It depends on the species that you have in your pond or lake. Given the opportunity, bass will absolutely eat smaller fish! Large catfish will also partake. We have found that catfish will not eat their younger counterparts. We recommend stocking your pond with fish that are close in size.  If you do restock you pond with smaller fish it is a good idea to have vegetation or other cover for the fingerling fish to hide in.  But expect some fingerling fish to be eaten!  Also, if you have a good forage base (sunfish or bluegill) they will keep the existing bass busy.