1.2 Reading passage: Australian lungfish, Neocreatodus Forsteri, threatened by a new dam

By Angela Arthington①

(①Angela Arthington: Professor of Australian Rivers Institute, Faculty of Environmental Science, Griffith University, Brisbane, Australia.“Australian lungfish, Neocreatodus Forsteri, threatened by a new dam”by Angela Arthington.2009. Environmental Biology ofFishes [J].Berlin: Springer-Verlag.pp.84:211—221.)

Introduction

Neoceratodus forsteri, commonly called the Australian or Queensland lungfish, has attracted tremendous scientific interest.Fossil records indicate that the range of N.forsteri extended to the centre of the Australian continent prior to the Pleistocene but today the Australian lungfish occurs naturally only in the Burnett and Mary Rivers in south-east Queensland, and as several self-sustaining populations descended from translocations of Burnett and Mary River stocks in the 1890s.Rivers supporting the lungfish have been modified and degraded by land clearing, forestry, grazing, agriculture, horticulture, loss and fragmentation of riparian corridors, bank erosion, gravel and sand extraction, channelization, urbanization, spread of alien plants and fish, and by river impoundment and regulation of river flows.Consequently N.forsteri is considered to be threatened throughout most of its range and has been listed as“vulnerable”under Australian Commonwealth legislation. This listing is intended to protect the lungfish from further disturbance of its natural habitats and to foster recovery actions.Yet a new threat lies ahead for Mary River populations in the form of a large dam on the main channel—the proposed Traveston Crossing Dam. This article is focused on the potential impacts of the new dam on lungfish populations in the Mary River and implications for the conservation of N. forsteri.

Conservation status of the lungfish

Neoceratodus forsteri is a sacred fish of the Gubbi Gubbi Aboriginal people living in the Mary River catchment who call the lungfish ‘Dala' and have revered and protected it from harm for thousands of years.It has been fully protected by the Queensland Fish and Oyster Act since 1914 and was placed on the CITES list in 1977.Fishing for lungfish is prohibited and collection for educational or research purposes requires a permit from the State of Queensland under the Fisheries Act 1994. The lungfish was formally listed as a Vulnerable species under the Environment Protection and Biodiversity Conservation Act 1999 (Cth; EPBC Act) in 2003. This designation means that any action or activity likely to have a significant impact on important populations of the lungfish must be referred to the Commonwealth Department of the Environment, Water, Heritage and the Arts(DEWHA) for permission to proceed or not, or to proceed under specified conditions.

The most recent development action that may threaten the lungfish within its natural range is the proposed Traveston Crossing Dam on the main channel of the Mary River about 27 km upstream from the town of Gympie. Traveston Crossing Dam is intended to help secure water supplies for the south-east corner of Queensland, where rapid population growth, prolonged drought and climate change are creating severe water shortages and citizens are demanding solutions.

Members of the local, regional and national community are deeply anxious about Traveston Crossing Dam and its environmental and social impacts on the Mary River and regional ecosystems.A special petition established in late 2006 by Professor Jean Joss from Macquarie University has gathered over 7,600 signatures and numerous individual expressions of concern In her introduction to the petition Joss (2007) says:

“The significance of the Australian lungfish cannot be overstated.As a living fossil it provides the only opportunity to study the development and physiology of the aquatic predecessors of all land vertebrates, including ourselves.Australia is the custodian of this invaluable information source for the rest of the world.The answer to Queensland's water problem lies in education on water use and smart new technologies, not in damming a fragile coastal river system and will fully extinguishing a uniquely important animal.”

Helen Pearson (2006) writing for Nature echoes these comments:

“Like all primitive fishes it has a lung, as well as gills.The immediate (but not very close) relatives of the lungfish include the coelacanth as well as the ancestors of all landliving vertebrates.This makes the lungfishes ‘living fossils' of great value in studying the biology of the earliest ancestors of land animals.Studying the species may provide a unique insight into how our own vertebrate ancestors made the journey from water to land.”

Potential impacts of Traveston Crossing Dam

If Traveston Crossing Dam is permitted to proceed, it is very likely that it will cause significant harm to important populations of the Australian lungfish in the Mary River.

The natural geographic range of the lungfish is limited to the Burnett River (420 km from source to sea) and the Mary River (307 km from source to sea) with the Mary supporting the most southern natural populations and the Burnett River being the northern limit of the natural range.The lungfish cannot live in saline water nor migrate through seawater, making the separation of the two present-day catchments and populations of N.forsteri absolute.The Mary River therefore supports an independent breeding population of N.forsteri, and is recommended conservation to protect the total genome.These considerations(distribution limits, contribution to breeding stocks and protection of genetic diversity) establish that lungfish populations in the Mary River are important for the species' long-term survival and recovery.

