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Dam removal is an effective and increasingly applied river restoration strategy. This has led to heightened calls for research and monitoring aimed at understanding physical and ecological outcomes following dam removal. While such research programs have increased, roles of terrestrial fauna in the restoration process remain poorly understood, although wildlife and invertebrate fauna are key components of restored ecosystems. Wildlife play reciprocal roles in restoration: they benefit from restored habitats and their activities affect restoration trajectories. Dam removal exposes substrates on former reservoirs and reconnects river corridors, providing new habitat and food resources for terrestrial fauna. Conversely, many wildlife may influence the river restoration process, with both short-term and long-term consequences for community composition, nutrient transfer, and ecosystem function. We assert that considering terrestrial fauna more directly in river restoration research and planning can enhance restoration outcomes. We illustrate these concepts by describing shortterm patterns and potential future processes expected from the recent removal of two large dams on the Elwha River in Washington State, the largest dam removal effort ever undertaken. We conclude that an ecosystem-level understanding of restoration following dam removal is critical to fully assessing the impacts and benefits of restoration. This includes measuring the roles and responses of terrestrial fauna to these ecologically and culturally significant restoration projects. [ABSTRACT FROM AUTHOR]

Abstract: In many species, males may exhibit alternative life histories to circumvent the costs of intrasexual competition and female courtship. While the evolution and underlying genetic and physiological mechanisms behind alternative reproductive tactics are well studied, there has been less consideration of the ecological factors that regulate their prevalence. Here, we examine six decades of age composition records from thirty‐six populations of sockeye salmon (Oncorhynchus nerka) to quantify associations between spawning habitat characteristics and the prevalence of precocious sneakers known as ‘jacks’. Jack prevalence was independent of neutral genetic structure among stream populations, but varied among habitat types and as a function of continuous geomorphic characteristics. Jacks were more common in streams relative to beaches and rivers, and their prevalence was negatively associated with stream width, depth, elevation, slope and area, but positively related to bank cover. Behavioural observations showed that jacks made greater use of banks, wood and shallows than guard males, indicating that their reproductive success depends on the availability of such refuges. Our results emphasize the role of the physical habitat in shaping reproductive tactic frequencies among populations, likely through local adaptation in response to variable fitness expectations under different geomorphic conditions. [ABSTRACT FROM AUTHOR]

One uncertainty associated with large dam removal is the level of downstream sediment deposition and associated short-term biological effects, particularly on salmonid spawning habitat. Recent studies report downstream sediment deposition following dam removal is influenced by proximity to the source and river transport capacity. The impacts of dam removal sediment releases are difficult to generalize due to the relatively small number of dam removals completed, the variation in release strategies, and the physical nature of systems. Changes to sediment deposition and associated streambed composition in the Elwha River, Washington State, were monitored prior to (2010-2011) and during (2012-2014) the simultaneous removal of two large dams (32 and 64 m). Changes in the surface layer substrate composition during dam removal varied by year and channel type. Riffles in floodplain channels downstream of the dams fined and remained sand dominated throughout the study period, and exceeded levels known to be detrimental to incubating salmonids. Mainstem riffles tended to fine to gravel, but appear to be trending toward cobble after the majority of the sediment was released and transported through system. Thus, salmonid spawning habitats in the mainstem appear to have been minimally impacted while those in floodplain channels appear to have been severely impacted during dam removal. [ABSTRACT FROM AUTHOR]

Growth and movement of juvenile salmonids influence the expression of individual life history traits and production of adults at the population scale. We individually marked and recaptured juvenile Oncorhynchus mykiss over the course of a year in Murderers Creek, a semi-arid tributary to the South Fork John Day River in Northeast Oregon. We tagged O. mykiss in three reaches with differing stream gradient, stream temperature and fish density. Mean growth rates differed significantly among reaches and seasons with a significant interaction between reach and season. Reaches with high growth rates shifted across Murderers Creek among seasons. Stream reaches with high growth during the winter had low growth during summer and vice-versa. The proportion of individuals moving at the reach scale during summer was low (≤2.6%), suggesting that individuals did not track resources at the reach scale. The spatio-temporal variation in growth indicates that monitoring stream salmonids across multiple seasons is necessary to accurately characterise the production of different stream reaches. [ABSTRACT FROM AUTHOR]

The presence of dams, stream-road crossings and other infrastructure often compromises the connectivity of rivers, leading to reduced fish abundance and diversity. The assessment and mitigation of river barriers is critical to the success of restoration efforts aimed at restoring river integrity., In this study, we present a combined modelling approach involving statistical regression methods and mixed integer linear programming to maximize resident fish species richness within a catchment through targeted barrier mitigation. Compared to existing approaches, our proposed method provides enhanced biological realism while avoiding the use of complex and computationally intensive population/ecosystem models., To estimate barrier passability quickly and at low cost, we further outline a rapid barrier assessment methodology. The methodology is used to characterize potential passage barriers for various fish species common to the UK but can be readily adapted to different planning areas and other species of interest., We demonstrate the applicability of our barrier assessment and prioritization approach based on a case study of the River Wey, located in south-east England. We find that significant increases in species richness can be achieved for modest investment in barrier mitigation. In particular, dams and weirs with low passability located on mid- to high-order streams are identified as top priorities for mitigation., Synthesis and applications. Our study shows the benefits of combining a coarse resolution barrier assessment methodology with state-of-the-art optimization modelling to cost-effectively plan fish passage barrier mitigation actions. The modelling approach can help inform on-the-ground river restoration decision-making by providing a recommended course of action that best allocates limited resources in order to restore longitudinal connectivity and maximize ecological gains. [ABSTRACT FROM AUTHOR]

The effects of restoration of impassable road culverts on the distribution of juvenile Atlantic salmon, Salmo salar L., were evaluated in seven small tributaries of the subarctic River Teno system, northernmost Finland/Norway. Restoration enabled the passage of juvenile salmon through the culverts and increased the distribution area of salmon parr in the seven streams by tens or hundreds of metres, depending on the natural slope of the tributary with a total of ≈1 km new area for ascending juveniles. Areas upstream of the culverts were colonised after varying number of years, mostly 2-3, following restoration. Age-1 and age-2 parr were the first salmon age groups entering the new territory after removal of the migration barrier. Although the restoration measures were conducted at the downstream outlet area of the culverts only, the connectivity was improved and increased the production area accessible to juvenile salmon. Such removal of migration barriers and securing habitat connectivity by passable culverts should be taken into account in environmental management strategies of river systems safeguarding the essential habitats of salmonid fish. [ABSTRACT FROM AUTHOR]

