Goldfish control in the Vasse River: summary of the 2008 programme

This report summarises the results of the 2008 round of the feral Goldfish control in the lower Vasse River and comparisons made with previous control efforts since 2004

Ascending the Avon: fishes of the Northam Pool, and the Swan-Avon catchment

The fish fauna in the vicinity of the Northam Pool Weir was sampled seasonally between winter 2008 and autumn 2009. The results indicate that the fish community was characterised by species that are halotolerant including two estuarine species, the Western Hardyhead and Swan River Goby that are likely to have undergone large upstream expansions in the Swan‐Avon catchment due to secondary salinisation. However, two freshwater endemic species, the Western Minnow and Nightfish were also recorded in the vicinity of the weir. These, and other freshwater endemic species, have undergone large range reductions in this catchment as a result of salinisation. The study found evidence that the weir may be impeding the upstream movements of native fishes as found elsewhere in south‐western Australia and that construction of a well‐designed fishway would enhance population connectivity and increase their sustainability. It is recommended that additional sampling occurs during the major spawning periods of the freshwater species immediately below the weir to determine precisely when a future fishway would need to operate to allow maximum usage by resident native species. It is also recommended that fresh refuge habitats for freshwater fishes be identified to allow effective management measures to be implemented in those systems to halt their decline and reduce the risk of complete loss of these species from the Swan‐Avon catchment

Distribution of the spotted minnow (Galaxias maculatus (Jenyns, 1842)) (Teleostei: Galaxiidae) in Western Australia including range extensions and sympatric species

Galaxias maculatus was captured from a number of rivers outside its previously known range. In Western Australia, it was formerly only known from rivers and lakes between the Goodga River (Two People's Bay, 30 km east of Albany) and the Dailey River (50 km east of Esperance), with additional records from the Boat Harbour Lakes (Kent River). An intensive survey of the inland fishes in rivers and lakes along the south coast of Western Australia has extended its distribution east by 50 km (Thomas River), west by approximately 40 km (Walpole River) and north by 400 km (Harvey River). The Western Australian Museum also has a specimen from the Canning River, a further 100 km north. Field salinity tolerance of G maculatus was high, with fish found alive in 81 mScm 1 (-45 ppt). The freshwater piscifauna east of, and including, the Pallinup River is depauperate, with G. maculatusbeing the only freshwater species present. All sympatric teleosts are tolerant of salinity and, with the exception of the introduced Gambusia holbrooki, are estuarine, including Pseudogobius olorum, Leptatherina wallacei and Acanthopagrus butcheri

Fish out of water: Aquatic parasites in a drying world

Although freshwater ecosystems are among the most diverse and endangered in the world, little attention has been paid to either the importance of parasitic disease as a threatening process for freshwater organisms, or the co-extinction risk of freshwater parasites. In this review, we use theoretical and empirical studies of host/parasite interactions to examine these issues, particularly with respect to the threat posed by climate change to fish and parasite communities in intermittent rivers. Intermittent rivers are those that cease to flow at any point in time or space, with isolated pools providing ecological refuges for freshwater biota between streamflow events. Intermittent rivers are the dominant river type in arid, semi-arid and Mediterranean regions; areas of the world that have experienced dramatic decreases in streamflow as a result of climate change. Reduced streamflow decreases the number, size and connectivity of refuge pools in intermittent rivers, with important consequences for free-living aquatic organisms, particularly fishes, and their parasitic fauna. As a result of more frequent and sustained periods of no flow, parasite diversity within refuge pools is expected to decrease, with a concomitant increase in the prevalence and intensity of those parasite species which do survive, particularly host generalists. Decreased connectivity between refuge pool communities should increase the spatial modularity of host/parasite interactions, leading to a greater structuring of host and parasite communities along the river. This increases the probability of species loss (for both hosts and their parasites), as local extinctions cannot be reversed by colonisation from other localities

