When I read the sign catch a trout in this picture it reminded me of a farm my grandfather owned near Elmvale Ontario in this picture. He had this pond dug out in the fifties and was going to charge people to fish in it. But after it was finished they decided against people fishing in it . It was stocked full of rainbow trout and the only time anyone fished in was me for about one week every summer when I was a kid. But the only way I was allowed to fish is if I didn't use a hook with a barb on it so I could put the fish back. Ever try to keep a fish on a hook without a barb?
They didn't evolve over long periods like most things. The transition from one to the other was stark to say the least. I remember seeing it without realizing it was happenning