· The lungfish habitat
· The age of lungfish
· Lungfish at risk
· The hatchling microhabitat
· Information from fossils
· The future prospects for lungfish
· Hidden values in lungfish
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Lungfish live in rivers and lakes in southeast Queensland. (Fig 3-01, map) Adult lungfish can live in stagnant water (Fig. 3-02), but clean flowing water is preferred (Fig. 3-03).
There are three natural habitats, in the Burnett, Mary and Brisbane Rivers. Lungfish from these three places can be distinguished by numerous small but consistent differences in young lungfish. For example, juveniles from the Mary River have yellowish skin with many large and obvious speckles (Fig 3-04) compared with young from the Burnett and Brisbane Rivers (Fig 3-05). These are darker, and the speckles are small.
Eggs from the Burnett River have less dark pigment than eggs from the Brisbane River, and the yolk globules are a paler green. There are other detailed differences in the way the eggs develop. Some people think that the Brisbane River is not a natural habitat for lungfish, and that the Brisbane River fish are descended from five fish, caught in the Mary River, that were placed in a dam near the source of the Brisbane River. These fish were supposed to have escaped from the dam during a flood, and started the population of fish in the Brisbane River. This may not have been the case. A few years after the fish were placed in the dam near the Brisbane River, there was a fish kill which included many lungfish. Five fish would not have made so many new fish in a few years. There are differences between Mary River fish and Brisbane River fish. Lungfish may move within a River system, to spawn or to find food, in a normal situation. It is possible that the five Mary River fish did move out of the farm dam and enter the Brisbane River. However, these fish were not in their normal environment. They had been taken from their own environment in the Mary River, kept in a dam for six months, and transported roughly to a new home. Three of the eight fish that were taken to the Brisbane River died on the way. The other five may not have been healthy by the time they were placed in the new dam, and they still had to wait for a flood to take them into the Brisbane River. It is unlikely that these five fish established the population in the Brisbane River.Lungfish may have been in the Brisbane River as long as they have been in the Mary and Burnett Rivers. All of these rivers are now affected by the creation of weirs and dams, and by reduced water levels in drought. The lungfish habitat, and places where lungfish like to spawn, has been significantly reduced in the last twenty years. In addition to the natural habitats of lungfish, there are several places where lungfish were introduced, between 1896 and 1901. Fish were taken from the Mary River, and placed in the Coomera and Condamine Rivers, and in lakes like Enoggera Reservoir and North Pine Dam in the hills to the west and north of Brisbane. Some of these populations are not doing very well now, because there are no good places for eggs to be laid, and no refuges for young lungfish. This happened in Enoggera Reservoir when water hyacinth was cleared after the 1974 floods. Until that time, lungfish did well in Enoggera Reservoir. Lungfish have not spawned successfully in Enoggera Reservoir since 1974. Now the lungfish in Enoggera reservoir are extinct. The individual There is no certain method of telling the age of a lungfish, unless it has been reared in captivity. A juvenile lungfish is several months old before any scales appear (Fig 3-06) Lungfish scales may show growth lines, but these cannot be related to the known age of the lungfish, in fish reared in captivity. (Fig 3-07) The head scales in the picture came from a lungfish raised in captivity for three years. They have many more than three lines. Similarly, the scale from a juvenile tail is from a fish of seven years, but there are no obvious growth lines (Fig. 3-08)
Unlike bony fish, otoliths are rare in lungfish. When they are found they have only a few growth rings, and are no use for working out how old they fish is. Most lungfish have only a few grains of calcified material inside the inner ear, and these have no growth rings at all. Bones of the skull have growth lines, but these do not give an accurate age. The lines are only visible in the thin margins of the bone, and not in the thick older bone. (Fig 3-09) Teeth are permanent, but wear away during life, and only the most recent growth lines can be counted. The bones from one fish suggest that it is 27 years old, and the teeth of the same fish have few lines (Fig. 3-10). The best we can say is that this fish may have been at least 27 years old. The Queensland Museum in Brisbane kept a lungfish for thirty three years, and Regents Park Zoo in London had one, taken there as an adult fish, for over fifty years. Some lungfish show signs of extreme age, such as fish from Enoggera Reservoir. Their teeth are rotten and abnormal, and their bones are weakened by age. (Fig 3-11)
However, there is no way of knowing exactly how old they are. My personal estimate is that fifty to seventy years would be an average life span for a wild lungfish. The group Uranolophus, the earliest known lungfish, appeared in the fossil record in the early Devonian, 410 million years ago. For comparison, the first amphibians appeared around 360 million years ago. The first lungfish did not look very like modern lungfish. They lived in the sea, in deep water, and many were quite small. Some, like Uranolophus, were massive. Lungfish were actually one of the last fish groups to appear in the fossil record. So lungfish are not particularly "ancient". Most other fish groups are much older. The genus and the species The age of the Australian lungfish, as a species, has been reported as anything between 100 and 150 million years old. This has almost become another myth about lungfish. This idea was originally based on an incomplete tooth plate from Lightning Ridge in New South Wales that looked a bit like a tooth plate from the living lungfish. When