In some instances little brookies reproduce like mad and then you get a population of stunted fish. This one and the one from the previous photo are from a 2 acre pond in Quebec. It's absolutely loaded with them but the one you see here is pretty big. Also, note the parr marks on this and especially the fish on the previous picture, and these are adult fish!
I remember fishing a beaver pond in northern NY state once. It was absolutely loaded with 4 to 7" dinks. a 9 incher was a trophy. Man are they gorgeous!