Tesi sul tema "Murray-Darling River"

Many aspects concerning the association of riverine fish with in-channel habitat remain poorly understood, greatly hindering the ability of researchers and managers to address declines in fish assemblages. Recent insights gained from landscape ecology suggest that small, uni-scalar approaches are unlikely to effectively determine those factors that influence riverine structure and function and mediate fish-habitat associations. There appears to be merit in using multiple-scale designs built upon a geomorphologically-derived hierarchy to bridge small, intermediate and large spatial scales in large rivers. This thesis employs a hierarchical design encompassing functional process zones (referred to hereafter as zones), reaches and mesohabitats to investigate fish-habitat associations as well as explore patterns of in-channel habitat structure in one of Australia's largest dryland river systems; the Barwon-Darling River. In this thesis, empirical evidence is presented showing that large dryland rivers are inherently complex in structure and different facets of existing conceptual models of landscape ecology must be refined when applied to these systems. In-channel habitat and fish exist within a hierarchical arrangement of spatial scales in the riverscape, displaying properties of discontinuities, longitudinal patterns and patch mosaics. During low flows that predominate for the majority of time in the Barwon-Darling River there is a significant difference in fish assemblage composition among mesohabitats. There is a strong association between large wood and golden perch, Murray cod and carp, but only a weak association with bony herring. Golden perch and Murray cod are large wood specialists, whereas carp are more general in there use of mesohabitats. Bony herring are strongly associated with smooth and irregular banks but are ubiquitous in most mesohabitats. Open water (mid-channel and deep pool) mesohabitats are characterised by relatively low abundances of all species and a particularly weak association with golden perch, Murray cod and carp. Murray cod are weakly associated with matted bank, whereas carp and bony herring associate with this mesohabitat patch in low abundance. Nocturnal sampling provided useful information on size-related use of habitat that was not evident from day sampling. Both bony herring and carp exhibited a variety of habitat use patterns throughout the die1 period and throughout their lifetime, with temporal partitioning of habitat use by juvenile bony herring and carp evident. Much of the strong association between bony herring and smooth and irregular banks was due to the abundance of juveniles (<100mm in length) in these mesohabitats. Adult bony herring (>100mm length) occupied large wood more than smooth and irregular banks. At night, juvenile bony herring were not captured, suggesting the use of deeper water habitats. Adult bony herring were captured at night and occupjed large wood, smooth bank and irregular bank. Juvenile carp (<200mm length) were more abundant at night and aggregated in smooth and irregular banks more than any other mesohabitat patch. Adult carp (>200mm length) occupied large wood during both day and night. There is a downstream pattern of change in the fish assemblage among river zones, with reaches in Zone 2 containing a larger proportion of introduced species (carp and goldfish) because of a significantly lower abundance of native species (bony herring, golden perch and Murray cod) than all other zones. In comparison, the fish assemblage of Zone 3 was characterised by a comparatively higher abundance of the native species bony herring, golden perch and Murray cod. A significant proportion of the amongreach variability in fish assemblage composition was explained at the zone scale, suggesting that geomorphological influences may impose some degree of top-down constraint over fish assemblage distribution. Although mesohabitat composition among reaches in the Barwon-Darling River also changed throughout the study area, this pattern explained very little of the large-scale distribution of the fish assemblage, with most of the variability in assemblage distribution remaining unexplained. Therefore, although mesohabitat patches strongly influence the distribution of species within reaches, they explain very little of assemblage composition at intermediate zone and larger river scales. These findings suggest that small scale mesohabitat rehabilitation projects within reaches are unlikely to produce measurable benefits for the fish assemblage over intermediate and large spatial scales in the Barwon-Darling River. This indicates the importance taking a holistic approach to river rehabilitation that correctly identifies and targets limiting processes at the correct scales. The variable nature of flow-pulse dynamics in the Barwon-Darling River creates a shifting habitat mosaic that serves to maintain an ever-changing arrangement of habitat patches. The inundation dynamics of large wood habitat described in this thesis highlights the fragmented nature of mesohabitat patches, with the largest proportion of total in-channel large wood remaining unavailable to fish for the majority of the time. At low flows there is a mosaic of large wood habitat and with increasing discharge more potential large wood habitat becomes available and does so in a complex spatial manner. What results in this dryland river is a dynamic pattern of spatio-temporal patchiness in large wood habitat availability that is seen both longitudinally among different river zones and vertically among different heights in the river channel. Water resource development impacts on this shifting habitat mosaic. Projects undertaking both fish habitat assessment and rehabilitation need to carefully consider spatial scale since the drivers of fish assemblage structure can occur at scales well beyond that of the reach. Fish-habitat associations occurring at small spatial scales can become decoupled by process occurring across large spatial scales, making responses in the fish assemblage hard to predict. As rivers become increasingly channelised, there is an urgent need to apply research such as that conducted in this thesis to better understand the role that in-channel habitats play in supporting fish and other ecosystem processes. Habitat rehabilitation projects need to be refined to consider the appropriate scales at which fish assemblages associate with habitat. Failure to do so risks wasting resources and forgoes valuable opportunities for addressing declines in native fish populations. Adopting multi-scalar approaches to understanding ecological processes in aquatic ecosystems, as developed in this thesis, should be a priority of research and management. To do so will enable more effective determination of those factors that influence riverine structure and function at the approariate scale.

Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008.
Committee Chair: Judith Curry; Committee Chair: Peter J Webster; Committee Member: Marc Stieglitz; Committee Member: Robert Black; Committee Member: Rong Fu.

