Devon Joel

I have a small 1/4 an acre pond that had blue gill, sunfish, and bass. There have been fish in that pond for over 50 years. But I haven't caught or seen a bass in 5 years. Last year the blue gill and sunfish where abundant in 2-3 inches. This year I see one every once in a while dart by but when I throw dough balls in the water there isn't a big swarm like here use to. I don't know what's wrong, there is a blue hearing that comes up there sometimes. Does any one have an idea of whats going on?