Inland aquatic systems and their fauna at Two Peoples Bay Nature Reserve, Western Australia, with emphasis on microinvertebrates

This review of inland aquatic fauna surveys focuses on south-western Australia, comprising a zone extending approximately from Kalbarri to Esperance and comprising seven bioregions (Fig. 2). Two Peoples Bay Nature Reserve lies in the southern part of the Jarrah Forest bioregion. Permanent or near permanent lakes are mostly restricted to the Swan Coastal Plain, Warren, southern Jarrah Forest, and Esperance bioregions, and are uncommon even in these regions. South-western Australia has a Mediterranean climate, albeit with less pronounced seasonality at Two Peoples Bay on the south coast. Albany, just west of Two Peoples Bay, has a mean monthly maximum temperature of 16°C in the coldest winter month and 23°C in the warmest summer month, and an annual rainfall of 921 mm (Table 1). Across most of the south-west, rivers flow for limited periods in winter and spring but near the coast may contain permanent water, especially in the wetter Warren region.

Fig. 2.

Interim biogeographical regions of south-western Australia and towns/sites used in rainfall statistics.

There is a long history of waterbird surveys at wetlands in Western Australia, often by amateur ornithologists. Large-scale, coordinated surveys with multiple surveys of sites and a clear conservation purpose did not begin until the 1980s. The main surveys have included inventory of waterbirds in nearly all nature reserves containing wetlands in the 1980s (Jaensch et al. 1988), censuses of ducks, coots, and swans across the south-west from 1986 to 1992 (Halse et al. 1995), and surveys of 251 wetlands on the coastal plain around Perth in 1990 and 1991 to assist water allocation planning (Storey et al. 1993). Waterbirds were surveyed across all of Western Australia in 2008 as part of a national census (Kingsford et al. 2012) and regular monitoring of the effects of salinisation at 25 wetlands began in the mid-1990s (Pinder et al. 2023). These broadscale surveys provide a context for the many surveys that have been conducted at individual wetlands or groups of wetlands, including the surveys at Two Peoples Bay Nature Reserve.

Important contributions to knowledge of inland fish in south-western Australia have been made by Gerry Allen (Allen et al. 2002) and Ian Potter, David Morgan, Luke Pen, and Howard Gill (Pen and Potter 1991; Morgan et al. 1998). Among the many benefits, surveys of fish in the past 30 years have led to new species being discovered (Morgan et al. 2013), the habitats and distributions of south-western Australian inland aquatic fish being known in detail (Morgan and Gill 2000) and fitted into a state-wide picture (Morgan et al. 2014), and managers being able to predict the likely impacts of increasing salinity on different fish species (Beatty et al. 2011). Dryland salinity is extensive in south-western Australia and has affected all aquatic life (Halse et al. 2003). The impact of invasive fish species has also been studied (Lymbery et al. 2010).

Several people have made outstanding taxonomic contributions that have supported inventory of aquatic invertebrates across Western Australia. They include Tony Watson for dragonflies (Watson et al. 1991), Chris Watts for beetles (Watts 1978), Peter Cranston and Don Edward for dipterans (Leung et al. 2013; Cranston 2019), Ian Bayly for calanoid copepods (Bayly 1992), Patrick De Deckker for ostracods (De Deckker 1983), Michael Geddes and Brian Timms for anostracans (Geddes 1981; Timms 2012), Adrian Pinder for oligochaetes (Pinder and Brinkhurst 1994), and Russell Shiel for rotifers and cladocerans (Shiel 1995).

Large-scale surveys of aquatic invertebrates have been undertaken on the coastal plain around Perth for water allocation planning (Davis et al. 1993), wetlands across the wheatbelt region of south-western Australia for conservation planning (Pinder et al. 2004), in rivers across Western Australia to provide the basis for using invertebrates as indicators of the ecological health of wetlands (Smith et al. 1999), and in rivers of the forested areas for conservation planning and monitoring of ecological condition (Pennifold et al. 2017). Many smaller scale surveys, including those along the south coast by Edward et al. (1994), Stewart (2009, 2011) and Timms (2008), have provided inventories and examined the effect of water chemistry on the invertebrate species present. Ecological processes in small streams were studied during the 1980s and 1990s in jarrah forest (Bunn 1988; Storey et al. 1990) and karri forest (Trayler and Davis 1998). The invertebrates of granite rock pools have also been a focus of attention (Pinder et al. 2000; Bayly et al. 2011).

