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Nutrients such as nitrogen and phosphorus are typically considered detrimental to wetland values, but waterfowl can be numerous on nutrient-rich wetlands. Waterfowl were counted three to six times per year on nine treatment lagoons and associated wetlands (2,025 ha) at the Western Treatment Plant (south-east Australia) from 2000, to help maintain ecological values of this Ramsar-listed wetland as well as treating sewage for a large city (Melbourne). Up to 185,000 waterfowl were counted, varying with season, continental rainfall and lagoon operation. Nutrient levels were reduced on Lake Borrie lagoon in 2005 (as part of an Environmental Improvement Program) and restored in 2015. Waterfowl declined on Lake Borrie lagoon from 2005 when it received treated effluent not raw sewage, and increased in 2015 when it received partially treated sewage. This pattern was highly significant for total waterfowl and most species and guilds at Lake Borrie but was not replicated on other lagoons. Modelling revealed positive relationships between waterfowl numbers and nutrient concentrations, including ammonia and nitrite, to moderate levels. This shows that with careful management nutrient enrichment can have positive benefits, allowing artificial wetlands such as wastewater treatment plants to support high densities of waterbirds and the food webs that sustain them. [ABSTRACT FROM AUTHOR]

Reserve systems are part of biodiversity conservation planning. However, reserves are rarely assessed for their contribution to population persistence. Here we address knowledge gaps on reserve effectiveness by developing a new approach to model protected area efficacy as a function of habitat suitability and natural disturbance regimes. We demonstrate the utility of the model through a detailed case study of the critically endangered Leadbeater’s possum ( Gymnobelideus leadbeateri) in south–eastern Australia. We defined reserve effectiveness for the species to be when there was no more than 5% probability of populations falling to (or below) 500 adult females in 40 generations. A reserve system established specifically for Leadbeater’s possum was found inadequate to ensure population persistence for the next 40 generations, given historical disturbance, habitat decline, and future fires. Simulation modelling of potential areas of reserve suggests that, depending on management risk tolerance, between 30% to 100% of current forest extent within the range of the species may be required to ensure population persistence. This study exemplifies the need to consider the size of reserves prior to their establishment to ensure an adequate reserve design that will be effective against future disturbance for conserving threatened species. [ABSTRACT FROM AUTHOR]

Conservation management of freshwater ecosystems often focuses on mitigating or reversing the negative effects of altered patterns of river discharge. Assessments of management interventions frequently focus on direct, short‐term responses to discharge without consideration of underlying population trends that span multiple years.We sought to determine the effects on fish populations of annual variation in river discharge and water temperature after accounting for underlying population trends. We used data on five native and one non‐native fish species, collected over 7–20 years in seven rivers in the Murray‐Darling Basin, south‐eastern Australia.Population trends explained 3.4%–24.6% of the total variation in abundance and biomass of our six study species, while discharge and water temperature explained a further 1.2%–11.4% of this variation. However, population trends confounded the effects of discharge and water temperature, which suggests that the effects of annual discharge conditions may be contingent on past conditions and factors intrinsic to populations (e.g. age structure).Failing to account for population trends led to a combination of plausible and implausible associations with discharge and water temperature. Plausible associations included positive associations with the magnitude of spring discharge and negative associations with the number of days where discharge was below the long‐term 10th percentile. Determining whether estimated associations are real or artefactual requires a greater focus on the processes that underpin multiyear population trends.Our results highlight the potential for underlying trends in populations to confound the short‐term effects of discharge. Potential confounding of short‐ and long‐term changes in populations underscores the need to assess responses to river discharge in the context of overarching environmental conditions, including factors other than discharge. [ABSTRACT FROM AUTHOR]

