State: Tests show no sign of invasive carp in Lake Michigan tributaries
While invasive carp have spread throughout the Mississippi River and have been found in Illinois, federal and state agencies testing for the non-native fish in Michigan's waterways haven't found any since tests began in 2013.
New testing by those agencies in several waterways in west Michigan is the most recent indication that the non-native fish species hasn't made its way to Lake Michigan, which feeds into the rest of the Great Lakes.
The U.S. Fish and Wildlife Service, in coordination with the Michigan Department of Natural Resources, collected and tested 336 samples from rivers and lakes connected with Lake Michigan for the presence of genetic material of bighead and silver carp.
Seth Herbst, aquatic species and regulatory affairs unit manager with the DNR, said in a statement that if any samples collected in Michigan waters tested positive for genetic material of invasive carp, the state department would attempt to locate the fish populations as well as use "electrofishing to capture and remove the invasive fish."
Water samples for the tests earlier this year were drawn from the Kalamazoo River, Spring Lake and Lake Macatawa, which flow into Lake Michigan. Water samples showed no evidence of genetic material from invasive carp.
At least one more series of tests is planned for the fall.
The DNR has participated with the Fish and Wildlife Service in its eDNA surveillance program since 2013 to sample waterways for the presence of genetic material, or eDNA, of the non-native fish.
These waterways were chosen, according to the DNR, because they are the closest to the Chicago-area waterway system that connects to the Mississippi River. Bighead and silver carp are found in the Mississippi River as far north as Minnesota.
In previous years, the two agencies have coordinated to perform testing in tributaries of all the Great Lakes excluding Lake Superior, which scientists say has a low-risk for introduction.
There have not been any positive test results followed up by carp captures in Michigan waterways since testing began.
In May, testing on Lake Calumet in Chicago, which is six miles downstream of Lake Michigan, resulted in positive test results for the genetic material of three silver carp and three bighead carp. After three days of searching by the Fish and Wildfire Service and partnering agencies, no fish were found.
According to the DNR, a positive result in a genetic material test doesn't necessarily mean live fish are present.
The major concern with these two types of carp is that they're efficient filter feeders, the DNR said, so they would eat a lot of the plankton that is consumed by native Great Lakes fish like lake whitefish, yellow perch and walleye. Silver carp are also known to jump out of the water when they sense disturbances from passing watercraft, causing safety concerns for boaters.
In addition to testing the state's waterways for the genetic material of invasive species, the DNR conducts fish population surveys and has a website where anglers can report invasive carp.