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Globally, river degradation has decimated freshwater fish populations. To help reverse this trend in a southeastern Australia river, we used multiple restoration actions, including reintroduction of instream woody habitat, riparian revegetation, removal of a weir hindering fish movement, fencing out livestock, and controlling riparian weeds. We monitored the responses of native fish at the segment scale (20 km) and reach scale (0.3 km) over 7 years to assess the effectiveness of the different restoration strategies. Two closely related species, Murray cod Maccullochella peeli and trout cod Maccullochella macquariensis, increased at the restored segment compared with the control segment. However, inherent differences between river segments and low sample size hampered assessment of the mechanisms responsible for segment‐scale changes in fish abundance. In contrast, at the reach scale, only M. peeli abundance significantly increased in reaches supplemented with wood. These differential responses by 2 closely related fish species likely reflect species‐specific responses to increased habitat availability and enhanced longitudinal connectivity when the weir improved passage around a fishway. Changes in M. peeli abundance in segments supplemented with and without wood suggest an increase in carrying capacity and not simply a redistribution of individuals within the segment, facilitated the observed expansion. Our findings confirm the need to consider individual fish species' habitat preferences carefully when designing restoration interventions. Further, species‐specific responses to restoration actions provide waterway managers with precise strategies to target fish species for recovery and the potential to predict fish outcomes based on ecological preferences.

In many animal populations, demographic parameters such as survival and recruitment vary markedly with age, as do parameters related to sampling, such as capture probability. Failing to account for such variation can result in biased estimates of population‐level rates. However, estimating age‐dependent survival rates can be challenging because ages of individuals are rarely known unless tagging is done at birth. For many species, it is possible to infer age based on size. In capture–recapture studies of such species, it is possible to use a growth model to infer the age at first capture of individuals. We show how to build estimates of age‐dependent survival into a capture–mark–recapture model based on data obtained in a capture–recapture study. We first show how estimates of age based on length increments closely match those based on definitive aging methods. In simulated analyses, we show that both individual ages and age‐dependent survival rates estimated from simulated data closely match true values. With our approach, we are able to estimate the age‐specific apparent survival rates of Murray and trout cod in the Murray River, Australia. Our model structure provides a flexible framework within which to investigate various aspects of how survival varies with age and will have extensions within a wide range of ecological studies of animals where age can be estimated based on size.

Recognition that many species share key life-history strategies has enabled predictions of responses to habitat degradation or rehabilitation by these species groups. While such responses have been well documented for freshwater fish that exhibit 'periodic' and 'opportunistic' life-history strategies, this is rare for 'equilibrium' life-history, due largely to their longevity and by comparison, more regular and stable levels of recruitment. Unfortunately, this limits the confidence in using life-history strategies to refine water management interventions to rectify the negative impacts of river regulation for these species. We addressed this knowledge gap for Murray cod Maccullochella peelii, a high-profile, long-lived recreationally popular equilibrium species in south-eastern Australia. We used monitoring data collected across a gradient of hydrologically altered rivers over two decades, to test various hypotheses linking recruitment strength with key attributes of the flow regime. Although Murray cod recruited in most years, as expected for an equilibrium species, responses to flow varied among and within rivers among years. We found links between recruitment strength and the magnitude and variation in discharge during the spring spawning period, as well as flows experienced by juvenile fish during summer and winter - the hydrological components most affected by river regulation. However, the specific slopes and directions of some of these links varied idiosyncratically across rivers. Our results emphasise the importance of accounting for flows that influence each of the key life stages during the recruitment process and lend support for managing rivers in accordance with the natural flow regime. It also shows the need for waterway-specific studies and further refinement of existing flow metrics to allow more credible transferability of results. The approach used in this study can also be applied to other species sharing life-history strategies for which long-term monitoring data has been compiled and length-at-age relationships established.

