Australian Freshwater Turtles Research Articles

No Ranaviral DNA Found in Australian Freshwater Turtles, 2014-19, Despite Previous Serologic Evidence.

Ranaviruses are pathogens of ectothermic vertebrates (fish, amphibians, and reptiles). Turtles are the most common group of reptiles reported with ranaviral infections. However, there have been no surveys for wild ranaviral infection in any turtles from the suborder Pleurodira, despite ranaviral distributions and experimentally susceptible pleurodiran turtle populations overlapping in several areas, including Australia. We assayed 397 pooled blood samples from six Australian freshwater turtle species collected from five different sites in northern Australia between 2014 and 2019. Historical serologic surveys in the area had found antiranaviral antibodies; however, we did not detect any ranaviral DNA in our samples. Discrepancies between historical serologic and our molecular results may be explained by low viral prevalence during the years that these samples were collected, survivorship bias, or possibly an age class bias in sampling.

Overwintering under ice: A novel observation for an Australian freshwater turtle.

Frozen water bodies provide a physiological challenge to fauna by physically limiting access to atmospheric oxygen. To tolerate low temperatures, reptiles use brumation as a physiological strategy in winter. Cryptodira vary in their tolerance to freezing conditions but the extent of tolerance in pleurodirans is largely unknown. Australia's freshwater turtles inhabit warmer regions with less severe winters and have well-developed mechanisms to cope with high temperatures and drying waterbodies, rather than extreme cold tolerance. Chelodina longicollis is a widespread Australian freshwater turtle species that tolerates high temperatures and desiccation during hot, dry periods while also undergoing brumation during winter months. Despite extensive research, limited observations exist on their behaviour during severe winter periods at the extremes of their range. In an 11-month tracking study, we monitored adult C. longicollis, noting their movements, locations, and temperature weekly. We observed an adult female C. longicollis which, during a seven-month period within a single creek pool, survived brumation in extreme cold water including a 15-day period of total freezing of the surface water. After the ice melted following a rain event, the turtle was recaptured alive. This marks the first observation of brumation for an Australian chelid species under ice.

1 Million Turtles: empowering communities to save Australian freshwater turtles

ABSTRACT Australian freshwater turtle populations have declined substantially, with consequent losses to aquatic ecosystem functions. A leading hypothesis is that turtles have declined through lost recruitment caused by high nest predation by invasive foxes. The ‘fox hypothesis’ is supported by experiments showing that nest predation rates exceed 95% in many regions. Furthermore, population surveys have repeatedly found absences of juvenile turtles, and headstarting experiments have successfully replaced those juveniles in some species. We are currently leading a nationwide citizen science program, ‘1 Million Turtles’ (1millionturtles.com), to engage local communities to protect turtles from threats like nest predation using a suite of novel approaches. Our key innovation is to leverage community passion and interest for turtles to create positive conservation impacts via a nationwide support network. We provide a data collection tool and framework (TurtleSAT) and self-guided training in conservation methods. We assist with guidance for gaining licencing and permission, and applying for grants. We are evaluating our approach through both the impacts on turtle populations as well as through surveys of our engaged citizen scientists. Ultimately, we aim to create a science-supported, national grassroots conservation model where community champions can lead their own evidence-based approaches to help wildlife.

Delving into the Aftermath of a Disease-Associated Near-Extinction Event: A Five-Year Study of a Serpentovirus (Nidovirus) in a Critically Endangered Turtle Population.

Bellinger River virus (BRV) is a serpentovirus (nidovirus) that was likely responsible for the catastrophic mortality of the Australian freshwater turtle Myuchelys georgesi in February 2015. From November 2015 to November 2020, swabs were collected from turtles during repeated river surveys to estimate the prevalence of BRV RNA, identify risk factors associated with BRV infection, and refine sample collection. BRV RNA prevalence at first capture was significantly higher in M. georgesi (10.8%) than in a coexisting turtle, Emydura macquarii (1.0%). For M. georgesi, various risk factors were identified depending on the analysis method, but a positive BRV result was consistently associated with a larger body size. All turtles were asymptomatic when sampled and conjunctival swabs were inferred to be optimal for ongoing monitoring. Although the absence of disease and recent BRV detections suggests a reduced ongoing threat, the potential for the virus to persist in an endemic focus or resurge in cyclical epidemics cannot be excluded. Therefore, BRV is an ongoing potential threat to the conservation of M. georgesi, and strict adherence to biosecurity principles is essential to minimise the risk of reintroduction or spread of BRV or other pathogens.

