I don't know about "fishing" ponds, I am guessing it is because the population is too small to sustain fishing.
I am guessing the message is saying that the area is not viable for fishing and whatever fish in there was probably caught.
I have only really done some fishing along the coast, as the fish lay their eggs in the water and replenish their numbers that way (I personally only really invest in sustainable butchery if I can help it)
I guess the water needs to be deeper or one needs to allow the fish to reproduce via their egg spawning, not too sure though as I haven't really dabbled much with fishing?