there are differences between the animal fauna in various parts of the volcano. for example, the oxygenated waters and availability of shrimp as food source attract eels to the summit of nafanua, while the crater floor displays a high animal mortality and is called the "moat of death"; polychaetes feeding on dead fish have been found on the crater floor. this is due to the very low availability of oxygen for respiration at the crater floor, unlike at the summit of nafanua cone.