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As a part of the project "Melting at Thwaites grounding zone and its control on sea level" (MELT), we developed a compact 750-MHz ice-penetrating radar for phase-sensitive measurements to infer basal melt and ice layer displacement using multiple passes. The radar operates with 300-MHz bandwidth and a peak output power of 400 W. It is equipped with a small antenna array designed to fit within the limited space underneath the floor of a Twin Otter aircraft (without out-of-mold-line protuberances). The radar was installed and deployed onboard a Twin Otter airplane from the British Antarctic Survey (BAS) as a part of the ongoing International Thwaites Glacier Collaboration (ITGC). We conducted multiple radar survey flights during two consecutive austral summer seasons, collecting ~5 TB of raw data. In this paper, we present an overview of the radar system and antenna implementations. We provide a summary of our field operations and present sample data products to illustrate the instrument capabilities to sound ice as thick as ~1,400 m and map internal reflecting horizons near the grounding line of TG with sub-m vertical resolution. We also discuss the utility of our repeat pass data for inferring ice shelf basal melt rates.

Restoration projects often rely on the assumption that a local intervention will restore diminished populations, without fully understanding the constraints that limit the target species in the first place. In rivers, one common restoration technique is to place large structures, such as wood and boulders, on the bed, with the assumption that fish will subsequently arrive and use them. Nonetheless, providing large habitat structure may not overcome demographic or resource constraints on fish populations, and thus may not aid recovery. We aimed to test if resource constraints (food and cover) are limiting local densities of fishes in a degraded stream by experimentally alleviating these constraints. If the abundance of one or more species is constrained by resource availability, then local numbers of these species should increase following an increase in resources. To test our prediction, we increased the availability of food and microhabitat complexity (cover) at sites in Hughes Creek, a degraded stream in south‐east Australia that has extensive accumulations of sand and limited in‐stream structure. At treatment sites, we hammered pairs of wooden stakes (25 cm apart) into the stream bed so that the ends of stakes protruded just above the water surface at moderate flows. Stakes effectively trapped passing sticks and leaves, which increased local detrital densities and, subsequently, invertebrate densities, hence providing food and cover for fish. Over the course of a year, we compared the changes in fish abundances at treatment sites to unmanipulated control sites. Fish responded quickly to enhanced retention of detritus, with assemblage differences observed between treatment and control sites. We caught more river blackfish (Gadopsis marmoratus), southern pygmy perch (Nannoperca australis), Macquarie perch (Macquaria australasica), and mountain galaxias (Galaxias olidus) at treatment sites on some occasions, indicating that these species may be subject to r

The Western Antarctic Peninsula (WAP) is a rapidly changing region with receding sea-ice cover. This region generally has increased phytoplankton productivity on the continental slope with a decrease observed in off-shelf waters located further northward. This study aims to improve the understanding of the distribution of iron (Fe) in this climatically important oceanic region during early sea-ice retreat, as well as the impact of receding ice cover on Fe concentrations and the importance of Fe and its sources at the beginning of the phytoplankton growth season. Five ocean transects were sampled along the Palmer Long Term Ecological Research (Pal-LTER) grid with an additional oceanward extension to access off-shelf waters during the austral spring (October and November) of 2014. High Fe inputs into the entire water column from ice melt as well as from sediments increased dissolved Fe (DFe) and total dissolvable Fe (TDFe) concentrations across the shelf (off-shelf DFe: 0.38 ± 0.30 nmol/L and TDFe: 2.23 ± 2.95 nmol/L versus shelf DFe: 1.54 ± 1.38 nmol/L and TDFe: 19.47 ± 23.82 nmol/L). The combination of meteoric meltwater and shallow sedimentary sources is strongest over the shelf and increased landward towards the WAP. Additionally, a winter sea-ice formation signature was detected in inner shelf waters that appeared to contribute to DFe concentrations. Relatively warm Circumpolar Deep Water (CDW) that flows onto the shelf through troughs is likely modified by non-reductive sedimentary input of Fe into the water column. The increase in Fe concentrations in WAP waters in early spring could trigger enhanced phytoplankton productivity across the shelf, although the highest productivity levels were observed in off-shelf waters, likely related to improved light conditions following receding sea-ice cover. The relatively high productivity levels in WAP off-shelf waters are presumably caused by two factors: (1) supply from below, and (2) the transport of Fe from the shelf

