genetic abnormality. Not common but not completely rare either.
Catch enough perch and you'll come across one.
I’ve seen them in Erie as well.
With Nipissings fishing regs in mind...the best and safest thing you can do with one, is bring it to me...along with any other perch you've caught...and I will dispose of them for you.
https://www.baytoday.ca/local-news/unusual-...p######-3302669