Basic principles The first to rot is blood, second is gill, third is organs, fourth is bone which carries the blood to all parts of the body and finally the skin which also the organ. The most common method to kill the living animals is to kill the brain which is the faster way to prevent the distortion of the muscles. For fish, the method is used " spinal destruction method" but the fish already dead, and usually the blood and vessels will be frozen, I cannot understand the purpose of bleeding the fish.