JRB, a shellcracker is a large member of the sunfish family also known as a red ear bream. They have teeth designed to crush snails and small mussels. They are generally bigger than blue gills and fight much harder but generally only bed once a year unlike blue gills which bed. Every full moon ( and to a lesser degree on the new moon) all summer long. A " blue pisser" is a male blue gill that guards the nest or bed. It is far more aggressive and is caught in great numbers over the "bed". Perhaps they give it the smell that I referred to earlier. When caught and held while taking out the hook, they will express a stream or urine that is amazing.