Most days, researcher Stefan Tucker, with trawls, trammel nets, trot lines and even electrofishing gear, is on his boat looking for sturgeon in the Rock River. The nearly 300-mile waterway winds through Illinois’ northwest corner, at depths between 15 to 50 feet, flowing and gurgling from Wisconsin down to the Iowa border, where it joins the Mississippi River.

Tucker is a fisheries ecologist with the Illinois Natural History Survey, and the sturgeon he seeks are the most abundant, and the smallest, in the country: the shovelnose. A species that lived with dinosaurs, the fish has a large nose, bony scoops instead of scales that can destroy fishing gear and fringed whisker-like structures near its mouth.

Shovelnose typically tip the scale at about seven pounds, but the Rock River fish are

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