Invasive mammalian predators commonly coexist with invasive mammalian herbivore prey. Managers often advocate controlling invasive prey in the belief that this will also reduce invasive predator abundance. Such an outcome would have desirable ecological and financial benefits, but there have been few tests of this hypothesis.We used large‐scale and long‐term monitoring data to test the prediction that invasive red fox Vulpes vulpes populations decline following control of invasive European rabbit Oryctolagus cuniculus populations in Australia. Both species severely impact natural and agricultural ecosystems, and significant resources are expended to reduce these impacts. We fitted a hierarchical state‐space model to spotlight counts of both species conducted at 21 transects between 1998 and 2015. The effects of rainfall, control activities (warren ripping and surface harbour removal), and density dependence on the population growth rates of both species were also evaluated.Control activities at 18 transects substantially reduced average rabbit abundances. Rabbit populations showed little response to rainfall, but exhibited negative density dependence and higher rates of increase during the autumn–spring interval.There was no numerical response of foxes to changes in rabbit abundance. Rather, fox populations increased rapidly after high rainfall and exhibited negative density dependence. The equilibrium abundance of foxes varied with rainfall and season, but was always <0.2 foxes per spotlight km.Synthesis and applications. We conclude that controlling rabbits to low abundances does not substantially reduce fox abundances in south eastern Australia. Rather, efforts to reduce fox abundance should directly target fox populations. Managers of invasive predator–invasive prey systems should not assume that controlling prey will, by itself, reduce predator abundances. Quantifying the numerical response is critical for understanding the likely response of predators to changes in prey abundance. We conclude that controlling rabbits to low abundances does not substantially reduce fox abundances in south eastern Australia. Rather, efforts to reduce fox abundance should directly target fox populations. Managers of invasive predator–invasive prey systems should not assume that controlling prey will, by itself, reduce predator abundances. Quantifying the numerical response is critical for understanding the likely response of predators to changes in prey abundance. [ABSTRACT FROM AUTHOR]

Abstract: Biological invasions by large herbivores involve the establishment of novel interactions with the receiving mammalian carnivore community, but understanding these interactions is difficult due to the large spatiotemporal scales at which such dynamics would occur. We quantified the functional responses of a native apex predator (the dingo (Canis familiaris), which includes wild dogs and their hybrids) and a non‐native mesopredator (red fox; Vulpes vulpes) to an invading non‐native ungulate (sambar deer; Cervus unicolor) in Australia. We predicted that the apex predator would exhibit a stronger functional response to increasing sambar deer abundance than the mesopredator. We used a state–space model to link two 30‐year time series: (i) sambar deer abundance (hunter catch‐per‐unit‐effort); and (ii) percentages of sambar deer in dingo (N = 4531) and fox (N = 5002) scats. Sambar deer abundance increased over fourfold during 1984−2013. The percentages of sambar deer in dingo and fox scats increased during this 30‐year period, from nil in both species in 1984 to 8.2% in dingoes and 0.5% in foxes in 2013. Dingoes exhibited a much stronger functional response to increasing sambar deer abundance than foxes. The prediction that invading deer would be utilized more by the apex predator than by the mesopredator was therefore supported. The increasing abundance of sambar deer during the period 1984−2013 provided an increasingly important food source for dingoes. In contrast, the smaller red fox utilized sambar deer much less. Our study demonstrates that prey enrichment can be an important consequence of large herbivore invasions and that the effect varies predictably with the trophic position of the mammalian carnivores in the receiving community. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editors discuss various reports within the issue on topics including the Native Fish Strategy, freshwater fishes in the Murray-Darling Basin (MDB), and future fish management.

Understanding the roles of different types of natural and artificial wetlands in providing habitat for waterbirds is crucial to active interventions to conserve wetland biodiversity. This study made use of a large database compiled over 22 years from the 'Summer Waterfowl Count' to determine the relative use of five wetland types by 18 species of waterfowl in Victoria, south-eastern Australia. The abundance of 14 species and density of 15 differed significantly (P < 0.05) according to wetland type. Waste stabilisation ponds supported significantly higher abundances and densities of many species, a greater number of species and a community structure that was markedly different from the other wetland types. Based on the findings of this study, we believe that the unique characteristics of each wetland type warrant the conservation of each. Moreover, waste stabilisation ponds are significant refugia for waterfowl in Victoria and the trend to modernise sewage treatment plants, to the detriment of waterfowl, should be approached with caution. It is suggested that these findings are probably applicable in other parts of the world, although further research is needed to confirm their universal application. [ABSTRACT FROM AUTHOR]