Introduced species are a major threat to freshwater biodiversity. Often eradication is not feasible, and management must focus on reducing impacts on native wildlife. This requires an understanding of how native species are affected but also how environmental characteristics influence population dynamics of both invasive and native species. Such insights can inform how to manipulate systems in order to take advantage of life-history traits native species possesses that invaders do not. The highly invasive fish, Gambusia holbrooki, has been implicated in the decline of many freshwater fish and amphibians. In south-eastern Australia, one of these is the threatened native fish, Galaxiella pusilla. As G. pusilla can survive periods without surface water, this presents an opportunity for adaptive management, given G. holbrooki lack these adaptations. We develop a stochastic population model to explore the impact of G. holbrooki on G. pusilla and test the feasibility of both natural and management-induced drying to protect this species. Our results support recent empirical studies showing G. holbrooki are a serious threat to G. pusilla persistence, especially through impacts on larval survival. While persistence is more likely in water bodies that frequently dry out, even optimal natural drying regimes may be insufficient when impacts from G. holbrooki are high. However, management-induced drying may allow persistence of G. pusilla in sites inhabited by both species. Given our model outcomes, the biology of these species and the habitats they occupy, we recommend maintaining or restoring aquatic and riparian vegetation and natural drying regimes to protect G. pusilla from G. holbrooki, in addition to undertaking management-induced drying of invaded water bodies. Our results provide insights into how the effects of G. holbrooki may be mitigated for other native species, which is important given this species is perhaps the most pervasive invader of freshwater ecosystems. We conclude with a discussion of the potential for using disturbance processes in the management of invasive species more broadly in freshwater and terrestrial systems.

Fish species that have no commercial or recreational value are often overlooked in conservation management, despite serious threats to their long-term future. This can be termed the ‘small threatened freshwater fishes’ paradigm. Population viability analysis (PVA) is a useful technique to assess threatened species and conservation management options. While the development and use of population models and population viability analysis is common in conservation, and often used for larger fishes, this has not been so for small threatened freshwater species. This study uses the PVA process to develop a stochastic population model for Nannoperca australis (southern pygmy perch) in temperate south-eastern Australia. The model was most sensitive to early life-history survival rates, for which there were no estimates from field data, compared with other model uncertainty. This study also found that the oldest age class had the highest reproductive value, providing unique support to the value of big, old, fat and fecund fish (BOFFFs) in sustaining natural populations. Modelling indicated that a population in stable habitat supporting about 2000 female adults would likely to be viable, able to withstand some disturbance and possibly be used as a source population for reintroductions. In reality, however, there are few populations in the wild of sufficient size to withstand such take for translocations and hence the production of fish through hatchery means may be required. This type of approach should prove useful for the conservation management of many similar species globally.

Most assessments of the effectiveness of river restoration are done at small spatial scales (

Globally, freshwater crayfish are imperilled, particularly large species harvested for human consumption. Crustacean fisheries typically rely on size- and sex-specific harvest regulations to counterbalance the adverse effects of over-harvesting which manifests within populations as disparate size truncation, and uneven sex ratios. A stochastic population model was used to examine the risk from harvest pressure on a threatened crayfish Euastacus armatus in south-eastern Australia. We compared a new indicator, size at functional reproduction (SFR – females with eggs), with the contemporary index of size at onset of maturity (SOM) when applying the current regulations of no-take for females with eggs. SOM under estimates risk compared with SFR. This risk difference was amplified with increasing harvest pressure, proving SOM inadequate for characterizing risk. Variable and increasing adult sex ratios with size was thought to indicate past harvest pressure and signs of recovery from harvest over-exploitation. However, in conjunction with evidence of differential encounter rates between female and male crayfish, we show that high sex ratios in catch data were not due to harvest pressure, pointing to problems with using sex ratio as a measure of exploitation and recovery. Our modelled results were unable to produce high sex ratios in catch data without a differential encounter rate included. If differential encounter rates exist, of the scenarios explored, the greatest risk was associated with the current harvest regulations. With recent declines in distribution and abundance, we argue that either the harvestable slot limit length be altered to account for our SFR results or that all female E. armatus be protected until the numerous uncertainties outlined herein are resolved. Finally, as SFR directly represents the biology of a species and will not inappropriately characterize risk compared with SOM, the new indicator SFR must replace SOM for monitoring, conservation and fisheries management of all decapods.

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.