History of cichlids in Western Australian aquatic ecosystems

Three species of the family Cichlidae have been reported from Western Australian waterways, including Tilapia zillii, Oreochromis mossambicus and Geophagus brasiliensis. While T. zillii was first found in 1975 and was successfully eradicated, O. mossambicus was first recorded in natural waterways of Western Australia in 1981, and has since spread to a further three river systems through either human-assisted dispersal or from flooding events. Recent research assessing the distribution and impact of the species in Western Australia suggests that O. mossambicus poses a serious threat to the unique aquatic fauna of Western Australian inland waters, including estuaries. The entry of other cichlids into the State’s waterways, including G. brasiliensis, which was first discovered in 2006, has the potential to impact Western Australia’s unique aquatic fauna in both inland freshwaters and estuaries

Resurvey of historical collection sites for Balston’s Pygmy Perch in the South West Linkages Target Area

Balston’s Pygmy Perch (Nannatherina balstoni) is one of the rarest native freshwater fishes endemic to south-western Australia (Morgan et al. 2011, 2014). The species inhabits near-coastal lakes, wetlands and flowing streams, and was historically distributed between the Moore River (north of Perth) and the Angove River (east of Albany) (Morgan et al. 2011, 2014). Numerous anthropogenic stressors including habitat destruction, pollution, river regulation, and water abstraction have resulted in an approximate 31% decline in the distribution, with the species apparently having been extirpated from the Swan Coastal Plain and a number of other systems across its range (Morgan et al. 2014). The contemporary distribution extends from the upper reaches of the Margaret River to the Angove River near Two Peoples Bay (Morgan & Beatty 2003; FFGFHU unpubl. data) (see Figure 1). Remnant populations are highly fragmented within this range (Morgan et al. 2014). In light of its typically low abundance and restricted distribution, N. balstoni has been formally recognised as Vulnerable to extinction under the Commonwealth Government’s Environment Protection and Biodiversity Conservation (EPBC) Act 1999 and is listed under Schedule 1 (“fauna that is rare or is likely to become extinct”) of the Western Australian Government’s Wildlife Conservation Act 1950. Accordingly, this fish is the flagship species of the current project entitled “Protecting threatened fishes in the South West Linkages Target Area”. A thorough review of the historical distribution of N. balstoni was conducted at the outset of this project and has now been published in the scientific literature (see Morgan et al. 2014). To complement this review, one of the project’s primary aims was to resurvey a number of historical collection sites in order to ground-truth the current status of resident N. balstoni populations. The results of this survey should provide valuable data for authorities in developing management and recovery strategies for the conservation of this threatened south-western Australian endemic

Influence of bar opening on the fish fauna of Toby Inlet

Despite its catchment being subjected to substantial anthropogenic modification to support agriculture and urban development, Toby Inlet is highly valued by the community and considered to provide important habitat for fish and waterbirds. This study aimed to quantify these perceived biological values by determining the fish and benthic macroinvertebrate species present in the system and elucidate whether the number of species, abundance, diversity and faunal composition differed among regions of the estuary and/or changed when the bar at the mouth of Toby Inlet was closed (November 2017) and open (March 2018). A total of 12,438 fish from 17 species were recorded in the shallow, nearshore waters of Toby Inlet across the two sampling occasion. Most of these are short-lived, small-bodied (< 50 mm total length), belong to the atherinids and gobys and complete their life cycle within the estuary. While the mean number of species, density and diversity remained similar among regions and seasons, faunal composition changed following the opening of the bar, but this was mainly due to the timing of reproductive cycles of these typically short-lived (1 year life cycle) species. It also reflects the fact that these species are generally highly euryhaline and able to tolerate even the hypersaline conditions that occurred in the upper region in March. In contrast to nearshore waters, the 620 fish caught and released in the offshore waters comprised mainly marine species. The composition of this fauna changed markedly following the opening of the bar as only four species were recorded in November, increasing to 12 after the bar had been open for several months. All of the species recorded only in March spawn in marine waters and where able to recruit to the estuary as the bar was open and salinities had increased markedly, facilitating their survival in the estuary. The changes in faunal composition were mirrored by changes in mean number of species and catch rates, both of which were greater in March. Regional differences in fauna were also detected, due to the declining influence of these marine species in the upper estuary and Deadwater. This latter region contained an impoverished fauna due to its shallow depths and limited connectivity to the ocean (the Station Gully mouth was closed throughout the study) and the lower region of Toby Inlet. The benthic macroinvertebrate fauna, which was only sampled in November, comprised a range of insect, crustacean, annelid and mollusc species typically found in either wetland or estuarine environments. This reflects the low salinities at the time of sampling (2-8) and the connectivity of the system to wetlands upstream of Caves Road Bridge. While some, annelids and molluscs were found in each of the four regions, some wetland insects and amphipods were more common and abundant in the upstream regions (upper estuary and the Deadwater), whereas the reverse was true for several estuarine species of annelids and a bivalve. The opening of the bar, allowed the immigration and emigration of fish species from the estuary and increased salinity. This influenced the fish fauna in offshore more than nearshore waters, as most of these species breed in marine waters and thus require the bar to be open to be able to recruit to the estuary. As invertebrates were only sampled in November, when salinities, were very low, there would be value in repeating the sampling when salinities were greater to elucidate what effect bar opening may have on that fauna, particularly as many species of fish and birds use this fauna as a critical food source. It should be noted that sampling was only conducted in areas of downstream of Caves Road Bridge, but that an option to construct a second mouth in the upper region of Toby Inlet would influence the fauna in that region and thus there is a need to collect some baseline data from that area to allow the potential impacts to be explored. However, the data in this report provide a robust baseline against which future changes in the fauna of Toby Inlet could be detected and also may help in the development of management strategies to improve the health of this highly-valued estuary

