More evidence of Asian carp expansion found
The samples were taken beyond the electric barrier meant to keep invasive species out of the Great Lakes system. The DNA found was from silver carp. (Department of Fisheries and Allied Aquacultures, Auburn University, Alabama, USA)
“The environmental DNA is indicative of the presence of a fish, although there’s no indication of how many fish might be there,” said Phil Moy, fisheries and invasive species specialist with the University of Wisconsin Sea Grant Institute.
The samples were taken beyond the electric barrier meant to keep invasive species out of the Great Lakes system. The DNA found was from silver carp.
“When we keep finding more eDNA past the (electronic) barrier, this is more of an indication that we need to move quickly on the study and implementation of the permanent separation of the Great Lakes and the Mississippi River basin,” said Jennifer McKay, policy specialist with Tip of the Mitt Watershed Council in Petoskey.
“This is just further affirmation that we need to act, and we need to act now.”
The electric barrier is a temporary solution, calibrated to give a certain number of volts per inch of fish, said Moy. Smaller fish receive smaller shocks.
“It’s not an infallible system. We also know once little Asian carp start to press their slimy little noses against that field, they can get through,” said Moy.
The number of positive eDNA samples has prompted a sweep of Lake Calumet with crews from government agencies that use electric jolts to stun fish. Commercial fishing boats then sweep the lake with nets in a search for Asian carp.
The threat of Asian carp prompted U.S. Sen. Debbie Stabenow, D-Lansing, to propose, in March, the Stop Asian Carp Act, legislation that would require the quick implementation of a plan to permanently separate Lake Michigan from the Chicago Area Waterway System.
Currently, all that separates Lake Michigan from the waterway system is a system of locks, which allow passage of commercial and recreational boats from the waterway system to the Great Lakes — as well as water potentially laden with invasive species.
“I strongly urge the Army Corps to close the locks now while they continue to determine the best way to permanently separate the Chicago Area Waterway System from the Great Lakes,” said Stabenow in a statement released two weeks ago.
Although a permanent barrier is necessary not only to keep Asian carp out of the Great Lakes, but also for other invasives such as viruses and plankton, such a barrier is a challenge, said Moy.
The problem lies in Chicago’s combined sewer system that conveys both wastewater and stormwater to treatment plants.
During large rainfall events, the combined system becomes full, and the combined water discharges into the river, taking the water downstream from Lake Michigan. The river’s direction was reversed in the 19th century for sanitation reasons, engineered to flow toward the Mississippi River basin rather than emptying into Lake Michigan.
Separating the river from Lake Michigan eliminates one venue into which discharged water can go, leaving only the lake.