Aquatic fauna refuges in Margaret River and the Cape to Cape region of Australia’s Mediterranean-climatic Southwestern Province

Margaret River and the Cape to Cape region in the extreme south-western tip of Australia are located between Cape Naturaliste in the north and Cape Leeuwin in the south and encompass all intervening catchments that drain westward to the Indian Ocean. The region has a Mediterranean climate and houses 13 native, obligate freshwater macrofauna species (i.e. fishes, decapod crustaceans and bivalve mollusc), four of which are listed as threatened under State and/or Commonwealth legislation. The most imperiled species are the Margaret River Burrowing Crayfish (Engaewa pseudoreducta) and Hairy Marron (Cherax tenuimanus), both of which are endemic to the Margaret River catchment and listed as critically endangered (also by the IUCN), and Balston's Pygmy Perch (Nannatherina balstoni) which is vulnerable. The region also houses several fishes that may represent new, endemic taxa based on preliminary molecular evidence. Freshwater ecosystems in the region face numerous threats including global climate change, a growing human population, introduced species, destructive land uses, riparian degradation, water abstraction, declining environmental flows, instream barriers, and fire. Here we review the current knowledge of the considerable aquatic biodiversity values of the region to provide a contemporary checklist, and to highlight actions that may be considered to protect these values in the face of both current and future conservation threats.

The south-west of Western Australia is a global hotspot of species endemism that is influenced by a Mediterranean climate (Myers et al., 2000;Olson & Dinerstein, 2002;Morgan et al., 2014a). The aquatic fauna of the region is species impoverished, yet the region has the highest rate of species endemism of any major drainage division in Australia, with >90% of the native aquatic macrofauna (i.e. fishes, decapod crustaceans, and bivalve molluscs) being endemic to this region (Morgan et al., 2011(Morgan et al., , 2014a. Some of these endemic species have suffered dramatic range declines during the past century, mainly due to impacts associated with deforestation and agricultural development, whilst others are naturally restricted to narrow ranges (Morgan et al., 1998(Morgan et al., , 2011Unmack, 2001;Allen et al., 2002;Klunzinger et al., 2015). While land clearing is now less prevalent, the entire regional aquatic fauna is becoming increasingly jeopardised by a number of anthropogenic stressors and environmental threats, not the least of which is human-induced global climate change (Suppiah et al., 2007;Morrongiello et al., 2011;Beatty et al., 2014;IPCC, 2014;Morgan et al., 2014a). Consequently, several of the region's endemic aquatic species are now imperiled and officially recognised as threatened under State and/or Commonwealth legislation (Morgan et al., 2011(Morgan et al., , 2014a. Situated within south-western Australia, the Cape to Cape region (CCR) (Figure 1) is globally recognised as a premier food and wine producing region, as well as a popular tourist destination. The population of the CCR has expanded in recent decades and land use patterns have shifted accordingly (CCG, 2005a(CCG, , 2005b(CCG, , 2006DoW, 2009DoW, , 2010. For instance, agriculture has intensified (particularly viticulture), resulting in a growing demand for surface and subsurface water resources (CCG, 2005a(CCG, , 2005b(CCG, , 2006. In light of this, the Department of Water (Government of Western Australia) recently proclaimed several unregulated water resources in the CCR for allocation under license (DoW, 2009) and addressed the need for water management reform in the South West Regional Water Plan 2010-2030(DoW, 2010. Balancing human water demands with ecological water requirements in a drying climatic region, where water demand is predicted to be at the limit of supply within 20 years, looms as a key management challenge (DoW, 2010). Moreover, the projected continuation of the current drying trend beyond this timeframe places further uncertainty on the long-term sustainability of some of the region's aquatic ecosystems (Suppiah et al., 2007;CSIRO, 2009a, b;Morrongiello et al., 2011).
The obligate freshwater macrofauna of the CCR comprises 13 native species (Morgan et al., 2011), four of which are listed as threatened under the Wildlife Conservation Act 1950 and/or Environment Protection and Biodiversity Conservation (EPBC) Act 1999. Two additional species are listed as 'priority taxa' by the Department of Parks and Wildlife, Government of Western Australia (Morgan et al., 2011(Morgan et al., , 2014a (Morgan et al., 2014b, Klunzinger et al., 2015. Notwithstanding the threat posed by climate change, these rare species also face a number of further specific threats (see Burnham et al., 2012;Duffy et al., 2014;Klunzinger et al., 2015).
With almost half of the CCR's native freshwater macrofauna recognised as threatened or requiring conservation management, freshwater ecosystems in the region have justifiably received considerable attention from natural resource managers, scientists and conservation organisations in recent years. Increasing resources have been channelled into conservation and landcare initiatives in the region, such as the construction of two rock ramp fishways on the Margaret River (Beatty et al., 2007), comprehensive foreshore assessments (e.g. CCG, 2005aCCG, , 2006CCG, , 2008, and research, monitoring and recovery work on the region's critically endangered species (e.g. Bunn, 2004;Bunn et al., 2008;Burnham et al., 2012;Duffy et al., 2014;Morgan et al., 2014b;Klunzinger et al., 2015). Given the burgeoning amount of unpublished literature pertaining to the catchments and resident aquatic macrofauna of the CCR, the aim of this review is to collate and interpret the available information and data, thus providing a framework for environmental managers to develop a conservation strategy that may be used to protect and enhance the region's aquatic biodiversity values.

