Every dawn, commercial fishers boat onto the rivers and waterways surrounding Chicago. They're hoping to bring back the catch of the day - and only the catch of the day.

'You may have 40 or 50 of them jump in the boat.'- Ronald Brown, fisher

"You have got to keep your open and look around because sometimes you may have 40 or 50 of them jump in the boat," captain Ronald Brown said, talking about silver Asian carp.

The silver Asian carp is one of a two big fish with an equally big appetite. The fish threatens the food supply and spawning space of fish native to the Mississippi River water system - and potentially, the Great Lakes.

There isn't just one species of Asian carp.There are four:

  • Black carp are legal in the U.S., but can't be intentionally released into waterways.
  • Grass carp lives in mainly in slow moving rivers standing ponds and lakes. The grass carp was legally introduced into at least 35 US states.
  • Silver carp grow to weigh as much as 27 kg or 60 lbs and jump from the river.
  • Bighead carp are filter feeders and can grow to 45 kg (100 lbs), but typically weigh 18 kg (40 lbs).

The bighead carp is the one that most concerns the Illinois Department of Natural Resources, which is trying to stop the spread of the invasive species.

The bighead carp threatens the multi-billion-dollar fishing industry on both sides of the U.S.-Canada border - the Lake Erie fishery alone is worth $35 million.

Every week fishers near Chicago fish the Illinois River and catch them by the boatload. They're then used as fertilizer and food for people.

The U.S. Army Corps of Engineers contends an electric barrier in a canal 37 miles from Chicago is preventing the carp from getting through to the Great Lakes.

Click here to see a graphic of the barrier.

'Marvel of science'

Lt. Col. Kevin Lovell said the barrier is the largest of its kind.

"This is a marvel of science and technology," he said.

The generators have been running for approximately five years. Generators send electricity through the ground and into the water. When carp try to pass through the electric barrier, they get a mild shock. It doesn't kill them, but it's enough to turn them around.

"Because Asian carp have not moved past this facility, this electric barrier, and established a sustainable population shows its effectiveness," Lovell said.

Still, in February of this year, a report found Asian carp DNA had been found on the wrong side of the electric barrier.

Several U.S. federal agencies, including the U.S. Army Corps of Engineers, said the genetic material could have been transported by bird feces, fish sampling gear, barges and storm sewers.

In Canada,  Ontario's Invading Species Awareness Program is working on ways to develop an Asian carp response plan, so boaters and fishers know what steps to take if they do spot an Asian carp.

No sightings in Ontario

So far, there have been no reported bighead or silver carp sightings in Ontario waters.

However, a grass carp was found in the Grand River south of Hamilton near Lake Erie earlier this year.

When Asian carp were first introduced to U.S. waterways in the 1970s,  it was thought they would control algae growth and parasites in aqua farms.

What is eDNA?

According to the Center for Aquatic Conservation at the University of Notre Dame, plants and animals shed cellular material in their surrounding environment, and this material can be collected and analyzed.  Traces of DNA extracted from environmental samples are used to determine if a target species have been in the vicinity using species specific molecular markers.

Today, governments on both sides of the border have pledged millions of dollars to ensure they don't make it into the Great Lakes.

Lindsay Chadderton, the Aquatic Invasive Species Director for the Nature Conservancy's Great Lakes Project, said governments must act now.

He spends time on the Illinois River now using environmental DNA, the earliest possible way to detect whether carp may be in the water.

if Asian carp were present, they would leave DNA evidence in urine, feces and scales shed in the lake.

"While [carp] are vulnerable to management versus waiting until we've got fish jumping out of the water, at which point you're always going to be on the back foot and it's going to be very difficult to do anything successfully, Chadderton said.

Ontario's Ministry of Natural Resources has a similar eDNA program. It started in 2011. As of July 2013, the ministry had not found any evidence of Asian carp being in any of the fisheries it sampled.