Can anyone identify this fish species? They have shown up in my pond this season. I haven't seen any mature fish yet. Common schooling habit, largest fry in front followed by a general same size class of 100 or so. They will breach the surface when threatened. Any info would be appreciated. 5 acre Pond in Northern Illinois. Known fish species: Grass Carp, Channel Catfish, Northern Bluegill, Hybrid Bluegill, Green Sunfish, Largemouth Bass, Black Crappie.