Combining landscape demographic and genetics models offers powerful methods for addressing questions for eco-evolutionary applications., Using two illustrative examples, we present Cost-Distance Meta-POPulation, a program to simulate changes in neutral and/or selection-driven genotypes through time as a function of individual-based movement, complex spatial population dynamics, and multiple and changing landscape drivers., Cost-Distance Meta-POPulation provides a novel tool for questions in landscape genetics by incorporating population viability analysis, while linking directly to conservation applications. [ABSTRACT FROM AUTHOR]

In the boreal forests of Canada, industrial development has resulted in the installation of thousands of culverted road crossings that act as barriers to fish movement and degrade habitat for native freshwater fishes. In view of culvert removals being expensive, prioritisation methods have been developed, but the efficacy of such methods has not been thoroughly investigated nor have they been tested on low-gradient boreal forest watersheds containing at-risk salmonids. The management utility of a novel GIS-based optimisation-planning tool to prioritise fish barrier remediation was tested in two highly developed watersheds. Region-specific parameter estimates of monetary variables (e.g. budget, individual barrier remediation costs), barrier passability and biologically relevant information for species on conservation concern (e.g. habitat suitability, dispersal ability) were incorporated. Results indicate that for Arctic grayling, Thymallus arcticus Pallas, and bull trout, Salvelinus confluentus Suckley, a large proportion (~61-83%) of currently isolated habitat can be reconnected with low investment (~$200-$500 K). This study demonstrates the management utility of barrier optimisation methods for use in boreal watersheds, particularly as it significantly reduces the technical expertise needed to perform relatively complex optimisation analyses. [ABSTRACT FROM AUTHOR]

Dams contribute to declines in fish abundance, in part, by blocking access to historical habitat. When fish ladders are infeasible, fish can be trapped below a dam and transported above to provide access to habitat. However, this conservation strategy has received little attention in the literature, and many questions regarding efficacy remain unanswered. Here, we used a genetic parentage approach to evaluate cohort replacement rate (CRR), defined as the number of future spawners produced by a spawner, for a spring Chinook salmon Oncorhynchus tshawytscha trap and transport reintroduction program. We used CRRs to determine if the population can sustain itself in the absence of immigration, which is important when assessing demographic viability. We also evaluated the effects of release locations and dates on the fitness of reintroduced fish. Counts of adult offspring per spawner were used to estimate fitness of salmon reintroduced in 2007 and 2008. We found that fitness decreased slightly as adults were released later in the spawning season in 2007, but not in 2008. Release location did not affect fitness in either year. We also found a seasonal decline in the likelihood that a Chinook salmon collected at the trap and transport facility was produced above the dam. Finally, 2007 and 2008 CRRs were both well below one, indicating that improvements are needed to achieve demographic stability. We demonstrate that genetic monitoring of a reintroduction program helped to inform demographic viability assessments, and suggest that our approach may be broadly applicable to other philopatric species. [ABSTRACT FROM AUTHOR]

Most reviews of stream fish connectivity have highlighted the urgent need for standardized methods to quantify the effects of barriers such as road crossings on fish movement and incorporate the complexity of fish behaviours. A question that has not been fully addressed yet in field assessments of fish stream connectivity is which conditions influence the detectability of road crossing effects. Failure to detect existing road crossing effects can result from shortcomings in sampling design that lead to low statistical power., Here, we propose general barrier dispersal models to allow for asymmetry in barrier permeability and changes in movement behaviours of fish confronting a barrier. Despite the increased realism of these ecological assumptions, it remains to be determined whether asymmetric barriers and altered movement behaviours can be unambiguously detected using mark-recapture trials. We used simulations within a modelling framework that explicitly incorporates barrier and behavioural effects to assess the statistical power of various mark-recapture sampling designs under different combinations of design and ecological constraints., Key insights from our simulations are that (i) the spatial extent of the study reach critically affects detectability of barrier effects; (ii) the number of recaptured individuals that cross a barrier has greater effect on detectability than the total number of recaptures on both sides of the barrier; and (iii) detectability of asymmetry in barrier permeability and of altered movement behaviours increases with both linear fish density and effect size., Synthesis and applications. The proposed dispersal models, incorporating asymmetric barrier permeability and changes in movement behaviours of fish confronting a barrier, are of broad importance in the quantification of habitat connectivity in streams and rivers. Our simulation approach provides precise guidelines for improving the sampling design by adjusting the spatial extent of the study reach based on a priori knowledge of ecological constraints. This study highlights the importance of evaluating the detectability of the effects of barriers such as road crossings and carefully planning the sampling design of mark-recapture studies before conducting costly field trials and provides quantitative tools to help achieve these goals. [ABSTRACT FROM AUTHOR]

Indigenous people are considered to be among the most vulnerable to food insecurity and biodiversity loss. Biodiversity is cited as a key component of indigenous food security; however, quantitative examples of this linkage are limited., We examined how species and population diversity influence the food security of indigenous fisheries for Pacific salmon ( Oncorhynchus species). We compared two dimensions of food security - catch stability (interannual variability) and access (season length) - across a salmon diversity gradient for 21 fisheries on the Fraser River, Canada, over 30 years, using linear regression models. We used population diversity proxies derived from a range of existing measures because population-specific data were unavailable., While both population and species diversity were generally associated with higher catch stability and temporal access, population diversity had a stronger signal. Fisheries with access to high species diversity had up to 1·4 times more stable catch than predicted by the portfolio effect and up to 1·2 times longer fishing seasons than fisheries with access to fewer species. Fisheries with access to high population diversity had up to 3·8 times more stable catch and three times longer seasons than fisheries with access to fewer populations., Catch stability of Chinook Oncorhynchus tshawytscha and sockeye Oncorhynchus nerka fisheries was best explained by the number of populations and conservation units, respectively, that migrate past a fishery en route to spawning grounds. Similar population diversity metrics were important explanatory variables for season length of sockeye, pink Oncorhynchus gorbuscha, coho Oncorhynchus kisutch and chum Oncorhynchus keta fisheries., Synthesis and applications. We show an empirical example of how multiple scales of biodiversity support food security across a large watershed and suggest that protecting fine-scale salmon diversity will help promote food security for indigenous people. The scales of environmental assessments need to match the scales of the socio-ecological processes that will be affected by development. We illustrate that upstream projects that damage salmon habitat could degrade the food security of downstream indigenous fisheries, with implications to Canadian indigenous people and to watersheds around the world where migratory fishes support local fisheries. [ABSTRACT FROM AUTHOR]

