Asian Carp: Science and the inference of the unseen

Image removed.

Over a century ago the great jurist Oliver Wendell Holmes, Jr. observed that the Supreme Court case over pollution flushed into communities downstream from the canals of the Chicago Diversion was based on “an inference of the unseen.” At the time he was remarking about cutting edge science that implied the presence of bacteria that threatened Chicago and motivated the construction of canals reversing the Chicago River to eliminate the threat of waterborne illness. His comments have become nearly prescient today.

Once again, cutting edge science shows us that an invisible danger necessitates action on the same waterways in the form of the invasive Asian carp.

This week the Supreme Court again rejected Michigan’s bid to close the locks on Chicago's waterways. Frankly, the news was not much of a surprise, as the Court rarely takes on issues of such immediacy (after all, they did not take up the challenge to the Chicago Diversion until after the canals were already completed). But we have heard that in mid-April the Justices will discuss whether the broader case’s merits warrant action. As that case is focused on forcing a permanent solution to the carp crisis, it will bring a welcome opportunity to look at this problem in totality instead of focusing on the daily push and pull over short-term tactics.

To this point, most of the public dialogue has been about where the carp are and whether the locks should be closed. But if we are going to fight this scourge off from the Lakes we have more---and bigger--- proverbial fish to fry. Don’t get me wrong: in the run-up to a permanent solution, we have to effectively foil  the carp’s movement into the Lakes, and the locks are a valuable tool to do so on a focused, temporary basis. But whatever the role of the locks, the door remains wide open to continued advance of invasive species migrating into the Great Lakes through the Illinois River until we restore a permanent separation of the Great Lakes and Mississippi River ecosystems---what is called “hydro separation.”

Oh, I know.  We hear it over and over, “they haven’t even found a fish past the barrier” so why take action? The tour boat operators say it. The Corps tweets it. And the Chamber repeats it over and over again.  And this is where Holmes’ words about scientific evidence and the “inference of the unseen” are so valuable and apt today. The scientists who know the Asian carp best say that we are unlikely to catch them in the canals despite their presence. The “show me a fish” crowd are all-too-willing to ignore the solid science around the eDNA tests that clearly demonstrate that the fish moving closer and closer to Lake Michigan. The tests have already been termed “actionable evidence” by the federal government. Lindsay Chadderton, one of the researchers responsible for the tests, nicely skewers those denying the validity of his work in this week’s Chicago Reader Asian Carp Edition:

The Army Corps of Engineers and state officials have repeatedly stated that no Asian carp have been found above the electric barrier. How confident are you of the DNA tests?

Yes, the DNA testing is new, and like any new tool, there's always going to be a healthy level of skepticism. But we are confident that our results are real, and the more testing we do this confidence increases. In the criminal justice system we regularly use DNA to place people at the scene of a crime. People, like other animals, shed DNA into the environment—skin, hair, bodily fluids. Carp do the same thing—DNA cells associated with mucus or sloughed off from the gills, attached to scales, shed from the gut system, and contained in feces and urine. Once those cells are released into the water they are held in suspension for some time and we are simply collecting them in the water column. We're looking for evidence of a species, instead of individuals like you do with people, but the principles are the same.

Could that DNA have gotten there by a mechanism other than fish being present? There have been various suggestions that carp could have got there by other pathways, like barges carrying water [from the Asian-carp-infested Illinois River]. But since August the barge operators have not discharged water [from downstream] above the barriers, and barges don't get into the North Branch of the Chicago River or the Des Plaines River, where we have found carp DNA. The other pathways like birds or wastewater also don't explain the overall pattern,

And the last thing that gives us confidence is the fact we can go back to certain places and repeatedly detect DNA. These results are not chance events, and the distribution is consistent with the movement of fish. For example, the number of positive samples decreases as we get closer to the barrier. That's consistent with an upstream invasion.

Echoing Chadderton’s assessment that the fish are there whether we see them or not, USGS carp expert Duane Chapman told the Grand Rapids News:

 "These fish are remarkably cryptic," said Chapman, who is with the U.S. Geological Survey in Columbia, Mo. "They are very sensitive to nets and boats. They are not caught by accident by guys with rods and reels."

By the time Asian carp make themselves known, they tend to be breeding and well-established, he said.

"It's typical for a species to putter along at a barely noticeable level for several generations," Chapman said. "But when you get the density high enough, you are definitely going to start noticing them."

 Further, he tells the Milwaukee Journal-Sentinel,

"You're never going to prove a negative," he said. "No matter how much you fish, you're never going to prove there is not a fish there."

Let’s be honest: the threat is real.  No one denies that the Asian carp are remarkably close to the Great Lakes and that they present a threat to the Great Lakes that warrants millions of dollars of investments to deter.  Before the need for a real, permanent solution through Hydro Separation became clear, neither the Corps, the MWRD or other parties questioned the existential threat they pose to the Great Lakes.  As the evidence becomes undeniably clear that the Chicago Waterway System is now a highway for invasive species into and out of the Great Lakes, the need for real, permanent hydrological separation is equally unassailable.

The fish are swimming headlong into a resource of essential economic and biological value and we are wasting time and money dithering about whether this is an issue or not. The science demonstrates that we need to take energetic and thoughtful action to protect 95% of this nation’s fresh water. Other invasive species are queued up to move between the Mississippi and Great Lakes ecosystems right behind the silver and bighead carp. The Corps originally started to work on their electric fish fence concept not to rebuff the carp’s advance, but to keep the round goby from making its way into the Mississippi (they failed). We simply must address this threat to both ecosystems.

Frankly, it is a real fear that what  we are seeing now is no more than a PR effort  to convince the public that action is being taken, and will suck up all the resources that will be available to fix the problem. The Asian Carp Control Strategy framework is overwhelmingly tipped towards short-term tactics, with only $1 million of their stated $78.5 million budget devoted to the study that is intended to determine the permanent solution. Bubble curtains and poisonings accompanying every lock opening are pricy and simply do not eliminate the risk to which we are now exposed.

We are all painfully aware that there is not a bottomless pit of money available to throw at this problem. Nor is there time for delay. Thankfully, despite the delaying tactics and intentional cognitive dissonance, we are starting to see more attention being paid to the essential long-term, permanent solutions. There is a growing consensus that ecological separation is necessary. The Great Lakes Commission, chaired by Illinois Governor Quinn and representing all of the Great Lakes states and provinces, recently agreed. The New York Times published a thoughtful article showing that it might even be an economic boon to Chicago and the region.

But nothing can happen until we get serious about moving on the permanent solution of physically separating the ecosystems. Just as in Holmes’ day, this whole thing hinges on the unseen. We can stick our heads in Lake Michigan’s iconic sand dunes but the impending threat is not going away, whether we choose to see it with our own two eyes or not…


Asian Carp - Shedd Aquarium image by Kate Gardiner via Flickr