Dams and weirs are widely implicated in large-scale declines in both the range and abundance of aquatic fauna. Although many factors are involved, such declines are commonly attributed to the prevention or reduction of migration, reductions in available habitat, alteration of natural flow regimes and changes to physicochemical characteristics. In Australia, studies into the ecological effects of these impacts are limited, and have concentrated mainly on species of recreational and commercial importance. Subsequently, the adverse effects of dams and weirs, and suitable methods of mitigation, remain largely unknown for many other taxa. Therefore, the major aim of this thesis is to investigate the ecological effects of dam and weir construction on previously unstudied migratory assemblages of fish and macroinvertebrates in the Murray-Darling Basin. It is anticipated that the results of these studies will feed back into improved management strategies that help arrest the previously observed declines of aquatic fauna. Initially, fish communities were sampled, by boat electrofishing, from both reference sites and downstream of Balranald and Redbank weirs on the lower reaches of the Murrumbidgee River, Australia. Sampling was stratified over large spatial and temporal scales to gain a comprehensive understanding of species most affected by the presence of these two barriers. In general, the weirs obstructed fish migrations during summer and autumn and many species of small-bodied fish such as Australian smelt, western carp gudgeon, fly-specked hardyhead and crimson-spotted rainbowfish accumulated downstream of Balranald Weir. In addition, downstream accumulations of juveniles of larger-bodied species such as bony herring, common carp and goldfish were also detected. Although many previous studies had either documented or hypothesised that upstream migrating fish accumulate downstream of migration barriers, none attempted to quantify the size of such populations. Therefore, a simple but efficient method to estimate the size of migratory populations was assessed at the Balranald Weir site. The application of two commonly used estimation techniques yielded relatively reliable results for seven species that accumulated downstream of the weir. Population size estimates were greatest for most species during summer and autumn, where accumulations as high as 800 fish per day were detected. The largest calculated population size estimates, in addition to the greatest temporal variation, of any individual species was observed in bony herring. Given the simplicity of the technique and the relative accuracy of population estimates, it was concluded that these methods could easily be applied to other weirs where the size of migratory populations is of particular interest. A study investigating the effects of Yanco Weir on the diets of three migratory percichthyid species, Murray cod, trout cod and golden perch was also conducted. Observed spatial variation in a number of trophic processes strongly implicated Yanco Weir as a major contributor to increased competition among percichthyid species on the Murrumbidgee River. The greater relative abundance of percichthyids from downstream samples, combined with increases in dietary overlap and a greater percentage of empty stomachs, also suggested percichthyids may be significantly affecting the relative abundance of potential prey items such as freshwater prawns and Australian smelt. These significant changes in dietary composition were likely related to migratory behaviour, as these species accumulated downstream of the weir, and could be readily expected at other sites where passage is obstructed. It was suggested that the construction of suitable fish passage facilities would effectively reduce the probability of migratory fish accumulating and, subsequently, potential effects of dams and weirs on trophic processes. Since it was established that dams and weirs of the Murrumbidgee River were significantly affecting migratory fish communities, an innovative but relatively inexpensive fishway design, the Deelder fish lock (after Deelder, 1958), was constructed and assessed for wider application throughout the Murray-Darling Basin. The Deelder lock was effective at mitigating the effects of Balranald Weir by providing passage for a wide range of size classes and species of fish; but importantly, the structure enabled the passage of most species previously observed to accumulate downstream of the structure. Most significant was the ability of the fish lock to pass substantial numbers of small-bodied fish, which were previously not considered migratory, suggesting that these species should be considered when developing options to mitigate the effects of other dams and weirs throughout the Murray-Darling Basin. A significant finding of this study was the realisation that substantially more species and size classes of Australian native fish are migratory than previously thought. Subsequently, it is recommended that, when designing facilities to mitigate the effects of a dam or weir, the structure of the entire migratory community is considered when developing operating parameters. Various options for mitigating the effects of dams and weirs are discussed, but it was concluded that the construction of effective fishways would be the most appropriate means of restoring migration pathways to Australian native fish. A strategic approach for assessing and adaptively mitigating the effects of dams and weirs is presented and discussed.

Using a multi-scale experimental approach, the research undertaken in this thesis investigated the role of the flood pulse in ephemeral floodplain wetlands of the River Murray, in order to better understand the impact of river regulation (and permanent inundation) on these wetlands. An ecosystem-based experiment was conducted on the River Murray floodplain, to compare changes in nutrient availability and phytoplankton productivity in three ephemeral wetlands (over a drying/reflooding cycle) with three permanently inundated wetlands. In the ephemeral wetlands, both drying and re-flooding phases were associated with significant increases in nutrient availability and, in some cases, phytoplankton productivity. It was demonstrated that the ?flood pulse?, as described by the Flood Pulse Concept (FPC), can occur in ephemeral wetlands in dryland river-floodplain systems, although considerable variation in the nature of the pulse existed amongst these wetlands. Results of this experiment suggest that factors such as the degree of drying and length of isolation during the dry phase, the rate of re-filling, timing of re-flooding and the number of drying/re-flooding cycles may be potentially important in producing the variation observed. Permanent inundation of ephemeral wetlands effectively removed these periods of peak nutrient availability and phytoplankton productivity, resulting in continuously low levels (of nutrient availability and phytoplankton productivity). It was concluded that alteration of the natural hydrological cycle in this way can significantly reduce nutrient availability, primary production and secondary production, essentially changing the structure and function, the ecology, of these wetlands. Equally, the results of this experiment indicate that some of the changes resulting from river regulation and permanent inundation can be somewhat reversed, within a relatively short period of time, given re-instatement of a more natural hydrological regime. A mesocosm experiment was used to examine the influence of the dry phase, specifically the effect of the degree of wetland drying, on patterns of nutrient availability and primary productivity comprising the flood pulse. Compared to permanent inundation, re-flooding of completely desiccated sediments increased carbon (C) and nitrogen (N) availability while partial drying generally decreased, or had little effect on, C and N availability after re-flooding. However, degree of drying had little effect on phosphorus availability or rates of primary production measured after re-flooding, and it is possible that these two factors are related. Partial drying reduced rates of community respiration after reflooding, possibly a reflection of the reduced carbon concentrations measured in these mesocosms in this phase of the experiment. Degree of drying also influenced the macrophyte community (measured after three months of flooding), with plant biomass generally decreasing and species diversity increasing as the degree of drying increased (with the exception of complete sediment desiccation which had lasting negative effects on both macrophyte biomass and species diversity). The results of the ecosystem and mesocosm experiments were utilised, in addition to results collected from the same experiment conducted at two smaller scales (minicosms and microcosms), to assess whether the effects of hydrological regime on nutrient availability at the ?wetland? scale could be replicated in smaller-scale experiments. None of the smaller-scaled experiments included in this investigation were able to replicate the specific response to hydrological regime recorded at the ecosystem scale, however the mesocosm experiment did produce results that were more similar to those at the ecosystem scale than those produced by the mini and microcosm experiments. The results of this study indicated that extrapolation of results from small-scale experiments should be undertaken with caution, and confirmed that a multi-scale approach to ecological research is wise, where large-scale field experimentation and/or monitoring provides a check on the accuracy, and hence relevance, of conclusions reached via mesocosm experiments.

Thesis (Ph.D.) -- University of Western Sydney, 2004.
"A thesis submitted for the degree of Doctor of Philosophy of the University of Western Sydney, Sydney, January 2004." Includes bibliography : leaves 359 - 369.

The golden perch (Macquaria ambigua Richardson 1845) is an iconic freshwater fish native to Australia’s Murray-Darling Basin. Like many other native fishes, golden perch have suffered declines in abundance and range since European settlement as a result of overfishing, habitat destruction, and dams that impede migration and regulate flows of the Murray-Darling river system. For more than four decades it has been widely considered that flow pulses and floods are proximate stimuli for spawning, and that floods enhance recruitment to sustain golden perch populations. It has, however, been shown recently that spawning and recruitment can occur in the absence of these conditions, that strongest recruitment events can occur outside of flood periods, and that both spawning and recruitment can occur during periods of low and even zero flows – at least in the dryland rivers of the Basin’s arid zones. Despite observations of golden perch spawning and recruitment across a range of hydrological conditions and locations, much speculation exists within the literature regarding the role of flow pulses and floods in the species’ life history, as there remain few observations of spawning in the wild and even fewer ecological studies of the early life history stages. The aims of this thesis are: to examine major aspects of golden perch life history with emphasis on the role of flows as stimuli to initiate spawning; to examine the role of floodplain habitats in the species’ early life history; to refine a conceptual model of the species’ life history and key life history events; and to evaluate the utility of this model by predicting and recording the role of river regulation in disrupting key life history processes for golden perch. The reproductive ecology of golden perch was examined in the Darling River throughout 2004-2006. During this period, temporal patterns of oöcyte maturity were examined to reveal that spawning could occur at almost any time of the year in the Darling River system. Distinct differences were also examined between the stages of oöcyte maturity observed for mature-aged females at various locations along a broad spatial gradient between Wilcannia and Menindee (~300 km), to reveal a prevailing spatial pattern in the occurrence of ‘ripe’, ‘transitional’ and ‘resting’ golden perch females within this reach of the Darling River.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