this information was published, we had very few fossils of similar size for comparison. Now we have better material, and the broken fossil may belong to one of the several fossil species living in Australia around 100 million years ago. A student has recently found some whole fossil tooth plates, and these look very like the teeth of modern lungfish. So it may be true that Neoceratodus forsteri lived in Lightning Ridge 100 million years ago. However, the teeth are small, from young fish, and may belong to another species of lungfish, called Metaceratodus wollastoni, common in that place at that time. The Queensland lungfish, Neoceratodus forsteri, may have lived in Central Australia around 25 million years ago, and more fossils of this species are Pliocene or Pleistocene in age, five to ten million years ago. Most scientists agree that individual species do not last 150 million years, or even 100. The current situation for lungfish Lungfish live a long time, and spawn every year. It is a normal strategy that very few of these eggs grow into adult lungfish, or there would be nothing but lungfish in the river. There is a difference between the production of eggs and the recruitment of juveniles to the adult population. Recruitment of a small number of young fish to the population every year is normal. However, this depends on an undisturbed environment. A damaged environment means no protection for young fish, and no juveniles survive. This means that lungfish are in trouble, partly because of the current drought, and partly because of changes to the rivers where they live. Weirs and dams created to supply water for towns and farms have fluctuating water levels, particularly in spring, so refuges for young do not get established. There are no water plants for the eggs, and small lungfish have nowhere to hide, and no food. The eggs and young die, and there are no new adults. Paradise Weir, the latest to be built across the Burnett River has floating islands, for lungfish to spawn on, and fish ladders. Lungfish do not apparently use the fish ladders to scale the weir. It is also unlikely that the islands are successful as spawning sites for the lungfish behind the weir. Artificial islands in the middle of a deep lake will not be the first choice for adults when they are spawning. Lungfish seem to prefer shallow water for spawning, and the islands are not in an area that they have used before. Floating mops of artificial material, an idea borrowed from commercial aquarists, do work, in my experience, if they are placed near a known spawning site, and in flowing water. I tested these experimentally in the Brisbane River in 2000-2001.. See report here (external link). Lungfish are not choosy about where they lay their eggs - natural water plants or floating islands are fine by them. But they come to the same area to spawn, and like flowing shallow water. Lungfish will not thrive in a large reservoir with fluctuating water levels in spring. In addition, poor quality water suppresses successful spawning. Water quality in weirs and reservoirs is poor. Many thanks to Peter Garrett, for his wise decision to stop the building of Traveston Dam and save the Mary River. The Hatchling Microhabitat Most lungfish eggs hatch into a protected microhabitat among the leaves of water plants or the submerged roots of Callistemon trees or water hyacinth. They do not need to search for a suitable habitiat, and there is plenty of food among the leaves or roots. They are also able to hide from predators. Hatchlings avoid light, and this means that they will stay where they have hatched. Lungfish eggs that are not laid among water plants of roots, and fall to the bottom of the river or lake, will hatch among detritus and rotting vegetation on the substrate. These hatchlings will have a difficult time, because such an environment is unsuitable for a young lungfish. There is little food, and few hiding places. There is no truth in the story that young lungfish spend the first three years of their lives buried in mud. No successful recruitment (external link) Information from fossils The fossil record shows that lungfish have faced similar problems before, albeit from natural causes. In the past, Australia had far more wetlands, lakes and rivers, and there were eleven species of lungfish in central and eastern areas. Some of these fish grew very large, up to 5 metres in length. (Fig. 3-12, 3-13)
Gradually, as Australia became drier, the lakes, rivers and wetlands were lost, and the lungfish were pushed out towards the coast of eastern and northern Australia. Only six species survived. The continent continued to dry out, and the northern lungfish disappeared. Eventually, only one of the two eastern species survived. This is no great surprise, and not much of a lesson. They died out because their environment changed. What is of interest is that several of the lungfish populations were in trouble before their lakes and wetlands disappeared, and their problems then were the same as the problems faced by lungfish now. Some lungfish lived in free flowing rivers with plenty of food, rather like the rivers of south east Queensland before the big push to turn them into reservoirs, to supply farms and cities with water. (Fig. 3--14, 3-15)
These lungfish were free of disease and spawned regularly, with many young recruited to the adult population. The northern lungfish lived in a poor environment. Many were sick. (Fig. 3-16) Some did not have enough food (Fig. 3-17). Although they could, and did, spawn, they were not able to grow to a large size. Turtles and other animals in these environments were also small. Lungfish in central Australia lived in large lakes with water levels that went up and down. No plants survived in the water close to the shore. (Fig. 3-18)
