Ontario's Ministry of Natural Resources spent Thursday near Windsor, Ont. looking for evidence that Asian carp live in Lake Erie.

Officials were gathering water samples that will be analyzed for the presence of environmental DNA.

Brian Locke, fisheries assessment supervisor for Lake Erie for the MNR, said if Asian carp were present, they would leave DNA evidence in urine, feces and scales shed in the lake.

"We sample water to look for fish that have been there. It’s relatively new," he said of the process. "It’s started to become en vogue for species at risk and invasive species."

The environmental DNA program in Ontario started in 2012.

"We haven’t found a thing. We have no positive samples in our environmental DNA collections or any other regular programs," he said. "And, we haven’t seen any [Asian carp] come into the commercial fisheries."

However, researchers with the University of Notre Dame, Central Michigan University and The Nature Conservancy detected DNA from the invasive species in samples taken from Lake Erie in 2011.

Joe Rabino is the captain of fishing boat Liddle Lady, based in Wheatley. He hasn't caught any Asian carp.

"I haven’t seen any yet. But it raises concern because they get so big and they cause a lot of damage to our gear," he said. "Plus, there’s no market for them; there’s no value on them. If we do start seeing them, it’s going to be a nuisance."

Asian carp could be more than a nuisance, Locke said.

"They have the potential to impact the whole ecosystem," Locke said. "There is an economic effect, too."

He said the Lake Erie fishery alone is worth $25-$35 million a year.

"We’re quite concerned," Locke said. "We’ve seen other locations where it’s taken hold and it’s really come and dominated fish communities."

Several varieties of carp imported from Asia have migrated steadily northward in the Mississippi River and its tributaries since escaping from Southern fish farms and sewage treatment ponds in the 1970s.

The fish have since been spotted in more than two dozen states and have advanced to within 90 km of Lake Michigan in the Illinois River, which connects with a shipping canal and other waters that reach Lake Michigan.

None of the carp are known to have reached the lakes.

Locke said prevention is almost mandatory.

"Early detection is the key for any kind of control measure," he said.

With files from the Associated Press