An Environmental Impact Statement (EIS) has been completed for the Traveston Crossing Dam(SKM2007) and is currently being evaluated by DEWHA for the evidence it presents concerning likely significant impacts on important populations of the lungfish and other threatened species and ecosystems.Many make the case that Traveston Crossing Dam is very likely to have significant impacts on lungfish populations in the Mary River.A significant impact under the EPBC Act may involve any or all of the issues discussed below.

1．The dam will have adverse effects on lungfish habitat.

Lungfish occur and are common in the Mary River main channel from the tidal barrage to the town of Conondale. Adult lungfish are usually found in flowing stream and river reaches with overhanging riparian vegetation along the banks, woody debris in the water and dense macrophyte beds.The impounded area will inundate 36.5 km (about 22%) of this type of habitat along the Mary River main channel upstream from Gympie, and will also extend into lungfish territory in several of the tributaries named above.Resting, feeding, spawning and juvenile habitats in the main channel will all go under water to an average depth of about 5 m.Although impoundments can provide habitat and feeding grounds for mature lungfish, far more fish have been captured in the headwater sections of ponded areas where there are shallow waters and more complex habitat structures than in deeper impounded areas.

When Traveston Dam fills the impounded water will not only inundate preferred main channel and tributary habitat for lungfish but will also spill out of the main channel to flood surrounding low lying terrain and create a number of shallow bays.Areas of still, shallow, nutrient rich water are likely to be colonized by aquatic vegetation.There is concern that alien weedy species already present in the Mary catchment will become established and spread in the Traveston impoundment and interfere with the development of natural vegetation stands preferred by lungfish.

2．The construction of Traveston Dam and inundation of core breeding habitat will disrupt the breeding cycle of the lungfish.

Lungfish spawning requirements

Neoceratodus forsteri is very selective in the choice of spawning site.Highest densities of early stage embryos are typically associated with intermediate flow velocities (0.2 m· s-1), low turbidity, a broad range of temperatures (maximum 36°C), high dissolved oxygen levels, depths of 40—60cm and moderate to high densities of aquatic macrophytes 16—35cm in height.Occasionally the lungfish spawns amongst the submerged roots of riparian trees.Structurally complex plant species with complex branching growth forms or leaf whorls contain higher densities of fertilized eggs than those of simpler growth form. Brooks observed that a rapid reduction in water level (25cm) in Bingera Weir on the lower Burnett River exposed many shallow spawning areas and caused the death of a large number of fertilized eggs.

Information on spawning behavior in the Mary River is very limited.Suitable macrophyte beds were rare in the Mary River between 1999 and 2002 as a consequence of a record high flow event in 1999 that scoured river banks.Main channel spawning habitats along the Mary River will be inundated upstream from Traveston Crossing Dam and into tributaries.Shallow inundated embayments with or without aquatic and riparian vegetation, little water movement and large expanses of open water may present very limited options for lungfish spawning.

Juvenile recruitment

Dense beds and banks of vegetation provide suitable microhabitat for developing lungfish embryos and newly hatched lungfish, where they feed on small invertebrates such as microcrustaceans, molluscs and worms.Impoundments with steep profiles and fluctuating water levels typically do not provide suitable nursery habitat and food resources for very young fish and juveniles ( ＜30cm) which rely on dense macrophyte beds in very shallow water for many months or years after hatching, until they move into deeper water.

Growth and longevity

Wild lungfish from the Burnett River may live for 50 years, with some evidence that lungfish can live up to 80—100 years in captivity. Lungfish begin to breed at around 15—17 years of age in males and 20—22 years in the wild.Johnson (2001) remarked that for a long-lived species with naturally low mortality rates, successful spawning and juvenile recruitment are not essential every year, and may only occur irregularly, possibly in medium to long-term cycles, even in natural systems.Such long cycles could easily mask low juvenile recruitment for many years whereas large adults could remain common and the mature populations appear viable for decades without there being any indication of incipient population decline.Recovery from gradual population decline or catastrophic mortality is likely to be very slow.

Movement

Although generally described as sedentary, the lungfish moves various distances away from its home range.In flowing sections of the Burnett and Mary rivers adults usually move around one or two pools at night and return each day to a certain resting retreat such as a submerged log, rock or patch of macrophytes.Individual fish may show high fidelity to the same daytime retreat over many consecutive months, even years.