Movement is a key driver of the distribution of animals and the structure of populations, communities, and ecosystems. Habitat loss and fragmentation can compromise movement and contribute to population declines. However, there is often insufficient knowledge about when, why, and where animals move, particularly in highly modified environments. We present results from an 8‐year study on the movement behavior of Murray cod Maccullochella peelii, an Australian freshwater fish species that has undergone major declines due in part to river flow regulations. We studied movement within and between different habitat types in a highly modified floodplain ecosystem in the lower Murray River to (1) identify the key environmental conditions associated with movement, (2) examine how a new regulating structure can be managed to influence movement behavior, and (3) explore movement mediated recovery following a hypoxic event. Movement within and between an anabranch and main river channel habitats increased during the core spawning period and during elevated discharge. The likelihood of Murray cod moving to an anabranch system from the Murray River declined substantially following construction of a new flow regulating structure (a weir and vertical slot fishway). Managed flows delivered through the anabranch after regulator construction in accordance with targeted recommendations (time‐of‐year and magnitude of discharge) increased the movement of adult fish within and between habitats. Finally, a hypoxic event caused not only high mortality but also resulted in a high proportion of fish migrating outside of the study reach, before returning to the system over several years. These results demonstrate how flow management can help a keystone species access habitats required to complete critical life history requirements including recovery from disturbance events. Importantly, the work provides an example of how timely and robust applied research has informed a major interve

As efforts to restore coastal habitats accelerate, it is critical that investments are targeted to most effectively mitigate and reverse habitat loss and its impacts on biodiversity. One likely but largely overlooked impediment to effective restoration of habitat-forming organisms is failing to explicitly consider non-habitat-forming animals in restoration planning, implementation, and monitoring. These animals can greatly enhance or degrade ecosystem function, persistence, and resilience. Bivalves, for instance, can reduce sulfide stress in seagrass habitats and increase drought tolerance of saltmarsh vegetation, whereas megaherbivores can detrimentally overgraze seagrass or improve seagrass seed germination, depending on the context. Therefore, understanding when, why, and how to directly manipulate or support animals can enhance coastal restoration outcomes. In support of this expanded restoration approach, we provide a conceptual framework, incorporating lessons from structured decision-making, and describe potential actions that could lead to better restoration outcomes using case studies to illustrate practical approaches.

Humans are altering marine ecosystems at unprecedented rates, and these changes can result in animals selecting poor‐quality habitats if the cues they use become misleading. Such “ecological traps” increase extinction risk, reduce ecosystem resilience, and are a consequence of human‐induced rapid environmental change. Although there is growing evidence for traps impacting terrestrial species, the phenomenon has so far received little attention from marine scientists. To explore why so few studies have attempted to identify traps in the ocean, we conducted a literature review of the major drivers of marine environmental change to determine how their impacts on habitat choice and species fitness are being assessed. From this we summarize the current evidence for marine traps, present case studies to show why the phenomenon is potentially common in the ocean, highlight ways to advance awareness and understanding of traps, and demonstrate how this information can help improve management of marine environments.

Anthropogenic alterations to river flow regimes threaten freshwater biodiversity globally, with potentially disproportionate impacts on species that rely on flow cues to trigger critical life history processes, such as migration for diadromous fishes. This study investigates the influence of river discharge on the abundance of juvenile fish moving into rivers by four temperate catadromous or amphidromous species (common galaxias Galaxias maculatus, spotted galaxias Galaxias truttaceus, climbing galaxias Galaxias brevipinnis and the threatened Australian grayling Prototroctes maraena). Fyke netting or fishway trapping was used to catch juvenile fish moving from estuaries into freshwater in five coastal waterways in south-eastern Australia during the spring migratory period. There was a positive relationship between the probability of high catch rates and mean discharge in September. We also found a positive relationship between discharge and the number of recruits captured 22-30 days later in a flow stressed system. In addition, day-of-year had a strong influence on catch rates, with the peak abundance of juveniles for three species most likely to occur midway through the sampling period (spotted galaxias in October, climbing galaxias in late October and Australian grayling in late October and early November). Our study shows that higher magnitudes of river discharge were associated with increased catches of juvenile catadromous and amphidromous fishes. With a limited supply of environmental water, environmental flows used to enhance immigration of these fishes may be best targeted to maintain small amounts of immigration into freshwater populations in waterways or years when discharges are low and stable. When there are natural, large discharge volumes, relatively large numbers of juvenile fish can be expected to enter coastal waterways and during these times environmental flows may not be required to promote immigration.