Understanding why related species have differing population-level responses to threats can be key to identifying conservation options for declining populations. However, this is difficult when multiple threats are implicated. Chytrid fungus (Batrachochytrium dendrobatidis: Bd) is implicated in at least 500 amphibian population declines globally, although few tangible options exist to mitigate pathogen impacts. Other threatening processes also invariably operate on most amphibians. Non-native fish, for example, can contribute to amphibian declines and may exacerbate Bd impacts. We disentangled the impacts of Bd and non-native fish upon two stream breeding frog species with differing conservation statuses to reveal vital rates that are crucial for species persistence. Litoria spenceri are threatened and historically occurred at elevations between 300–1100 m asl in southeastern Australia. Litoria lesueurii are non-threatened and sympatric with L. spenceri at some sites. Using mark-recapture derived demographic rates known to correlate with climate and elevation, discrete-time deterministic population models were constructed for each species at high, moderate and low elevation sites, and multiple management scenarios. Our study reveals that age to maturation, clutch size and egg-year 1 survival influenced interspecific and intraspecific population-level responses of the two frogs to Bd impacts. Importantly, our results highlight that an amphibian population’s capacity to counteract Bd-mediated adult mortality is clearly constrained by other threats and environment interactions that moderate species recruitment. Furthermore, understanding limits to recruitment may help identify Bd mitigation strategies. In our study, disease mitigation may be best achieved at some sites by enhancing recruitment through non-native fish management.

Many freshwater fishes are imperilled globally, and there is a need for easily accessible, contemporary ecological knowledge to guide management. This compendium contains knowledge collated from over 600 publications and 27 expert workshops to support the restoration of 9 priority native freshwater fish species, representative of the range of life-history strategies and values in south-eastern Australia’s Murray–Darling Basin. To help prioritise future research investment and restoration actions, ecological knowledge and threats were assessed for each species and life stage. There is considerable new knowledge (80% of publications used were from the past 20 years), but this varied among species and life stages, with most known about adults, then egg, juvenile and larval stages (in that order). The biggest knowledge gaps concerned early life stage requirements, survival, recruitment, growth rates, condition and movements. Key threats include reduced longitudinal and lateral connectivity, altered flows, loss of refugia, reductions in both flowing (lotic) and slackwater riverine habitats, degradation of wetland habitats, alien species interactions and loss of aquatic vegetation. Examples and case studies illustrating the application of this knowledge to underpin effective restoration management are provided. This extensive ecological evidence base for multiple species is presented in a tabular format to assist a range of readers.

Globally, overharvest contributes to population declines of fish and invertebrates. Quantifying the effects of fishing and associated harvest is essential to preventing such declines. Murray crayfish Euastacus armatus exhibit slow growth and late age at maturity, and were historically abundant in Australia’s Murray–Darling Basin, but river regulation, pollution and overfishing have reduced their range and abundance. Diminished recreational fisheries still exist, but data to quantify catch, effort and harvest are not available to inform management decisions. We used a population model to assess the status of a harvested Murray crayfish population, informed by data collected from a fishery-dependant survey. Quantitative fisher surveys were undertaken in the Murrumbidgee River during the 2012 Murray crayfish open season (May–August inclusive). Shortly after the surveys, and in light of fishery-independent data that indicated a Murray crayfish decline, the crayfish recreational fishery was spatially reduced and shortened to a 3-month season (June–August), bag limits were reduced and size limits were changed from a minimum length limit of 90mm to a harvest-slot length limit (HSLL) of 100–120mm. Modelling of the Murray crayfish population indicated it was most likely to be relatively small with a mean population size of 2777 individuals and affected by a high rate of crayfish harvest (harvest probability 0.4), indicating vulnerability to further decline should fishing effort and harvest persist. The population model was used to assess the regulation change to a HSLL, with the results supporting the regulation change and indicating that implementation of the HSLL would stabilise the population, albeit over many years. This study demonstrates that empirical data and population modelling are crucial to inform fishery regulations for threatened species.

The number of threatened species continues to increase due to a range of anthropogenic disturbances, and many species continue to decline increasing their risk of extinction. Translocation is a widely used management technique to establish new populations to reduce the risk of extinction. There are, however, a range of issues to be considered. For example, for some species the donor population may be impacted by translocation, for other species it must be decided whether to translocate adults or juveniles to establish new populations. The question then becomes who do you move? The endangered Macquarie perch in south-eastern Australia is continuing to decline, with the recent Millennium Drought (1997–2010) and associated events (e.g., bushfires) contributing to dramatic local declines and the need for emergency responses. Successful historic translocations of this species involved adult fish, however the removal of significant numbers of adult fish may now impact source populations and alternative translocation approaches needed investigating. The use of sub-adult or juvenile fish, that would be expected to experience higher mortality, may be an approach to establishing new populations which would have less severe impacts on source populations. However, the number of fish required, frequency of translocation and likelihood of population establishment are unknown. This study outlines the development of a population model to assist in trialling translocation scenarios for establishing new populations of Macquarie perch. The model predicts that translocations of young-of-year fish (age 0+) is unlikely to be successful unless ∼600 females are released annually for five years. If translocating yearling (age 1+) fish, annual translocations of >100 females is required to achieve success, with stocking for at least five consecutive years required. If the frequency of recruitment failure or magnitude of Allee effects increases, then translocations of increased numbers of yearlings or prolonged stocking (10 years) is required to achieve success. The addition of small numbers of adult fish in combination with yearlings decreases the number of yearlings required, and increases the chance of success under more stressful scenarios.

