Why are dead fish laying on the surface of the water above the dam.? What killed the fish.? Was it all of the population.? First time for me to see him.

There really isn't "all the pollution" you think in the Grand River... The DNR will occasionally "seed" the river with small fish and some times they don't make it. If it's small fish, this could be the case. Other times people will leave some of the fish they catch on the bank out of laziness and disregard for the Eco system

Apparently you haven't seen the larger two and three pound fish floating on the surface. It's not fish left on shore or the so called "seed" fish. Or the natural kill off that occurs most generally in the spring time of the year.This is July. Suggestion go look.