Asian Carp eDNA: New hits point to danger in Chicago Waterways delays

Silver carp image courtesy of Michigan Sea Grant

Over and over the Asian carp debate gets dumbed down into "fish vs. barges." Usually it relates to pushback against any changes being made to the Chicago Waterways System, but also pops up in the increasingly common occurrence of eDNA tests that show genetic material of the invasive Asian carp present in the river system that transects the Chicago region. The “status quo” enthusiasts assert that the evidence of a pervasive presence of invasives in the river does not require a change for the waterways.  The excuse for “no action”  usually goes, "we don't think there are actually fish here, but if they are in the system, they may very well have hitched a ride on a barge or gotten into barge bilge water tanks..." to explain away the tests.

That brings us to the most recent red alert. This one announced yesterday regarding n the North Shore Channel, which connects to the north branch of the Chicago River in the city and leads directly to Lake Michigan at an MWRD pump station and sluice gate in the suburb of Wilmette.

Here's the thing: barge traffic between the Chicago River and the drainage channel is almost completely nonexistent on that portion of the waterway system.

So the announcement of three straight batteries of tests showing the presence of silver carp genetic material in the area is troubling. Aside from birds dumping a half dozen plus fish (don't forget, these fish get really big!) into the channel after flying them from miles and miles away, there aren't any other particularly plausible explanations (and really, despite the fact it gets repeated ad nauseum, the bird thing just doesn't pass the laugh test).

So, it will be interesting to see what happens with the aggressive fishing that will occur in response to the hits next week. Of course, officials have compared these efforts to finding a needle in a haystack. And they are being conducted a couple weeks after the initial eDNA water samples were collected (fish do swim), but then the entire response to the movement of invasive species into the Chicago waterway system (and the Great Lakes for that matter) has been slow, late, reluctant, and lackadaisical...

We hope that there are not invasive fish in the North Shore Channel---or anywhere else in the river system. But this latest test results in the northern reaches of the waterway system, as well as the spate of recent eDNA hits in the main stem of the Chicago River by the Navy Pier and the Chicago Lock which also connects with Lake Michigan, is causes continuing concern. The increased rate of detection in distinct places beyond the barrier implies an increased threat that we cannot ignore.

But as I noted last week, the Army Corps of Engineers just released an interim report outlining their response to Congressional orders for a speedup in offering a solution to this issue that was passed over the summer. The Corps signaled that they will not meet the deadline.

The newest eDNA results once again illustrate why that delay in response is a problem and why more aggressive action that permanently closes pathway for invasive species must to be taken. This is not about fish vs. barges. It’s about fish vs. Heads in the Sand.

Silver carp image courtesy of Michigan Sea Grant via Flickr.

About the Authors

Henry Henderson

Director, Midwest program

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