Chicago Area Waterway System adds to fish diversity

Austin Happel finds brook silversides in his studies of the Chicago River system. You’re not alone if you’ve never heard of them. I had to look them up, too.

They are usually found in clear-water lakes with vegetation.

Which made Happel wonder, “What habitat are they finding in the South Branch. What are you doing here and why are you living here?”

Austin Happel, research biologist at the Shedd Aquarium, working in the Chicago Area Waterway System (CAWS).

Shedd Aquarium/ Brenna Hernandez

So, not only are brook silversides there, but they are surviving well enough to reproduce.

They first showed up in 2007 in an adult survey; mostly in the Calumet system. Now Happel, research biologist at the Shedd Aquarium, is finding decent numbers in the Chicago River in his larval surveys.

It’s part of a pattern of improved fish diversity in the Chicago Area Waterway System (CAWS).

What anglers know from fishing, Happel, the lead author, and Dustin Gallagher, an aquatic biologist for the Metropolitan Water Reclamation District of Greater Chicago, demonstrated in “Decreases in wastewater pollutants increased fish diversity of Chicago’s waterways.” It was published in the “Science of The Total Environment” last month.

They showed “efforts to reduce contaminants and improve water quality in . . .CAWS correlate with increases in fish diversity in waterways like the Chicago River and Calumet River systems.”

This is more than documenting increases in fish numbers and fish species in CAWS, something that academics and anglers alike have noted, but it “shows that the improvements to wastewater handling and treatment directly led to these important fish recoveries in the local waterways.”

Anybody who has seriously fished the CAWS over the last 25 years knows there is a definitive shift.

“Back in the ‘80s, most prevalent species were common carp, goldfish, bluntnose minnows and bluegill; they can survive bad water quality,” Happel said.

As time went on, species “”more picky about water quality” and lots of native species began to show up.

“Pretty cool to see native species and sensitive species coming back,” Happel said.

Channel catfish began to take hold in 2000s. Spotfin shiners started showing up and so did more sensitive ones like mimic shiners. I first encountered mimic shiners fishing the clear waters of Wisconsin’s Geneva Lake, so to think they are now found in CAWS is an “aha moment.”

Austin Happel, research biologist at the Shedd Aquarium, working in the Chicago Area Waterway System (CAWS). Credit: Shedd Aquarium/ Brenna Hernandez

Austin Happel, research biologist at the Shedd Aquarium, working in the Chicago Area Waterway System (CAWS).

Shedd Aquarium/ Brenna Hernandez

When I asked what species he would like to show up, Happel said, “The ones that pop to my mind: We should have some type of pickerel or gar.”

If they showed up and were spawning, it would say something positive about emergent vegetation.

Happel would also like to see even more natural shorelines spreading around CAWS.

As to the forage base, he said, “We have seen large golden shiner, bluntnose and spotfin shiner. The abundance is going up, so there should be food for larger bass.”

He would like to know a lot more about fish movement around CAWS, especially how different species move back and forth through the O’Brien Lock and Dam on the Calumet River and the Chicago Harbor Lock on the Chicago River.

“We are hoping to set up a telemetry survey,” Happel said.

I would love to see the results of that. Anglers have long thought that perch come through the Chicago Harbor Lock and set up in the main stem of the Chicago River in winter, then move back out to Lake Michigan as spring comes.

There’s so much more to enjoy with the rebound of CAWS, and so much more to learn and study.

A close-up of two small bluegill collected during a survey on Chicago Area Waterway System (CAWS). Credit: Shedd Aquarium

A close-up of two small bluegill collected during a survey on the Chicago Area Waterway System (CAWS).

For “Decreases in wastewater pollutants increased fish diversity of Chicago’s waterways,” visit doi.org/10.1016/j.scitotenv.2022.153776.

For the Shedd’s research on CAWS, visit sheddaquarium.org/care-and-conservation/shedd-research/understanding-urban-freshwater-ecosystems.

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