First tracking of the oceanic spawning migrations of Australasian short-finned eels (Anguilla australis).

Anguillid eel populations have declined dramatically over the last 50 years in many regions of the world, and numerous species are now under threat. A critical life-history phase is migration from freshwater to distant oceans, culminating in a single life-time spawning event. For many anguillids, especially those in the southern hemisphere, mystery still shrouds their oceanic spawning migrations.

Does life history mediate discharge as a driver of multi-decadal changes in populations of freshwater fish?

Understanding how and why the size of populations varies is critical knowledge for conservation and management. While considerable work has explored how different demographic parameters affect population growth, less is known the drivers of variability in these parameters. Long-term time series tracking population size that are coupled with empirical data to examine the relative importance of different drivers are rare, especially in freshwater systems.

Global COVID-19 lockdown highlights humans as both threats and custodians of the environment.

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence.

Using multiple sources during reintroduction of a locally extinct population benefits survival and reproduction of an endangered freshwater fish.

Through using different sources, population reintroductions can create genetically diverse populations at low risk of harmful inbreeding and well equipped for adaptation to future environments. Genetic variation from one source can mask locally nonoptimal alleles from another, thereby enhancing adaptive potential and population persistence. We assessed the outcomes in survival, growth and reproduction of using two differentiated sources (genetically diverse Yarra and moderately diverse Dartmouth) for translocations and stocking to reintroduce the endangered Australian freshwater Macquarie perch into the Ovens River.

Linking flow attributes to recruitment to inform water management for an Australian freshwater fish with an equilibrium life-history strategy.

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.

Increased population size of fish in a lowland river following restoration of structural habitat.

Most assessments of the effectiveness of river restoration are done at small spatial scales (<10 km) over short time frames (less than three years), potentially failing to capture large-scale mechanisms such as completion of life-history processes, changes to system productivity, or time lags of ecosystem responses. To test the hypothesis that populations of two species of large-bodied, piscivorous, native fishes would increase in response to large-scale structural habitat restoration (reintroduction of 4,450 pieces of coarse woody habitat into a 110-km reach of the Murray River, southeastern Australia), we collected annual catch, effort, length, and tagging data over seven years for Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua) in a restored "intervention" reach and three neighboring "control" reaches. We supplemented mark-recapture data with telemetry and angler phone-in data to assess the potentially confounding influences of movement among sampled populations, heterogeneous detection rates, and population vital rates.

Combining capture-recapture data and known ages allows estimation of age-dependent survival rates.

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.

Spawning-stock characteristics and migration of a lake-bound population of the endangered Macquarie perch Macquaria australasica.

The intrapopulation variability in the size and age structure of the spawning stock and migration of the threatened Macquarie perch Macquaria australasica in Lake Dartmouth was investigated between 2008 and 2016. Sampling centred on the core reproductive period (October-December) when mature fish migrate from the lake into riverine habitat to spawn. Spawning fish were predominantly large, spanning a broad age structure, with a high proportion of fish (25%) aged 15-30 years.

Signatures of polygenic adaptation associated with climate across the range of a threatened fish species with high genetic connectivity.

Adaptive differences across species' ranges can have important implications for population persistence and conservation management decisions. Despite advances in genomic technologies, detecting adaptive variation in natural populations remains challenging. Key challenges in gene-environment association studies involve distinguishing the effects of drift from those of selection and identifying subtle signatures of polygenic adaptation.

Severe consequences of habitat fragmentation on genetic diversity of an endangered Australian freshwater fish: A call for assisted gene flow.

Genetic diversity underpins the ability of populations to persist and adapt to environmental changes. Substantial empirical data show that genetic diversity rapidly deteriorates in small and isolated populations due to genetic drift, leading to reduction in adaptive potential and fitness and increase in inbreeding. Assisted gene flow (e.

A novel approach to spatially assessing instream woody habitat densities across large areas.

Fish habitat restoration efforts frequently involve the reintroduction of instream woody habitat (IWH) in areas where large scale removal has taken place over time. Identifying areas of low IWH density for reintroduction requires a 'current state' spatial representation of the IWH densities that is traditionally a labour intensive and costly exercise. We present a meso-macro scale assessment procedure that incorporates a rapid on-ground field survey method with a novel analytical approach to map IWH densities.