Stephen Beatty

Western Australia’s Pilbara region is world renowned for its rugged natural beauty and spectacular landscapes. Perhaps less well known is the region’s inland fish fauna which features an array of species that display unique adaptations to the prevailing harsh and unpredictable conditions. This compact volume contains full colour illustrations and information on the entire inland fish fauna of the region from the De Grey River in the north to the Irwin River in the south. It will serve as an educational resource for schools, community groups, and governmental departments. It is our hope that this field guide will help in the conservation of the unique aquatic biodiversity of the Pilbara for current and future generations.

Severe surface flow reduction is exacerbating the impacts of the existing stressors on aquatic ecosystems in southern Australia. River regulation via the creation of instream barriers such as dams and weirs is known to have wide ranging impacts on aquatic ecosystems and mitigating these barriers can greatly benefit aquatic fauna, particularly freshwater fishes. Given the continued reduction in surface flows and aging of barrier infrastructure, there will be an increasing need to assess, prioritise and decommission such structures particularly in southern Australia. Whilst considerable attention has been given to barrier mitigation and prioritisation in eastern Australia, there is less information on how barriers impact the ecosystems in the often intermittent rivers across southern Australia; particularly with regard to the relationship between barriers and refuge pools. There is also limited information on the impacts of complete barrier removal as opposed to barrier retrofitting and there is no consistent process for identifying and prioritising barriers for mitigation or removal across southern Australia. The current project aimed to review the global literature on the impacts of barriers and the processes that exist for prioritising their removal. It then aimed to develop and trial a process for instream barrier prioritisation tailored specifically for systems in southern Australian. Mitigation of instream barriers through the construction of fishways has been increasingly undertaken in Australia and internationally to reconnect fish communities however, whilst often partially effective, they are limited in terms of fully reconnecting fish communities and are also costly. Complete removal of barriers has therefore increasingly been undertaken particularly in the United States and Europe to completely reconnect river reaches. Both strong advocacy and opposition can exist to instream barrier removal projects and it is vital to have broad stakeholder involvement; particularly at a local level. Artificial instream barriers can also actually create important refuge habitats that may increase in significance particularly as surface flow reductions continue in southern Australia. However, spatial information on refuge pools across southern Australia is limited as are their relative ecological significance. Barrier prioritisation processes in Australia have usually utilised score and ranking systems but little regard has been given to optimising multiple barrier mitigations. The barrier identification and prioritisation process we developed is a stepwise protocol that is underpinned by broad stakeholder involvement and can be applied on multiple scales from single rivers to multiple catchments. It identifies existing information on barriers and aquatic fauna and also confirms barrier and refuge information using a cost-effective surveying protocol. It includes a score and ranking system that weights both the positive and potential negative impacts of removing instream barriers and incorporates information on species diversity, habitat availability, and spatial information on barriers and refuges. The process was trialled in three catchments in south-western Australia. Information on potential barrier locations and fish distributions was obtained by accessing GIS and distributional databases and undertaking local landholder surveys. The rapid aerial survey technique was found to be highly effective at confirming GIS information and identifying new barriers. The score and ranking system revealed that the least modified catchment had the highest scoring barriers. The information contained in this review will be of considerable interest to managers of fluvial ecosystems in temperate Australia and the prioritisation process will be a valuable and easily implemented tool in identifying and mitigating the impacts of in-stream barriers in southern Australia in a drying climate.

Freshwater fishes have been used as indicators of aquatic ecosystem health as many teleosts are sensitive to water quality and habitat decline. Developing field derived thresholds, or tolerance indicator values (TIVs), based on matching distributions with prevailing water quality and habitat variables is a common approach that allows modelling of population viabilities under changing environmental conditions such as declines in water quality or hydrology. The freshwater fish fauna of south-western Australian is depauperate but has the highest rate of endemism of any Australian Drainage Division (82%). It is highly imperilled due to existing anthropogenic stressors such as secondary salinisation and riparian degradation. Secondary salinisation in particular has caused considerable inland range reductions of stenohaline species and the distributions of most are now limited to the western and southern parts of the region. The importance of fresh groundwater in maintaining lentic and lotic refuge habitats during the naturally dry summer and autumn in the region has also recently been recognised. For example, groundwater discharge during baseflow in the NCCARF project study area in the Blackwood River maintains habitat connectivity for the largest freshwater fish of the region, Tandanus bostocki and provides refuge habitat for the nationally endangered Nannatherina balstoni. However, modelling future population viabilities under projected surface and groundwater level reduction scenarios has been limited by the lack of TIVs for most species. Therefore, the current study aimed to analyse an extensive database of fish distributions and water quality variables across south-western Australia (1098 sampling points) to develop TIVs for species that could then be used in a risk assessment and decision making framework for managing groundwater dependent ecosystems (GDEs) subjected to declining water levels in the Blackwood River. There were significant differences between species in TIVs relating to water temperature and conductivity. For example, some of the species that occupied narrow ranges and are considered to be threatened, such as Galaxiella munda and N.balstoni, occupied the coolest environments, whereas the common and widespread introduced Gambusia holbrooki and native Galaxias occidentalis occupied warmer and more saline environments. The findings from the current supporting document were subsequently incorporated into the Bayesian Belief Networks (Supporting Document 6) that modelled the likelihood of population declines for species following groundwater level reductions in the Blackwood River during baseflow. The BBNs were then mapped (Supporting Document 7) to spatially represent likelihood of population declines in the Blackwood River study area. The TIVs developed here will also be extremely useful for modelling population declines in response to other projected environmental changes in south-western Australia, such as increasing temperature and salinity.