STUDY AREA
This review focuses on the area between Cape Naturaliste (33.53° S, 115.00° E) and Cape Leeuwin (34.38° S, 115.14° E) and encompasses all intervening catchments draining westward to the Indian Ocean ( Figure 1). The geology of the region features a coastal strip of sandy soil overlying limestone with occasional outcroppings of the underlying granitic and gneissic bedrock (Leeuwin Block), whilst further inland the topography is undulating and low-relief (20-100 m above sea level) with a mixture of gravelly and sandy soils in upland areas and alluvial sandy loams on drainage lines and floodplains (Tille & Lantzke, 1990;CCG, 2003).
The CCR has a Mediterranean climate characterised by hot, dry summers and mild, wet winters. Long-term mean annual precipitation at Margaret River is 1131 mm, and is similar at other weather stations in the vicinity, but considerably higher than areas to the region's north (BoM 2015). Precipitation decreases to around 900 mm further inland near the headwaters of the Margaret River catchment (BoM, 2015). On average, >75% of precipitation falls in the five months from May to September (BoM, 2015). Evaporation rates in the region are around 1.5 times higher than precipitation rates (Taylor & Tinley, 1999;BoM, 2015) resulting in highly seasonal flows, with most drainage systems becoming a series of isolated pools during the dry summerautumn period.

CATCHMENT CONDITION IN THE CAPE TO CAPE REGION
Although small on a global scale, the Margaret River is the largest river system in the CCR, draining an area of 477 km2 and features extensive permanent pool habitats throughout the middle and upper reaches. The river is in relatively good condition and has not become impacted by secondary salinisation, unlike many other rivers in south-western Australia . Almost the entire upper Margaret River catchment and significant portions of the lower catchment are forested (Green et al., 2010) and only 21% of the catchment has been cleared of native vegetation (CCG, 2003;DoW, 2008). In contrast, other CCR catchments are much smaller and most have been cleared more extensively (Table 1). Agriculture (predominantly livestock and viticulture) is the dominant land use across the CCR, with the proportion of cleared land typically exceeding 60% (Table 1). Wilyabrup Brook is the most highly modified catchment in the CCR (Table 1) with unrestricted access of livestock to riparian habitats prevalent (CCG, 2006).  The proliferation of on-stream dams is a key issue impacting catchments across the CCR (Table 1). Wilyabrup Brook, for instance, has ca 100 on-stream dams (CCG, 2006), and the density of dams is even higher in the Gunyulgup Brook and Boodjidup Brook catchments (Green et al., 2010; Table  1). The exception to this trend is the Margaret River main channel, which has only three low-level weirs, although there are 670 dams on its numerous tributaries including 43 of commercial size (i.e. >8 ML storage capacity) (Green et al., 2010; Table  1). Water is also pumped directly from the river in the middle and lower reaches for anthropogenic uses (Green et al., 2010). A report on the Ecological Water Requirements (EWR) in two representative reaches of the lower and middle section of Margaret River suggested that current levels of water abstraction were within ecologically sustainable limits but ongoing monitoring was required to ensure these limits would not be exceeded with future allocation of water licenses and climate change (Green et al., 2010). In Cowaramup Brook, however, a similar study found that water abstraction was already close to the ecologically sustainable yield, with only a limited capacity for the system to accommodate increased consumption (Donohue et al., 2010).