Local adaptation to heterogeneous environments generates population diversity within species, significantly increasing ecosystem stability and flows of ecosystem services. However, few studies have isolated the specific mechanisms that create and maintain this diversity. Here, we examined the relationship between water temperature in streams used for spawning and genetic diversity at a gene involved in immune function [the major histocompatibility complex ( MHC)] in 14 populations of sockeye salmon ( Oncorhynchus nerka) sampled across the Wood River basin in south-western Alaska. The largest influence on MHC diversity was lake basin, but we also found a significant positive correlation between average water temperature and MHC diversity. This positive relationship between temperature and MHC diversity appears to have been produced by natural selection at very local scales rather than neutral processes, as no correlation was observed between temperature and genetic diversity at 90 neutral markers. Additionally, no significant relationship was observed between temperature variability and MHC diversity. Although lake basin was the largest driver of differences in MHC diversity, our results also demonstrate that fine-scale differences in water temperature may generate variable selection regimes in populations that spawn in habitats separated by as little as 1 km. Additionally, our results indicated that some populations may be reaching a maximum level of MHC diversity. We postulate that salmon from populations in warm streams may delay spawning until late summer to avoid thermal stress as well as the elevated levels of pathogen prevalence and virulence associated with warm temperatures earlier in the summer. [ABSTRACT FROM AUTHOR]

Seasonal variation in river water levels creates a shifting mosaic of habitat conditions associated with variables such as water temperature, chemistry and prey availability to consumers. Previous work has shown that fishes can exploit spatial variation in water temperature, but less is known about how they respond to shifts in the spatial arrangement of habitat conditions through time., Juvenile coho salmon ( Oncorhynchus kisutch) are the numerically dominant fish species in many southwest Alaskan streams, which exhibit seasonal variation in water level and temperature due to changes in precipitation and snowmelt. We assessed the degree to which juvenile coho salmon exploit the associated shifting mosaic of water temperature by monitoring the spatial distribution of water temperatures and juvenile coho salmon in the lake-influenced reaches of a southwest Alaskan stream. We also monitored the diets of juvenile coho salmon relative to the spatial distribution of prey taxa., Juvenile coho salmon exhibited two scales of movement to track spatiotemporal variation in habitat conditions. First, over the course of 6 weeks, individuals moved among off-channel units, tracking shifts in the location of warm water habitat caused by receding water level. Second, individuals moved at diel time scales, foraging on benthic macroinvertebrates in the cold thalweg of the stream at night and then digesting prey in warmer off-channel habitats during the day., Seasonally asynchronous variation in water temperature among off-channel habitat units produced portfolio effects in habitat conditions, such that coho salmon had continual access to warm habitat for digestion despite its ephemeral availability at discrete locations., Our study demonstrates that behavioural thermoregulation by juvenile fishes can be important throughout the growing season and is not restricted to ephemeral events such as resource pulses or heat stress. Our results have implications for the conservation of highly connected, heterogeneous landscapes, and their ability to support economically and ecologically important species such as coho salmon. [ABSTRACT FROM AUTHOR]

1. In many intermittent, dryland rivers, fish are confined to isolated waterholes for much of the year. It is only during brief flow events, which typify the hydrology of these systems, that fish are able to move between waterholes and explore surrounding habitat. Because most of the river channel will dry afterwards, there is a strong advantage for selection of persistent waterholes. 2. Two hundred and fifteen individual fish of three common large-bodied species were tagged in two isolated waterholes in the Moonie River (Queensland, Australia) over 3 years. Their movements were monitored to identify the flow events that trigger fish movement between waterholes, differences in response among species and size classes and refuge selection preferences. 3. Some individuals of all species moved during flow events and others remained within the same waterhole. There was no clear upstream or downstream preference, and most individuals used a reach of up to 20 km, although some individuals ranged over more than 70 km in only several days. Above a threshold flow of 2 m above commence-to-flow level, timing of flow was more important than magnitude, with most movement occurring in response to the first post-winter flow event, independent of its magnitude and duration. Many of the fish that moved displayed philopatry and subsequently returned to their starting waterhole either by the end of a flow event or on subsequent events, suggesting ability to navigate and a preference for more permanent refuge pools. Maximising survival in a highly variable environment provides a plausible mechanism for maintaining these behaviours. 4. Modifications to both flow regime and hydrological connectivity may reduce movement opportunities for fish in intermittent rivers. Our findings show that fish in intermittent systems use networks of waterholes and that management and conservation strategies should aim to maintain movement opportunities at large spatial scales to preserve population resilience. [ABSTRACT FROM AUTHOR]

1. Intermittent rivers are increasingly viewed as shifting mosaics of lotic (flowing water), lentic (standing water) and terrestrial (dry riverbed) habitats. The diversity, spatial arrangement, temporal turnover and connectivity of these habitats are controlled by the magnitude, frequency, duration and extent of drying and rewetting events, which maintain habitat heterogeneity and control biodiversity and biogeochemical processes in intermittent rivers. 2. We consider intermittent rivers as spatiotemporal landscape mosaics to identify the implications such a view has for empirical and theoretical developments in landscape and river ecology. Using observational data of flow states collected by citizen scientists along 1400 km of river channels in western France, we used landscape metrics and ecologically scaled indices for four hypothetical, aquatic species (two fish and two insects) to describe the dynamics of intermittent river mosaics for five catchments. 3. Dry patches dominated most observation dates but flowing patches had the longest average length and occupied the greatest proportion of channel length. At the start of each summer, catchments were almost entirely composed of flowing patches but lentic and dry patches could represented up to 80% of the catchments as summer progressed. Patch dynamics were typified by high levels of spatiotemporal variability. In contrast, ecologically scaled indices did not vary greatly among catchments within species. The ecologically scaled indices representing small fish were the most affected by habitat fragmentation. 4. Such a landscape perspective could affect understanding of biodiversity patterns and biogeochemical processes in intermittent rivers. We outline the methodological developments required to integrate landscape approaches into intermittent river research, the associated challenges and current limitations in landscape ecology tools and models and the benefits of citizen science data sets. The continued quantification of shifting habitat mosaics in intermittent rivers will provide multiple opportunities to advance river and landscape ecology. [ABSTRACT FROM AUTHOR]

