Respiration in Fishes Objective ? Understand how gaseous exchange takes place in fish ? To outline similarities and differences between gaseous exchange in fish and in mammals How do fishes obtain sufficient O2 effectively? ? Dissolved oxygen in the water is around 5 ml of oxygen per Liter of water ? For land animals there is approximately 40 times more oxygen available at 210 ml of oxygen per liter of air we breathe External Anatomy Structure: Gills ? Gills are covered by the operculum ? Consist of the gill arch and the gill filaments. ? Each gill arch contains a large number of gill filaments ? Gill filaments has thin walls and are richly supplied with blood capillaries. Gill ventilation