FRESHWATER MACROFAUNA OF THE CAPE TO CAPE REGION
The CCR houses a total of six native fish species (  Figure 3); although some of these species may no longer be present in the region (see below).
The CCR also houses nine decapod crustacean species (Table 3), seven of which are native (Figure 4) 1880)) have occasionally been reported from fresh waters of the CCR; however, these species generally only use freshwater habitats opportunistically and will not be covered further in this review.    Morgan et al., 1998Morgan et al., , 2013Morgan & Beatty, 2003, 2004a, 2005, 2007aBeatty et al., 2006Beatty et al., , 2007Beatty et al., , 2008

Climate change
South-western Australia has experienced a 10-15% reduction in rainfall since the mid-1970s with some parts of the region experiencing a 50% reduction in surface runoff during this time (Silberstein et al., 2012). Global Climatic Models unanimously project further reductions in rainfall (ca 8%) and runoff (ca 24%), and an increase in the number of no-flow days (by up to 4 months) by 2030 (Suppiah et al., 2007;CSIRO, 2009a, b;Barron et al., 2012;Silberstein et al., 2012). Compared with baseline period between 1986-2005, median estimates of average annual rainfall decrease for the region by 2090 are 12% under intermediate emissions scenario (RCP 4.5), and 18% under high emissions scenario (RCP 8.5); the latter could result in ca 65% reductions in annual runoff (Hope et al., 2015). Drought periods and days of extreme heat are also projected to increase, which will cause higher evaporation rates (CSIRO, 2009a, b, Hope et al., 2015. These changes are likely to have a profound impact on freshwater ecosystems in the region, in particular on the quantity and quality of available baseflow refuge habitat. The anticipated decline in biological carrying capacity of freshwater ecosystems due to climate change may lead to localised extirpations or even extinctions of the rarest and most vulnerable species (IPCC, 2013(IPCC, , 2014DEC, 2008).
A recent survey of key baseflow refuge habitats in the Margaret River has revealed dramatic declines in the abundance of both Pouched Lamprey and Western Mud Minnow. Pouched Lamprey larvae (i.e. ammocoetes) were not found at 75% of previous known sites and not a single individual Western Mud Minnow was captured despite thorough sampling of sites where the species was previously common (see Morgan & Beatty, 2003). Land use and water quality in the Margaret River catchment have not changed markedly over this time period; indeed, the historical Western Mud Minnow sites were all located within a conservation reserve that was established many years prior to the initial fish survey. Whilst the spread of invasive Eastern Gambusia may be a factor in the decline of Western Mud Minnow (discussed in the Introduced species section below), a more likely explanation for the observed fish declines in the Margaret River is the sharp drop in annual stream discharge in recent years. Five of the lowest discharge years on record (since 1970 when record keeping commenced in the catchment) have occurred since 2006. Western Mud Minnow has been shown to spawn in temporarily flooded riparian zones and its recruitment success is likely to be linked to stream flow as has been demonstrated for other south-western Australian fishes including lampreys (Morgan et al., 1998;Beatty et al., 2007Beatty et al., , 2014. Moreover, Western Mud Minnow typically has a short lifespan with most individuals spawning at age one and perishing shortly afterwards (Pen et al., 1991), therefore population numbers are probably susceptible to dramatic inter-annual fluctuations depending on the suitability of environmental conditions from year to year. The prolonged drought conditions in recent years may account for the severe population decline of these species in Margaret River, as well as providing a bellwether of the potential for climate change to impact freshwater species in this system and throughout the southwest region.
The burrowing crayfishes (Engaewa spp.) are likely to be particularly vulnerable to climate change as they are restricted to ephemeral habitats that may cease to function effectively in the future due to rainfall reductions and declining water tables (Commander, 2000;DEC, 2008). It is unknown if these species will have the capacity to burrow to sufficient depths in order to withstand predicted water table declines in the region and interventionary actions may be required to maintain populations in their natural habitats. The Margaret River Burrowing Crayfish (E. pseudoreducta) is already critically endangered due to its small geographic range, limited dispersal capability, specialised ecological requirements and small population size (DEC, 2008). These attributes combine to make it the most imperiled aquatic species in the CCR (and arguably in the entire south-western Australian region), and its conservation warrants top priority. Captive breeding programs may need to be considered in the future to avoid extinction of this species (DEC, 2008).