Carp are a highly successful invasive fish species, now widespread, abundant and considered a pest in south-eastern Australia. To date, most management effort has been directed at reducing abundances of adult fish, with little consideration of population growth through reproduction. Environmental water allocations are now an important option for the rehabilitation of aquatic ecosystems, particularly in the Murray–Darling Basin. As carp respond to flows, there is concern that environmental watering may cause floodplain inundation and provide access to spawning habitats subsequently causing unwanted population increase. This is a management conundrum that needs to be carefully considered within the context of contemporary river flow management (natural, environmental, irrigation). This paper uses a population model to investigate flow-related carp population dynamics for three case studies in the Murray–Darling Basin: (1) river and terminal lakes; (2) wetlands and floodplain lakes; and (3) complex river channel and floodplain system. Results highlight distinctive outcomes depending on site characteristics. In particular, the terminal lakes maintain a significant source carp population regardless of river flow; hence any additional within-channel environmental flows are likely to have little impact on carp populations. In contrast, large-scale removal of carp from the lakes may be beneficial, especially in times of extended low river flows. Case studies 2 and 3 show how wetlands, floodplain lakes and the floodplain itself can now often be inundated for several months over the carp spawning season by high volume flows provided for irrigation or water transfers. Such inundations can be a major driver of carp populations, compared to within channel flows that have relatively little effecton recruitment. The use of a population model that incorporates river flows and different habitats for this flow-responsive species, allows for the comparison of likely population outcomes for differing hydrological scenarios to improve the management of risks relating to carp reproduction and flows.

Murray cod Maccullochella peelii (Mitchell) is a large, iconic Australian fish species targeted by anglers but also listed as nationally threatened. A consultative process that included conservation and fishery interests helped to develop a population model for this species and agree on management scenarios to be tested. The modelled scenarios illustrated that threats to populations (risk of decline) can be substantially reduced and catch rates increased through harvest slot length limits (HSLL) rather than minimum legal limits (MLL). A 600- to 1000-mm HSLL provided lower risk of decline and greater catch rates than the existing 500-mm MLL, but better results were achieved with a 400- to 600-mm HSLL. Importantly, a range of other impacts (fish kills, stocking, thermal impacts, larval mortalities, habitat changes) were recognised and incorporated. This study provides an example of the utility of a population model to improve management decision-making for both conservation and fishery objectives.

With maritime transport of crude oil from Alaska to California, there is significant potential for a catastrophic spill which could impact migrating salmon. Therefore, this study compared the lethal and sublethal metabolic actions of the water-accommodated fraction (WAF) and the chemically enhanced WAF (CEWAF, via Corexit 9500) of Prudhoe Bay crude oil in smolts of Chinook salmon (Onchorhyncus tshawytscha). After 96-h exposure to the CEWAF, the resulting LC50 was some 20 times higher (i.e., less toxic) than that of the WAF. Muscle and liver samples from surviving fish were collected and low-molecular weight metabolites were analyzed using one-dimensional (1)H and projections of two-dimensional (1)H J-resolved NMR. Principal component analysis (PCA), employed to analyze NMR spectra and identify most variance from the samples, revealed age-related metabolic changes in the fish within the replicated studies, but few consistent metabolic effects from the treatments. However, ANOVA results demonstrated that the dose-response metabolite patterns are both metabolite- and organ-dependent. In general, exposure to either WAF or CEWAF resulted in an increase of amino acids (i.e., valine, glutamine and glutamate) and a decrease of both organic osmolytes (i.e., glycerophosphorylcholine) and energetic substrates (i.e., succinate). The simultaneous increase of formate and decrease of glycerophosphorylcholine in the liver, or the decrease of glycerophosphorylcholine in muscle, may serve as sensitive sublethal biomarkers for WAF or CEWAF exposures, respectively. In conclusion, dispersant treatment significantly decreased the lethal potency of crude oil to salmon smolts, and the NMR-based metabolomics approach provided a sensitive means to characterize the sublethal metabolic actions.

