When bass have what looks like scratches on its head, gill covers or sides it most likely means the bass are foraging on crawfish. As they jut their heads into rock crevices, under rock bluffs and even on gravel bottoms, they will often get these telltale markings. It would then be wise to switch to a crawfish imitating bait. There may even be sand and or gravel in the back of their mouth, another giveaway that they are bottom feeding.