I spent parts of my boyhood fishing for chain pickerel in the Charles River where it runs through South Natick, MA so I am accustomed to thinking of fish when I hear pickerel.
In all honesty, when I looked up this plant's ID, I was rather taken aback as I thought all pickerels were fish...go figure the plant namers. But, it is a good looking plant and the purple against the green is right pretty.