Northern crayfish may help keep HBG recruitment down. From the "Crayfish of Nebraska" publication.
Northern crayfish will eat fish eggs and sac-fry. One study tested the impact of egg predation of Northern crayfish on pumpkinseed (Lepomis gibbosus) and bluegill (Lepomis macrochirus) in ponds. In densely vegetated ponds, pumpkinseed had delayed reproduction and lower young-of-year biomass due to crayfish predation. In less vegetated ponds, crayfish prevented bluegill reproduction except in crayfish proof exclosures.50