Extensive coastal acid sulfate soil (CASS) oxidation was observed in the River Murray Estuary (RME), South Australia, during an extreme drought (the Millennium Drought, 1996–2010). CASS oxidation causes significant surface water and porewater acidity, and the mobilisation of toxicants, negatively impacting proximal ecosystems and infrastructure. In this thesis I argue that the Millennium Drought acidification event provides a test case globally for how meteorological drought triggers extreme CASS oxidation, and how other variables can exacerbate the issue. I therefore present a systemic investigation of CASS acidification within the RME and identify the boundary conditions and exogenous variables that control acidification risk. Elements mobilised from oxidised CASS (Fe, Mn, Al, V, Cr, Co, Ni, Cu, Zn, Cd, Pb, and REE) are accumulating in the sediments of the RME, and spatial patterns of enrichment and REE fractionation can be used as environmental tracers of acidic drainage. Transport and accumulation of these elements is controlled by hydrodynamic and geomorphic processes in the estuary. Multiple depositional regimes apparent in the sediment record show that hydrodynamic and geomorphic processes have, however, changed during the history of the RME in response to sea-level and anthropogenic impacts, impacting the formation of CASS and the likelihood of extreme acidification within the system. Adopting a systems approach, it is apparent that the extremity of the Millennium Drought acidification event was intensified by factors other than drought, and that the triggering of extreme CASS acidification often exhibits a non-linear relationship to boundary condition changes, meaning negative impacts can be sudden and disastrous. Wave-dominated estuaries are particularly vulnerable systems, and changes predicted for an anthropogenically heated future will likely shift estuarine systems closer to thresholds where severe acidification can be expected.

This thesis describes the influences of meander geometrics on thermally stratified open-channel flow. Results of this study contribute toward a greater understanding of the physical characteristics of flow in riverine environments. The presence of thermal stratification due to short-wave solar heating from above inhibits mixing, resulting in oxygen stratification and accumulation of contaminants and nutrients - conditions that have been found to cause long-term damage to the ecosystems. Reduced flow rates can also lead to acute damage events such as cyanobacterial outbreaks and mass fish kills. These conditions are progressively found in nature, linearly with the recent changing in climate and global warming. Topography, precisely the geometrical aspect, is one crucial factor that influences the evolution of thermal stratification in natural rivers. Hence, it is essential to investigate the effect of geometrical parameters on the thermally stratified flow. Direct Numerical Simulation results for turbulent open-channel flow through idealized meanders with and without an internal heat source are used to investigate these effects. The computational domain was meshed using an orthogonal, curvilinear coordinate system with velocity represented using physical components on a staggered grid arrangement. For a very sharp meander, a comparison between stratified and neutral flows is carried out to investigate the distribution of secondary circulations, temperature field, vortices, and turbulence characteristics. Five different channel curvatures at a moderate sinuosity are then used to investigate the effect of curvature on the flow features, stratification, mixing, and the energy transfers between the global potential and kinetic energy reservoirs. Finally, simulation results of neutral and stratified flows at four different channel sinuosities at a moderate curvature are presented to explore the effects of meander geometry on the flow separation and boundary shear stress.

Six rivers within the upper Mumbidgee catchment were sampled for larval and juvenile fish. The rivers represented both regulated and unregulated flow regimes and varied widely in size. There was wide variation in the larval fish communities supported by each river, both in terms of the species diversity and total abundance of fish sampled. The highly regulated reach of the Mumbidgee River sampled during this study had the highest numbers of native species and native individuals of any river sampled. In the two rivers selected for further study, the Murmmbidgee and Goodradigbee, there was a high level of inter-annual consistency in the species composition within the reaches sampled, despite considerable change in the temperature and flow regimes of both rivers. This indicates that at least some spawning of those species sampled may occur each year, regardless of environmental conditions. Estimates of the relative abundance of each species sampled changed markedly between years, and it is argued, on the basis of growth information contained in the otoliths, that differential survival of larvae and juveniles was largely responsible for this shift in relative abundance. Otolith microstructure provided information on the date of spawning and early growth patterns of all species sampled in the upper Mumumbidgee catchment. In addition to determining the age and thus 'birth-date' of an individual, the effect of a particular event or series of events has on growth, and subsequent survival, is permanently recorded in the otolith microstructure. This enables accurate back-calculation and correlation to management actions or natural events. No other research tool has this ability to retrospectively assess, on a daily basis, the impacts of management actions on condition and subsequent survival of fish larvae. Species sampled could be separated into three groups based on spawning requirements; those linked with flow, those linked with temperature and generalist species that appear to have river independent cues, such as photoperiod or moon phase. Patterns in growth rate during the early life history stages enabled quantification of the consequences of variation in environmental conditions on the survival and recruitment of various species. Growth was not always highly correlated with water temperature, in fact, for mountain galaxias, high temperatures appear to negatively affect larval condition and subsequent survival. Conversely, carp exhibited a strategy more consistent with common perceptions, with growth and survival increasing with increasing temperature. The study uncovered spawning and growth patterns that were unexpected. Age analysis of western carp gudgeon demonstrated that they had undertaken a mid-winter spawning, when the water temperature in the main channel was far lower than that at which spawning was previously recorded for this species. Redfin perch from the unregulated Goodradigbee River exhibited growth rates exceeding the published upper limits for this and other closely related species. This growth could not be correlated with either temperature or flow, indicating that there are additional factors that dominate growth rates of redfin perch in the Goodradigbee River. The proportion and abundance of native species alone is not necessarily indicative of a 'healthy' or pristine system; some native species may be positively affected by river regulation, at least as juveniles. Comparison of the current larval fish community with likely pre-European fish communities does provide an indication of change to the system. The results of this study suggest that larval fish growth rates can be strongly influenced by environmental conditions, thus providing a powerful tool for monitoring future change and the factors which cause it. This study has demonstrated the value of larval and juvenile fish age and growth information, derived from otolith microstructure techniques, for many aspects of river management. Current river management priorities for which these techniques provide unique information include the determination of environmental flow regimes and the control of undesirable exotic species such as carp.

This study investigated the causes of high level of intra-and inter-population variation known to occur in the morphology of fish in the genus Hypseleotris Eleotride in southern Australia, particularly within the Murray-Darling river system. The three major objectives of the study were, identify the number and distribution of species,determine the genetic structure of the populations and analyse relationships between species and consider the process of speciation in this species complex. The investigation of morphological variation in Hypseleotris confirmed the presence of two well known species i.e. H. compressa and H. galli, in the coastal rivers and also of the inland species H. klunzingeri. Populations of Hypseleotris klunzigeri sensu lato in inland river were found to be very highly variable and analysis using discriminant functions and principle component analysis showed the widespread presence of three forms (A, B1 and B2). The analysis was confused by the presence of north/south clines and upstream/downstream variation in characteristic in each form. After these factors were removed, there was still a great deal of variation in each population. The presence of hybrids between each pair of inland species, identified by both morphological and genetic data, further confused the analysis and makes identification of all specimens to species in the field difficult. Examination of type material of H. Klunzingeri showed that this belonged to form B2. The other forms can be related to the undescribed species, Midgley's carp gudgeon and Lake's carp gudgeon. Keys to the species in the complex in southeastern Australia are given. The morphological and genetic data show that H. compressa and H. klunzingeri are sister species, primarily separated by the eastern uplands. Similarly, the coastal species, H. galli is related to form B1 and more distantly, to form A. Possible scenarios for the complex are given.
Doctor of Philosophy (PhD)

Ever since the laborious consultation process to set the National Greenhouse Response Strategy (1991-1992), stakeholder 'consultation' has been something Australian governments do. Or attempt to do. A recent trend in NSW in particular has been to expand the concept and practice of consultation to multi-party, collaborative decision-making, also referred to as participatory democracy. One such initiative officially begun in August 1997 is the River Management Committee (RMC) exercise. For this tremendous outlay of financial and human resources, the government is taking a punt that the committee will deliver better decisions, and more timely actions, on river flows and water quality in each of the major regulated river valleys in the state. The set up and first year of operation of the RMC exercise is the subject of this thesis. Specifically it examines the design of the process and its appropriateness to the task at hand; the reality of consensus decision-making amongst people with opposing views; the democratic ideal of participants learning to be 'other directed' in terms of putting aside their own positions to work for the common good; and affordability of such exercises from both the government and non-government participants' points of view. The themes emerging from this thesis have become the focus for further research.

