In contrast to northern temperate environments, where day length and temperature changes are obvious proximate cues for movement to resource-rich breeding habitats, the cues for movement used by birds in an often resource-poor, stochastic environment are less obvious. We recorded long-distance movements of 23 Grey Teal Anas gracilis using satellite telemetry for up to 879 days and examined the relationship between those movements and environmental factors, such as heavy rainfall and flooding, at the destination site. We identified 32 long-distance (> 150 km) movements that met our criterion for minimally interrupted flight between origin and destination. Thirteen of these flights coincided with rainfall and/or flooding events up to 1050 km from the origin. However, some ducks moved without any clear beneficial conditions at the destination onto small wetlands in regions with little surface water. The data suggest that there are two types of long-distance movement -ranging and directed. These flights occurred over distances up to 1200 km across the arid inland. The rates and distances of movement suggest that long-distance movements of Grey Teal entail high energy costs as in waterfowl elsewhere. We conclude that the proximate controls of directed movements need not be very different from those of their temperate counterparts.

The ranavirus, epizootic hematopoietic necrosis virus (EHNV), is endemic to southern Australia with natural outbreaks resulting in mass mortality events in wild Redfin Perch Perca fluviatilis (also known as Eurasian Perch) and less severe disease in farmed Rainbow Trout Oncorhynchus mykiss. To further investigate the host range for EHNV, 12 ecologically or economically important freshwater fish species from southeastern Australia were exposed experimentally to the virus. A bath-challenge model at 18 ± 3°C was employed with limited use of intraperitoneal inoculation to determine if a species was likely to be susceptible to EHNV. Of the species tested, Murray-Darling Rainbowfish Melanotaenia fluviatilis and Dewfish Tandanus tandanus (also known as Freshwater Catfish) were considered to be potentially susceptible species. EHNV was isolated from approximately 7% of surviving Eastern Mosquitofish Gambusia holbrooki, indicating this widespread alien fish species is a potential carrier. The infection of Silver Perch Bidyanus bidyanus and Macquarie Perch Macquaria australasica and the lack of infection in Murray Cod Maccullochella peelii peelii and Golden Perch Macquaria ambigua ambigua after exposure to EHNV via water confirmed earlier data from Langdon (1989). Five other species of native fish were potentially not susceptible to the virus or the fish were able to recover during the standard 35-d postchallenge observation period. Overall, it appeared that EHNV was less virulent in the present experimental model than in previous studies, but the reasons for this were not identified. Received May 21, 2012; accepted November 1, 2012.

The contributions of nursery habitats to recruitment of non-native common carp (Cyprinus carpio) were estimated via analysis of water and otolith 87Sr/86Sr and otolith trace element concentrations (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) over 3 years in the Lachlan River, Australia. Water samples and otoliths of postlarval carp were analyzed to characterize 87Sr/86Sr and multi-elemental signatures of nursery habitats. Considerable temporal variation occurred in both water 87Sr/86Sr and otolith multi-elemental signatures, which limited our ability to directly match water and otolith 87Sr/86Sr in nurseries of the lower catchment. However, spatial variation in multi-elemental signatures was sufficient to allow accurate classification of nurseries within years. Assignment analysis of young-of-year fish suggested that several wetland and floodplain systems made significant contributions to young-of-year recruitment in the lower catchment. These contributions were strongly influenced by river flows and water management. Nurseries contributed fewer recruits to the main channel as distance from the nursery increased. Fish from the upper catchment originated from local sources, and there was no evidence of mixing of recruits between the upper and lower catchments. We conclude that identification of recruitment “hotspots” via otolith chemical analysis can assist in developing strategies to control invasive fishes in large river networks.

The nomadic or dispersive movements of many Australian waterfowl in response to irregular environmental cues make satellite telemetry studies the only means by which these long-distance movements can be tracked in real time. Unlike some large-bodied soaring species, attaching satellite transmitters to small-bodied waterfowl (<1 kg) is not straightforward because ducks have high wing loadings and need to maintain active flapping to stay aloft. In the present paper, we detail one harness design and attachment method that enabled us to track grey teal (Anas gracilis) for up to 879 days. In addition, we detail rates of data loss, changes in data quality over time and variation in data quality from solar-powered satellite-tags deployed on ducks in Australia and Papua New Guinea. Up to 68% of all locational fixes have a nominal accuracy of less than 1 km, and satellite-tags deployed on wild birds can provide up to 22 location fixes per day and store enough energy during the day to run continuously throughout the night.