Partitioning of PFAS to serum, tissues, eggs, and hatchlings of an Australian freshwater turtle

Turtles are a potential sentinel species of aquatic ecosystem health as they inhabit aquatic ecosystems, are long lived, and potentially have high exposure to anthropogenic chemicals via food and water. This study investigated per- and polyfluoroalkyl substances (PFAS) tissue partitioning in female Emydura macquarii macquarii turtle, and the maternal offloading of (PFAS) into eggs and then hatchlings as well as the accumulation of PFAS in male and female Emydura macquarii macquarii serum. Significantly higher levels of perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs) were measured in the male serum compared to the female turtle serum, whereas perfluoroalkane sulfonamides (FASAs) were significantly higher in the female turtle serum. Perfluorooctane sulfonate (PFOS) was the predominant PFAS in the turtles whereas PFHxA was the predominant PFAS found in the surrounding water. PFHxA was not reported in any turtle tissue or the serum. The short-chain PFSAs and FASAs appeared to be highly associated with blood; long-chain PFSAs and PFCAs were more likely to be associated with tissue. Half of the PFHxS and all the long-chain PFSAs and PFCAs reported in the yolks were transferred into the hatchlings (by mass), suggesting a potential intergenerational effect.

A misconstrued alien: the freshwater turtle Emydura macquarii in the Greater Sydney region

ABSTRACT Many freshwater turtle species have spread beyond their natural distributions through human agency, but introduced populations can be difficult to differentiate from natural ones. The occurrence of an Australian freshwater turtle, Emydura macquarii, in the Greater Sydney region, Australia’s most populous urban and peri-urban area, has alternatively been assumed to be natural or deduced to be due to anthropogenic introduction. I apply multiple lines of evidence to show that the occurrence of E. macquarii in the Sydney region is not natural and that the species has proliferated and spread there much more than the notoriously invasive red-eared slider turtle, Trachemys scripta elegans. The E. macquarii population of the Sydney region is highly diverse morphologically, with individuals variously resembling E. macquarii from Queensland, the north coast of New South Wales, and the Murray–Darling Basin. Better understanding is needed of the population genetics of E. macquarii in the Sydney region, the interactions among the region’s native and introduced turtles, and the impacts of E. macquarii on biota other than turtles.

Conservation implications of isotopic variation in nails and blood with wetland quality in three species of Australian freshwater turtle

Abstract Australian freshwater turtles are declining, reflecting global turtle trends. Understanding variation in turtle diets and habitat requirements can guide protection and restoration of ecosystems. Diet and niche overlap were investigated in three co‐existing species of turtle—the broad‐shelled turtle Chelodina expansa, the eastern long‐necked turtle C. longicollis and the Macquarie turtle Emydura macquarii, in three rivers in the Murray–Darling Basin, Australia, in relation to environmental variables. Dietary variation in relation to water quality (salinity) and macrophyte cover was investigated using stable isotope analyses (δ15N and δ13C) of turtle tissues (plasma, red blood cell, whole blood and nail) representing food assimilation over different antecedent periods. These stable isotope results were consistent with current dietary understanding based on stomach flushing, indicating that isotope analyses are a non‐invasive method for obtaining dietary information. There were temporal dietary differences, with strong shifts between spring and summer sampling periods, particularly in the blood plasma. Intraspecific variation in diets reflected in δ15N and δ13C related to body size. There was evidence of high dietary overlap among the three species, potentially creating competition, particularly when they co‐occur or resources might be limited. Continued degradation of turtle habitats and water quality affects turtle diet and reduces habitat availability, forcing the three species of turtle to co‐exist in diminishing refugia, increasing interspecific competition for food. Protecting and restoring freshwater ecosystems, including maintaining freshwater refugia, is essential to conserve already declining populations of the three Australian freshwater turtle species.