This thesis addresses the question “What is the essence of the Murray Darling river system conundrum that is usually posed as an issue of environmental remediation?”- following perceptions of problems in catchment strategy formulation regarding project selection and public consultation. The question is initially seen as having four facets – governance, public, participation and remediation. An initial literature review indicated that previous examination of these topics seemed insufficiently radical or comprehensive for the enquiry’s purposes, seeming not to attribute full humanness to members of the public. A fieldwork program of quasi-anthropological nature was conducted. Interpretation of the fieldwork reports focuses primarily on the lack of attribution of full humanness to members of the public. Interpretive techniques including a phenomenological-style process was applied and found that the district houses a number of unrecognised people “nexors’ occupying linking or nexus roles who exercise personal skills and initiatives to underpin effective remediation outcomes. Towards the end of the fieldwork program, further literature indicated that the initial four-facet nature of the enquiry should be reformulated, to include the overall nature of western society as it appears in the district (in place of participation), to reconstitute the concept of remediation more radically. Governance as a topic is broader than the ways in which it appears in the examined district, and suitable hybridizing of competing world view concepts remains unresolved in this thesis
Doctor of Philosophy (PhD)

Australia’s largest and most important waterway- the Murray-Darling Basin (MDB) - is under threat owing to predicted increases in temperature extremes and reduction in rainfall - runoff in the coming decades. Management strategies are required that incorporate an understanding of dispersal patterns of the MDB fauna and flora. Patterns of dispersal have typically been studied through direct organismal studies but genetic approaches, in which the movement of genes in the landscape is used as a correlate of species dispersal, can provide a more comprehensive view by investigating at a much larger temporal and spatial scale. Genetic connectivity (dispersal) is influenced by the biology of the species, and by flow regime and the dendritic pattern of the network in riverine landscapes. An understanding of the relative influence of each on connectivity is required to deliver informed management strategies. Decisions regarding whether management for conservation is necessary also require an understanding of a species susceptibility to a changing environment. Species already exhibiting deleterious trajectories under current flow regimes in the basin may require more drastic measures than those that have remained unaffected.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

An ecological study of Emydura macquarii macquarii in the south-east region of Australia was conducted between October 1995 and March 1998. E. m. macquarii is an abundant and widespread species of short-necked turtle that is highly variable in morphology and related life history attributes. No study in Australia had previously looked at geographic variation in biological traits in freshwater turtles, hence the level of variation in E. m. macquarii had been poorly documented. The principal aims of this study were to investigate the plasticity of life history traits across populations of E. m. macquarii and to speculate on possible causes. A more intensive study was also conducted on a rare and suspected declining population of E. m. macquarii in the Nepean River to determine whether relevant management and conservation measures; were required. The study involved comparing various life history attributes between five populations of E. m. macquarii (Brisbane River, Macleay River, Hunter River, Nepean River and Murray River). The populations were specifically chosen to account for the range of variation in body size within this subspecies. Body size (maximum size, size at maturity, growth rates), population structures (sex ratios, age and size structures), reproductive traits (clutch mass, clutch size, egg size, egg content, etc.) and other attributes were collected for each population. Patterns of life history traits, both within and among populations, were explored so that causes of variation could be sought. Geographic variation in Body Size and other Related Life History Traits Body size in E. m. macquarii differed markedly between populations. Females ranged in maximum sizes (carapace length) of 180 mm in the Macleay River to over 300 mm in the Murray River. E. m. macquarii was sexually dimorphic across all populations with females larger than males in all cases. Maximum body size was positively related to the size at which a turtle matures. The size at maturity in turn was positively related to juvenile growth rates. Age was a more important factor for males in terms of timing of maturity whereas in females it was body size. Morphological variation was not only great between populations, but also within populations. Maximum body size was unrelated to latitude; hence it was inferred that habitat productivity had the most important influence on geographic variation in body size. Population structures also differed between populations. Sex ratios did not differ in the Brisbane, Macleay and Murray Rivers. However, a male bias was present in the Nepean River population and a female bias in the Hunter River. Juveniles were scarce in the Brisbane and Macleay Rivers but numerous in the Nepean and Hunter Rivers. Geographic Variation in Reproduction There was large variation in reproductive traits across populations of E. m. macquarii. Nesting season began as early as mid-September in the Brisbane River and as late as December in the Hunter River, and continued until early January. Populations in the Hunter and Murray Rivers are likely to produce only one clutch per season while populations from the Macleay and Nepean Rivers can produce two, and on some occasions, three clutches annually. The majority of females would appear to reproduce every year. Clutch mass, clutch size, and egg size varied greatly both within and among populations. A large proportion of variation in reproductive traits was due to the effects of body size. E. m. macquarii from large-bodied populations such as in the Brisbane and Murray Rivers produced bigger eggs than small-bodied populations. Within a population, clutch mass, clutch size, and egg size were all correlated with body size, except the Nepean River. The variability of egg size was smaller in large-bodied populations where egg size was more constant. Not all variation in reproductive traits was due to body size. Some of this variation was due to annual differences within a population. Reproductive traits within a population are relatively plastic, most likely a result of changing environmental conditions. Another source is the trade-off between egg size and clutch size. A negative relationship was found between egg size and clutch size (except the Brisbane River). Reproductive variation was also influenced by latitudinal effects. Turtles at lower latitudes produces more clutches, relatively smaller clutch sizes, clutch mass and larger eggs than populations at higher latitudes. Annual reproductive output is greater in tropical populations because they can produce more clutches per year in an extended breeding season. Eggs that were incubated at warmer temperatures hatched faster and produced smaller hatchlings. Incubation temperatures above 30�C increased egg mortality and hatchling deformities, suggesting this is above the optimum developmental temperature for E. m. macquarii. Hatchling size was positively related to egg size, hence hatchling sizes was on average larger in the Murray and Brisbane rivers. However, population differences remained in hatchling size after adjustments were made for egg size. For example, hatchlings from the Hunter River were smaller than those from the Macleay River despite the egg size being the same. These differences were most likely due to the shorter incubation periods of hatchlings from the Hunter River. Nepean River The Nepean River population of E. m. macquarii is at the southern coastal limit of its range. This is a locally rare population, which is believed to be declining. This study aimed at determining the distribution, abundance, and population dynamics to assess whether any conservation management actions were required. E. m. macquarii in the Nepean River was mainly concentrated between Penrith and Nortons Basin, although even here it was found at a very low density (10.6 - 12.1 per hectare). The largest male caught was 227 mm while the largest female was 260.4 mm. Males generally mature between 140 - 150 mm in carapace length and at four or five years of age. Females mature at 185 -195 mm and at six to seven years of age. Compared with other populations of E. macquarii, Nepean River turtles grow rapidly, mature quickly, are dominated by juveniles, have a male bias and have a high reproductive output. Far from being a population on the decline, the life history traits suggest a population that is young and expanding. There are considered to be two possible scenarios as to why the Nepean River population is at such a low density when it appears to be thriving. The first scenario is that the distribution of the population on the edge of its range may mean that a small and fluctuating population size may be a natural feature due to sub-optimal environmental conditions. A second scenario is that the population in the Nepean River has only recently become established from dumped pet turtles.