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. Even rarer are studies that collect this information concurrently from multiple species with contrasting life history strategies in the same system to assess whether population size and the relative importance of drivers also vary. We studied changes in the abundance and size structure of four native freshwater fish species in the Murray River, southeastern Australia, over a continuous 19-yr period. Two species with traits typical of "equilibrium" species (Murray cod Maccullochella peelii and trout cod Maccullochella macquariensis) and two with traits of "periodic" species (golden perch Macquaria ambigua and silver perch Bidyanus bidyanus) were sampled annually and capture-mark-recapture modeling was used to ask (1) how did population size change during this period, (2) how were changes in population size related to variability in hydrology, and (3) how were changes in population size driven by different processes (local recruitment or migration events)? Populations of all four species varied throughout the study, and our results are consistent with the notion that local recruitment is an important driver of this variability for Murray cod and trout cod, whereas immigration is more important for the two other species. Increases in spring river discharge strongly influenced these responses for trout cod and golden perch. Our study provides fundamental insights into the population dynamics of these valued species, and how management strategies might differ based on their life histories. Management should focus on allow

Over half of global rivers and streams lack perennial flow, and understanding the distribution and drivers of their flow regimes is critical for understanding their hydrologic, biogeochemical, and ecological functions. We analyzed nonperennial flow regimes using 540 U.S. Geological Survey watersheds across the contiguous United States from 1979 to 2018. Multivariate analyses revealed regional differences in no‐flow fraction, date of first no flow, and duration of the dry‐down period, with further divergence between natural and human‐altered watersheds. Aridity was a primary driver of no‐flow metrics at the continental scale, while unique combinations of climatic, physiographic and anthropogenic drivers emerged at regional scales. Dry‐down duration showed stronger associations with nonclimate drivers compared to no‐flow fraction and timing. Although the sparse distribution of nonperennial gages limits our understanding of such streams, the watersheds examined here suggest the important role of aridity and land cover change in modulating future stream drying.

Culverts reduce connectivity for aquatic animals by being both a hydraulic and physical barrier. However, altered light intensity may also be a behavioural barrier to fish movement, especially for diurnal species that have adapted to moving when it is light. We propose that knowledge of optical physiology and fish behaviour, two important mechanisms underpinning movement, can inform efforts to improve fish movement through culverts. We firstly review the sensory systems of fish with reference to visual sense and explore how this affects fish movement. We then highlight theoretical knowledge that can help us understand fish behaviour and the potential mismatch between the conditions under which fish have evolved and altered conditions within culverts. We describe potential knowledge gaps and directions for future research to improve our understanding of how culverts may affect fish movement. Finally, we explore the potential costs and ecological benefits of different mitigation options to identify those with the most promise for managing the light environment in culverts to facilitate movement. For researchers and managers exploring this subject, we suggest an approach that: (a) identifies light requirements for movement by different species, (b) tests movement under different light conditions and (c) considers an integrative assessment method for testing fish behaviour around culverts. Understanding how optical physiology, fish behaviour and culvert design influence fish movement can improve connectivity for a range of species.

Restoring degraded habitat to increase biodiversity is a global challenge. While habitat restoration for animals should lead to self‐sustaining breeding populations of target species, often this does not occur. Understanding the factors constraining progress toward this goal and how these constraints can be overcome is vital. We use a review to highlight how insights from animal behavior can help plan restoration projects, and identify and ameliorate some of the reasons why restoration may fail to meet biodiversity goals. We present a decision tree to highlight how behavioral knowledge can identify and address two ways in which restoration can fail when: (1) target animals do not colonize restored sites and (2) they colonize restored sites but experience conditions that do not match their habitat requirements. Investing in the collection of behavioral information may be difficult for management agencies when funding is limited. We highlight when behavioral information is likely to be most important, and some of the practical considerations for its application in restoration projects. We conclude by identifying key knowledge gaps and future directions that can improve restoration outcomes for biodiversity by incorporating behavioral knowledge. Restoration is needed to ameliorate the effects of habitat loss, degradation, and fragmentation on fauna. Unfortunately, restoration does not always lead to the intended optimal outcomes for target animals. A greater consideration of animal behavior and its consequences can help during both the planning and evaluation of restoration projects. We hope to stimulate dialogue between restoration and behavioral ecologists to improve restoration outcomes for animals.