Marron, more than a meal. Harvey River restoration, Western Australia

The Southwestern Province has the highest proportion of endemic fishes and crayfishes on the continent, and is a globally recognosed endemic hospot. Over the last few decades, there has been a growing body of evidence that has suggested that the inland aquatic fauna of the Southwestern Province of Western Australia is declining. Much of this decline has been driven by large scale modification to habitat quality and quantity. The loss of suitable habitats through stream channelisation, river regulation, land clearing, flood abatement and the impact of introduced species, has resulted in large-scale losses of aquatic fauna. This, coupled with the increasing impact of climate change driven reductions in rainfall and subsequent run-off and aquifer recharge continue to challenge the aquatic fauna and necessitates adaptive management to help with their conservation. Since the turn of the Century, five of the region’s freshwater fish species, four freshwater crayfish species and the sole species of freshwater mussel have been listed as threatened under the Federal Government’s Environment and Biodiversity Conservation Act (EPBC Act 1999). Other species are variously listed under State legislation. Surprisingly, in 2013, the significant discovery of a previously undetected fish species was made, and since that time, several other species have been discovered in the region, but await formal description. The Marron (Cherax cainii) is recognised as a south-western Australian aquatic icon, not only for the important and unique recreational fishery that it supports, but also for its aquaculture potential and the sheer size to which it attains; while also being considered a delicacy and a biological indicator of ecosystem health. The Marron, More than a Meal Project aims to demonstrate how the restoration of drainage channels can lead to an improvement of the aquatic ecosystems

Introduced freshwater fishes in a global endemic hotspot and implications of habitat and climatic change

Introductions of alien freshwater fish species into the Mediterranean-climatic South-west Coast Drainage Division of Australia have impacted a highly endemic (≈82%) yet depauperate (11 species) native freshwater fish fauna. This study updates the current known introduced freshwater fishes in Western Australia, assesses the historic rate of introductions and how habitat, water quality and climatic changes have facilitated those introductions. South-western Australia has undergone a ≈63% increase in alien freshwater fish introductions since 1970 (44% increase over the past decade) to 13 species; overtaking the number of native fishes. Aquarium species represent 80% of the latest introductions (46% of total number) and the majority (54%) of introduced fishes in the region are of sub-tropical or tropical origin. As found elsewhere, species with broad environmental tolerances and generalist diets are likely to continue to be the main colonizers in this region. We propose that past and future climatic and habitat changes in the Mediterranean-climatic south-west region will facilitate continued invasion of tropical and sub-tropical aquarium fishes and that strategic monitoring, control and public education programs are required to halt future introductions