We certainly don't get Great Egrets in Wisconsin, but if they are anything like the Herons or the Egrets we do get up here the problem is not the fish that they eat, it's the fish they try to eat. If they eat small fish they just do the job you are looking to have your predators do anyway. I just hate finding my nicest and largest fish dead with holes in them or big cuts on each side of them. There isn't much limit on what size fish they will try to catch. My Hybrid Bluegills are completely gone. I think Cecil shares my love for the birds for the same reason. Just like any hunter I respect what they catch to eat but despise what they wound and leave to die.