Water abstraction
Groundwater abstraction can reduce flow from natural springs (CSIRO, 2009b), which has been shown to be vital in maintaining important aquatic refuges in some catchments in south-western Australia (Beatty et al., 2014). It will be critical to ensure that abstraction from major aquifers, particularly the south-west Yarragadee and Leederville, does not exacerbate the effects of climate change in reducing the amount and quality of baseflow refuge pools; particularly those in the upper Margaret River. Other water abstraction issues include the illegal pumping of river water, noncompliance by private land holders in the installation and use of flow-bypass valves in dams, and the impact of timber plantations intercepting run-off and causing draw-down of water tables (DoW, 2009). In the Cowaramup Brook catchment, water abstraction is already very close to the maximum sustainable level necessary to maintain aquatic ecological functions (Donohue et al., 2010). Further EWR studies would be beneficial in order to determine if water use is encroaching on ecologically sustainable limits in other catchments of the region. The State Government's water authorities have embarked on a massive public educational campaign to raise awareness of the precarious state of potable water supplies in south-western Australia and to encourage strategies for limiting water wastage. Clearly, authorities will need to closely monitor and, where required, impose restrictions on human water use in the CCR and across the broader region in order to balance human demands with ecological requirements as the region continues its transition to drier and warmer climatic conditions.

Introduced species
Over the past 40 years, the rate of species introductions has soared (75% increase since 1970) in fresh waters of southwestern Australia (Beatty & Morgan, 2013). The earliest introductions were government sanctioned for the purpose of creating enhanced recreational angling opportunities (e.g. Redfin Perch, Rainbow Trout) and for the biological control of mosquitos (i.e. Eastern Gambusia). More recently, popular aquarium and aquaculture species (e.g. Goldfish, Carp, Yabby, Smooth Marron) have become established in natural waterways via the dumping of unwanted animals or via their escape from ponds and dams during flooding (Morgan & Beatty, 2004b, 2007bMorgan et al., 2004Morgan et al., , 2011Beatty & Morgan, 2013). Invasive aquatic species have been shown to have adverse impacts on Australian native species through predation, competition for food and space resources, agonistic behaviour, habitat degradation, and as vectors of diseases and parasites (e.g. Fletcher et al., 1985;Horwitz, 1990;Gill et al., 1999;Morgan et al., 2002Morgan et al., , 2004Morgan & Beatty, 2007b;Tay et al., 2007;Lymbery et al., 2010;Beatty & Morgan, 2013).
Six introduced aquatic macrofauna species have been recorded in fresh waters of the CCR (Tables 2; 3). Additionally, despite being a south-western Australian endemic, translocation of Smooth Marron into the Margaret River catchment has pushed the Hairy Marron to the brink of extinction (Bunn, 2004;de Graaf et al., 2009;Duffy et al., 2014). In response, the Department of Fisheries, Government of Western Australia, has established a captive breeding program of genetically validated pure-strain Hairy Marron for supplementation of wild stocks (de Graaf et al., 2009;Duffy et al., 2014), and has overseen the removal of large numbers of Smooth Marron and hybrid specimens from the upper Margaret River since 2004, which has slowed but not reversed the overall decline of Hairy Marron in this system (de Graaf et al., 2009).
Generally, once established, introduced species prove impossible to eradicate from the wild (Horwitz, 1990;Rowe et al., 2008). On the one hand, Smooth Marron and Eastern Gambusia have become well established and widespread in the CCR (Figures 5 and 6), with the latter species recently being discovered for the first time in Canebrake Pool, one of the most important baseflow refuge habitats in the Margaret River (Allen et al., 2015). This noxious pest species has rapidly become one of the most abundant fishes at this site, underlining its highly invasive traits. Its impact on the native aquatic fauna has been significant, with >90% of native percicthyids captured from this site showing signs of caudal fin damage due to fin-nipping by Eastern Gambusia (Figure 7). Its establishment in Canebrake Pool may have also contributed to the decline of Western Mud Minnow at this site. However, as the abundance of Western Mud Minnow has also dropped to undetectable levels in refuge pools further upstream that are not yet colonised by Eastern Gambusia, the decline is more likely attributable to climate change driven flow reductions.  16 Threatened fauna of Australia's Cape to Cape region DOI: 10.29094/FiSHMED.2017.002 The Yabby is also in the early stages of establishing itself in the region ( Figure  6). Unfortunately, this species is very adaptable to local conditions and eradication is unlikely via conventional control methods. The Yabby is of particular concern as it occupies an equivalent ecological niche to endemic Cherax spp. and directly competes with them for food and habitat resources (Beatty, 2006;Lynas et al., 2007). It is also capable of breeding multiple times per year, allowing it to rapidly colonise habitats and potentially outnumber native species (Beatty et al., 2005).
The remaining alien species have either failed to establish self-sustaining populations (e.g. Rainbow Trout and Redfin Perch), or their spread in the region has, thus far, been effectively contained through targeted fishing (e.g. Goldfish and Common Carp). Goldfish have been eradicated from Darch Brook (a tributary of Margaret River) via a combination of habitat dewatering, netting and chemical icthyocide (rotenone) application (Allen et al., 2013). As far as the authors are aware, this represents the first successful eradication of the species from an aquatic system in Western Australia. The only other record of Goldfish in the CCR is from an artificial pond in the Wilyabrup Brook catchment near Cowaramup, where >1,000 individuals were removed in 2011 (Freshwater Fish Group, Murdoch University, unpubl. data). However the species remains at liberty in the catchment.
The strategy of targeted fishing effort has had mixed success in mitigating the environmental risks of introduced freshwater species in the CCR, but undoubtedly a more cost-effective and practical strategy would be to prevent further introductions from occurring in the first instance. This is probably best achieved through educational programs designed to raise awareness and appreciation of native biodiversity whilst also emphasising the negative impacts that introduced species can have on native wildlife. The biosecurity branch of the Department of Fisheries (Government of Western Australia) has recently launched an educa-tional campaign to address this growing threat.