Recruitment variability in many fish populations is postulated to be influenced by climatic and oceanographic variability. However, a mechanistic understanding of the influence of specific variables on recruitment is generally lacking. Feeding ecology is one possible mechanism that more directly links ocean conditions and recruitment. We test this mechanism using juvenile Chinook Salmon ( Oncorhynchus tshawytscha) collected off the west coast of Vancouver Island, British Columbia, Canada, in 2000-2009. Stable isotopes of carbon ( δ13C), an indicator of temperature or primary productivity, and nitrogen ( δ15N), an indicator of trophic position, were taken from muscle tissues of genetically stock-identified salmon. We also collated large-scale climate indices (e.g., Pacific Decadal Oscillation, North Pacific Gyre Oscillation), local climate variables (e.g., sea surface temperature) and copepod community composition across these years. We used a Bayesian network to determine how ocean conditions influenced feeding ecology, and subsequent survival rates. We found that smolt survival of Chinook Salmon is predicted by their δ13C value, but not their δ15N. In turn, large-scale climate variability determined the δ13C values of salmon, thus linking climate to survival through feeding ecology, likely through qualities propagated from the base of the food chain. [ABSTRACT FROM AUTHOR]

Ash flows and flooding associated with wildfires represent important but understudied sources of disturbance for fish populations. Knowledge concerning these disturbances is especially limited for larger streams where warm water species dominate. Fire-related disturbances have been hypothesised to differentially affect native and non-native fishes, although this hypothesis has only been tested for salmonids. The objective of our research was to contrast effects of uncharacteristically large wildfires followed by flooding on metapopulations of native and non-native fishes in the Gila River of southwest New Mexico. Probabilities of occupancy, colonisation and local extinction of fishes were calculated across sites before and during disturbance and were also measured across a broader spatial scale during disturbance to identify potential refuge locations. Occupancy was higher for native fishes than non-natives, but multiple wildfire and flood events increased extinction probabilities of native species. Responses of non-native species to wildfires were mixed; extinction of non-native salmonids increased during disturbance, while extinction of several warm water species remained unchanged or decreased. Several undisturbed sites were poor refugia for natives as they were impacted by non-native piscivores, dewatering, and fragmentation. However, despite exposure to multiple disturbances, sites located in large tributary and valley reaches were consistently occupied by native species, suggesting these habitats provided refugia. We suggest that management actions (forest thinning; prescribed burning) that restore a more natural disturbance regime of small and less severe fires coupled with habitat remediation activities (non-native removal; decreased water withdrawal; improved connectivity) might diminish extinction risk for native fishes exposed to wildfire disturbance. [ABSTRACT FROM AUTHOR]

Adult coho salmon Oncorhynchus kisutch return each autumn to freshwater spawning habitats throughout western North America. The migration coincides with increasing seasonal rainfall, which in turn increases storm water run-off, particularly in urban watersheds with extensive impervious land cover. Previous field assessments in urban stream networks have shown that adult coho are dying prematurely at high rates (>50%). Despite significant management concerns for the long-term conservation of threatened wild coho populations, a causal role for toxic run-off in the mortality syndrome has not been demonstrated., We exposed otherwise healthy coho spawners to: (i) artificial storm water containing mixtures of metals and petroleum hydrocarbons, at or above concentrations previously measured in urban run-off; (ii) undiluted storm water collected from a high traffic volume urban arterial road (i.e. highway run-off); and (iii) highway run-off that was first pre-treated via bioinfiltration through experimental soil columns to remove pollutants., We find that mixtures of metals and petroleum hydrocarbons - conventional toxic constituents in urban storm water - are not sufficient to cause the spawner mortality syndrome. By contrast, untreated highway run-off collected during nine distinct storm events was universally lethal to adult coho relative to unexposed controls. Lastly, the mortality syndrome was prevented when highway run-off was pretreated by soil infiltration, a conventional green storm water infrastructure technology., Our results are the first direct evidence that: (i) toxic run-off is killing adult coho in urban watersheds, and (ii) inexpensive mitigation measures can improve water quality and promote salmon survival., Synthesis and applications. Coho salmon, an iconic species with exceptional economic and cultural significance, are an ecological sentinel for the harmful effects of untreated urban run-off. Wild coho populations cannot withstand the high rates of mortality that are now regularly occurring in urban spawning habitats. Green storm water infrastructure or similar pollution prevention methods should be incorporated to the maximal extent practicable, at the watershed scale, for all future development and redevelopment projects, particularly those involving transportation infrastructure. [ABSTRACT FROM AUTHOR]

The dispersal ecology of most stream fishes is poorly characterised, complicating conservation efforts for these species. We used microsatellite DNA marker data to characterise dispersal patterns and effective population size ( N e) for a population of Roanoke logperch Percina rex, an endangered darter ( Percidae). Juveniles and candidate parents were sampled for 2 years at sites throughout the Roanoke River watershed. Dispersal was inferred via genetic assignment tests ( ATs), pedigree reconstruction ( PR) and estimation of lifetime dispersal distance under a genetic isolation-by-distance model. Estimates of N e varied from 105 to 1218 individuals, depending on the estimation method. Based on PR, polygamy was frequent in parents of both sexes, with individuals spawning with an average of 2.4 mates. The sample contained 61 half-sibling pairs, but only one parent-offspring pair and no full-sib pairs, which limited our ability to discriminate natal dispersal of juveniles from breeding dispersal of their parents between spawning events. Nonetheless, all methods indicated extensive dispersal. The AT indicated unrestricted dispersal among sites ≤15 km apart, while siblings inferred by the PR were captured an average of 14 km and up to 55 km apart. Model-based estimates of median lifetime dispersal distance (6-24 km, depending on assumptions) bracketed AT and PR estimates, indicating that widely dispersed individuals do, on average, contribute to gene flow. Extensive dispersal of P. rex suggests that darters and other small benthic stream fishes may be unexpectedly mobile. Monitoring and management activities for such populations should encompass entire watersheds to fully capture population dynamics. [ABSTRACT FROM AUTHOR]

