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1st thought: heterozygous DNA code for no stripes
Cool stripeless perch1st thought: heterozygous DNA code for no stripes2nd thought: immature walleye? (but probably not, looking at fin positions)
I think you are on the right track there...but it would probably be a homozygous recessive of some sort (having two of the same and very uncommon alleles).
Two of them are Blue perch... there are a few threads over the last two years. They are a genetic mutation that lacks, I think the yellow pigment. It gives them a blueish color.