IDNR responded to the NewsTribune with a comment
A Tonica man estimated seeing nearly 500 dead fish on Monday near Interstate 39 between La Salle and Oglesby.
Bill Jaegle of Tonica sent photos of dead fish he saw from Interstate 39 between La Salle and Oglesby.
Mike McClelland, chief of fisheries with the Illinois Department of Natural Resources, provided a response to the NewsTribune:
“During recent flooding along the Illinois River, fish became trapped in the backwater when the river came up, a common side effect of floods. Unfortunately, when the water receded the fish did not return to the river and died due to depleted oxygen levels in the shallow water.”
Jaegle described the fish as being on both sides of I-39 (but most were seen from the east side), and they were located on the east and south of the Illinois River in what was flood water.