Climate change is expected to alter the occurrence of extreme climatic events, including major floods. Future shifts in the frequency and intensity of extreme floods will vary by region and could modify the geomorphological character of riverine habitat., The geomorphological structure of rivers determines the quality and quantity of habitat available for resident biota, and thus, changes to morphology from more extreme floods are likely to affect river ecology over and above the direct effects of the flood events themselves., Extreme floods can exacerbate the effect of multiple anthropogenic stressors, with potentially dramatic effects on freshwater ecosystems. For instance, high flows mobilise nutrients, sediment and toxic chemicals, and aid dispersal of invasive species, whereas land-use change and channelisation impair flood refugia and constrain recolonisation pathways., Extreme floods may also benefit riverine and riparian biota, overwhelming current anthropogenic constraints and infrastructure to increase habitat complexity and floodplain area., Management to protect human life and infrastructure from severe river flooding can alter channel geomorphology, habitat quality and ecology. However, flood prevention engineering that incorporates the natural form of rivers could potentially mitigate anthropogenic flood damage, in turn restoring habitat and historical ecosystem functioning., We examine potential changes in river channel and floodplain geomorphological characteristics resulting from altered extreme flooding regimes and consider likely implications for the management of the world's freshwater biota. [ABSTRACT FROM AUTHOR]

Extreme hydrological events (floods, droughts) in flowing waters can alter habitat availability and structure and produce significant shifts in biodiversity, species assemblages and ecosystem processes., Extreme floods and droughts occur over large spatial extents and can greatly alter links between streams and their catchments. The nature and strengths of these links differ between degraded and intact streams and their catchments, strongly influencing the responses to and recovery from extreme events. It is essential that these catchment-stream linkages be identified and considered when planning stream restoration., Despite the scarcity of comprehensive, long-term monitoring of most stream restoration projects, our understanding of the influence of extreme events on running waters suggests both positive and negative impacts on restoration efforts. Extreme hydrological events can impair stream restoration efforts giving rise to delays or complete failures in achieving restoration objectives. Alternatively, extreme floods may facilitate progress towards restoration goals by engendering key ecological processes., Understanding the impacts and the temporal-spatial scales over which extreme events alter the ecological structure and function of streams (in both natural and damaged systems), as well as their underlying mechanisms, is a challenge for stream restorers that will only progress with the accumulation of long-term data. Restorers should recognise and plan for hydrological extreme events and their interactions with other disturbances (e.g. fire, urban development). Increasing connectivity of restoration efforts along with their spatial extent can lessen the negative effects of extreme hydrological events on stream restoration., Successful ecological stream restoration requires long time spans and thus with a changing climate the prediction of more frequent and intense extreme events only strengthens the need to incorporate their likelihood into restoration planning and implementation. [ABSTRACT FROM AUTHOR]

Stocking is an important management tool for enhancing fisheries resources, but its actual contribution to fisheries resources is controversial, taking into consideration both the positive and negative effects. This study compared density and biomass of hatchery (otolith thermal marked) and wild masu salmon parr between stocked and unstocked rivers to evaluate the contribution of stocking with hatchery-reared fish. Density and biomass of all fish did not differ between stocked and unstocked rivers. Moreover, density and biomass of wild fish in the stocked rivers were lower than those of the unstocked rivers. Density and biomass of hatchery fish in a non-natural reproducing river were similar with those of all fish in natural reproducing rivers. These results indicate that hatchery stocking does not have positive effects on population density or biomass but replaces wild fish with hatchery fish and that non-natural reproducing areas are more suitable as stocking sites. [ABSTRACT FROM AUTHOR]

We compared the assemblage structure, spatial distributions, and habitat associations of mountain whitefish ( Prosopium williamsoni) morphotypes and size classes. We hypothesised that morphotypes would have different spatial distributions and would be associated with different habitat features based on feeding behaviour and diet. Spatially continuous sampling was conducted over a broad extent (29 km) in the Calawah River, WA ( USA). Whitefish were enumerated via snorkelling in three size classes: small (10-29 cm), medium (30-49 cm), and large (≥50 cm). We identified morphotypes based on head and snout morphology: a pinocchio form that had an elongated snout and a normal form with a blunted snout. Large size classes of both morphotypes were distributed downstream of small and medium size classes, and normal whitefish were distributed downstream of pinocchio whitefish. Ordination of whitefish assemblages with nonmetric multidimensional scaling revealed that normal whitefish size classes were associated with higher gradient and depth, whereas pinocchio whitefish size classes were positively associated with pool area, distance upstream, and depth. Reach-scale generalised additive models indicated that normal whitefish relative density was associated with larger substrate size in downstream reaches ( R2 = 0.64), and pinocchio whitefish were associated with greater stream depth in the reaches farther upstream ( R2 = 0.87). These results suggest broad-scale spatial segregation (1-10 km), particularly between larger and more phenotypically extreme individuals. These results provide the first perspective on spatial distributions and habitat relationships of polymorphic mountain whitefish. [ABSTRACT FROM AUTHOR]

While there is an increasing emphasis in terrestrial ecology on determining the influence of the area that surrounds habitat patches (the landscape 'matrix') relative to the characteristics of the patches themselves, research on these aspects in running waters is still rather underrepresented., Here we outline conceptual foundations of matrix ecology for stream and river ecosystems ('riverscapes'). We discuss how a hierarchical, patch-based perspective is necessary for the delineation of habitat patches and the surrounding matrix, through which we may identify two classes of habitat edges in riverscapes (i.e. edges between the terrestrial-aquatic interface and edges within streams)., Under this conceptual framework, we discuss the role of the matrix in influencing between-patch movement, and resource quality and quantity within and among habitat patches in riverscapes. We also review types of empirical and modelling approaches which may advance our understanding of fragmentation effects in these systems., We identify five key challenges for understanding fragmentation and matrix effects more completely: (i) defining populations and their status (i.e. quantifying the demographic contribution of habitat patches to metapopulation dynamics), (ii) scaling from metapopulations to metacommunities (particularly searching for generalities in species responses to landscape heterogeneity), (iii) scaling from metacommunities to metaecosystems (i.e. exploring the interactive role of the terrestrial-aquatic and within-stream matrix effects on the flow of material and energy at the network scale), (iv) understanding temporal dynamics in matrix permeability and (v) revealing the utility of different patch and matrix representations for modelling connectivity relationships., Fragmentation of habitats is a critical issue in the conservation and management of stream networks across spatial scales. Although the effects of individual barriers (e.g. dams) are well documented, we argue that a more comprehensive patch-matrix landscape model will improve our understanding of fragmentation effects and improve management in riverscapes. [ABSTRACT FROM AUTHOR]