Carp (Cyprinus carpio L.) is a pest species in Australian waterways, and cyprinid herpesvirus 3 (CyHV-3) is being considered as a potential biological control (biocontrol) agent. An important consideration for any such agent is its target specificity. In this study, the susceptibility to CyHV-3 of a range of non-target species (NTS) was tested. The NTS were as follows: 13 native Australian, and one introduced, fish species; a lamprey species; a crustacean; two native amphibian species (tadpole and mature stages); two native reptilian species; chickens; and laboratory mice. Animals were exposed to 100-1000 times the approximate minimum amount of CyHV-3 required to cause disease in carp by intraperitoneal and/or bath challenge, and then examined clinically each day over the course of 28 days post-challenge. There were no clinical signs, mortalities or histological evidence consistent with a viral infection in a wide taxonomic range of NTS. Furthermore, there was no molecular evidence of infection with CyHV-3, and, in particular, all RT-PCRs for viral mRNA were negative. As a consequence, the results encourage further investigation of CyHV-3 as a potential biocontrol agent that is specific for carp.

Numerous freshwater species are recreationally harvested, yet conservation concerns are often ignored. This may lead to conflict between fisheries and conservation management for a species. Approximately one‐third of freshwater crayfish species globally are threatened with extinction, including the Murray crayfish, Euastacus armatus (von Martens, 1866) in south‐eastern Australia. There has been substantial commercial and recreational fishing of E. armatus since European settlement, as well as other threats such as poor water quality (e.g. hypoxic ‘blackwater events’ during floods). A stochastic population model was developed for three regional populations of male and female E. armatus, and was used to examine the effects of fishing and hypoxic blackwater disturbance on a Murray crayfish population in a lowland region. The results indicate that the Murray crayfish population in the lowland region faces increasing risks from increasing fishing pressure, together with low frequencies of hypoxic blackwater disturbance only. Testing various fishery regulations, the modelling demonstrated that recent changes to the ‘slot size’ in occipital carapace length of 10–12 cm for legally harvesting crayfish was a suitable protection measure given the background levels of hypoxic blackwater disturbance, balancing fishing and conservation concerns. Although higher slots (11–13 cm and 12–14 cm) were less sensitive to higher fishing pressures, the recreational harvest declined. The model was most sensitive to early life‐history survival rates; however, sensitivity analysis of model variability also indicated that E. armatus may be susceptible to highly variable environments (not to be confused with highly variable flows). This study demonstrates the successful integration of fishing and conservation in a flexible risk framework for this threatened freshwater crayfish species; furthermore, fisher expectation can be managed by assessing the impact on harvest of potential changes to fishing regulations. This approach is easily transferable and would improve the management of other recreationally fished species facing multiple threats.

Understanding dispersal traits and adaptive potential is critically important when assessing the vulnerability of freshwater species in highly modified ecosystems. The present study investigates the population genetic structure of the Murray crayfish Euastacus armatus in the southern Murray–Darling Basin. This species has suffered significant population declines in sections of the Murray River in recent years, prompting the need for information on natural recruitment processes to help guide conservation. We assessed allele frequencies from 10 polymorphic microsatellite loci across 20 sites encompassing the majority of the species’ range. Low levels of gene flow were observed throughout hydrologically connected waterways, but significant spatial autocorrelation and low migration rate estimates reflect local genetic structuring and dispersal limitations, with home ranges limited to distances <50-km. Significant genetic differentiation of headwater populations upstream of barriers imposed by impoundments were also observed; however, population simulations demonstrate that these patterns likely reflect historical limitations to gene flow rather than contemporary anthropogenic impacts. Dispersal limitations, coupled with its biological traits, suggest that local populations are vulnerable to environmental disturbance with limited potential for natural recolonisation following population decline. We discuss the implications of these findings in the context of managing the recovery of the species.

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