October Monitoring Run

by Carl Strang

Last weekend’s warm weather allowed me to make a late dragonfly monitoring run on the Des Plaines River at Waterfall Glen Forest Preserve. Looking back through my records, I find that in all the monitoring I have done since 2003, I never have made a formal outing in October. It was worth trying for that reason, if no other. Besides, it was a nice day to be on the river in my sea kayak. There isn’t a lot to report as far as dragonflies and damselflies go. The only dragonflies were a pair of common whitetails, the female laying some last ditch eggs. I saw a couple familiar bluets,

a few orange bluets,

a stream bluet, 3 eastern forktails and 7 American rubyspots.

The last confirmed that this species is active late in the season, supporting my sighting at Fullersburg (which at first I thought was a smoky rubyspot). I also made some singing insect observations, the best of which were jumping bush crickets singing in the early afternoon on both sides of the river. This adds to my local range for this species, which clearly has shifted north of where you will find it mapped in references. The shallow lagoon at the downstream end of my monitoring area was hosting a gathering of great egrets.

The gorilla in the room, however, was a major construction project underway on the south side of the river. A fence was being built.

With much machinery, much shouting and an impressively speedy progress (I saw no sign of this when I last was there in late August), a metal framework is being erected and filled with fine-meshed screening.

The fence is parallel to the Centennial Trail, which has been closed for this project. The fence is only 6 feet tall or so, enough to disrupt the view of trail users but not enough to be a significant barricade to wildlife, I thought. A little research on the Internet revealed the purpose of this structure. It is a fish barrier. That may seem strange, but high water levels could lift the river high enough to reach the fence. The target fish are Asian carp, a group of 4 species which have been much in the news because of concerns that they might cross from the Mississippi River drainage (which includes the Des Plaines) and the Great Lakes. The Des Plaines River is paralleled by a canal, so the fence apparently is intended to keep the carp from going between the two. Would tiny baby carp be stopped, though? I’m not enough of a fisheries biologist to judge. For more information on the fish species and other information, here is a link.

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