Several reviews or analyses of the aquatic fauna of the south-west have been undertaken, including a comprehensive review of all groups of aquatic fauna and flora using rivers by Davies and Stewart (2013), who considered 43% of species in rivers to be endemic to south-western Australia. Reviewing stream studies in south-western Australia in the 1980s, Bunn and Davies (1990) highlighted the depauperate nature of the recorded fish and macroinvertebrate faunas and suggested this is associated with the isolation of south-western Australian streams from other stream systems (the south-west is surrounded by arid regions), the occurrence of much greater aridity in the south-west in the past than occurs now (hence the fauna reflects a more arid situation), and a very low level of primary productivity. In an analysis of available information on aquatic invertebrates, fish and frogs in the Warren bioregion (Fig. 2), Trayler et al. (1996) found records of 156 described invertebrate species, 22 frogs, and 14 native fish in lotic and lentic systems and concluded 86% of the species were protected by their occurrence in various forms of nature reserves, although external impacts (including salinisation) may reduce the protection provided by some reserves. Analysing results of sampling for aquatic invertebrates in peatlands and shrublands of southern parts of the Warren and Jarrah Forest bioregions, Horwitz (1997) found endemism to be higher in the coastal plain of the Warren region than elsewhere, perhaps because this area was less impacted by salinity, both currently and historically, than further north. A similar analysis by Horwitz et al. (2009) for aquatic invertebrates in lentic waterbodies around Perth in the Swan Coastal Plain bioregion found 520 species had been recorded, with the coastal wetlands having higher average richness than wetlands further inland in more arid areas. However, only 16% of species recorded by Horwitz et al. (2009) are endemic to south-western Australia.

Forty-two species of waterbird were recorded from the three lakes of Two Peoples Bay Nature Reserve between 1973 and 1990 during surveys by the Birdlife Australia and Department of Conservation and Land Management staff (Table 3, see Jaensch et al. 1988 for details). This represents comparatively high species richness for wetlands of south-western Australia: Jaensch et al. (1988) surveyed 197 nature reserves in the south-west during the same time period and ranked Two Peoples Bay 25th in terms of number of species. The individual lakes showed considerable differences in waterbird richness, with Miialyiin/Angove supporting fewer species (17) than Kaiupgidjukgidj/Moates (29) and Tyiurrtmiirit^y/Gardner (35) (Table 3), although Miialyiin/Angove was surveyed much less often and the lower number of species may be partly attributed to lower survey effort (Jaensch et al. 1988).

Waterbird abundance was low in all three lakes. Tyiurrtmiirit^y/Gardner was ranked 83 in abundance out of the 285 wetlands in the reserves surveyed by Jaensch et al. (1988). Kaiupgidjukgidj/Moates and Miialyiin/Angove support even lower abundance (Table 3). The waterbird conservation value of the lakes lies chiefly in the diversity and composition of species.

Species occurring in highest numbers are Eurasian coot, Pacific black duck, Australian shelduck, blue-billed duck, musk duck, red-necked stint, and red-capped plover (scientific names are given in Table 3). The occurrence of most of these species is sporadic, however. Those most frequently observed in Tyiurrtmiirit^y/Gardner are musk duck (85% of surveys), black swan (85%), and white-faced heron (70%). The most frequently observed species in Kaiupgidjukgidj/Moates are little pied cormorant (70%), little black cormorant (63%), and spotless crake (53%). There were too few surveys of Miialyiin/Angove for this analysis.

Musk duck, darter, little pied cormorant, Pacific black duck, spotless crake, and purple swamphen have been recorded breeding in the Reserve; musk ducks have bred at all three lakes (Table 3). Several other species may breed around the lakes (Jaensch et al. 1988), including Australasian bittern, which is listed under State and Commonwealth legislation as endangered. Kaiupgidjukgidj/Moates Lake area, in particular, is considered to be important habitat for this comparatively rare species (Department of Biodiversity, Conservation and Attractions 2018).

