A survey recently conducted by the U.S. Army Corps of Engineers showed positive evidence for genetic material from silver carp in southwest Chicago.
The May 22 test showed 17 positive identifications for the DNA of silver carp in 112 sites sampled in Lake Calumet and Little Calumet River through a process called "eDNA," or environmental DNA testing. The test involves filtering water samples for fragments of DNA shed by target species.
Genetic material left from carp tissue, mucus, feces or urine is not a certain indication of the presence of a live Asian carp; the DNA found in testing could have come from dead fish or water from another source.
Researchers also tested for bighead carp in the area, another species of Asian carp, though all results were negative.
The AP reports:
Jared Teutsch, water policy advocate for the Alliance for the Great Lakes, said in a statement Monday the findings mean "another year of worry" about Asian carp.
Bighead and silver carp were imported from Asia. They have migrated up the Mississippi River and its tributaries. An electric barrier is meant to block them.
Dozens of water samples taken beyond the barrier in recent years have contained Asian carp DNA, although just one actual carp has been found there.
-Elaine Ezekiel, Michigan Radio Newsroom