Summary 1 Koala Phascolarctos cinereus populations sometimes exhibit eruptive dynamics, increasing to peak abundance and then crashing to low abundance. This dynamic is considered unacceptable because koalas die from starvation and food trees are killed by defoliation. There is concern that such dynamics may be occurring at a number of sites in south-eastern Australia. The only management option is fertility control of females. 2 We constructed a simulation model of koalas interacting with their food supply (manna gum Eucalyptus viminalis) in Mount Eccles National Park, Victoria, Australia. The amount of manna gum leaves consumed changed the survival and fecundity rates of koalas, and the amount of leaves removed changed the survival and transition rates of manna gums. 3 Without fertility control the koala population was predicted to increase to peak abundance within 10–18 years before crashing. The predicted dynamics of manna gum were more variable but abundance increased in most simulations for up to c. 5 years before declining to c. 25% of peak abundance within 20–30 years and then increasing subsequently. The maximum rate of koala population decline was an important determinant of the interaction between koalas and manna gum. 4 The best management strategy that was analysed involved estimating the number of unsterilized females in the population annually and then sterilizing a variable number to maintain a population of 1000 koalas: this strategy generated the least decline in manna gum at a consistently low cost. However, there was a delay between imposing fertility control and consequent reduction in koala abundance because of high adult female survival rates. Hence manna gum was predicted to decline for 5–10 years before increasing. 5 Synthesis and applications. Our results highlight important time-lags between implementing fertility control, reducing the abundance of a herbivore with high survival rates and subsequent changes in the abundance of its food supply. Our model is useful for understanding how controlling ‘overabundant’ herbivores impacts upon the dynamics of both the herbivore and its food supply.

A one-dimensional hydrodynamic reservoir model is coupled with a stochastic fish population model to examine the impacts of cold water pollution (CWP) on the Australian freshwater fish, Murray cod, downstream of Hume Dam, Australia. Mitigation of CWPthroughtheintroductionofselectivewithdrawalcapabilitiestoaccessnear-surfacewaterispredictedtoincreasedischarge temperatures during the crucial spring-early summer post-spawning period by 4‐68C for normal operating conditions, that is, a full reservoir in early spring. No improvement in discharge temperature was predicted for drought conditions characterized by relatively low storage levels in early spring. The predicted temperature increase using selective withdrawal increased the predicted average minimum female population abundance by 30‐300% depending on the assumed spawning behaviour. Increased discharge temperatures appear to be achievable and are expected to reduce the stress currently impacting Murray cod populations due to CWP during crucial post-spawning periods. This provides evidence that mitigation of this problem may assistinrehabilitatingMurraycodpopulationsintheMurrayRiverdownstreamofHumeDam.Copyright#2007JohnWiley& Sons, Ltd.

The effects of cold water releases, as a by-product of storing irrigation water in large dams, has been a source of great concern for its impact on native freshwater fish for some time. The Mitta Mitta River, northeast Victoria, is impacted by altered thermal regimes downstream of the fourth largest dam in Australia, Dartmouth dam, with some daily temperatures 10–12°C below normal. Murray cod (Maccullochella peelii peelii) were endemic to the Mitta Mitta River; however, resident Murray cod have not been found in this river since 1992. The response of eggs and hatched larvae from Murray cod to different temperature gradients of water were measured and the post-spawning survival recorded. As a case study, post-spawning survival was then inferred from flow data for each year of operation of Dartmouth Dam, recorded since first operation in 1978, and included in a stochastic population model to explore the impact of the altered (historical) thermal regime on population viability. Experimental results revealed no egg and larval survival below 13°C and predicted historical temperature regimes point to more than 15 years of low temperatures in the Mitta Mitta River. Population modelling indicates that the impact of cold water releases on post-spawning survival is a significant threatening process to the viability of a Murray cod population. Additionally, we consider changes to the thermal regime to explore how the thermal impact of large dams may be minimized on downstream fish populations through incrementally increasing the temperature of the releases. The modelled Murray cod population responds to minor increases in the thermal regime; however, threats are not completely removed until an increase of at least 5–6°C. Copyright © 2005 John Wiley & Sons, Ltd.