This thesis brings together two responses to the question ‘how can the law extend the timeframe for environmentally relevant decision-making?’ The first response is drawn from the context of institutional investment, and addresses the timeframe and breadth of environmental considerations in pension fund investment decision-making. The second response is related to the context of public environmental decision-making by legislators, the judiciary, and administrators. Three themes underlie and bind the thesis: the challenges to decision-making posed by the particular temporal and spatial characteristics of environmental problems, the existence and effects of short-termism in a variety of contexts, and the legal notion of the trust as a means for analysing and addressing problems of a long-term or intergenerational nature. These themes are borne out in each of the four substantive chapters. Chapter III sets out to demonstrate the theoretical potential of pension funds to drive the reduction of firms’ environmental impact, and, focusing particularly on the notion of fiduciary duty, explores the barriers that stand in their way. Chapter IV provides a practical application of the theoretical recommendations outlined in its predecessor. It provides a framework outlining how pension funds might implement a longer term, more sustainable approach to investing. The second half of the thesis, operating in the context of public environmental decision-making, is centred upon a particularly poignant legal notion with respect to the environment and time: the concept of intergenerational equity. Just as the first half of the thesis deals with the timeframes relevant to investment decision-making by pension funds within the bounds of fiduciary duty, largely a private law affair with public implications, the second half of the thesis is concerned with the principle of intergenerational equity as a means for extending the decision-making timeframe of legislative, judicial and administrative decision-makers. As previous analyses of the concept of intergenerational equity provide little insight into its practical implications when applied to particular factual situation, Chapter V sets out the structure of the principle of intergenerational equity as revealed by case law. Chapter VI brings together the issues from the first three papers by conceptualising intergenerational equity in resource management as an issue of long-term investment. Long-term environmental decision-making faces many obstacles. Individual behavioural biases, short-term financial incentive structures, the myopic pressures of the electoral cycle and the tendency of the common law to reinforce the (often shorttermist) status quo all present significant barriers to the capacity of both private and public decision-makers to act in ways that favour the longer term interests of the environment. Nonetheless, this thesis argues that there is reason for hope: drawing upon the three themes that underlie all of the substantive Chapters, it articulates potential legislative changes and recommends the adoption of particular governance structures to overcome barriers to long-term environmental decision-making.

This thesis is an investigation into the effects of farming and river regulation on billabong (floodplain lake) ecology. The study region is in the southeast comer of the Murray-Darling Basin. Billabongs comprise a significant natural freshwater lake system in the one million km2 drainage basin dominated by semi-arid conditions. The region was settled by Europeans in the middle 1800's, and early farming, activities, mainly the running of cattle and sheep, were particularly intense. Extensive timber extraction also occurred at this time. Both these activities have probably declined to a degree since the early 1900's but are practised in the region today. Fertiliser use became widespread in the 1930's. River regulation did not begin in earnest until the construction of the Hume Dam in 1930. In the study region regulation has decreased monthly variation in river flows, mainly by maintaining unnaturally high flows during summer irrigation demand, increased daily flow variability with short-term releases, decreased the frequency of minor flooding, slightly increased flood duration, and decreased sediment loads near weirs. These and other impacts of European settlement on the regional landscape are profound, and may have an effect on billabong limnology. Concepts of disturbance ecology are used as a framework for assessing changes to the biota living in billabongs resulting from European settlement. Two complementary lines of evidence are followed, one physicochemical and one biological, and evidence for the impacts of farming and regulation is sought from both historic and present day patterns of limnology. The limnology of 43 billabongs influenced to varying degrees by farming and regulation were surveyed every 2 months over a 15 month period. The billabongs vary in mean depth from about 0.3 to 4.5 m, and significant fluctuations in depth occur, both seasonally and between wet and drought periods. Natural variation in total nitrogen, total phosphorus, turbidity, and secchi depth billabongs is marked and dominated by temporal factors; mainly fluctuations in depth accompanying seasons and droughts, but also flooding. Significant shorter-term temporal variation is also implied from the data. In contrast, natural variation in pH is minor and salinity is always low. Maximum depth is the only systematic source of natural spatial variation revealed, apart from a slight east-west shift in major ion balance; the main determinants of nutrient limnology and light environment of billabongs found in this study are temporal factors. Since natural variation in physicochemistry is dominated by relatively cyclical factors (seasons and floods), much natural disturbance in billabongs appears to be of the pulse variety, and to be moderately to highly predictable. It is likely the biota have evolved adaptations for this variation. Farming only affects phosphorus and salinity, but the effect on phosphorus is minor in comparison to natural variation, and salinity levels remain low. In contrast, river regulation has important direct effects on billabong depth, which on the decadal scale translates to billabong permanence. The indirect effects of regulation on nutrients and the light environment, from effects on depth, are likely to equal natural variation. However, most of the anthropogenic variation mimics natural variation, and the biota may already possess the adaptations to deal with it (may be 'preadapted'). The pattern of rapid depth fluctuations and summer flooding of low-lying billabongs created by regulation is 'new' to the ecosystem, at least in the current climatic regime, and the biota may not cope as well with this. Based on the skeletal remains of Cladocera in the surface sediments of 41 billabongs, farming and river regulation cause a relatively minor impact on the cladoceran fauna. Farming and regulation both affect some uncommon species, and regulation affects the overall diversity, richness and equitability of assemblages. Farming therefore has less of an effect than regulation, which is consistent with the patterns of physicochemistry observed. However, on the whole, assemblages from farmed and regulated billabongs are not very different from those in billabongs remote from farms and on unregulated river reaches, suggesting that the Cladocera are 'preadapted' to anthropogenic environmental variation by relatively high natural variation in physicochemistry. The above conclusions of no or low impact of farming and regulation on billabongs rely on billabongs remote from farms and on unregulated river reaches being unimpacted by these land use activities. This assumption is tested by examining the historical sedimentary record of billabongs. The historical record of physicochemistry in 8 billabongs was examined. Sedimentation rates are currently about 5 mm per year, but have increased by an order of magnitude since settlement. Based on the stratigraphy of sediment structure, organic matter content, and the atomic ratio Fe:Mn, redox conditions have changed in a minimum of 4 billabongs and a maximum of 6 since settlement. These include billabongs on unregulated river reaches and presently distant from farms. The direction of change is usually towards more oxidising conditions, but it is possible that the interpretation of the direction of changing redox (as distinct from the occurrence of changing redox) has been corrupted by the higher sedimentation rates following settlement. External phosphorus loading has, if anything, declined since settlement, but it is more likely that no change has occurred at all and that the patterns of phosphorus are due to the changing redox conditions. Because redox conditions have changed in billabongs considered as low-impact controls, assessments of impact based on the present day limnology of billabongs may underestimate the effects of farming and river regulation. The historical record of both Cladocera and the extent of macrophyte cover are inferred from the stratigraphy of cladoceran assemblages in the sediments, and the record of siliceous algal productivity is obtained from profiles of loosely bound silica. Aquatic macrophyte abundance in 5 of 7 billabongs examined decreases markedly at settlement, notwithstanding that taphonomic alteration of assemblages increases. The pattern is most pronounced in large, deep billabongs, and absent from small billabongs. The decline in macrophytes appears to have resulted in the demise of a group of closely related Rak or Ephemeroporus species that are codominant before settlement. Otherwise, the regional diversity of Cladocera has changed little with settlement, and possibly even increased from the introduction of exotic species. However, temporal trends in 7 species suggest they will be pushed towards regional extinction in the future. Siliceous algal productivity appears to have decreased in 4 of 7 billabongs with settlement, although the patterns may be an artefact of increasing sedimentation rates. The patterns are most pronounced in small billabongs, and due to their timing an early land use activity is again implicated. The historical data suggest that the aquatic macrophyte flora and associated fauna declined due to an early land use activity related to farming. It is likely that the change in redox occurred due to the decline in macrophytes, which lowered organic matter supply to the profundal zone. Furthermore, the persistence of depressed macrophyte levels, and continuing trends of changing relative abundance of some cladoceran species, suggest that the farming impacts are of the press variety, yet direct farming activity on the floodplain may have decreased this century. The macrophyte-free state may been maintained in large, deep billabongs, in spite of the removal of the disturbance agent, because of the existence of alternative stable states in the aquatic vegetation. Early farming may have caused the large, deep billabongs to switch from natural macrophyte dominance to natural phytoplankton dominance, as has been suggested to occur in shallow lakes in Europe. If so, it is quite likely that the decline of macrophytes in large, deep billabongs is reversible by temporarily lowering water levels in the spring time, and this would greatly benefit billabongs and the greater floodplain ecosystem. Once macrophyte beds are reestablished they should be stable unless further unnatural perturbations occur. If properly designed, attempts to restore macrophytes in billabongs can be used to test the hypothesis of alternative stable states in billabong vegetation, so that such attempts offer an opportunity to meld management and science in one project. This work demonstrates that even in ecosystems with high rates of turnover, events with return times on the order of centuries can have significant impacts on the ecosystem. Assessments of anthropogenic impacts to billabongs that do not include an historical component are likely to provide underestimates of the full impacts. While disturbance concepts appear to explain some of the patterns observed in the biota, other traits of the ecosystem (e.g. alternative stable states in the vegetation) may be required to explain the broad-scale patterns observed.

