When I first saw "white lines" it was a big mystery to me. But I do think I'm getting a bit closer in understanding a bit of the mystery. And that is there are thousand if not millions of these sacred "piled" creature memorials and at least in some instances squiggly white lines are related to taking out the creatures that are bulging of the piles and putting them up to the top or placed in a cavity on the top of the sacred pile!
Noticed how in the photo of the piles of fish, that some are sticking out at the bottom, I drew squiggly lines to the top and then you see pincher like "hands" that are designed to mean they are the vacant area and are about to be filled with dead creatures in a slot or cavity and surrounding layers are represented to be filled up with the sacred dead!