A stochastic population model has been developed for exploring the conservation management of the endangered fish trout cod (Maccullochella macquariensis) in the circumstances of incomplete understanding of the ecology of the species as well as the absence of appropriate data for the estimation of some vital rates. The model includes a stage-structured approach with environmental and demographic variation, and examines three types of density dependence: Beverton–Holt, Ricker and a biomass approach that we have developed to incorporate intraspecific competition beyond recruitment to 1-year olds. The stochastic model was used to explore the current and future status of the protected and last self-sustaining natural population of trout cod, restricted to a 200 km section of the Murray River in south-eastern Australia, under the different density-dependent mechanisms. Current practices for reintroducing trout cod were also evaluated. The analysis indicates that the protected natural population may be stable provided that it remains free from any significant disturbance. However, the analysis also indicates that trout cod may be very sensitive to any reduction in adult survival and remain potentially vulnerable to continued anthropogenic disturbance, in particular fishing. The analysis also indicates that the current practice of releasing fingerlings to establish a reintroduced population was more likely to fail than releasing on-grown 1-year-old fish at reintroduction sites. Furthermore, the traditional density-dependent mechanisms have less support than the applied biomass approach. The stochastic population model developed becomes a resource for guiding the conservation management and further research into the ecology of trout cod.

As part of an ongoing program of management for a critically endangered fish, we explored adaptive management as a method to overcome pervasive uncertainty regarding the reintroduction of trout cod (Maccullochella macquariensis Cuvier). We simulated the entire adaptive management cycle to explore the suitability of the approach for guiding threatened species management and to identify problems and barriers to "learning by doing". During the planning phase, a number of compromises were identified between specification of goals and objectives, the available management options, and current monitoring capacity. Undertaking a simulation of the implementation of alternate adaptive approaches to this reintroduction provided a number of insights into adaptive management in general. First, identifying the weak link in the process of inference emphasized the need to consider whether goals and objectives are achievable and meaningful and whether they complement monitoring and (or) any other limitations of the system. Second, in natural resource management, it is crucial to negotiate objectives in the light of what one can measure. Third, although there are lessons to be learned from each stage of the adaptive management cycle, there is value in simulating the entire adaptive management cycle, including management actions, monitoring, and the states of the system that lead to management intervention.

In 1998 the protected population of Perameles gunnii (eastern barred bandicoot) at Woodlands Historic Park, Victoria, Australia became functionally extinct following removals of individuals for translocation between 1994 and 1996. Population viability analysis and data collected whilst the population was in decline are used to explore the impact that these removals had on the decline of the P. gunnii population at Woodlands. Due to some ambiguities in the life history of P. gunnii at Woodlands, two structurally different population models were used. Explicitly including the removal of animals in the analysis indicates that there may be at least a three-fold increase in the risk of quasiextinction due to removals. In some scenarios, over 17% of the trajectories decrease to a level less than or equal to 10 females within the observed time period of the collapse of the population, that is by April 1998. The modelling approach identified a number of critical factors in the decline of the population, such as variation in survival rates. By representing the life history strategy using two alternate models, quantitative statements about the impact that removals had on the population decline at Woodlands are made. While removals probably contributed to the collapse of the population, removals were not the sole cause of population decline. The real reasons for decline remain unknown; however, it is likely to be closely linked to habitat decline, difficult environmental conditions and predation. If P. gunnii are reintroduced to Woodlands again, then the models presented here may help to develop management strategies to establish a self sustaining population, as well as exploring translocations options.

Uncertainty about which model structure best describes the life history of a species may be a problem for the development of some population viability analysis (PVA). This paper describes the development and exploration of two structurally different stochastic population models when there is uncertainty about the life history of a species. Delayed reproduction was observed in a protected population of the small marsupial Perameles gunnii (eastern barred bandicoot) at Woodlands Historic Park, Victoria, Australia. This previously undocumented feature of P. gunnii may be considered to be either a component of the seasonal breeding cycle or it may be delayed development to sexual maturity. A delayed development model is compared to a standard development model where the parameter estimates of each model were obtained from a long-term mark-recapture study at Woodlands Historic Park. While the growth rate of the delayed development model is less than that of the standard model, the predicted risks of extinction/quasiextinction were higher for the standard model. This discrepancy is the result of different interpretations placed upon the available data underpinning the two models, the most important of which is the difference between the estimated variance in survivorship of the sub-adult stage. The results highlight the need for conservation assessments based on stochastic modelling to explore the degree to which the predicted extinction risk is affected by the incomplete knowledge of the species’ basic biology and parameter values.

