Intraspecific body size determines isotopic trophic structure of a large river fish community.

Food web interactions are generally considered to be size-structured and occur at the individual or group level within species, yet many ecological models and tests of theory assign species-level values to define trophic position or niches. Such studies ignore potential ontogenetic or within-species size-based changes in consumer behaviour and trophic dynamics that can occur as individuals grow. We use stable isotope analysis of δN and δC to explore the effects of body size on fish community trophic structure and niches in one of Australia's largest river basins-the Murray-Darling.

Location of capture sufficiently characterises lifetime growth trajectories in a highly mobile fish.

Variation in somatic growth plays a critical role in determining an individual's body size and the expression of its life history. Understanding the environmental drivers of growth variation in mobile organisms such as fishes can be challenging because an individual's growth expression integrates processes operating at different spatial and temporal scales. Traditionally, otolith (ear stone) based growth analyses have focussed on temporal environmental variation by assuming an individual spends its whole life at its capture location.

Otolith and Genomic Data Reveal Temporal Insights Into Stocking Across a Large River Basin in a Mobile, Long-Lived Australian Freshwater Fish Species.

Freshwater ecosystems and their biota are under increasing pressure from anthropogenic stressors. In response to declining fish stocks, hatchery and stocking programmes are widely implemented as core components of restoration and management strategies, with positive outcomes for some wild populations. Despite this, stocking remains contentious due to potential genetic and ecological risks to wild populations.

Genomic Vulnerability to Climate Change of an Australian Migratory Freshwater Fish, the Golden Perch (Macquaria ambigua).

Genomic vulnerability is a measure of how much evolutionary change is required for a population to maintain optimal genotype-environment associations under projected climates. Aquatic species, and in particular migratory ectotherms, are largely underrepresented in studies of genomic vulnerability. Such species might be well equipped for tracking suitable habitat and spreading diversity that could promote adaptation to future climates.

2019-2020 Bushfire impacts on sediment and contaminant transport following rainfall in the Upper Murray River catchment.

During the 2019-2020 Australian bushfire season, large expanses (~47%) of agricultural and forested land in the Upper Murray River catchment of southeastern (SE) Australia were burned. Storm activity and rainfall following the fires increased sediment loads in rivers, resulting in localized fish kills and widespread water-quality deterioration. We collected water samples from the headwaters of the Murray River for sediment and contaminant analysis and assessed changes in water quality using long-term monitoring data.

Lifetime movement history is associated with variable growth of a potamodromous freshwater fish.

Directional or stabilising selection should drive the expression of a dominant movement phenotype within a population. Widespread persistence of multiple movement phenotypes within wild populations, however, suggests that individuals that move (movers) and those that do not (residents) can have commensurate performance. The costs and benefits of mover and resident phenotypes remain poorly understood.

Stage-dependent effects of river flow and temperature regimes on the growth dynamics of an apex predator.

In the world's rivers, alteration of flow is a major driver of biodiversity decline. Global warming is now affecting the thermal and hydrological regimes of rivers, compounding the threat and complicating conservation planning. To inform management under a non-stationary climate, we must improve our understanding of how flow and thermal regimes interact to affect the population dynamics of riverine biota.

Using a Population Model to Inform the Management of River Flows and Invasive Carp (Cyprinus carpio).

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.