My first thought is those are not crappie ....not sure what they are but they don't look quite right to me ...lots of fish will "ball" up like that at times though and look deceptively like stacked up crappie .
We call those ant mounds when we find them and they are typically white bass drum and kitty fish stacked on the bottom , now mind ya there may be crappie in that mix , a slab with a jig about 16 inches above it and bounce it repeatedly off the bottom maybe ?