In the region of drought-dominated inland eastern Australia now known as the MurrayDarling Basin, floods occupy a special status. Although relatively infrequent, they are crucial sources of water for people, animals, and plants. They drive hydrology in the region, supplying most of the surface and ground water. Floods are often transformative events for people as well as the non-human environment. This thesis explores Australian settlers' changing relationships with, and understandings of, the rivers and floodplains of the Murray and Darling river systems from 1850 to the present. It analyses floods in terms of the two dominant roles that they have played in settler history in the Murray and Darling river systems: as 'natural disasters' and as part of the wider hydrology of rivers. Four key flood events are closely examined. The selected flood episodes - 1852, 1890, 1956, and 1990 - . illuminate changing ways of knowing and managing rivers, floods, and floodplains over a century and a half, and some of the long-term consequences for people, rivers, and ecologies. Analysis is also anchored in an examination of a number of themes: regional tension with centralised governments over decision-making processes; the particular forms of river management that centralised government enables (such as largescale riverine engineering); different kinds of knowledge of the rivers, especially regional (or local) knowledge, scientific knowledge, and government (and managerial) knowledge; tensions and cooperation between the custodians of these different kinds of understanding; and the emergence of the Murray-Darling Basin as a managerial unit. The thesis aims to present a 'floods-eye-view' of the history of the area (and, partly, of Australia) and explore the ways that settlers, the rivers, and the floods have re-made each other. v

The primary contributions of this thesis are the economic studies of proposed water use reductions and climate change, and the development of an integrated hydro-economic model for the Murray-Darling Basin, Australia. This water model not only simulates the land and water use in the Basin, but also optimises these uses for certain targets such as environmental flows. More importantly, this model can be applied to evaluate policy options for the Basin, such as water buybacks, and provide estimates of the possible impacts of climate change. The thesis consists of three main essays focusing on issues in water modelling and management in the Basin. The first essay describes the development of a water model. This model is applied to estimate the impacts of water use reductions in the second essay; and climate change in the third essay. Other issues related to the Basin's water management, such as a review of existing water modelling, the background of the Basin, water trading, possible policy implementations and future research are also discussed. The first essay (Chapter 4) describes the construction of the Integrated Irrigated Water Model (IIA WM) including the structure of llA WM and the data sources. Using the latest hydrological data and revised catchment boundaries, llA WM can simulate and optimise land and water use in the Basin. To address the criticism that existing models have failed to consider water trading barriers, the physical constraints on water trading have been incorporated in llA WM. The model can also evaluate various water policies and estimate the impacts of physical condition changes. The second essay (Chapter 5) evaluates the impacts of proposed water use reductions by the Australian government. To balance the use of water between irrigated industries and environmental purposes, the Australian government draft plan released October 2010 proposed to reduce the volume of used water in the Basin from 3,000 to 4,000 GL/year. Simulations from IIA WM indicate that the impacts from proposed water use reductions will be modest, although there may be substantial impacts in particular locations. The third essay (Chapter 6) investigates the impacts of climate change in the Basin. A full range of climate change scenarios from modest to severe have been applied using IIA WM. This thesis finds that with water trading, profit reductions are substantially smaller than the water use reductions.

This thesis examines the applicability of the Murray-Darling Basin (MDB) model of Integrated River Basin Management to the Ganges Basin by utilising the lessons from the Mekong experience of adopting the MDB model. The Ganges is one of the major rivers in the world and the sharing of its water has long been an issue of dispute between the riparian countries. Fragmented and uncoordinated upstream management of the Ganges has caused serious ecological and economic loss in the downstream environment posing a threat to future sustainability of river resources. Cooperation among the riparian countries of the Ganges in order to embrace an integrated and basin-wide management approach is rapidly becoming more important. Integrated River Basin Management (IRBM) is a concept widely advocated in different forums for managing the river basins of the world and is adopted in many transboundary river basins. The Australian example of managing the Murray-Darling Basin is considered as a model in the field. The Murray-Darling Basin Commission is well known internationally as a good example of a multi-jurisdictional water management institution. Similar river basin institutions are also evolving in other regions such as the Mekong River Commission for the management of the Mekong River in South-East Asia. The countries sharing the Ganges could learn lessons from the Murray-Darling and Mekong experiences and adopt a basin-wide approach for the better management of the Ganges. However, the policy transfer from a developed country to a developing country context is a challenging process. The highly pertinent contextual differences in social, economic, political, environmental and hydrological settings of the three cases need to be carefully addressed. The research critically examines these factors in the Murray-Darling, Mekong and the Ganges contexts, identifies the similarities and differences between them and attempts to understand the influence/s of these in the policy transfer or policy development process. This research adopted multiple-case studies involving both qualitative and quantitative methods. The cases of the Murray-Darling and Mekong were studied to understand the process and to utilise the lessons learned for the institutional development towards integrated and basin-wide approach for the Ganges. The study analyses the interview results from the experts in the relevant fields to get an insight of different issues and also to collect their opinions. The responses from the stakeholder interviews in Bangladesh were analysed to understand their perspective in this regard. The thesis concludes that adoption of the Murray-Darling Basin model of integrated management needs modification in the Ganges context and recommends a specific institutional structure for the basin-wide management of the Ganges. The thesis contributes to an area of knowledge in recent times by providing a greater understanding of the Integrated River Basin Management in a multi-jurisdictional context. It critically examines the issues in policy transfer from a developed to a developing country focussing on a little studied but significant international river basin, the Ganges. It is hoped that this thesis will contribute towards better policy options for the sustainable management of the international river system.
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Thesis (Ph.D.) - University of Adelaide, School of Social Sciences, 2008

