The Great Lakes ecosystems remain under a significant threat from Asian carp. These unwelcome invaders can crowd out other fish species by outcompeting them for food resources. The carp have already overrun parts of the Illinois River, in some cases, accounting for more than 90% of the fish biomass. The presence of Asian carp in the Great Lakes could have devastating results for the region.

Between 2002 and 2011, the US Army Corps of Engineers (USACE) installed three electronic barriers in the Chicago Sanitary and Ship Canal near Romeoville to prevent the transfer of aquatic invasive species between the Great Lakes and Mississippi River basins.  All information to date suggests the barriers are effective at preventing all but the smallest fish from passing upstream toward Lake Michigan.

“Fortunately for us, successfully reproducing populations of Asian carp are located over 100 miles downstream from the Barrier,” said Vic Santucci, a fisheries biologist with the Illinois Department of Natural Resources (IDNR.)

For more than two years, the IDNR and US Fish and Wildlife Service have been monitoring the areas between the barrier and Lake Michigan, working with other federal, state and local partners (including the Forest Preserve District) to complete several intensive sampling efforts to catch and remove any Asian carp that may be present in the waterway.

In over 20,000 hours of sampling, only one bighead carp has been captured upstream of the barrier, a fish caught in Lake Calumet by an IDNR contracted commercial fisher in June 2010.

“Since then we have been coming up empty-handed,” Santucci said.

But another technique researchers have been using to detect the carp has yielded different results. Using water sample analysis, Asian carp environmental DNA, or eDNA, has been turning up all over the Chicago Area Waterway System, and more recently in Lake Erie near Sandusky Bay.

“This led the U.S. Army Corps of Engineers, in consultation with the U.S. Army Geological Survey and U.S. Fish and Wildlife Service to hypothesize that the eDNA was getting help from one of our native species, a fish-eating bird known as the double-crested cormorant.”

The double-crested cormorant is a large bird native to our region, often found basking near the water, holding out its long wings to dry in the sun. It is a voracious predator of fish, well known for the deposition of copious amounts of fecal material wherever it roosts or nests.  These birds are abundant in the Chicago Area Water System (CAWS) and are known to fly long-distances on a daily basis for foraging and roosting purposes.

“The hypothesis is that the cormorants are eating the Asian carp in the Illinois River, then flying around and voiding (e.g., depositing carp eDNA through their feces),” said Chris Anchor, the District’s head wildlife biologist.

With that in mind, a crew from the ERDC-EL, US Army Corps of Engineers, and the USDA (National Wildlife Research Center [NWRC], Starville, MS) came up from Mississippi to begin a study. When their original site fell through at the last minute, they called the Forest Preserve District to see if biologists could assist with a new site.

Over Memorial Day weekend, the team captured and tagged fifteen cormorants at the rookery at Baker’s Lake Nature Preserve in Barrington. The banding included the attachment of a Satellite tag that uses Doppler technology to estimate the location of individual birds (100-500 m accuracy).  The data is downloaded from the ARGOs satellite System to regional datahouses and available to researchers online.

“We expect this study to address the current conundrum, ‘how are we obtaining positive carp eDNA results with little or no presence of actual carp?’ We are proving, that at least in part, that carp eDNA is being deposited in the CAWS by fish-eating birds like the cormorant” said Dr. Michael Guilfoyle, Research Wildlife Biologist with ERDC-EL.

“Personnel with the Forest Preserve District were extremely accommodating in our request to capture and tag birds at Baker’s Lake.  Furthermore, they were indispensable in assisting us with the processing of captured birds, working with us until late in the evening. Without their help, I don’t believe we could have completed this project,” continued Guilfoyle.

Because the study is ongoing and likely won’t have significant results until early 2013, the team is reluctant to discuss any findings. However, they have already tracked one cormorant all the way to northern Michigan, in the middle of August, well before its migration season.

“That’s why I’m a proponent of telemetry,” says Anchor. “People say all kinds of things about where animals go, but when you actually put a transmitter on them, then you know.”