The freshwater and estuarine fish populations of Two Peoples Bay Nature Reserve have been surveyed on several occasions (current authors in 1990; Morgan et al. 1998, 2006; Morgan and Beatty 2006; N. Coy, unpubl. data), with fish collected from both the Angove and Goodga drainage systems. No fish have been recorded from the Maardjitup Gurlin/Mt Gardner Headland systems. The above surveys, combined with Western Australian Museum records and anecdotal records from several local people with a long-term interest in the area, suggest nine Indigenous freshwater species occur (Table 4).

Although not unique, the fish assemblage of the area is noteworthy for supporting common south-west Western Australian species towards the eastern extent of their range, as well as supporting several galaxiids that are restricted to south coast catchments. Pseudogobius olorum (Swan River goby) and Galaxias maculatus (common jollytail) are the most widely distributed species in the Reserve. Morgan et al. (1998) reported Galaxias occidentalis (western minnow) from six locations in the system, however, a subsequent study on galaxiid passage on the Goodga River (Morgan and Beatty 2006) failed to mention this species and so the previous records may have been an error.

The coastal sections of both river systems appear to be nurseries for the euryhaline Leptatherina wallacei (hardyhead), Aldrichetta forsteri (yellow-eye mullet), and Acanthopagrus butcheri (black bream) (Table 4). Prior to 1980, a local family (the Wilsons) netted 40–60 cm long yellow-eye mullet and a variety of small, unidentified ‘bait fish’ (likely G. maculatus) from Tyiurrtmiirit^y/Gardner Lake several times each year. Acanthopagrus butcheri has been caught in Tyiurrtmiirit^y/Gardner Lake and Gardner Creek. Although it has not been collected, it is likely that Geotria australis (pouched lamprey) occurs in the Angove and Goodga systems (Miller et al. 2021). Large spawning runs of this species usually occur each winter in nearby King Creek, Waychinicup River, and the Kalgan River.

The presence of Galaxias truttaceus (trout minnow) and Galaxias maculatus in a relatively landlocked situation in the Goodga and Angove rivers is notable. Studies in the eastern states of Australia on G. truttaceus (Humphries 1989) and G. maculatus (Pollard 1971) have shown the former is usually anadromous (going upstream from the sea to spawn) and the latter catadromous (going downstream to the estuary to spawn), although both species can adapt to landlocked situations.

Galaxias maculatus was formerly known only from rivers and lakes between the Goodga River and the Daley River (50 km east of Esperance), with additional records from the Boat Harbour Lakes (Kent River). An intensive survey extended its distribution east by 50 km (Thomas River), west by approximately 40 km (Walpole River), with outlier records from the Harvey River (400 km north) and the Canning River (a further 100 km north; Western Australian Museum record) (Morgan et al. 2006).

The trout minnow, Galaxias truttaceus Valenciennes, 1846, is known from Western Australia, South Australia, Tasmania, and Victoria, and King, Flinders, and Clarke islands in Bass Strait (Allen et al. 2002). Although Western Australian populations of the species were originally described as a discrete taxon (Galaxias truttaceus hesperius Whitely, 1944), more recent studies synonymise G. truttaceus hesperius with G. truttaceus. Notwithstanding this, G. truttaceus hesperius is listed federally as ‘critically endangered’ under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), and ‘endangered’ by the Western Australian Government under the Biodiversity Conservation Act 2016 (BC Act). The critically endangered Western Australian population of Galaxias truttaceus has been categorised by Allen (1982) as ‘our rarest species of native minnow’, and is known currently from the Goodga, Angove and King rivers in the south-west, with outlying, more western occurrence in the Kent River catchment (Colman 2010). Additional populations occur in south-eastern Australia but genetic and ecological investigations (Morgan et al. 2016) indicated there is limited contemporary gene flow between the eastern and western populations and concluded that the south-west population should be considered an evolutionary significant unit. In contrast to many eastern populations that are diadromous, all western populations are potamodromous. Adults live and spawn in riverine habitats and larvae drift downstream to coastal lakes, where they spend several months, before undertaking a distinct upstream recruitment migration as juveniles to colonise riverine habitats (Morgan and Beatty 2006; Morgan et al. 2016).

Goodga River also harbours the scarce Nannatherina balstoni (Balston’s pygmy perch) (Allen 1982, 1989), listed as ‘vulnerable’ under both the BC and EPBC Acts. This is another species that has experienced range contraction. Christensen (1982) collected it at only four of 120 sampling sites along the south coast hinterland between Augusta and Albany.

