When I was a kid in Ohio they were not that unusual in the wild. After the Chagrin River would flood in the spring, it would fill all the holes in the gravel pit behind our house, and fish left there would breed. Late in the summer and fall we'd go down with minnow nets and bread and "fish" for the fry to put in our aquariums. As I recall, maybe one pull in every five or six might contain either an all gold one or one that was gold with a black back. That was what we were after. When we moved back to town andI got older I gave my aquarium to the East Cleveland Library, and for a long time, they had a nice exhibit of "gold fish" that were actually my caught wild carp. :^)