Stephen Beatty

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.

Storm surge barriers are structures created across rivers, estuaries or tidal inlets to prevent coastal flooding. However, along with halting upstream water movement, they also have the potential to impede the movement of fishes. The Vasse and Wonnerup estuaries are located near the City of Busselton, Western Australia. Both estuaries have downstream storm surge barriers to prevent the flooding of low-lying coastal land and have ‘fish gates’ integrated into them to enable fish passage during the low flow period. Owing to poor water quality that regularly occurs immediately upstream of the Vasse barrier, fish kill events have regularly occurred there during summer and autumn with Black Bream being particularly vulnerable. However, no information existed on the movement patterns of Black Bream in the system nor on how fish passaged through the fish gates. This study aimed to determine the movement patterns and spatial and temporal distribution of the Black Bream within the Vasse-Wonnerup system using acoustic tags that were internally implanted in 41 Black Bream. The study revealed that Black Bream are highly mobile within parts of the system. Key habitats identified include the Wonnerup Inlet and the Deadwater with habitat further upstream of the either surge barriers not often accessed even when passage through the gates was not impeded. Crucially, the study revealed that the Black Bream that passaged through the Vasse fish gate only did so down a gradient (head loss), and once upstream of the barrier, did not (or could not) return downstream. Therefore, the study indicated that instead of the gates allowing the fish to escape from poor water conditions that occurred upstream, the Bream appear to be ‘stuck’, which initiating a review of the management of the fishgates for the mitigation of fish kills.

This study considers the impact of climate change on two aestivating species, Salamanderfish, Lepidogalaxias salamandroides Mees and Black-stripe Minnow, Galaxiella nigrostriata Shipway, from a drying region, Australia’s Southwestern Province. Lepidogalaxias salamandroides is unique in that it is the sole member of the family Lepidogalaxiidae basally placed as the sister taxon of all Euteleosteomorpha (Li et al., 2010). Both L. salamandroides and G. nigrostriata are highly restricted in distribution to the ephemeral, acidic wetlands in the extreme south-western corner of the region (Berra & Allen, 1989a, b; Morgan et al. 1998), and are small bodied, have relatively short life cycles and annually aestivate underground (Pusey, 1989). This study aimed to quantify any changes in their geographical range and losses of populations, identify the factors that best explain their current distributions, and assess the overall threats to the viability of remnant populations. We hypothesised that: (i) there has been a decline in the distribution of both species since previous surveys, and (ii) the environmental drivers of this distributional decline will be directly linked to climate change.

Temperate wetlands and estuaries are widely regarded as the most degraded of all aquatic ecosystems, largely due to their exposure to a range of deleterious anthropogenic influences. In the case of the Vasse-Wonnerup Wetland System (VWWS) near Busselton, such impacts have included, land clearing for agriculture and associated severe eutrophication, the diversion of river flow and the construction of barriers (floodgates) to prevent the intrusion of saltwater into the wetland. Although the prevention of flooding and maintenance of surrounding pastoral land has been achieved, the VWWS has also suffered from numerous fish kill events and algal blooms. Current managers are thus faced with the problem of managing the legacy of historical management decisions, while also being under community and political pressure to introduce additional (but non-compromising) measures to reduce the frequency and severity of fish kills and algal blooms. This presentation details the anthropogenic changes that have occurred in the VWWS over the last 200 years and describe the resultant changes in environmental conditions, particularly salinity. The implications of these changes are then explored by comparing the fish and macroinvertebrate communities within different parts of the wetland in different seasons and also to those fauna recorded in other local systems. These analyses show that while the invertebrate fauna comprises wetland/freshwater species, the fish fauna of the VWWS is typical for an estuary. The compositions of both faunas undergo marked seasonal and regional changes in response to changes in salinity. The preliminary results of an acoustic tracking study demonstrate that, by understanding the movements of selected fish throughout the VWWS, management strategies could be refined to mitigate the effects of poor water quality and prevent or reduce the severity of fish kills.

Findings from my Honours research were presented at the ASFB Conference in Sydney 2015. The presentation begins by briefly introducing the definition behind aestivation, before touching on the climate change that has occurred within the south-west of Western Australia. Following this, the two model species, salamanderfish and black-stripe minnow were introduced, before aims of research, methods and results were discussed. Finally, I concluded the talk with the significance of the findings including potential increases in listing for both species, the potential for creating artificial refuge pools to help increase the resilience of each species, and finally areas of future research. Acknowledgements for co-authors, and collaborators are listed at the end, and my sincere apologies if I have left anyone from this. This presentation provides bullet points on each slide, and is best viewed accompanying the full thesis paper

Goldfish Carassius auratus has been widely introduced across the globe and feral populations are known to have considerable ecological impacts within the receiving environments. Despite centuries of domestication and its current widespread distribution, there is a dearth of information on the spatial and temporal movement patterns of this species, which limits the understanding of the impacts of introduced populations and hampers the development of effective control measures. The current study examined the movement patterns of an introduced population of C. auratus in a regulated south-western Australian river using passive acoustic telemetry. The species had a high residency index within the array (mean 0.64 ±0.06 S.E.). Mobility was high, with the mean minimum distance travelled within the array for individuals over the study period equalling 81.5 rkm (linear river kilometres, which was the sum of the distances of all movements between receivers and an underestimation of actual distances travelled); with one fish moving 231.3 km (including 5.4 km in a 24 hour period). Importantly, C. auratus displayed notable seasonal movement patterns including a clear shift to certain habitats during its breeding period; with most individuals being detected in an off channel wetland during that time. The results of this study have considerable implications for developing control programs for the species, such as targeting connections to off-channel lentic systems during the breeding period. Finally, the presentation will touch on the subsequent study that tracked the movements of Black Bream in the heavily modified estuary habitat downstream of the Goldfish acoustic array that aimed to refine the operation of floodgate barriers.

Covering nearly one-third of the Australian continent, Western Australia comprises five of Australia’s 10 ichthyological (fish) provinces and this includes the Southwestern, Pilbara, and Kimberley provinces, all of which are wholly contained within Western Australia, whereas the western edge of the Northern Province and the western portion of the Paleo Province also occur in Western Australia (see Unmack 2013, Morgan et al. 2014a, b). The study focuses on the fish fauna of the Pilbara Province, and was a joint initiative of the Rangelands NRM Coordinating Group and the Western Australian Government’s State NRM Program and co-funded by the Australian and State Governments.