if you were marking schools of perch up high it probably wasnt perch, it was probably some type of other bait fish. as for your trolling you might have been going to deep for the eyes. sometimes if the baitfish are up high the eyes will be up high also. were you marking any big marks up high?? if so next time try something that will run alittle shallow. it has paid off for me before to run something about 10 to 12 ft down. just a suggestion.
sherman