Aim To review existing literature on the ability of waterbirds to spread aquatic alien and invasive species, and to assess the relevance of bird-mediated dispersal for the conservation of freshwater ecosystems. Location Global. Methods Literature Review. Results A systematic review of the literature revealed that quantitative studies investigating dispersal of alien organisms by waterbirds are rare ( n = 14). Most studies citing waterbird dispersal rely on anecdotes or inferences from morphological dispersal syndromes. However, evidence from each stage of dispersal (i.e. emigration, transport and immigration) shows that waterbirds can carry alien plants and invertebrates internally and externally; transport them between water bodies at a variety of spatial scales; and deposit viable propagules in sites suited to aquatic invasive species. Main conclusions Our review suggests that waterbirds can and do act as important dispersal vectors for freshwater invasive species. Further experimental and field based research on the numbers and viability of moved alien propagules, and the roles of different species in the bird community, is needed. Furthermore, consideration of the spatially explicit manner in which birds move is imperative to understanding invasive spread. Populations of alien aquatic species in seemingly isolated wetlands can no longer be considered contained if they are able to be spread through waterbird-mediated dispersal, and containment measures must recognize such opportunities for further spread. Changing waterbird movement patterns, driven by climate and land use change, further add to the challenge of managing invasive species and offers an interesting opportunity for future research. The study of waterbird-mediated dispersal of aquatic alien invasive species provides insights not only into species invasions, but more generally into movement ecology, population ecology and biogeography. [ABSTRACT FROM AUTHOR]

The reintroduction of beaver ( Castor canadensis) into arid and semi-arid rivers is receiving increasing management and conservation attention in recent years, yet very little is known about native versus non-native fish occupancy in beaver pond habitats. Streams of the American Southwest support a highly endemic, highly endangered native fish fauna and abundant non-native fishes, and here we investigated the hypothesis that beaver ponds in this region may lead to fish assemblages dominated by non-native species that favour slower-water habitat. We sampled fish assemblages within beaver ponds and within unimpounded lotic stream reaches in the mainstem and in tributaries of the free-flowing upper Verde River, Arizona, USA. Non-native fishes consistently outnumbered native species, and this dominance was greater in pond than in lotic assemblages. Few native species were recorded within ponds. Multivariate analysis indicated that fish assemblages in beaver ponds were distinct from those in lotic reaches, in both mainstem and tributary locations. Individual species driving this distinction included abundant non-native green sunfish ( Lepomis cyanellus) and western mosquitofish ( Gambusia affinis) in pond sites, and native desert sucker ( Catostomus clarkii) in lotic sites. Overall, this study provides the first evidence that, relative to unimpounded lotic habitat, beaver ponds in arid and semi-arid rivers support abundant non-native fishes; these ponds could thus serve as important non-native source areas and negatively impact co-occurring native fish populations. [ABSTRACT FROM AUTHOR]

This study evaluated the importance of the environment and spatial distribution of juvenile fish for the adoption of alternative migratory tactics in a partially anadromous population of rainbow trout ( Oncorhynchus mykiss) from the Santa Cruz River. We captured young-of-the-year fish along the river during autumn 2009, 2010 and spring 2010 and determined their maternal origin (anadromous vs. resident) using strontium to calcium ratios in the otolith core. Relative proportion of anadromous offspring, modelled with logistic regression, increased towards headwaters and in areas with deeper channels and larger substrate composition. Body length, modelled with linear multiple regression, varied positively with site depth, water velocity, substrate size and anadromous maternal origin. Based on evidence for limited juvenile movements (<25 km), the spatial extent of this study (240 Rkm) and the identification of large, contrasting reaches along the river, it is likely that the observed spatial distribution of juveniles and their association to sites with coarse substrate composition reflects maternal spawning activity. Results further indicate that anadromous females breed predominantly in middle and upper river sections in areas with coarse substrate. Given that body size in this system has been positively related to propensity for anadromy, we propose that female spawning choice affects their offspring's spatial distribution, providing the adequate physical template for anadromous offspring to reach or maintain larger body sizes and display anadromy themselves. Relevance of this study is also discussed in the context of alterations in response to future dam construction in one of the latest free-flowing rivers sustaining anadromous O. mykiss. [ABSTRACT FROM AUTHOR]

Data-rich restoration experiments offer opportunities to test the ability of bioassessment tools, such as those currently used to assess the 'ecological status' of waterbodies targeted by the European Water Framework Directive, to detect observed ecological changes., Minimum flow increases in four regulated reaches of the French Rhône River modified the invertebrate and fish communities in a predictable way, as detailed in other articles of this Special Issue. We tested the ability of several fish and macroinvertebrate metrics currently used in bioassessment to detect these changes. In addition, we considered changes in metrics that are expected to respond specifically to flow increase. These metrics were related to the habitat requirements of species, the ecological specialisation of communities and the abundance of macroinvertebrate functional groups (seen as surrogates for ecosystem attributes)., For invertebrate communities, bioassessment metrics based on richness had equivocal responses to restoration and the Potamon-Type Index demonstrated no or contradictory responses to restoration. The French biotic index was not sensitive to restoration and instead depicted spatial differences in biological quality. For fish communities, the French fish index was marginally sensitive in the reach with the largest minimum flow increase and some of its metrics were sensitive in other reaches., Contrasting with commonly used bioassessment indices and metrics, several metrics related to habitat requirements appropriately indicated the observed changes in community structure. Large flow changes increased the proportion of fish and macroinvertebrate individuals with preferences for midstream habitats, fast currents, deep waters and/or coarse substrates. However, these changes did not translate into the expected increase in ecological specialisation. In addition, functional metrics indicated that restoration led to higher proportions of grazers and higher availability of suspended food for filtering collectors, suggesting a return to the ecological conditions of a large river., The mixed and potentially contradictory responses of the different metrics confirm the difficulty of establishing benchmarks for ecological indicators in large-regulated rivers and the need to design appropriate bioassessment metrics. [ABSTRACT FROM AUTHOR]