There are no confirmed records, but there are anecdotal reports of both Oncorhynchus mykiss (rainbow trout) and Perca fluviatilis (redfin perch) occasionally breaking the surface of Kaiupgidjukgidj/Moates Lake. Rainbow trout were first introduced to the Two Peoples Bay area in 1913 and were sporadically released in the Angove and Goodga systems by the Acclimatisation Society of Western Australia and the Albany, Denmark and Plantagenet Acclimatisation Society until after the Reserve was gazetted in 1967. Both Oncorhynchus mykiss and Salmo trutta (brown trout) maintain self-sustaining populations in nearby King Creek and O. mykiss also occurs in the Kalgan and Waychinicup Rivers (Lenanton 1974).

Both the Angove and Goodga rivers have relatively high V-notch weirs in their upper reaches (Fig. 4), which are barriers to upstream fish passage, with no fish recorded upstream of either the Angove (A. Storey, unpubl. data) or Goodga weirs (Morgan and Beatty 2006) in early surveys. A vertical slot fishway, designed to function during low flows to coincide with the upstream spawning migration of Galaxias truttaceus, was constructed on the Goodga Weir in 2003. Subsequent monitoring showed upstream movement of G. truttaceus and G. maculatus through the fishway and into the upper reaches of the Goodga, providing additional valuable habitat to both species (Morgan and Beatty 2006).

Samples of aquatic invertebrates were collected from the major flowing (Angove and Goodga rivers, West and Websters gullies) and standing (Miialyiin/Angove, Tyiurrtmiirit^y/Gardner, and Kaiupgidjukgidj/Moates lakes) waterbodies in the Two Peoples Bay area in June 1990 and February 1991 (Fig. 1). Additional samples of Cladocera were collected from the three lakes in September 1991 (see Storey et al. 1993 for details of sampling). Standard sampling techniques were used with 250 μm mesh nets in streams and both 50 μm and 250 μm mesh nets in lakes.

At least 248 species of aquatic invertebrate were collected (Appendix 1, Fig. 8). The lakes contained more species (171) than streams, with 72 taxa occurring in Tyiurrtmiirit^y/Gardner Lake, 97 in Miialyiin/Angove and 85, in Kaiupgidjukgidi/Moates Lake (Table 5). Twelve per cent of the invertebrate fauna was common to all three lakes.

Fig. 8.

Microinvertebrates collected at Two Peoples Bay Nature Reserve. (a) Copepod Paracyclops chiltoni, (b) cladoceran Macrothrix cf. breviseta, (c) ostracod Alboa worooa, (d) rotifer Platyais quadricornis, (e) copepod Gladioferans imparipes, (f) cladoceran Dunhevedia crassa. Scale bars = 0.1 mm. (Credit: J. McRae).

Sampling was sufficiently standardised to show that Tyiurrtmiirit^y/Gardner Lake contained the greatest biomass of invertebrates (despite lower species richness) and Kaiupgidjukgidi/Moates Lake the least, although biomass in all three lakes was low compared with many wetlands in agricultural parts of the Western Australian Wheatbelt (Pinder et al. 2004) and Swan Coastal Plain (Storey et al. 1993). None of the lakes contained many benthic animals. Chironomids and ostracods, both of which are abundant in most nutrient-enriched lakes, occurred in low numbers. Several species with marine affinities (e.g. Gladioferans imparipes and Schizopera clandestina) occurred in Tyiurrtmiirit^y/Gardner Lake, reflecting potential seasonal connection to the sea. The occurrence of the harpacticoid copepod S. clandestina is of interest but is perhaps a problematic record; it is the first time this west European species has been recorded in the southern hemisphere. More significantly, the cladoceran Gondwanothrix halsei collected from Miialyiin/Angove Lake represents a new family related to Macrothricidae (Van Damme et al. 2007) and highlights, together with the work of Frey (1998), that endemism in the cladoceran fauna of south-western Australia is much greater than suggested by Smirnov and Timms (1983). Similarly, more recent examination of the rotifers more widely in south-western Australia in the light of the richness of the Reserve’s lakes has shown that what was considered to be a cosmopolitan group has relatively high endemism in the south-west (Segers and Shiel 2003; Suatoni et al. 2006).

