Like others have said, walleyes and smallies co-exist in most of the rivers here.
There was a nearby river that had smallmouth but no walleyes in it, then a dam on an ISU research pond broke, and a few hundred nice-sized walleyes ended up in the river. Fishermen thought they'd found HEAVEN. Within a year or so, the walleye were harvested, and reports of walleyes in that river ceased. The smallies are still there, however.