The document discusses various methods of accessory respiration in fishes, primarily focusing on how some species adapt their respiratory systems under environmental stress. It details structures such as skin, branchial epithelium, pharyngeal epithelium, and specialized organs like labyrinthine and arborescent organs that facilitate aerial respiration. These adaptations ensure that fishes can survive in low-oxygen environments by supplementing their gill-based respiration with alternative methods of oxygen uptake.