By Jim Hagerty
Officials in Wisconsin have still not identified the cause of a carp kill in the Horicon Marsh, Lake Sinissippi and upper Rock River or whether fish will die along the more than 300-mile stretch in Illinois.
According to the Wisconsin Department of Natural Resources, the kill is believed to have begun around July 17, and thousands of dead carp were still scattered throughout the area last weekend.
“Our first thought was low oxygen levels, but our measurements show the oxygen levels are fine, and so far, it is affecting only common carp,” Laura Stremick-Thompson, a biologist with the DNR in Horicon, Wisconsin, said. “Northern pike, fathead minnow and bullhead have not been impacted.”
Bacteriology tests have shown the presence of columnaris, a common bacteria that has killed fish in Wisconsin in the past. What is puzzling, however, is that the columnaris is not often seen in carp but can cause gill-rot disease within the species. This leads officials to believe there may be a co-pathogen involved.
Lake Sinissippi Improvement District Treasurer and Rock River Trail Coordinator Greg Farnham said the kill seems to be limited to the Horicon Marsh and upper head of the Rock River. Until the presence of another pathogen is discovered or ruled out, officials are warning communities south of the marsh.
“The Lake Sinissippi Improvement District is monitoring the situation closely and keeping the lake community aware of what’s going on,” Farnham said. “Officials as far south as Janesville are being informed so they are watchful in case this is caused by a virus, which can spread.”
Landowners with dead fish on their shorelines are reminded to wear gloves or use a shovel or rake to collect carcasses. Decay bacteria present in a decomposing fish could cause a harmful reaction in humans if directly contacted or ingested. Fish carcasses can be put in a trash bin, composted or buried for disposal.
About common carp
The common carp is one of the most abundant and widely distributed fish in America. Mostly considered a rough species, they are common in larger rivers and lakes with ample organic matter at their bottom. Carp also adapt well in warm-water bodies containing sewage and agricultural runoff.
Weighing as much as 50 or 60 pounds, the common carp is an omnivore, feeding on insects, crustaceans and small mollusks. While the species is important in elimination of harmful vegetation, an abundance of carp can destroy macrophytes and lend to the presence algal blooms.
Carp are considered a delicacy and are fished using dough balls, worms and corn. They are also taken by bow and arrow.
From the July 30-Aug. 5, 2014, issue