Effects of wetland connectivity on overwintering and movement behaviours of Australian freshwater turtles

AbstractFreshwater turtles are important consumers in Australian freshwater ecosystems. They serve as scavengers, nutrient regulators, and as food sources and Totems for Traditional Owners throughout Australia. Despite their importance, most Australian freshwater turtle species are declining. The impact of winter wetland drying on turtle populations remains unknown, and winter exposure of hibernating turtles may be an important additional source of mortality. We aimed to examine turtle responses to seasonal and episodic wetland drying in wetlands using acoustic telemetry and active trapping. Wetlands were chosen that spanned a range of hydrological connectivity to the adjacent Edward/Kolety‐Wakool River. We found that tagged Emydura macquarii typically exit wetlands disconnected from the adjacent permanent river prior to winter, and overwinter in the river. Female E. macquarii rapidly re‐entered ‘home’ wetlands (wetlands in which they were initially tagged) the following spring, whereas males tended to leave the study area, returning occasionally. Although we were not able to evaluate a winter drying event, one of the wetlands experienced partial summer drying. All three local turtle species (E. macquarii, Chelodina expansa, C. longicollis) exited the wetland long before winter drying would have become a potential threat. Our results suggest that turtles in this system may be protected from winter wetland drying because they move to the adjacent permanent river prior to winter. Spending the winter in the river channel reduces the risks of being trapped in a drying wetland as temperatures drop in winter.

Turtles in trouble. Conservation ecology and priorities for Australian freshwater turtles

AbstractThe Australian freshwater turtle fauna is dominated by species in the family Chelidae. The extant fauna comprises a series of distinct lineages, each of considerable antiquity, relicts of a more extensive and perhaps diverse fauna that existed when wetter climes prevailed. Several phylogenetically distinctive species are restricted to single, often small, drainage basins, which presents challenges for their conservation. Specific threats include water resource development, which alters the magnitude, frequency, and timing of flows and converts lentic to lotic habitat via dams and weirs, fragmentation of habitat, sedimentation, nutrification, and a reduction in the frequency and extent of floodplain flooding. Drainage of wetlands and altered land use are of particular concern for some species that are now very restricted in range and critically endangered. The introduced European red fox is a devastatingly efficient predator of turtle nests and can have a major impact on recruitment. In the north, species such as the northern snake‐necked turtle are heavily depredated by feral pigs. Other invasive animals and aquatic weeds dramatically alter freshwater habitats, with consequential impacts on freshwater turtles. Novel pathogens such as viruses have brought at least one species to the brink of extinction. Species that routinely migrate across land are impacted by structural simplification of habitat, reduction in availability of terrestrial refugia, fencing (including conservation fencing), and in some areas, by high levels of road mortality. We report on the listing process and challenges for listing freshwater turtles under the Australian Environment Protection and Biodiversity Conservation Act, summarize the state of knowledge relevant to listing decisions, identify the key threatening processes impacting turtles, and identify key knowledge gaps that impede the setting of priorities. We also focus on how to best incorporate First Nations Knowledge into decisions on listing and discuss opportunities to engage Indigenous communities in on‐ground work to achieve conservation outcomes.

Opportunities for research and conservation of freshwater turtles in Australia

AbstractAustralia's freshwater turtles have high endemicity and many are threatened by extinction. Following a symposium held at the 2022 conference of the Australian Society of Herpetologists, we summarized the current status of research and conservation for Australian freshwater turtles and identified opportunities for future research. Eight species (32%) of Australia's 25 native freshwater turtles are listed as threatened by Australia's Federal Government. Symposium discussions on the primary gaps in research identified the lack of baseline data to inform population modelling as a key deficiency. Knowledge of the most effective conservation actions, the effectiveness of attempts to aid population recovery, and whether these actions are required at all, remains lacking for many species. A heavy bias exists between some well‐studied species compared with others for which little or no information is published. Community science, engagement with First Nations people, advances in technology, and recognition of the importance of turtles are contributing to better knowledge.

Molecular detection of novel herpesviruses and adenoviruses in two species of Australian freshwater turtles

Cutaneous lesions were observed in a wild population of freshwater turtles during routine disease surveillance at Alligator Creek, Townsville, Australia. Previous attempts to identify the causative agent of these lesions were unsuccessful; however, existing evidence suggests viral etiology. To further investigate these events, blood samples and lesion, oral and cloacal swabs collected from 128 freshwater turtles at two locations (Alligator Creek and Ross River) were screened for herpesvirus, adenovirus, poxvirus and papillomavirus by polymerase chain reaction. We detected three novel herpesviruses (chelid herpesvirus 1–3) as well as three adenoviruses (saw-shelled turtle adenovirus 1–3). Phylogenetic analyses showed that the herpesviruses formed a distinct clade with the tumour-associated chelonid alphaherpesvirus 5 (Scutavirus chelonidalpha5) within the subfamily Alphaherpesvirinae. The adenoviruses clustered with members of the genus Testadenovirus. Although the novel herpesviruses and adenoviruses could not be linked to the occurrence of cutaneous lesions, further characterisation will help provide better insights into their clinical, epidemiological and conservation significance.