Crude oil spills from tankers remain a serious threat along coastal California. Resource managers require information on the acute toxicity of treated and untreated oil, and their sublethal effects on wildlife. This investigation compared the toxic actions of the water-accommodated fraction (WAF) and the chemically-enhanced WAF (CEWAF; Corexit 9500) of Prudhoe Bay crude oil in pre-smolt Chinook salmon ( Oncorhynchus tshawytscha ) via nuclear magnetic resonance (NMR)-based metabolomics. Metabolite profiles from muscle samples, after 96 h exposures, were measured using 1D 1 H NMR and compared via principal component analysis. It was determined that both WAF and CEWAF produced similar profiles in which amino acids, lactate and ATP comprised the highest intensity signals. Overall, metabolic substrates and growth measurements did not show residual effects of short-term exposure on long-term development. In conclusion, the 96 h LC 50 s indicate dispersant application significantly decreased hydrocarbon potency and identified metabolites may be bio-indicators of hydrocarbon stress from hydrocarbon exposure.

Context When environmental, economic and/or social effects of wildlife are considered undesirable and need to be reduced, managers require knowledge of the effectiveness of candidate control techniques, particularly the relationship between control effort and change in abundance. Aims We evaluated the effects of control on the abundances of introduced red deer (Cervus elaphus scoticus) and sika deer (Cervus nippon) at three New Zealand forest sites (two North Island, one South Island) in an 8-year adaptive-management experiment. Methods We identified paired areas of 3600 ha at each site that were as similar as possible in geology, physical environments and forest composition and applied deer control (helicopter- and/or ground-based hunting) to a randomly selected member of each pair. The abundances of deer were monitored in each treatment and non-treatment area for up to 7 years by using faecal pellet counts on 50 randomly located transects. Key results The difference between deer abundances in the treatment and non-treatment areas was significantly negative at one site, significantly positive at one site and indistinguishable at the other site. Faecal pellet abundances declined with increasing helicopter-based hunting effort but did not change with increasing ground-based hunting effort. There was evidence that aerially sown 1080 baits used for possum control in two treatment areas reduced deer abundances. Conclusions The substantial uncertainty surrounding the relationships between deer control effort and changes in deer abundance means that managers cannot assume that the environmental, economic and/or social problems caused by deer will be alleviated with the quantum of control effort applied in the present study. Implications Reducing the abundances of deer in forests may require substantially more control effort than is currently believed.

Recovery of threatened species is often necessarily a long-term process. The present paper details the progress towards the recovery of trout cod, Maccullochella macquariensis, an iconic, long-lived fish species first listed as threatened in the 1980s. The objectives, actions and progress over three successive national recovery plans (spanning 18 years) are assessed, documenting changes to population distribution and abundance and updating ecological knowledge. Increased knowledge (especially breeding biology and hatchery techniques, movements, habitats and genetics) has greatly influenced recovery actions and the use of a population model was developed to assist with management options and stocking regimes. Key recovery actions include stocking of hatchery-produced fish to establish new populations, regulations on angling (including closures), education (particularly identification from the closely related Murray cod, M. peelii) and habitat rehabilitation (especially re-instatement of structural woody habitats). In particular, the establishment of new populations using hatchery stocking has been a successful action. The importance of a coordinated long-term approach is emphasised and, although there is uncertainty in ongoing resourcing of the recovery program, much has been achieved and there is cautious optimism for the future of this species.

Internationally, re-introductions of endangered species into their former ranges have largely failed. Here we assess a successful reintroduction program of the endangered trout cod (Maccullochella macquariensis) and examine factors contributing to this success. Stocking of marked fish (all stocked fish were marked) occurred between 1997 and 2006 in the Ovens River, south-eastern Australia, where trout cod were historically abundant but locally extinct by the 1980s. We found no natural recruits (i.e. from spawnings of stocked fish in the wild) over the age of six, indicating that natural recruitment started at most five years after stocking began. Of the 83 fish we examined for sexual maturity, 12 were immature, 20 were male, and 51 were female. The body length at which 50% of the population can be considered mature was 325 and 250 mm for females and males, respectively. The length at which 90% of the population was mature was 394 and 318 mm for females and males, respectively. The smallest mature female was 245 mm. Average relative fertility was 9 eggs g–1 fish weight. The results we obtained provide valuable insights into the aspects contributing to the success of reintroduction programs for endangered freshwater species.