Southern Australia is becoming warmer and drier as climate change progresses, creating serious threats to freshwater ecosystems that are dependent on the presence of water for their existence. The overall aim of this research project was to develop and evaluate four potential methods for enhancing the role, function and resilience of refuges for freshwater biodiversity in southern Australia. It focussed on means to maintain the physical conditions in refuges within ranges tolerable for species and to maintain connectivity that allows species to retreat to, and expand from, refuges. The four approaches studied were: • the feasibility of using cool-water releases (CWR) from reservoirs and shandying to control water temperature in rivers; • a method for deciding where streamside re-vegetation should occur in catchments to ensure maximum long-term negative effects on stream temperature; • the potential for artificial urban wetlands (i.e. anthropogenic habitat) to act as refuges for freshwater biodiversity against climate change; • a method for identifying redundant river regulation infrastructure and prioritizing artificial structures for removal during river restoration to improve connectivity along river channels for fauna movement. These four approaches were found to have the potential to address a range of objectives for refuge management, such as: reduce temperatures in refuges (1 & 2), increase number of refuges that act as colonization sources (all), assist dispersal into and out of refuges (all), increase biodiversity within refuges (all), increase permanence or resilience of refuges (all) and increase resistance or resilience of refuges during extreme events (1, 2 & 3). In particular, CWR could potentially be used to mimic natural thermal regimes, reduce the frequency and duration of extreme high temperature events and to assist movement of fish between thermal refuges, but further information and trials are required (1). Riparian planting can be used to reduce in-stream temperatures over the long-term and the tool developed here permits users to determine the optimal planting locations within catchments to maximise cooling effects for a given replanting investment (2). Perennial artificial wetlands can be used to provide refuges for biodiversity from wetland drying, and artificial wetlands can be modified to support higher biodiversity (3). The removal or modification of in-stream barriers can be used to create, protect or link refuges for freshwater species, especially fish, and the method developed here allows users to determine which artificial barriers have priority for removal within catchments (4). There are synergies with catchment restoration, such as environmental flows (CWR, barrier removal and modification), and revegetation (riparian replanting, anthropogenic refuges).Therefore, the four refuge management approaches described in this project should be integrated into existing river and wetland restoration practices within catchments. Refuges across all types of waterbodies in catchments should be managed in an integrated way, comprising multiple waterbodies of each type to provide the diversity of habitat types required by freshwater species.

The objective of this research was to develop and test a risk assessment and decision-making framework for managing groundwater dependent ecosystems (GDEs) with declining water levels due to climate change, anthropogenic extraction, land use and land management. The framework was developed by a multidisciplinary team of ecologists, modellers and hydrogeologists in south-western Australia, a biodiversity hotspot that has already suffered three decades of below average rainfall and consequently declining groundwater levels due to increased groundwater abstraction and land use change. This has provided a ‘living experiment’ providing validation of the framework against observed changes (not just modelled projections). The combination of this research together with input from a suite of end-users, other scientists and experts from across Australia has provided a robust and adaptable framework. The report outlines how the framework was developed and tested on three different types of GDEs: surface expression of groundwater in 1) wetlands on the Gnangara Groundwater System in Perth and 2) the Blackwood River, and 3) the subterranean expression of groundwater in the Leeuwin Naturaliste Ridge Cave System. However, the framework could be adapted to any type of GDE or surface water system. The framework integrates a standard risk assessment protocol enabling the approach to be easily transferred to sites within Australia and internationally. The framework is based around the construction of a conceptual model which identifies the interrelationships between climate, hydrology, water quality and/or biotic resources and the biota in an ecosystem. Before the framework is undertaken, management issues are identified and the site is characterised in terms of the type of GDE, its spatial extent, hydrogeology and assets within the site location. The framework then proceeds through five steps: identify the hazard, determine the exposure and vulnerability of the GDE, assess the effects of the hazard, characterise risk and then manage the risk. A suite of tools are provided by this framework for managing risk and climate change adaptation including: the identification of hazards and their cause(s), exposure and vulnerability of GDEs to hydrological stress, key drivers that cause ecosystem change, thresholds of tolerance of the biota for these key drivers, conceptual models, and risk assessment and decision-making tools in the form of Bayesian Belief networks and spatial models of risk.