Towards a Diagnostic Tool for Turtle Ootaxonomy: Investigation of Microstructural Differences in the Eggshells of Australian Freshwater Turtles

Researchers frequently encounter turtle nests after the nest has been raided, finding only eggshell fragments that are difficult to identify. Valuable information on the breeding biology and needs of different species might still be collected from these nests if remains could be confidently assigned to a particular species. However, this can be difficult if there are multiple turtle species nesting within an area at a given time, and gross-scale characteristics such as egg size and shape are no longer available due to damage. This study examined eggshell microstructure, by scanning electron microscopy (SEM), among multiple species of freshwater turtle eggshell fragments, with the aim of potentially developing a diagnostic tool for species identification. Eggshell fragments were collected from known sources of four species of turtle native to eastern Australia: Eastern Long-necked Turtle (Chelodina longicollis), Murray River Turtle (Emydura macquarii), Bell's Turtle (Myuchelys bellii), and Bellinger River Turtle (M. georgesi). Fragments were scanned and analyzed for microstructural and ultrastructural features, and measured for differences in feature size across species. Central plaque diameter emerged as a potential diagnostic feature for separating species, with longneck turtle eggshells having no visible plaques, Murray River Turtle eggshells having relatively small mean plaque size (19.8 µm ± 10.28 SD), while Bell's Turtle (43.5 µm ± 14.16 SD) and Bellinger River Turtle eggshells (41.9 µm ± 15.41 SD) had relatively large plaques with little overlap between genera. Other measured features (shell unit size, basal knob size, and shell unit density) significantly differed in means among species but overlapped in range, or showed a lack of statistical difference, likely preventing the technique being definitive with a single measure. Some of this variance may be due to inherent confounding factors, such as the replicability of fragment preparation, condition of eggshells, and stage of embryonic development at the time of collection. These results suggest that use of measurements of microstructural features has promise as a means for distinguishing the provenance of eggshell fragments, and further investigation is warranted to develop site-specific protocols for use as a diagnostic tool for turtle ootaxonomy.

Nesting Refuge Structures Are Ineffective at Protecting Bell's Turtle (Myuchelys bellii) Nests from Red Fox (Vulpes vulpes) Depredation

Invasive red foxes (Vulpes vulpes) are a serious conservation issue for Australia's freshwater turtle species, including the endangered Bell's turtle (Myuchelys bellii). As many as 96% of Australian freshwater turtle nests may be depredated in a season by foxes. Current methods of turtle nest protection rely on early detection of nesting activity, followed by nest-specific structures to prevent predation. An alternative method to provide protection against fox raiding was tested: nesting refuge structures based on a design successfully used in the United States to protect diamondback terrapin (Malaclemys terrapin) nests. Six wood and chicken wire structures were placed at different sites beside large riverine pools on the Macdonald and Gwydir rivers, northeastern New South Wales, Australia, in the summers of 2019–2020 and 2020–2021. Sites were chosen for known previous nesting activity or presence of mature females, and each structure was placed in typical Bell's turtle nesting habitat at known nesting sites. Prior to placement, the soil was tilled with a rotary hoe to make the interior of the structure more enticing as nesting habitat, because Bell's turtles had been previously seen to nest in disturbed soils. Although females did approach the structures and in one case entered, no females were recorded nesting inside. Further, severe flooding in both years damaged and/or displaced 4 of the 6 structures. Rigid nest protection structures were therefore not shown to be an effective nest protection method for this species, despite their success in other regions for other species. Negative results such as these are important for conservation studies because they guide conservation efforts away from expending limited resources on ineffective methods and strategies.

Parasites in feral

Feral populations of Chelodina longicollis (Shaw, 1794) have established in Tasmania but many aspects of their biology in the wild remain unknown. A number of C. longicollis specimens were available for examination for parasites. Two species of digenean parasites were found in three of the 11 turtles examined: a Choanocotyle sp. and Thrinascotrema brisbanica Jue Sue & Platt, 1999. This is the first report of parasites from feral turtles in Tasmania. Due to the lack of native populations of freshwater turtles in Tasmania, these parasites must also have been introduced to Tasmania and have established life cycles in the new environments. The implications of such introductions, without suitable definitive hosts available to assist in establishing parasite infections, is discussed. An updated list of digenean parasites reported from Australian freshwater turtles is presented.