The movements of lungfish are restricted by natural barriers (waterfalls, gorges and ephemeral river reaches), and by man-made barriers such as dams (wall height ＞15m), weirs (wall height ＜15m), tidal barrages and road culverts.Lungfish sampled downstream from Claude Wharton Weir on the Burnett River in 2004 were in poorer condition(they were lighter for their length) than those in other parts of the river.If Traveston Crossing Dam is built it will sever the main river channel upstream from Gympie and effectively isolate upstream and downstream populations of lungfish unless effective fish transfer facilities can be provided.Lungfish can be injured or killed when they pass over the top of dam walls and tidal barrages during high water flows.In the lower Burnett River lungfish have been observed stranded downstream of the tidal barrage, unable to return to freshwater because the fish were too large to use the vertical slot fishway at this barrage.Stranding and mortality have also been observed below the Mary River tidal barrage and at the spillway of North Pine Dam after a rapid release of water there.

3．The dam will result in the establishment of harmful invasive species

Large dams like Traveston Crossing Dam will transform a lotic system into a lentic one by flooding riverine habitats and creating a large artificial lake.These dramatic changes usually have significant effects on riverine biota and one of them is to facilitate the establishment and spread of alien species of plants and fish.There are also concerns that the lungfish could be threatened by alien and translocated fishes that have been introduced into the Burnett and Mary catchments.The ubiquitous mosquito fish preys on the eggs and juveniles of native fishes and competes with small species for food and habitat, while other alien species may compete for breeding habitat or contribute to the decline in number of breeding adults.One of the most worrisome alien species, the Mozambique mouthbrooder or tilapia, has been declared a noxious and threatening alien species in Queensland.It is present in Boondooma Dam on the Burnett River and could well become established within the natural range of N.forsteri in that catchment, and be spread to the Mary through deliberate or accidental human interventions.Oreochromis mossambicus is already well established in North Pine Dam and other impoundments in south-east Queensland.

Mitigation options

A Water Resource Plan has set environmental flow targets for flora and fauna at various nodes throughout the catchment.These flow targets is intended to maintain the habitat, food resources, passage and breeding requirements of fish and other biota throughout the Mary River.The EIS for Traveston Crossing Dam asserts that these targets will be achieved by appropriate water releases from the dam, and that they will maintain lungfish spawning sites, juvenile habitat and recruitment processes downstream.The maintenance of adequate low flows will be most important because N.forsteri is incapable of surviving complete desiccation.The Australian lungfish can only survive out of water for a few days using the lung, but only if the surface of the skin is constantly moist.It tends to use the lung for respiration when it is active and requires more oxygen, usually at night while foraging, when swimming in floodwaters and when spawning.

The EIS promises that fish bypass facilities will be provided at Traveston Crossing Dam similar to those at Burnett Dam on the Burnett River, i.e.a“state-of-the-art” fish lift to enable upstream movement past the dam wall.The Burnett Dam fish lift is already operating and successfully transferring a range of fish species upstream, however the number of lungfish that entered the downstream lock and exited upstream on one monitoring occasion was very low, only partially compliant with Commonwealth requirements under the EPBC Act.As well as the installation of fish transfer facilities to enable movements upstream and downstream into suitable living and breeding habitats, consideration will be given to the translocation of N.forsteri individuals and/or juveniles reared from broodstock into areas of the Mary catchment where natural and man-made barriers limit or prevent access to potentially suitable habitat.Population enhancement based on the release of fish bred in captivity does not necessarily guarantee beneficial outcomes for endangered fishes, mainly because of the genetic bottlenecks associated with small population size.

Conclusions

Neoceratodus forsteri has already been listed as a vulnerable species under the Commonwealth EPBC Act and is the subject of a Recovery Plan that will guide management actions and permissible activities in and around lungfish habitats.A first principle of recovery planning is to protect existing habitats and to maintain or restore landscape and local processes that generate and maintain habitat structure.Traveston Crossing Dam will inevitably interfere substantially with such recovery actions for the lungfish.It will destroy and fragment essential larval, juvenile and adult habitats along the main channel of the Mary River and several tributaries, and while the new lacustrine habitats created will probably support mature lungfish they appear unlikely to be suitable for lungfish spawning and for juvenile recruitment, which appear to be sporadic and unsustainably low.

The Australian lungfish is vulnerable to reduced river flows, dry spells and complete desiccation.Traveston Crossing Dam will store incoming river flows and regulate natural patterns of river flow below the dam, with potentially severe consequences for lungfish if low flow spells become more frequent and prolonged.Lungfish require very long periods to recover from catastrophic mortality and population decline as a consequence of their slow growth rate, long generation time and the high vulnerability of larval and juvenile lungfish.

Even though sophisticated fish transfer facilities are proposed to allow upstream and downstream movements of lungfish in the Mary catchment there is no guarantee that the fish lift and sluice will be effective enough to maintain the original levels of population connectivity and genetic mixing.The ecological and genetic consequences of population fragmentation and isolation could be significant for a species of such low genetic diversity and high extinction risk.

