eDNA puts us in search for Asian carp in the Great Lakes

Researchers from the University of Notre Dame have devised a technique for tracking environmental DNA from Asian carp, such as this 20-pounder caught in Lake Calumet in Illinois. The technique allows scientists to de­tect their pres­ence be­fore the fish be­come wide­spread in a body of water.

When a group of scientists and mathematicians at the University of Notre Dame developed the sleuthing technique called eDNA, or environmental DNA, for finding Asian carp, it was generally hailed as a very valuable addition to the Sherlock Holmes toolbox that biologists could utilize in the fight to keep the invasive species from setting up shop in the Great Lakes.

The eDNA technique allowed the aquatic detectives to take water samples from rivers and lakes, and through careful analysis, determine if any of the nasty critters have been in the area. The bad guys, in this case Asian carp, would leave their fingerprints, or fin prints, in the water via their DNA.

It was no longer necessary to net or catch individual exotic invaders in order to determine if they were present in the waterway. As they passed through the water, these fish sloughed off scales or slime or waste with their DNA return address pasted all over it.

This was CSI playing out in real life, in real laboratories, and the method created a new front line in the battle against Asian carp. Very early detection was now on our side.

Well, the celebration of eDNA came to an abrupt halt in certain corners when the highly innovative method worked exactly the way it was supposed to work, but found what it was not supposed to find.

When water samples pulled from areas where the bureaucrats assured us there were no Asian carp indicated the nasty fish were indeed present, eDNA became the target instead of the weapon in this prolonged fight.

In 58 of more than 800 water samples taken in 2009 and 2010 from beyond the Chicago Area Waterway System electrical barrier that is supposed to keep the millions of Asian carp in the Mississippi River basin from reaching the Great Lakes, Asian carp eDNA was present.

To the researchers at Notre Dame, and most everyone else who paid attention in sixth-grade science class, that meant Asian carp had moved beyond the invisible wall and were huffing and puffing at the door, within just a few miles of Lake Michigan.

To some in the government/politics/waterway management community, those notes did not match the tune they had been singing, so they ignored the fish and attacked the science. The messenger, in this case the eDNA team, was shot full of arrows.

Instead of admitting the canary was teetering on its perch and it might be time to get everyone out of the coal mine, we got an infuriating demonstration of bureaucratic dilly-dallying.

The Army Corps of Engineers floated theories that the Asian carp DNA, which had also shown up in water samples taken from Sandusky Bay and North Maumee Bay in 2011, could be the result of waste water from restaurants where carp were being cleaned working its way into storm sewers, and then into the waterway.

Another theory that was run up the flagpole said Asian carp had possibly jumped out of the water, as silver carp are prone to do, landed on the deck of a barge, died there, and then the carcasses ended up in the water elsewhere.

My personal favorite — right up there with the time-tested “the dog ate my homework” tale — was the bird-poop tale. This imaginary tale floated by the eDNA naysayers claimed that fish-eating birds would consume dead Asian carp on the down-river side of the electrical barrier, and then these flying fiends would go airborne to the opposite side of the barrier before opening the bomb bay doors for their guano drop.

Despite the fact that peer reviews, such as one published by the Society for Conservation Biology, supported and validated its work, the Notre Dame-led eDNA team continued to face fire. Their lab was audited and passed with flying colors — we assume the gold and blue of the Fighting Irish.

They also spent a tremendous amount of laboratory hours and energy putting all 2,800 water samples through an elaborate synthesis, and the results of that effort brought us right back to where we were a few million Asian carp ago.

In a study released Thursday and published in the Canadian Journal of Fisheries and Aquatic Sciences, the Notre Dame scientists and their collaborators from the Nature Conservancy and Central Michigan University showed that the positive hits they found in their eDNA tests occurred only in those areas where live, rogue, adult Asian carp had been discovered in the past.

The flop-on-the-barge theory, and the fish-guts-down-the-drain theory, and the bird-poop theory were tossed into the chum bucket. Apparently, the confluence of random events that would be required for a bird to eat carp in Illinois and fly 200-plus miles before a manure deposit in Maumee Bay has not yet happened.

“It’s really very telling that the only places DNA has been recovered are where Asian carp have been captured,” said Notre Dame research professor Christopher Jerde. “If birds or boats were commonly spreading the DNA, then we should be detecting DNA in other places we have surveyed in the Great Lakes.”

Too bad scientists and mathematicians don’t trash talk, because he could have stated that a lot less diplomatically.

Jerde went on to say the most recent work does carry a portion of positive information — a rarity in the long conflict with the Asian carp, which escaped from fish farms in the south during floods in the 1990s and has now spread throughout the Mississippi River watershed, dominating the ecosystem in many areas.

“The good news is that we have found no evidence that Asian carp are widespread in the Great Lakes basin, despite extensive surveys in southern Lake Michigan and parts of lakes Erie and St. Clair,” said Jerde, who was the lead author of the paper outlining the recent study.

David Lodge, the director of Notre Dame’s Environmental Change Initiative who also worked on the study and the report, indicated that Asian carp washing up on shore or clogging commercial nets would serve notice that the clock has moved past midnight in this tense battle of wits with the aggressive and prolific fish.

“If we wait for the telltale signs of Asian carp jumping out of the water, then we are likely too late to prevent the damages,” Lodge said. “Environmental DNA allows us to detect their presence before the fish become widespread.”

The moral of this saga appears to be that the deoxyribonucleic acid (DNA) does not lie. All of our funds and resources and efforts should be focused on keeping a breeding population of Asian carp out of Maumee Bay, Lake Michigan, and anyplace else connected to our Great Lakes, and not wasted on silly theories of bird poop and mitochondrial strands of denial.

With their DNA trail, the Asian carp are telling us where they are. We should listen.

Contact Blade outdoors editor Matt Markey at: mmarkey@theblade.com or 419-724-6068.