is there any kind of stream leading into this pond? if there is even the slightest stream; i mean a trickle of water flowing thru mud into the pond, then that is a "highway" for crawfish to get into the pond. i found a small beaver pond in my woods that had a super small stream flowing into it, and since it was in the middle of nowhere, it was obviously untouched. well i set out a minnow trap just to see if there was anything in it, i figured i'd get nothing. 3 days later i returned and found a few huge crawfish in it, about 30 huge bullfrog tadpoles, a couple water beetles, various insect nymphs/larvae about 7 newts, and 3 yellow spotted salamanders. so you'd be suprised in what lives in a supposedly "empty" pond.
as for baits to fish, stick to the natural looking stuff cuz you have already had success with that. fish plastics and maybe a few silent crankbaits (rapala shad rap) since you said the fish are kinda spooky. even though there are no baitfish (which there may actually be, you just dont know it) the bass will still instinctivley hit crankbaits.