The downstream movement of coho salmon fry and parr in the fall, as distinct from the spring migration of smolts, has been well documented across the range of the species. In many cases, these fish overwinter in freshwater, but they sometimes enter marine waters. It has long been assumed that these latter fish did not survive to return as adults and were 'surplus' to the stream's carrying capacity. From 2004 to 2010, we passive integrated transponder tagged 25,981 juvenile coho salmon in three streams in Washington State to determine their movement, survival and the contribution of various juvenile life histories to the adult escapement. We detected 86 returning adults, of which 32 originated from fall/winter migrants. Half of these fall/winter migrants spent ~1 year in the marine environment, while the other half spent ~2 years. In addition, the median return date for fall/winter migrants was 16 days later than spring migrants. Our results indicated that traditional methods of spring-only smolt enumeration may underestimate juvenile survival and total smolt production, and also overestimate spring smolt-to-adult return ( SAR). These are important considerations for coho salmon life cycle models that assume juvenile coho salmon have a fixed life history or use traditional parr-to-smolt and SAR rates. [ABSTRACT FROM AUTHOR]

An extensive body of theory suggests that density-dependent habitat selection drives many fundamental ecological processes. The ideal free distribution and the ideal despotic distribution make contrasting predictions about the effect of total population size on relative abundances among habitats. Empirical assessment of these habitat selection models is uncommon because data must be collected over large temporal and spatial scales., I ask whether fluctuation in Chinook salmon ( Oncorhynchus tshawytscha) spawner population size through time leads to different relative densities over space., Twenty-six years of monitoring data on spawning Chinook salmon across the entire coast of Oregon, USA, were used to evaluate models that make contrasting statements about the interactions of a latent population abundance parameter with physical habitat characteristics., There is strong information-theoretic support for models that include terms that allow the spatial variation in density to change as population size changes through time. Analysis of the best model reveals nonlinear isodars, which suggests a 'despotic' or 'preemptive' distribution of individuals across habitats, indicating that dominant or early-arriving individuals exclude others from breeding sites., This finding has implications for genetic dynamics, population dynamics and conservation metrics of these highly valued fish. The novel application of modelling techniques used here to assess mechanisms of habitat selection from observational data can be used in the emerging field of eco-evolutionary dynamics. [ABSTRACT FROM AUTHOR]

Reservoirs are important for various purposes including flood control, water supply, power generation, and recreation. The aging of America's reservoirs and progressive loss of water storage capacity resulting from ongoing sedimentation, coupled with increasing societal needs, will cause the social, economic, environmental, and political importance of reservoirs to continually increase. The short- and medium-term (<50 years) environmental consequences of reservoir construction and operation are well known and include an altered flow regime, lost connectivity (longitudinal, floodplain), an altered sediment regime, substrate compositional change, and downstream channel degradation. In general, reservoir-related changes have had adverse consequences for the natural ecosystem. Longer term (>50 years) environmental changes as reservoirs enter 'old' age are less understood. Additional research is needed to help guide the future management of aging reservoir systems and support the difficult decisions that will have to be made. Important research directions include assessment of climate change effects on aging and determination of ecosystem response to ongoing aging and various management actions that may be taken with the intent of minimizing or reversing the physical effects of aging. [ABSTRACT FROM AUTHOR]

The inland fisheries of North America (i.e. Canada and the United States of America) are diverse in terms of the sectors that harvest fish, the waters fished and the species targeted. Aboriginal fisheries have a long tradition of harvesting fish for food and ceremonial purposes using gears such as dip nets and spears, and targeting species such as suckers ( Catostomidae) and upriver migrating salmon ( Salmonidae). The commercial sector includes large-scale industrial operations on the Great Lakes and Mississippi River as well as smaller-scale fisheries throughout North America that harvest fish for food or the bait industry. The recreational fishery is the largest sector (millions of participants) and includes everything from specialised catch-and-release fisheries for muskellunge, Esox masquinongy Mitchill and black bass ( Micropterus spp.) to put-and-take fisheries for rainbow trout, Oncorhynchus mykiss ( Walbaum). All sectors provide substantial socio-economic benefit and regionally can have significant cultural value and yield an important amount of food protein. Using the best available information and a number of assumptions, total harvest for all three sectors in the inland waters of North America was estimated to be >480 000 t yr−1. Nonetheless, there are a number of internal threats that face these fisheries including over-exploitation, bycatch/release mortality as well as external threats such as inter-sectoral conflict, environmental change, water availability, invasive species and habitat alteration. Given that most inland fisheries are managed at the state/provincial level, there is a need to adopt management strategies that are holistic, coordinated and trans-jurisdictional if inland fisheries in North America are to be sustainable in the future. There is also a critical need for information management systems that enable regional data to be scaled up to the national or continental level, which would facilitate the generation of inland fisheries status reports and the monitoring of trends through time. All stakeholders must recognise that while inland fisheries tend to not receive the same attention from the media, public or politicians as marine fisheries, the potential for local and broad-scale irreversible changes exist and need to be identified and addressed if the many ecosystem services that inland fisheries provide are to be maintained. [ABSTRACT FROM AUTHOR]

Aim Our goal was to predict road culvert passability, as defined by culvert outlet drop and outlet water velocity, for three fish swimming groups using remotely collected environmental variables that have been shown to influence the passability of road culverts. Locatio Laurentian Great Lakes Basin, north-eastern North America, on the Canada- USA border. Methods We generated four boosted regression tree models, one for road culvert outlet drop and one each for the three culvert outlet water velocities, and predicted the probability of impassable road culverts on low-order streams (Strahler 1-4) based on the models. Independent variables in the models included the upstream area draining to the culvert, slope at the culvert, stream segment gradient and stream reach gradient. Results Gradient of the stream segment was the most important predictor in the outlet drop model, while upstream drainage area was the most important predictor in the three water velocity models. A majority of road culverts on low-order streams are estimated to be passable even for weaker swimming fishes. Moderate to highly impassable road culverts are distributed across many low-order streams throughout the basin, but particular regions are predicted to have higher densities than others due to topography. Main conclusions Predicted passability of road culverts by migratory fish is related to natural gradients in topography and stream size. While the probability of any particular culvert being impassable is low, the vast number of culverts in the basin means that, together, they could pose a greater challenge to migratory fish than dams. Our modelling framework could be used in any region where culverts are prevalent in the riverscape. The resulting estimates of passability to fishes can guide surveys towards the most problematic hydrological regions and structures and contribute to broad-scale prioritization of barrier removals to restore ecological connectivity. [ABSTRACT FROM AUTHOR]