The construction of dams and weirs, and associated changes to hydrological and hydraulic (e.g., water level and velocity) characteristics of rivers is a key environmental threat for fish. These multiple stressors potentially can affect fish in a variety of ways, including by causing changes in their movement, habitat use and activity. Understanding how and why these changes occur can inform management efforts to ameliorate these threats. In this context, we used acoustic telemetry to examine habitat use, longitudinal movement and activity of two lowland river fishes, Murray cod Maccullochella peelii and golden perch Macquaria ambigua, in a weir pool environment in south-eastern Australia. We compared our results to published studies on riverine populations to determine if their behaviours are similar (or not). We show that M. peelii and M. ambigua in a weir pool exhibited some similar behaviours to conspecific riverine populations, such as strong site fidelity and use of woody habitat for M. ambigua. However, some behaviours, such as large-scale (tens-hundreds of kilometres) movements documented for riverine populations, were rarely observed. These differences potentially reflect flow regulation (e.g., stable water levels, loss of hydraulic cues) in the weir pool. The two species also exhibited contrasting responses to dissolved oxygen conditions in the weir pool, which may reflect differences in their life history. Overall, this study shows that although some aspects of these two native fishes' life history can continue despite flow regulation, other aspects may change in weir pools, potentially impacting on long-term population persistence.

Streamflow observations can be used to understand, predict, and contextualize hydrologic, ecological, and biogeochemical processes and conditions in streams. Stream gages are point measurements along rivers where streamflow is measured, and are often used to infer upstream watershed-scale processes. When stream gages read zero, this may indicate that the stream has fully dried; however, zero-flow readings can also be caused by a wide range of other factors. Our ability to identify whether or not a zero-flow gage reading indicates a dry fluvial system has far reaching environmental implications. Incorrect identification and interpretation by the data user can lead to hydrologic, ecological, and/or biogeochemical predictions from models and analyses. Here, we describe several causes of zero-flow gage readings: frozen surface water, flow reversals, instrument error, and natural or human-driven upstream source losses or bypass flow. For these examples, we discuss the implications of zero-flow interpretations. We also highlight additional methodss for determining flow presence, including direct observations, statistical methods, and hydrologic models, which can be applied to interpret causes of zero-flow gage readings and implications for reach- and watershed-scale dynamics. Such efforts are necessary to improve our ability to understand and predict surface flow activation, cessation, and connectivity across river networks. Developing this integrated understanding of the wide range of possible meanings of zero-flows will only attain greater importance in a more variable and changing hydrologic climate.

Removal of instream woody habitat (IWH) is one factor attributed to declines in fish populations worldwide. Restoration of IWH to help fish populations recover is now common; however, quantitative predictions about the outcomes of these interventions is rare. As such, quantitative links between IWH and fish abundance is of interest to managers to inform conservation and restoration activities. Links between instream habitat attributes, especially IWH, and selected fish species of recreational, cultural, and ecological significance were explored at 335 sites spanning eight streams across south‐eastern Australia. Data were collected on fish abundance and length, IWH density and a range of other habitat attributes at a scale that incorporated at least one of each of the major mesohabitat types (functional river elements). The data were analysed using Bayesian hierarchical generalized linear mixed models to examine fish habitat associations and used to make quantitative predictions of responses to future restoration. Strong positive relationships were found between fish abundance and IWH density and the strength of this relationship varied between species and waterways. Murray cod (Maccullochella peelii), a species commonly targeted by IWH interventions, displayed the strongest association with IWH density. River blackfish (Gadopsis marmoratus) also showed a significant relationship with IWH, but this effect was waterway specific. Fish length was only related to IWH for river blackfish. These results may reflect differences in the life histories of these two species. We suggest that differences in habitat association through ontogeny may be more relevant at smaller spatial scales. The results generated in this study can be used to guide waterway restoration and develop quantitative predictions about how fish might respond to IWH interventions across south‐eastern Australia. This approach provides a powerful quantitative framework within which to explore managem

Theory predicts that animals should prefer habitats where their fitness is maximized but some mistakenly select habitats where their fitness is compromised, that is, ecological traps. Understanding why this happens requires knowledge of the habitat selection cues animals use, the habitats they prefer and why, and the fitness costs of habitat selection decisions. We conducted experiments with a freshwater insect, the non-biting midge Chironomus tepperi to ask: (a) whether females respond to potential oviposition cues, (b) to explore whether oviposition is adaptive in relation to metal pollution and conductivity, and (c) whether individuals raised in poor quality sites are more likely to breed in similarly poor locations. We found the following: (a) females responded to some cues, especially conductivity and conspecifics, (b) females preferred sites with higher concentrations of bioavailable metals but suffered no consequences to egg/larval survival, (c) females showed some avoidance of high conductivities, but they still laid eggs resulting in reduced egg hatching, larval survival, and adult emergence, and (d) preferences were independent of natal environment. Our results show that C. tepperi is susceptible to ecological traps, depending on life stage and the relative differences in conductivities among potential oviposition sites. Our results highlight that (a) the fitness outcomes of habitat selection need to be assessed across the life cycle and (b) the relative differences in preference/suitability of habitats need to be considered in ecological trap research. This information can help determine why habitat preferences and their fitness consequences differ among species, which is critical for determining which species are susceptible to ecological traps.

