I have no doubt a good percentage of the fish sold to your were in fact emerald shiners. However, in larger northern lakes emerald shiners and common shiners are often found together. So when the dealer you bought your emerald shiners from collected the emerald shiners, he no doubt ended up with some common shiners mixed in. With you waterfall, you have habitat suitable for the common shiners to reproduce. I doubt the emerald shiners will though. The common shiners may actually be a better forage fish for what you are trying to accomplish.