N.forsteri is not genetically diverse, a feature shared with other endangered species and often associated with population declines and high extinction risk.Low genetic diversity implies low potential for evolutionary adaptation to changing and new environmental conditions, while the low recruitment of juvenile lungfish, their slow growth and long generation times will severely limit the species' capacity to adapt rapidly to sudden changes in environmental conditions associated with the new dam.

In conclusion, building a large storage reservoir on the main channel of the upper Mary River appears highly likely to risk significant decline and fragmentation of important natural populations of the Australian lungfish.This risk seems far too high for a species already declared vulnerable and urgently in need of recovery in its remaining natural habitats.

New words

translocation n．移动

stock n．河干

degrade v．退化

graze v．放牧

horticulture n．园艺业

fragmentation n．碎片

riparian a．河边的，河岸的

erosion n．侵蚀

gravel n．砂砾

extraction n．抽出

urbanization n．城市化

impoundment n．围于水坝中的水

vulnerable a．易受伤害的；易受攻击的

foster v．养育，抚育

catchment n．集水处(水库或集水盆地)

designation n．指示

proceed v．继续进行

upstream ad．向上游；逆流地

secure v．保护

petition n．请愿；请求

overstate v．夸大叙述

physiology n．生理学

aquatic a．水生的

predecessor n．前辈

vertebrate n．脊椎动物

custodian n．监护人；保管人

extinguish v．压制

gill n．腮

coelacanth n．矛尾鱼；空棘亚目科

saline a．盐的

genome n．基因组

genetic a．遗传的；起源的

adverse a．不利的；相反的

tidal a．潮的

barrage n．拦河坝

overhang v．悬于……之上；(危险、邪恶等)逼近

vegetation n．植被

debris n．碎片

macrophyte n．大型植物

inundate n．泛滥；淹没

tributary n．支流

spawn v．产卵

juvenile a．青少年的

ponded a．筑成池塘

shallow a．浅的

spill v．溢出，流出

terrain n．地形

bay n．海湾

disrupt v．破坏

embryo n．胚胎

velocity n．速率；迅速

dissolve v．溶解；消失

moderate a．适度的

clump n．丛

terrestrial a．陆地的

whorl n．螺纹

predominantly ad．支配地；主要地

scour v．冲刷

embayment n．海湾，海沟伸入陆地的深水湾

option n．选择权

recruitment n．新生代；补充

invertebrate n．无脊椎动物

microhabitat n. (动、植物的) 微(小) 环境(如粪块、腐烂的根等)

mollusk n．软体动物

worm n．蠕虫

steep a．陡峭的

profile n．外形；剖面

curve n．曲线

mortality n．死亡数

viable a．能养活的；能生育的

incipient a．起初的

catastrophic a．灾难的

sedentary a．定栖的

retreat n．休息寓所

log n．园木

patch n．斑点；碎片

fidelity n．真相，真实性

consecutive a．连续不断的

barrier n．障碍物

gorge n．峡谷

ephemeral a．短暂的

culvert n．暗渠

weir n．堰，坝

downstream ad．下游地，顺流而下

sever v．断绝；分开

stranded a．搁浅的

vertical a．垂直的

slot n．狭槽；水沟

fishway n. (使鱼得上瀑布或堤堰之)鱼道

spillway n．溢水口，溢洪道

invasive a．攻击性的

lotic a．生活于流水中的

lentic a．生活于静水中的

riverine a．在河岸上的

biota n．生物区

ubiquitous a．普遍存在的

prey v．捕食

tilapia n．罗非鱼

deliberate a．故意的

mitigation n．减轻；缓和

node n．节点

desiccation n．干燥

respiration n．呼吸

forage v．搜寻

bypass n．旁路，支路

partially ad．部分地

rear v．跳出

broodstock n．蟹类亲本培育

bottleneck n．障碍物

substantially ad．实质上；大体上

larval a．幼虫的

lacustrine a．湖泊的

sporadic a．零星的；分散的

spell n．一段时间

sluice n．水闸

extinction n．消失

Exercises

1．Make True or False judgments.

(1) Sophisticated fish transfer facilities have been proposed to allow upstream and downstream movements of lungfish so that we can maintain the original levels of population and genetic mixing.

(2) The Australian lungfish can survive out of water for quite a few days, because it can breathe with a lung as we human beings do.

(3) The shallow bays which are created by the spilt impounded water are not in favor of the survival of Australian lungfish.

(4) The Burnett River and the Mary River support two independent breeding populations of N.forsteri, both of which play significant roles in the species' long-term survival and recovery.

(5) Australia owns a unique natural geographical condition as a result of eras of landsea isolation.

2．Answer questions.

(1) What is the main idea of the paper?

(2) Why is lungfish so significant to Australia?

(3) How has the Traveston dam influenced the lungfish population?