Instream barriers
Artificial barriers on waterways (e.g. dams, weirs, road crossings) can impact on aquatic species in a number of ways. Most crucially, they reduce longitudinal connectivity in lotic systems, which blocks or restricts the access of migratory species to vital habitats such as breeding grounds, seasonal feeding areas, or nurseries (Lucas & Baras, 2001;Morgan & Beatty, 2003;Koehn & Crook, 2013). For example, a number of native freshwater fishes (e.g. Western Minnow, Nightfish) move upstream to spawn in lower order tributaries with the onset of winter flows (Beatty et al., 2014). Not only do instream barriers restrict the migration of such species through physical blockage, they also delay the onset of seasonal flows that provide spawning cues, thus shortening the duration of the breeding season. In the CCR, hundreds of instream barriers (mainly gully dams) have been installed in recent decades (e.g. CCG, 2005aCCG, , 2006), yet only three fish passage structures have been built during this time (Beatty et al., 2007;Beatty & Allen, 2008). Furthermore, these fishways have been shown to effectively allow passage of only a subset of the resident fish fauna (i.e. Western Minnow, Pouched Lamprey and Western Pygmy Perch) while blocking upstream passage of other fishes (Morgan & Beatty, 2004;Beatty & Allen, 2008;Beatty & Morgan, 2008). Thus, there is a need for further research into modifications or alternative designs that will allow the full suite of migratory native aquatic species to bypass instream barriers in the CCR and more broadly throughout south-western Australia.
A simpler and more effective means of mitigating the impacts of instream barriers on migratory species may be the decommissioning and removal of artificial barriers (see Beatty et al., 2013). However, these structures are rarely redundant and may even provide ecological benefits such as the provision of permanent refuge habitats in their associated impoundments (an eco- logical function that will become increasingly valuable in a drying climatic region), or by limiting the dispersal of introduced species. In Boodjidup Brook for instance, the absence of Eastern Gambusia from the majority of the upper catchment is presumably due to the presence of an instream barrier, which may, in part, explain why the Western Mud Minnow persists in reasonable numbers in this system (Morgan & Beatty, 2008).