There was substantial focus on microinvertebrates when identifying the animals in Reserve’s lake samples and 57% of the fauna identified were rotifers or microcrustaceans (Table 5). Analysis of the results of other surveys in south-western and eastern Australia suggests microinvertebrates nearly always contribute substantially to invertebrate richness in lentic waterbodies and that surveys targeting only macroinvertebrates usually provide a very incomplete picture of inland aquatic biodiversity. For example, sampling in south-western Australia by Pinder et al. (2004) in the Avon Wheatbelt region and Halse et al. (2000) in a semi-arid area north of the Geraldton Sandplain, collected only slightly fewer than 50% microinvertebrates (Table 5). This suggests that the 40 Swan Coastal Plain lakes sampled by Davis et al. (1993), which on average yielded 53 species, would likely have shown similar or greater richness than the Reserve’s lakes if rotifers and harpacticoid copepods had been identified in that study. Similarly, the omission by Edward et al. (1994) of rotifer identifications and lumping of identification of cyclopoid and harpacticoid copepods to order level in the 23 wetlands sampled along the coast in the Warren region would have significantly reduced reported richness in that study. It is likely that the true richness of these lakes is similar to the Reserve’s lakes. Eastern Australian lakes also appear to have substantial proportions of microinvertebrates, based on sampling of saline lakes in southern Queensland at Lake Wyara (Timms 1998) and the Paroo (Timms 1993) (Table 5). Shiel et al. (1998) reported a very large assemblage (252 species) of rotifers from pools on the Murray River floodplain, though most individual sites had relatively low numbers of species and the proportion of rotifers and other microinvertebrates in the pool communities could not be calculated.

Overall, 110 species were collected from the river and creek sites. Eighty-three species were found in the two ‘lowland’ rivers and 56 in the two headland streams. Fifty-three species were collected from Angove River, with 55, 40, and 43 species taken from Goodga River, West and Webster’s Gullies, respectively. Eleven per cent of the invertebrate fauna was common to all four sites, 23% were recorded only from the two headland streams and 49% was restricted to the two lowland rivers.

All the known major components of the aquatic invertebrate fauna of south-western Australian flowing waters were represented in the rivers and streams of Two Peoples Bay Nature Reserve (Bunn et al. 1986; Storey and Edward 1989; Storey et al. 1990; Growns and Davis 1991, 1994). The absence of decapod crustaceans from the headland streams may reflect an absence of suitable habitats, since these streams were fast flowing, possessed few large pools, had small accumulations of organic matter, and a coarse substratum. The lowland rivers were slow flowing, consisted of large deep pools, exhibited large accumulations of fine organic matter, and supported large populations of decapods.

Values for species richness in winter at each flowing water site (23–36 species) were mostly higher than reported by Bunn et al. (1986) for winter samples from 10 perennial ‘stream’ sites in the Wungong and North Dandalup catchments south-east of Perth (18–26 taxa). The higher values may be the result of different sampling methods, particularly since Bunn et al. (1986) sampled only riffle zones, whereas the present study sampled all major habitats, but also reflect the richness of the south coast aquatic fauna.

According to Morrissy (1978), marron Cherax cainii are not indigenous to the drainage systems of Two Peoples Bay Nature Reserve. He reports Fisheries Inspector Goodlad stating in 1939 ‘There are places just outside Albany where marron have been put in by private persons. Angove Creek for instance’ and was told of another translocation from waters west of Albany into Kaiupgidjukgidi/Moates Lake in about 1940. Although marron are now abundant in Goodga River and Kaiupgidjukgidi/Moates Lake, the average size caught by marroners decreased during the 1980s, most likely because of fishing pressure (N. Morrissy, pers. comm.).

The introduced yabby Cherax destructor was not evident in the waters of the Reserve in the early 1990s, but had reputedly been released into nearby farm dams (D. Wilson, pers. comm.). In the long-term this species, with its greater fecundity and environmental tolerance, could replace the Indigenous freshwater crayfishes of the Reserve (Lake and Sokol 1986). According to Morrissy (pers. comm.) most farmers in the region are unaware of the animals’ introduced status and misname it as the endemic koonac (C. plebejus or C. preissii).