A very interesting read, I just thought I would add a bit.
I am in Adelaide ,Australia and would like to clarify, perch are eaten here and are classed as one of the best eating freshwater fish.
The law does say we are not allowed to release them, but unless they are kept to eat I know they are released unharmed by most. I have never heard of them being wasted.
Carp are treated different as they are considered a pest.
One difference here is they can't be wiped out, many have tried.
They are also so easy to catch here it's not funny, no small hooks and specially methods needed here.
Heavy lines and big hooks will catch big carp here, although trying to get them on 1 pound line is more fun.
I would say that all of our freashwater contains carp and plenty contain perch as well, I caught my first recently on a softplastic lure first cast. We caught quite a few that day.
I wont get too involved with whether they should be eaten or not over there.
I guess it makes interesting fishing if the fish become harder to catch after a few times.
I admit I do eat fish I catch, mainly saltwater varieties, but I also release alot, probably more than I would keep.