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seems to me like the perch may spawn a little early this year. i was out at one of my bluegill fishing spots with a buddie the other day and he caught 10 perch, " but the thing is we were in 3 ft of water!" they were defenitly their to spaw.
They could have been there for alot of reasons besides spawning. Food, cover, temp, oxygen levels, barametric pressure and weather, fishing pressure. There is no good way to tell WHY a fish is where it is. It is there because it wants to be, for some reason. But it is very early to see perch spawning, or even staging for prespawn. They are still more worried about food and safety than spawning this early in the season.