great Lakes would be through the Chicago Sanitary and Ship Canal, a man-made link between the Mississippi Watershed and Lake Michigan. An electrical barrier operated about 30 miles from Lake Michigan is intended to keep them out of the Great Lakes, but biologists and politicians in Ohio and Michigan have clamored for a closing of the canal.
The Block News Alliance consists of the Pittsburgh Post-Gazette and The Blade of Toledo, Ohio. Matt Markey is outdoors editor at The Blade.