This thesis examines the applicability of the Murray-Darling Basin (MDB) model of Integrated River Basin Management to the Ganges Basin by utilising the lessons from the Mekong experience of adopting the MDB model. The Ganges is one of the major rivers in the world and the sharing of its water has long been an issue of dispute between the riparian countries. Fragmented and uncoordinated upstream management of the Ganges has caused serious ecological and economic loss in the downstream environment posing a threat to future sustainability of river resources. Cooperation among the riparian countries of the Ganges in order to embrace an integrated and basin-wide management approach is rapidly becoming more important. Integrated River Basin Management (IRBM) is a concept widely advocated in different forums for managing the river basins of the world and is adopted in many transboundary river basins. The Australian example of managing the Murray-Darling Basin is considered as a model in the field. The Murray-Darling Basin Commission is well known internationally as a good example of a multi-jurisdictional water management institution. Similar river basin institutions are also evolving in other regions such as the Mekong River Commission for the management of the Mekong River in South-East Asia. The countries sharing the Ganges could learn lessons from the Murray-Darling and Mekong experiences and adopt a basin-wide approach for the better management of the Ganges. However, the policy transfer from a developed country to a developing country context is a challenging process. The highly pertinent contextual differences in social, economic, political, environmental and hydrological settings of the three cases need to be carefully addressed. The research critically examines these factors in the Murray-Darling, Mekong and the Ganges contexts, identifies the similarities and differences between them and attempts to understand the influence/s of these in the policy transfer or policy development process. This research adopted multiple-case studies involving both qualitative and quantitative methods. The cases of the Murray-Darling and Mekong were studied to understand the process and to utilise the lessons learned for the institutional development towards integrated and basin-wide approach for the Ganges. The study analyses the interview results from the experts in the relevant fields to get an insight of different issues and also to collect their opinions. The responses from the stakeholder interviews in Bangladesh were analysed to understand their perspective in this regard. The thesis concludes that adoption of the Murray-Darling Basin model of integrated management needs modification in the Ganges context and recommends a specific institutional structure for the basin-wide management of the Ganges. The thesis contributes to an area of knowledge in recent times by providing a greater understanding of the Integrated River Basin Management in a multi-jurisdictional context. It critically examines the issues in policy transfer from a developed to a developing country focussing on a little studied but significant international river basin, the Ganges. It is hoped that this thesis will contribute towards better policy options for the sustainable management of the international river system.
Thesis (Ph.D.) - University of Adelaide, School of Social Sciences, 2008

Murray cod Maccullochella peelii peelii is an iconic freshwater angling species that has suffered declines in abundance and is now listed as a nationally vulnerable species. Despite recognition of the need for biological knowledge to provide future management directions, little is known of its ecology. This thesis examines that ecology to provide new knowledge and recommendations for improved conservation management. (For complete abstract open document)

Research Doctorate - Doctor of Philosophy (PhD)
The impacts of multi-temporal scale climate variability occurring over the Pacific and Indian Oceans on the rainfall and runoff regimes of eastern Australia are explored in this thesis. Three modes of natural climate variability are studied, the El Niño/Southern Oscillation (ENSO), the Interdecadal Pacific Oscillation (IPO) and the Indian Ocean Dipole (IOD). An analysis of historical rainfall and streamflow data for Queensland (QLD), New South Wales (NSW) and Victoria (VIC) reveals strong relationships between indices of ENSO and IPO variability and seasonal rainfall and streamflow totals in the spring and summer months. In addition, it is shown that a strong connection exists between a number of Indian Ocean SST indices and winter rainfall in eastern Australia, offering an improved understanding of year-round seasonal climates. A climate impact assessment is carried out for a regulated irrigation and domestic water supply system located in NSW (the Lachlan River Valley) to determine the main climatic drivers in the region. It is shown that ENSO, the IPO and the IOD have a strong impact on rainfall, evaporation and inflows, while storage volumes, water allocations and sustainable crop areas are also related to the state of ENSO and the IPO. The research presented in this thesis highlights the importance of understanding the role that natural climate variability plays in influencing the climate, water resources and agriculture in eastern Australia. A simple stochastic framework for use in long term drought risk assessment is developed that specially incorporates multi-decadal persistence of rainfall, brought about by changes in the IPO. The drought risk framework is applied to water resource assessment in the Lachlan River Valley, providing greater insight into the frequency, magnitude and duration of hydrological droughts than present approximations that use the limited instrumental record alone. Importantly, the results presented in this thesis highlight the fact that water resource management in eastern Australia must be developed to cope with the full range of natural climate variability, irrespective of future impacts of anthropogenic climate change, to aid in drought proofing our climate sensitive infrastructure.

