That is a big walleye for the Cedar River or any river for that matter. I’d imagine that a 30″ walleye (approximately 10 Lbs) that is belly hooked would put up quite a fight. I’m sure you released the fish seeing how it is illegal to keep game fish not hooked in the mouth in Iowa. I’ve heard of a few walleyes that large being taken from the Cedar through the years. I lived in Cedar falls for a couple years way back when and I would catch a few walleyes below the low head dams but the biggest I ever caught on the Cedar were maybe 20″.
The interior rivers here in Iowa have decent populations of walleye in them but they don’t get nearly the fishing pressure that the big river or some of the lakes get. Many of the smaller interior rivers are regularily stocked with walleye and while other rivers have some natural reproduction. I know the DesMoines, Cedar and Wapsi rivers all have some reproduction but also receive supplimental stocking. Rivers like the Turkey and Upper Iowa are stocked and have no natural reproduction but are loaded with walleye.