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Thom Cmar’s Blog

Fishing for an Asian Carp Needle in a Haystack

Thom Cmar

Posted August 3, 2011

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The state and federal agencies who collectively participate in the Asian Carp Regional Coordinating Committee have all gone fishin’ this week.  It may be August, but this isn’t a pleasure trip:  they are looking for live Asian carp in Lake Calumet after recent environmental DNA (“eDNA”) sampling has shown that some of the fish are likely present in the area

Ramping up the conventional monitoring (fishing and netting) in Lake Calumet is a logical response to these positive eDNA results.  Short of poisoning every fish in Lake Calumet, there is not much else that the agencies could be doing at this point…  and I can understand the agencies’ not wanting to undertake (and spend money on) another fish poisoning operation at this stage.

The problem, though, is that the Regional Coordinating Committee is once again talking about this fishing operation like it is somehow going to prove whether live Asian carp are present in the area.  As I’ve blogged about in the past, the Army Corps and other agencies have frequently downplayed, or written off entirely, the significance of positive eDNA results in an apparent effort to convince the public that they have the invasion under control

These agencies should know better, though, because both Government experts (such as Duane Chapman of USGS) and outside experts (such as University of Notre Dame Professor David Lodge) have said that the conventional monitoring techniques are unlikely to succeed in catching Asian carp in the Chicago waterway system when they are present only in small numbers – and that eDNA is a better tool for determining whether carp are present. 

As John Dettmers of the Great Lakes Fishery Commission recently pointed out in a live chat sponsored by the Detroit Free Press (I imagine John was typing fast, which explains the two typos):

I think that the Asian carp that have been caught in Lake Erie were caught essentially by luck. We know that conventional fishing gear is very ineifficeint [sic] when trying to colelct [sic] Asian carp when only a few are present. Nevertheless, fishing gear does capture Asian carp now and then, as happen[ed] last July in Lake Calumet.

In other words, fishing for Asian carp in the Chicago waterway system is kind of like using a pitchfork to search for a needle in a haystack.

It’s true that the eDNA results, without more, cannot tell you exact number or location of carp that are being detected, but the only plausible explanation for explaining the positive eDNA hits is the presence of some live Asian carp in the Chicago waterway system.  Although a number of other possible explanations have been offered to explain the positive eDNA results, I agree with David Lodge’s view:  none of those alternative explanations seem plausible, much less likely, given the overall pattern of positive results that has been detected.

So, in sum, I’m glad the agencies are looking for Asian carp in Lake Calumet this week, and I hope they don’t find any.  But even if they don’t find any, it doesn’t prove the negative.  Just because you don't find a needle in a haystack doesn't necessarily mean it's not there, no matter how much hay you've thrown around. 

As long as there’s a direct waterborne path between the two watersheds, they will both face unacceptable risks of further ecological and economic harm from invasive species moving in both directions.  That’s why we need to move as quickly as possible toward a permanent solution, a separation barrier that prevents movement of invasive species between the Great Lakes and the Mississippi River Basin.  Doing that will require rethinking the entire Chicago waterway system, but as my colleague Henry Henderson wrote about last week, that kind of creative rethink and modernization of Chicago’s moribund wastewater and goods movement infrastructure is long overdue

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