Lung Fish

Have you seen a sleeping fish? How about a fish that can survive in the air? The Dipnoi are a group of sarcopterygiian fish, or are commonly known as the lungfish. Their "lung" is a modified swim bladder, which in most fish is used for buoyancy in swimming, but in the lungfish , the swim bladder is not only used for buoyancy, but also for absorbing oxygen and removes wastes.

During the drought in Africa and South America, the lungfish are able to survive when their pools dry up by burrowing into the mud and sealing themselves within a mucous-lined burrow. This is called aestivation. At this time, they breathe air through their swim bladder instead of through their gills, and they reduce their metabolic rate dramatically in order to last through the drought without having to eat. Strangely, these fish will even drown if they are kept underwater and are not allowed to breathe air!

Evidence suggests that in recent years only small numbers of young lungfish are growing-up into adult fish. In addition, changes to the quality and extent of breeding habitat are reducing the likelihood of successful spawning. Two of the key problems affecting the lungfish are the flooding of suitable spawning sites and physical barriers that block the adult lungfish from moving to the remaining breeding sites. While the waters of dams and weirs provide feeding habitat for the species, they rarely provide the shallow water and dense cover of water plants like ribbonweed which the lungfish need for successful spawning. In addition, dams and weirs do not provide suitable nursery habitat for the species as the young also require a cover of water plants.

Because of the long life span of the lungfish (with some research suggesting that the fish may live up to 100 years) the lack of breeding success may not become evident in the adult population for many years. It is estimated that there has been a 26 per cent loss or reduction in the amount of breeding and nursery habitat for the Lungfish. As a result, the adult breeding population is likely to decline substantianally within the next three generations. In addition, exotic and translocated native fishes, such as the exotic Tilapia (Oreochromis mossambica) are believed to prey on lungfish eggs and young and compete with adults for breeding habitat.