If the fish are really, really black they could be bullheads. But there are minnows and even fingerling BG can look black from the top in shallow water. So they could be about anything.
If you want to buy a minnow trap and throw it in shallow water with some crushed up bread or dog food or fish food for bait, you can see what some of your other small fish are. Post pictures and the experts can tell you what they are and the rest of us can try.
