Size needed to avoid LMB predation also depends on the species. Those that are spiny and round wouldn't need to be as large as a species that isn't round and spiny. Although the stocked fish may not be big enough to completely avoid predation, there are other factors which help to ensure their survival. If LMB are not over crowded and already have a proper forage base present, they will be less likely to feed on your new stockers. The amount of available cover for the newly stocked fish to take cover in will also factor into survival rates.