Adaptive Management to Reduce Nest Inundation of a Critically Endangered Freshwater Turtle: Confirming the Win-win

Inundation of Australian freshwater turtle nests has been identified as a threat to recruitment and long-term viability of species such as the critically endangered white-throated snapping turtle (Elseya albagula). Water level fluctuations within water storage infrastructure can inundate significant proportions of E. albagula nests in any year. Using an ecological risk assessment framework, operating rules for a water storage in the Burnett River (South East Queensland, Australia) were implemented to support nesting of E. albagula. Turtles were encouraged to nest at higher elevations on riverbanks by maintaining higher water levels in the impoundment during the nesting season, followed by lowering of water levels during the incubation period to minimise rates of nest inundation from riverine inflows. To verify the success of the new rules, a three-year confirmation monitoring program of nest heights and water levels was undertaken. Results of confirmation monitoring showed that 3% (2018), 11% (2019) and 0% (2020) of E. albagula nests were inundated under the new operating rules, compared to previously estimated nest inundation rates of >20% in ~24% of years of a 118-year simulation period (1890–2008) under previous storage operating rules. Emergency releases from an upstream storage in 2019 and 2020 for dam safety did not affect the success of the rule, demonstrating its resilience to natural and artificial flow regimes. This study demonstrates the importance of confirmation monitoring in verifying the efficacy of targeted changes to water management, and highlights potential application across other water storage infrastructure with threatened freshwater turtle populations requiring adaptive management.

Abundance and nutritional status of freshwater turtles to guide delivery of environmental flows in the Murray‐Darling Basin, south‐eastern Australia

Abstract Almost half of Australian freshwater turtle species are formally listed as threatened, but little is known about the effects of water management and other factors on the abundance and health of freshwater turtles in arid and semi‐arid regions. This study investigated how river flows (including the controlled release of water from an upstream storage facility, or ‘environmental flow’) and water quality might affect the abundance and nutritional status of three freshwater turtle species in three dryland rivers of the Murray–Darling basin in south‐eastern Australia. No response in abundance or nutritional status of the broad‐shelled turtle, Chelodina expansa, the eastern long‐necked turtle, Chelodina longicollis, and the Macquarie turtle, Emydura macquarii, was detected in relation to river flows, possibly because of the small magnitude of the environmental flow. However, for C. expansa, the catch per unit effort (CPUE) was negatively related to increasing macrophyte cover, electrical conductivity (EC, an indicator of salinity), and turbidity. CPUE for C. longicollis was positively related to macrophyte cover and EC, and for E. macquarii it was positively related to macrophyte cover. Haematological measurements suggested that the turtles had healthy nutritional status. Body condition and blood glucose and protein were related significantly to EC, whereas haematological measurements varied significantly among species and between spring and summer. The main conclusion is that water management measures to help the conservation of these turtles should include sufficient environmental flow to produce overbank flooding, thereby creating and maintaining a wide range of habitat suitable for the differing needs of the individual species.

Changes in participant behaviour and attitudes are associated with knowledge and skills gained by using a turtle conservation citizen science app

Abstract Citizen science has become a popular way to collect biodiversity data and engage the wider public in scientific research. It has the potential to improve the knowledge and skills of participants, and positively change their behaviour and attitude towards the environment. Citizen science outcomes are particularly valuable for wildlife conservation, as they could help alleviate human impacts on the environment. We used an online questionnaire to investigate the consequences of participating in an Australian turtle mapping app, TurtleSAT, on skills and knowledge gain, and test for any association between these gains and behavioural or attitudinal changes reported by the participants. One hundred and forty‐eight citizen scientists completed our questionnaire, mostly from the states of New South Wales and Victoria. TurtleSAT was the third most common source of correct answers about turtle ecology and conservation, after a talk about turtles and personal observations/research. Citizen scientists who participated more often were more knowledgeable about turtles than infrequent users. Self‐reported gains in knowledge and skills were positively linked to attitudinal and behavioural changes, such as being more aware of turtles on roads. However, behaviour and attitude changes were not related to participation rate. Respondents also reported that after learning about the current decline in turtle populations, they adopted several turtle‐friendly practices, such as habitat restoration or moving turtles out of harm's way, underlining the importance of increasing people's awareness on species declines. The reported changes in attitudes and behaviours are likely to positively impact the conservation of Australian freshwater turtles. Engagement with citizen science projects like TurtleSAT may result in participants being more interested in the natural world, by learning more about it and being more exposed to it, and therefore contributing more actively to its protection. A free Plain Language Summary can be found within the Supporting Information of this article.