Loss and degradation of riparian vegetation
Riparian vegetation provides multiple benefits for both terrestrial and aquatic fauna and plays a vital role in maintaining aquatic ecosystem function and health (Pen, 1999). In the past, riparian vegetation was commonly destroyed during the development of agricultural land. The infamous case of the extirpation of a population of critically endangered Margaret River Burrowing Crayfish at the type locality in 1985 following the construction of a dam and establishment of a timber plantation (DEC, 2008) highlights the severity of the impact that such practices can have on aquatic macrofauna. Although the rate of clearing of riparian vegetation has declined in recent years, degradation of remnant vegetation is an ongoing issue across the region, mainly due to unfettered access of livestock to stream lines and this threatens aquatic ecosystems through processes of erosion, sedimentation and increased nutrient inputs.
Mature overstorey vegetation is vital in moderating water temperature and evaporation rates through shading (Pen, 1999;Davies et al., 2007), and provides instream habitat for native aquatic species such as Nightfish and Marron in the form of woody debris (Pen, 1999). Additionally, the leafy material that falls into the water is a vital source of carbon that drives aquatic food webs in a region where primary productivity in streams is naturally low (Pen, 1999). Deep rooted riparian vegetation also keeps salt-ladened groundwater at a sufficient depth to prevent secondary salinisation of streams, which has led to the extirpation of native species in some of the major rivers of south-western Australia (Pen, 1999;Morgan et al., 1998. Much riparian rehabilitation and fencing work has already been undertaken in the region (D. McKenzie, Cape to Cape Catchments Group pers. comm.) and our review revealed that further work is needed. From the standpoint of conserving aquatic fauna, future works should focus on sites that house threatened or rare aquatic species, particularly Burrowing Crayfishes (Engaewa spp.), Balston's Pygmy Perch, and Western Mud Minnow.

Fire
Native vegetation has long been burnt on a multi-annual rotational schedule as a land management tool for reducing fuel loads and associated risk of destructive wildfires, and to stimulate native plant growth and reproduction (Christensen & Kimber, 1975). Given the prevalence of fire in the Australian landscape (and particularly in the south-west of Australia); it is surprising that its impact on aquatic ecosystems has not yet been studied in detail. Concerns have been raised about the impact of fire on Engaewa spp., especially the highly restricted E. pseudoreducta (DEC, 2008). The restricted range of this species leaves it extremely vulnerable to habitat disturbance that may occur during fire management activities such as the clearing of firebreaks and containment lines, or in the use of fire retardant chemicals (DEC, 2008). In the Engaewa Recovery Plan it was stated that there was an "urgent need to improve the understanding of the effects of fire on Engaewa spp." (DEC, 2008) but little has been done to address this knowledge gap, and we contend that the same applies to other native aquatic species, and aquatic ecosystem more generally, as well. The threat of wild fires is likely to escalate as the region's climate becomes hotter and drier; therefore managing associated risks is likely to become more prevalent in the future.

CONCLUSIONS
The Cape to Cape Region is an iconic part of Mediterranean climatic Australia. It has an expanding population and is also one of the premier tourist destinations in Western Australia due to the climate and natural beauty. This review has highlighted that the aquatic macrofauna of the region, whilst depauperate, has exceptional rates of endemism and contains a number of threatened species. We recommend that sites within the CCR known to house these species (Figures 8 and 9) be monitored on a regular basis in order to maintain an up-todate knowledge of the conservation status of threatened populations and their habitats so that immediate threats can be identified and addressed (e.g. riparian zone degradation, water quality issues, novel species introductions). The importance of such monitoring was highlighted during the recent survey of baseflow refuge pools in Margaret River, where a severe decline in abundance of both Western Mud Minnow and Pouched Lamprey was detected, as was the spread of invasive Eastern Gambusia into the upper Margaret River (Allen et al., 2015).
One of the major environmental challenges faced in the region is finding a balance between human water demands and those of the environment. Many of the aquatic ecosystems in the region are degraded, while the areas that remain near pristine face a number of serious threats. The work on improving the management of aquatic ecosystems in the CCR to date has been commendable, but our review reveals a clear need for ongoing and adaptive management, as well as further monitoring and onground works that will contribute to the protection of the aquatic fauna values of the CCR.

ACKNOWLEDGEMENTS
We wish to thank the Department of Parks and Wildlife (DpaW, formerly DEC), Government of Western Australia, for providing the funding to undertake this project. We thank Drew McKenzie from the Cape to Cape Catchments Group for assisting with the project, Dr Quinton Burnham (Griffith University) for providing images and valuable feedback on Engaewa, Dr Rodney Duffy (Department of Fisheries) for information on Hairy Marron conservation initiatives, Mike Klunzinger (Murdoch University) for information on freshwater bivalves, and Sue Morrison and Andrew Hosie (Western Australian Museum) for contributing historical collection records. We thank Dr Gerald R. Allen (Western Australian Museum), Rudie Kuiter, Robert McCormack, and Simon Visser for allowing us to use their images. Lastly, we also acknowledge the original environmental custodians and traditional owners of the CCR -the Wardandi people.

AUTHOR CONTRIBUTIONS
Each of the authors contributed to the collection of data, and writing of the manuscript 19