Understanding how animals interact with their environment is a fundamental ecological question with important implications for conservation and management. The relationships between animals and their habitat, however, can be scale-dependent. If ecologists work at suboptimal spatial scales, they will gain an incomplete picture of how animals respond to the landscape. Identifying the scale at which animal-landscape relationships are strongest (the "scale of effect") will improve our ability to better plan management and conservation activities. Several recent studies have greatly enhanced our knowledge about the scale of effect, and the potential drivers of interspecific variability, in particular life-history traits. However, while many marine systems are inherently multiscalar, research into the scale of effect has been mainly focussed on terrestrial taxa. As the scales of observation in fish-habitat association studies are often selected based on convention rather than biological reasoning, they may provide an incomplete picture of the scales where these associations are strongest. We examined fish-habitat associations across four nested spatial scales in a temperate reef system to ask: (a) at what scale are fish-habitat associations the strongest, (b) are habitat elements consistently important across scales, and (c) do scale-dependent fish-habitat associations vary in relation to either body size, geographic range size or trophic level? We found that: (a) the strongest fish-habitat associations were observed when these relationships were examined at considerably larger spatial scales than usually investigated; (b) the importance of environmental predictors varied across spatial scales, indicating that conclusions about the importance of habitat elements will depend on the scales at which studies are undertaken; and (c) scale-dependent fish-habitat associations were consistent across all life-history traits. Our results highlight the importance of considering how

Habitat restoration is vital to ameliorate the effects of anthropogenic disturbances on animal habitats. We reviewed the peer‐reviewed literature to examine where and how habitat restoration is undertaken. Our aim was to identify key knowledge gaps as well as research and monitoring needs that can inform future restoration actions. We found: (1) marine and terrestrial actions focus most commonly on restoring vegetation, and freshwater actions focus on restoring the in‐channel habitat; (2) arthropods are the most common focal group; (3) there is often no collection of pre‐restoration data, so certainty in attributing environmental changes to restoration actions is limited; and (4) population and community measures are most commonly used in monitoring programs, which only show if animals are present at restored sites and not whether they are able to grow, survive, and reproduce. We highlight three important considerations for future restoration actions. First, more integration of knowledge among freshwater, marine, and terrestrial systems will help us to understand how, and why, restoration outcomes might vary in different contexts. Second, where possible, restoration projects should be assessed using before‐after‐control‐impact designs, which will provide the strongest evidence if desired restoration responses occur. Third, if the goal of restoration is to develop self‐sustaining breeding populations of target animals, then measures of fitness (i.e. breeding, survival) should be collected. These recommendations will hopefully help guide more effective restoration practices and monitoring in the future.

Urban sprawl and the rising popularity of water-sensitive urban design of urban landscapes has led to a global surge in the number of wetlands constructed to collect and treat stormwater runoff in cities. However, contaminants, such as heavy metals and pesticides, in stormwater adversely affect the survival, growth, and reproduction of animals inhabiting these wetlands. A key question is whether wildlife can identify and avoid highly polluted wetlands. We investigated whether pond-breeding frogs are attempting to breed in wetlands that affect the fitness of their offspring across 67 urban wetlands in Melbourne, Australia. Frog species richness and the concentration of contaminants (heavy metals and pesticides) were not significantly related, even in the most polluted wetlands. The proportion of fringing vegetation at a wetland had the greatest positive influence on the number of frog species present and the probability of occurrence of individual species, indicating that frogs inhabited wetlands with abundant vegetation, regardless of their pollution status. These wetlands contained contaminant levels similar to urban wetlands around the world at levels that reduce larval amphibian survival. These results are, thus, likely generalizable to other areas, suggesting that urban managers could inadvertently be creating ecological traps in countless cities. Wetlands are important tools for the management of urban stormwater runoff, but their construction should not facilitate declines in wetland-dependent urban wildlife.