Small lungfish in these lakes had no refuges, and no recruitment to the adult population was possible. The adult fish grew to a huge size, got older and older, and sicker. But there were no new fish. There were no young, and the populations eventually died out. That is what is happening now, in big weirs and reservoirs. It has already happened in Enoggera reservoir. Lungfish are good environmental indicators. If lungfish are doing well, so is the locality. Where lungfish are established as a viable breeding population, the lake or river has clean fresh water. Young lungfish and eggs provide food for water birds, other fish and insect larvae. They even provide food for their own parents. Adult lungfish feed by sucking food into their mouths. This is another reason why the young need a protected microhabitat. Nobody knows what will happen to rivers and lakes in south east Queensland if there are no lungfish. The condition of Wivenhoe Reservoir, Walla Weir and the Paradise River Dam suggests that the freshwater environment of the future will be unpleasant, with foetid water and few living plants and animals. Lungfish of all ages are part of the environment, part of the food chain, part of Australia's biodiversity. They are important, and have a place in the system. The future prospects for lungfish The outlook for lungfish and for other endangered plants and animals in southeast Queensland is poor, unless politicians listen to the views of conservationists and try to help. What we need are unaltered reaches of the rivers, and special reservoirs set aside as reserves for lungfish and the animals and plants that live with them. Since we do not know what, exactly, creates an environment that lungfish like, it would be best to preserve, as National Parks, unchanged parts of the Burnett, Mary and Brisbane Rivers for lungfish and for other animals that live with them. If this is done, lungfish may survive. Fish kill in Southeast Queensland Recent heavy rain in the winter of 2009, in the catchments of several dams in southeast Queensland, caused the deaths of many species of fish, including lungfish. Fish came over the spillway when the water level rose. Post mortems of a number of the lungfish revealed significant external bruising and in one case a broken jaw. The fish were battered when they fell onto rocks or a concrete spillway below the wall of the reservoir. All of the fish were adults, and some were in poor condition. In every case, the intestines were empty, except for a few strands of filamentous algae and fragments of leaves in the rectum. An adult lungfish that had been actively feeding would have an intestine full of partly digested food, such as filamentous algae, small clams and snails, and prawns. These fish had not been feeding for some time, weeks or even months. The Australian lungfish undergoes a period of quiescence in winter months, almost hibernation, and may not feed during this time. The recent fish kill was spectacular, and received widespread and unfortunate publicity in the press. It is not however an isolated occurrence. Fish kills of this magnitude have happened many times, everytime there is a major flood in the catchment of a dam or reservoir with a high wall. Spawning event in Wivenhoe Reservoir. Lungfish will spawn in a reservoir, even if conditions are not entirely suitable for eggs and young. Spawning occurred in Enoggera Reservoir after the water hyacinth was cleared, but in the absence of suitable submerged water plants for the eggs, nothing survived. Enoggera Reservoir, in the parts where lungfish used to spawn, is deep with steep banks. The issue is not whether the fish spawn in a reservoir, but whether successful recruitment of juveniles to the adult population can follow a spawning event. Wivenhoe Reservoir was created from a part of the Brisbane River in 1984. Prior to this time, lungfish spawned regularly in the river and juveniles were recruited to the adult population. Lungfish may have continued to spawn in the reservoir, as they did downstream of the dam wall, but if they did few eggs would have been able to survive because there were no water plants to shelter the young. Heavy rain in the winter of 2009 raised water levels in Wivenhoe reservoir to submerge parts of the bank that had been dry for many years. The water covered paddock grass and cow pooh, and water hyacinth moved into the shallows. Filamentous algae filled much of the space to a depth of about 50 cm. In this unpropitious home, numerous lungfish eggs have been laid. They were simply shed into the water, and not among water plants as is more usual for lungfish. A single hatchling was found among the dead grass and leaves where the fish had been spawning. Other researchers report similar results. Semon found one, in 1893. Bancroft who worked for twenty years in the Burnett River found none. A low survival rate of hatchlings is normal for lungfish. An attempt was made to raise some of the eggs in the laboratory, using methods that have worked well before. Forty five percent of the eggs laid in Wivenhoe Reservoir were either dead when collected or dead when they arrived in the lab. In most spawning sites the mortality is less than 15%. The surviving embryos hatched far too soon, between stages 36 and 38, before any sense organs had developed, and before the normal range of muscular movements was present. Embryos as young as stage 36 are completely vulnerable to predators, and would not be able to seek out or move to a suitable habitat, even if one had been present among the filamentous algae, rotting paddock grass and cow pooh. Most lungfish embryos and hatchlings, even ones as young as stage 36, move when stimulated. The hatchlings from Wivenhoe did not move at all. When offered food, the hatchlings did not feed. They all died by stage 47, when the yolk supply was exhausted. Analysis of the fish using scanning electron microscopy reveals that their skins are abnormal, with no cilia and no sense organs. Young fish without cilia on the skin cannot keep themselves clean and are likely to be infected by bacteria in the environment. It could be that the lungfish in Wivenhoe Reservoir can no longer produce normal eggs, or that the parents of these eggs have a genetic abnormality. The same problem has recently been found in another reservoir in southeast Queensland, Lake Samsonvale. All of the eggs laid in 2010 and 2012 have died, and the eggs collected in 2013 look equally unhealthy.
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