The decline of floodplain vegetation along the Lower River Murray, South Australia, has evoked recommendations for ‘environmental flows’ to restore and maintain the health of the ecosystem. To assist managers to maximize benefits from environmental flows, this thesis considers the significance of water for germination and recruitment in key floodplain plant species. Three dominant species are considered, including two trees, river red gum (Eucalyptus camaldulensis) and black box (E. largiflorens), and an understorey shrub, tangled lignum (Muehlenbeckia florulenta). The soil seed bank was dominated by terrestrial annual native plants. Among 1400 seedlings, a single river red gum was found, and no black box or lignum, suggesting that these species do not contribute to the persistent soil seed bank and rely instead on aerial seed banks (serotiny). Sampling of the soil seed bank was continued to determine when seed fall might coincide with appropriate soil moisture conditions. Responses of the soil seed bank to varied water regimes were compared to determine requirements for seedling survival. The results indicated that species richness, rapidity of response and survival time were all promoted by sustained soil moisture. Stands of eucalypts in various states of health (from very stressed to very healthy) were monitored to identify seasonal patterns in bud crops, flowering, fresh leaves and volumes of seed released from the aerial seed bank. Distinct seasonal phenological patterns were apparent, and suggested alternating flowering among individual trees (biennial for red gum, bi-annual for black box), producing an annual peak in summer. Peak seed rain occurred in summer (December–March) in healthy trees for both red gum and black box, with light seed rain continuing throughout the year. Seed fall from stressed trees was much reduced. Stressed trees responded after a second watering event, with much more varied and extended annual seed fall patterns. Lignum showed a spring peak in flowering and seed production. There was a prolific response of flowering and seeding to rainfall, but few seedlings survived. Vigorous vegetative growth occurred in existing plants in response to rainfall and watering but no new cloned plants were found during the study. An investigation of chromosomes as a potential tool to appraise the balance between sexual and asexual reproduction in lignum proved inconclusive, although a previous report of octoploidy in lignum was confirmed. Seeds from all three species and lignum cuttings were tested for their responses to varied watering regimes, based on combinations of simulated rain and flood conditions. The optimal soil moisture for continued growth and survival in all seeds and cuttings was 10 25%, with moisture values <10% causing wilting and death. The results also suggested that red gum and black box seeds which germinate in water under flooded conditions need to be stranded onto moist soil at the water’s edge within 10 days, for the seedling to continue to grow. It was also concluded that germination on rain-moistened soil is a key supplementary mechanism for recruitment, particularly between irregular flood events. For greatest benefit, the timing of environmental flows should complement any seasonal rainfall and irregular flooding that may occur. Extension of suitable soil moisture conditions (10-25%) for as long as possible after >5 mm rainfall, or after over-bank flows, would increase chances for survival of seedlings. December is the most likely month for maximal benefit from watering in the Lower Murray Valley, for germination and recruitment, based on regional rainfall and flooding patterns.
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Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Freshwater turtle populations have been declining globally due to a combination of natural and anthropogenic factors, with nearly half of the world freshwater turtles threatened with extinction. Australia is high on the list of contributing countries, with one third of its native species threatened with extinction. The Murray River is an obvious example with populations of its native species Emydura macquarii declining by 69% and Chelodina longicollis declining by 91% over the past 30 years. Nest predation by the red fox and the installation of water regulators, which have affected dispersal and changed water quality, are likely main causes of these population declines This thesis used meta-population and population viability analyses to evaluate the impacts of dams on turtle populations in areas where recruitment may be severely limited because of predation by foxes. The aims are to determine levels of recruitment required throughout a system to eliminate risks of extinction, as well as determine how the placement of dams and weirs may restrict movement and potentially increase risks of extinction. I show that turtle populations of the Murray-Darling Basin (MDB) can sustain relatively high losses of source recruitment populations, if relief populations are located between dams and impoundments. Areas of South Australia are of most concern. The scarcity of available habitats between dams, combined with high nest predation rates, increases the risk of extinction significantly. Water quality is also another significant factor that has hastened population declines and led to localised extirpation of MDB turtle populations. Management of MDB turtles centres on increasing the number of source populations for several species, increasing connectivity between populations and minimising risks for species moving terrestrially. This study also used modelling and population viability analysis to compare the cost to benefit ratio of two management techniques; headstarting and 1080 poison baiting, to determine which management technique would require the least cost to be the most effective. Vortex modelling showed that headstarting is significantly more efficient, economically beneficial, and uniformly more successful than baiting. Headstarting cost up to 40 times cheaper than baiting yet produced the same results. Headstarting cost an average of $0.22 AUD per hectare, whilst baiting cost as much as $8.73 AUD per hectare. Furthermore, modelled headstarting success was unaffected by the proportion of waterbodies in an area, the proportion of waterbodies baited/supplemented into or the proportion of forests (areas of lower nest predation) present, and could be used uniformly throughout the river. However, baiting required more baits when a lower number of waterbodies and low proportion of forests were present and would therefore need to be tailored to the area.

This study investigated the causes of high level of intra-and inter-population variation known to occur in the morphology of fish in the genus Hypseleotris Eleotride in southern Australia, particularly within the Murray-Darling river system. The three major objectives of the study were, identify the number and distribution of species,determine the genetic structure of the populations and analyse relationships between species and consider the process of speciation in this species complex. The investigation of morphological variation in Hypseleotris confirmed the presence of two well known species i.e. H. compressa and H. galli, in the coastal rivers and also of the inland species H. klunzingeri. Populations of Hypseleotris klunzigeri sensu lato in inland river were found to be very highly variable and analysis using discriminant functions and principle component analysis showed the widespread presence of three forms (A, B1 and B2). The analysis was confused by the presence of north/south clines and upstream/downstream variation in characteristic in each form. After these factors were removed, there was still a great deal of variation in each population. The presence of hybrids between each pair of inland species, identified by both morphological and genetic data, further confused the analysis and makes identification of all specimens to species in the field difficult. Examination of type material of H. Klunzingeri showed that this belonged to form B2. The other forms can be related to the undescribed species, Midgley's carp gudgeon and Lake's carp gudgeon. Keys to the species in the complex in southeastern Australia are given. The morphological and genetic data show that H. compressa and H. klunzingeri are sister species, primarily separated by the eastern uplands. Similarly, the coastal species, H. galli is related to form B1 and more distantly, to form A. Possible scenarios for the complex are given.

Freshwater ecological systems throughout the world are extensively altered, with threatening processes being physical, chemical and biological. Data is often lacking to describe the processes within the system and their interactions. This thesis explores how modelling can be used to help understand and manage such complex systems under limited data and knowledge, by examining two Australian case studies. The first case study explores how fish species are distributed in the Murray-Darling Basin (MDB), Australia's largest river system, and attempts to understand the variations in fish assemblages across the Basin. The second case study involves the development and evaluation of a habitat suitability model for an endangered species Astacopsis gouldi, the Giant Tasmanian Crayfish. The MDB fish case study adopted a suite of multivariate analysis techniques, including cluster analysis and non-metric multidimensional scaling, which were applied within the framework of a data-mining process, Knowledge Discovery from Data. This is the first known study to describe the large-scale patterns in fish assemblages in the Basin. The analysis identified regions in the Basin sharing similar fish assemblages; these patterns were generally consistent with the temperature, precipitation and elevation of the streams and the temperature and water quality preferences of the species. The delineation of the Basin into regions can be an important basis for future ecological studies, for example by providing context for finer-scale studies or a benchmark for studies examining temporal changes to the fish communities. Bayesian networks were applied to model A. gouldi habitat suitability in the second case study, with a focus on the evaluation process. A series of 18 models were built and tested, based on the same structure but with their parameters estimated from different combinations of expert opinion and training datasets. The data-based A. gouldi habitat suitability models achieved better performance accuracy than the expert models. The combined data- and expert-based models performed equally well as the data-based models but were considered more robust. The model evaluation process revealed interesting insights into the habitat suitability of the species, including that elevation seemed to have little influence on habitat suitability, contrary to other studies. It was also found that the species is not in equilibrium with its environment, suggesting that future models must consider temporal dynamics and avoid using species presence-absence as an indicator of habitat suitability. Both case studies highlighted the subjective nature of modelling and the importance of good modelling practice in producing meaningful and purposeful outputs. Good practice guidelines are provided for Bayesian network modelling, with emphasis on the need of thorough evaluation of the model and its results, and transparent reporting of the modelling process. For models built under limited data and knowledge, it is especially important to acknowledge and embrace the uncertainties. Modelling cannot overcome a lack of data, but can help to integrate information, develop and test hypotheses, and refine knowledge about the system and its processes. Modelling can also help guide future monitoring and research toward data and knowledge gaps most crucial to our understanding of the system.

This thesis addresses the question “What is the essence of the Murray Darling river system conundrum that is usually posed as an issue of environmental remediation?”- following perceptions of problems in catchment strategy formulation regarding project selection and public consultation. The question is initially seen as having four facets – governance, public, participation and remediation. An initial literature review indicated that previous examination of these topics seemed insufficiently radical or comprehensive for the enquiry’s purposes, seeming not to attribute full humanness to members of the public. A fieldwork program of quasi-anthropological nature was conducted. Interpretation of the fieldwork reports focuses primarily on the lack of attribution of full humanness to members of the public. Interpretive techniques including a phenomenological-style process was applied and found that the district houses a number of unrecognised people “nexors’ occupying linking or nexus roles who exercise personal skills and initiatives to underpin effective remediation outcomes. Towards the end of the fieldwork program, further literature indicated that the initial four-facet nature of the enquiry should be reformulated, to include the overall nature of western society as it appears in the district (in place of participation), to reconstitute the concept of remediation more radically. Governance as a topic is broader than the ways in which it appears in the examined district, and suitable hybridizing of competing world view concepts remains unresolved in this thesis