David Morgan

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.

Remote underwater video, established in marine ecosystems, has infiltrated the toolbox of researchers in estuarine and freshwater systems more recently. Arguably, the greatest limiting factor in the application of underwater video for surveying many freshwater and estuarine ecosystems is water clarity. Indeed some systems are perpetually turbid while others are intermittently turbid in response to flow events or tidal fluctuations. We used Baited Remote Underwater Video Stations (BRUVS) to survey the fish assemblage in a turbid tropical estuary on Cape York in northern Australia. Poor water clarity in the upper estuary prevented the identification of fishes that were not close to the baits. In an attempt to address this issue, we tested the attractiveness of two bait types and unbaited camera controls and employed Underwater Dark Channel Prior (UDCP) to enhance image quality and enable more accurate identification of species with a greater degree of certainty. In addition we present the outcomes of deploying a camera within the immediate area of interest of a large estuarine reptile.

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.

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.

Temperature affects most physiological processes which in turn impact animal behaviour and ecology. In ectotherms, both short- and long-term variations in temperature impact physiological (i.e. locomotor and metabolic capacity) and ecological (i.e. body condition and growth) performance and thus affect survival. It is therefore critical to understand the mechanisms driving these relationships. Here, we investigated the impact of seasonally changing temperature on the ecological and physiological performance of juvenile free-ranging largetooth sawfish (Pristis pristis) in its riverine nursery in North Western Australia. Animal-attached accelerometers, revealed that despite a 10°C increase in temperature, sawfish were active and displayed substantial burst-swimming capacity. Physiological performance, as ascertained by locomotory capacity, increased in the warmer late dry season conditions, whereas timing and duration of activity did not. Contrary to the physiological performance, late season sawfish were poorer condition that those in the early season. Activity was primarily crepuscular, irrespective of the season. This suggests that even though locomotory performance of juvenile sawfish increased at greater temperature, foraging activity and thus energy intake was not sufficient to maintain body condition, resulting in declining growth. Contrary to popular belief, seeking warmer temperatures can represent a disadvantage for juveniles under certain scenarios. Especially for individuals that are intake limited, greater temperatures and associated metabolic rates are disadvantageous and can result in lower growth rates and potentially starvation. Physiological and ecological performances may thus respond differently to warming temperatures, emphasizing that ‘optimal’ temperatures may be highly context dependent. Ecological scenarios responsible for mediating growth performance are discussed and integrated into a classic bio-energetics framework.

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.

Rivers, streams and wetlands of southwestern Australia support populations of fish found nowhere else in the world. Many of these species are threatened and populations are declining in both abundance and distribution. In order to help understand the drivers of these declines and devise management actions to halt them, this collaborative project aimed to fill key knowledge gaps relating to the ecology of three of south-western Australia’s most threatened freshwater fishes, the Western Trout Minnow, Balston’s Pygmy Perch and the Little Pygmy Perch, one of Australia’s ‘newest’ fishes.