Introduced red foxes (

It has been asserted that introduced red foxes (Vulpes vulpes) destroy ∼95% of nests of freshwater turtles in south-eastern Australia, are more efficient predators of freshwater turtle nests than Australian native predators, and are driving Australian freshwater turtle species to extinction. Available information was reviewed and analysed to test these assertions. Nest predation rates for all predators including foxes averaged 70% across Australia and 76% for south-eastern Australia compared to 72% for North America where freshwater turtles co-exist with many native predators, including foxes. Predation rates on Australian freshwater turtle nests did not differ significantly where foxes were included in the identified nest predators and where they were not, but sample sizes were very small. Evidence was lacking of foxes being the primary driver of population declines of Australian freshwater turtles, and some turtle populations are stable or increasing despite exposure to fox predation. Australian native species can be effective nest predators, and their role has probably been usurped by foxes to some degree. Where research shows that increased recruitment is necessary to conserve Australian freshwater turtle populations, strategies such as electric fencing of nesting beaches, nest protection cages and ex situ incubation of turtle eggs will probably be more cost-effective than efforts to reduce fox numbers. Further research is also needed to better understand the biological and environmental factors that regulate nest predation rates.

Behavioural thermoregulation by Australian freshwater turtles: interspecific differences and implications for responses to climate change

The abilities of freshwater turtles to control their body temperatures by behavioural means have implications for activity, food ingestion and digestion, growth, reproduction and potential responses to climate change. I compared various forms of basking in nature, and responses to aquatic and aerial photothermal gradients in the laboratory, among three species of Australian chelid turtles: Chelodina expansa, C. longicollis and Emydura macquarii. Proclivity for behavioural thermoregulation varied substantially among these species, being highest in C. longicollis and lowest in C. expansa. However, C. expansa had a thermophilic response to feeding. For C. longicollis and E. macquarii, behavioural thermoregulation may enhance colonisation of more southerly latitudes or higher elevations as climatic warming proceeds. However, increasing air temperatures may pose a hazard to turtles dispersing or sheltering terrestrially (for example, when water bodies dry during drought). C. longicollis appears the best placed of the three species to avoid this hazard through its abilities to thermoregulate behaviourally and to aestivate in terrestrial microenvironments that are buffered against temperature extremes.

The influence of a new water infrastructure development on the relative abundance of two Australian freshwater turtle species

Development of water infrastructure benefits water security and agriculture but poses risks to habitat and aquatic fauna. Wyaralong Dam was constructed on Teviot Brook in 2010 to provide future urban water supplies for South East Queensland, Australia. Construction of the dam created a large impoundment area and environmental impact assessment predicted significant impacts upon resident freshwater turtle species and their habitats. Differences in habitat requirements, life-history characteristics and sensitivity to change between the Macquarie River turtle (Emydura macquarii macquarii) and the common saw-shelled turtle (Myuchelys latisternum) were expected to influence the impact of the dam on the spatial and temporal abundance of these species. The relative abundance of each species was monitored at sites located within, upstream and downstream of the impoundment across wet and dry seasons during the dam’s first five years of operation. The results of this monitoring program indicate that spatial and temporal variability in the relative abundance of E. macquarii macquarii and M. latisternum occurred during the study but not all expected impacts were realised. Contrary to expectation, the relative abundance of E. macquarii macquarii did not increase over time within, upstream or downstream of the dam. M. latisternum showed greater temporal variability at some sites; however, no clear relationship between relative abundance and operational years was observed during the monitoring program. Spatial variability in relative abundance between sites was dependent upon season, with trends generally consistent across both turtle species. Where differences between species were observed, these are suspected to have resulted from the influence of environmental conditions on species-specific movement behaviours. The monitoring program confirmed the use of the upper limits of the impoundment and the plunge pool below the dam wall by both turtle species but relative abundance within the main body of the impoundment remained low throughout monitoring. The results of the study allow for consideration of the suitability of predefined management measures and the development of recommendations for future monitoring programs prescribed for water infrastructure developments.