Quantifying the variability in the delivery of ecosystem services across the landscape can be used to set appropriate management targets, evaluate resilience and target conservation efforts. Ecosystem functions and services may exhibit portfolio-type dynamics, whereby diversity within lower levels promotes stability at more aggregated levels. Portfolio theory provides a framework to characterize the relative performance among ecosystems and the processes that drive differences in performance., We assessed Pacific salmon Oncorhynchus spp. portfolio performance across their native latitudinal range focusing on the reliability of salmon returns as a metric with which to assess the function of salmon ecosystems and their services to humans., We used the Sharpe ratio (e.g. the size of the total salmon return to the portfolio relative to its variability (risk)) to evaluate the performance of Chinook and sockeye salmon portfolios across the west coast of North America. We evaluated the effects on portfolio performance from the variance of and covariance among salmon returns within each portfolio, and the association between portfolio performance and watershed attributes., We found a positive latitudinal trend in the risk-adjusted performance of Chinook and sockeye salmon portfolios that also correlated negatively with anthropogenic impact on watersheds (e.g. dams and land-use change). High-latitude Chinook salmon portfolios were on average 2·5 times more reliable, and their portfolio risk was mainly due to low variance in the individual assets. Sockeye salmon portfolios were also more reliable at higher latitudes, but sources of risk varied among the highest performing portfolios., Synthesis and applications. Portfolio theory provides a straightforward method for characterizing the resilience of salmon ecosystems and their services. Natural variability in portfolio performance among undeveloped watersheds provides a benchmark for restoration efforts. Locally and regionally, assessing the sources of portfolio risk can guide actions to maintain existing resilience (protect habitat and disturbance regimes that maintain response diversity; employ harvest strategies sensitive to different portfolio components) or improve restoration activities. Improving our understanding of portfolio reliability may allow for management of natural resources that is robust to ongoing environmental change. [ABSTRACT FROM AUTHOR]

To evaluate the effects of large wood ( LW) on benthic habitats and macroinvertebrates in sand-bed lowland rivers, we compared invertebrate communities recorded on four pieces of LW (12 samples in total) and around them (60 samples) with those in four control sites in the same river (four samples)., Mean flow velocity was 32% lower in the channel areas surrounding the LW than in control sites, while median sediment grain size was 50% higher, and the organic matter content of the riverbed sediments was 287% higher. At the same time, habitat conditions showed threefold to 1000-fold increases in variance for five key abiotic habitat descriptors in the surrounding channel extending at least 60 cm upstream and 160 cm downstream of the LW., Three habitat patches typically occurred around the LW pieces: scouring pools, sand bars and accumulations of organic matter. These patches were colonised by distinctive invertebrate communities (e.g. accumulations of organic matter and gravel hosted 15 and 2 indicator taxa, respectively) that overall harboured 110% more taxa and exhibited a 168% higher diversity than control sites. The LW itself contributed only a small fraction to these increases, exhibiting a 15% increase in taxa richness and a 21% increase in species diversity compared to the control sites., The diversification of benthic invertebrate communities colonising streambed sediments around LW could be directly linked to the much more heterogeneous habitat conditions recorded there. Thus, local additions of large wood within river restoration programmes have the potential to promote the establishment of diverse invertebrate communities in extended areas of a river channel. [ABSTRACT FROM AUTHOR]

Daily movements of mobile organisms between habitats in response to changing trade-offs between predation risk and foraging gains are well established; however, less in known about whether similar tactics are used during reproduction, a time period when many organisms are particularly vulnerable to predators., We investigated the reproductive behaviour of adult sockeye salmon ( Oncorhynchus nerka) and the activity of their principal predator, brown bears ( Ursus arctos), on streams in south-western Alaska. Specifically, we continuously monitored movements of salmon between lake habitat, where salmon are invulnerable to bears, and three small streams, where salmon spawn and are highly vulnerable to bears. We conducted our study across 2 years that offered a distinct contrast in bear activity and predation rates., Diel movements by adult sockeye salmon between stream and lake habitat were observed in 51·3% ± 17·7% (mean ± SD) of individuals among years and sites. Fish that moved tended to hold in the lake for most of the day and then migrated into spawning streams during the night, coincident with when bear activity on streams tended to be lowest. Additionally, cyclic movements between lakes and spawning streams were concentrated earlier in the spawning season., Individuals that exhibited diel movements had longer average reproductive life spans than those who made only one directed movement into a stream. However, the relative effect was dependent on the timing of bear predation, which varied between years. When predation pressure primarily occurred early in the spawning run (i.e., during the height of the diel movements), movers lived 120-310% longer than non-movers. If predation pressure was concentrated later in the spawning run (i.e. when most movements had ceased), movers only lived 10-60% longer., Our results suggest a dynamic trade-off in reproductive strategies of sockeye salmon; adults must be in the stream to reproduce, but must also avoid predation long enough to spawn. Given the interannual variation in the timing and intensity of predation pressure, the advantages of a particular movement strategy will likely vary among years. Regardless, movements by salmon allowed individuals to exploit fine-scale habitat heterogeneity during reproduction, which appears to be a strategy to reduce predation risk on the spawning grounds. [ABSTRACT FROM AUTHOR]

Life-history strategies can buffer individuals and populations from environmental variability. For instance, it is possible that asynchronous dynamics among different life histories can stabilize populations through portfolio effects., Here, we examine life-history diversity and its importance to stability for an iconic migratory fish species. In particular, we examined steelhead ( Oncorhynchus mykiss), an anadromous and iteroparous salmonid, in two large, relatively pristine, watersheds, the Skeena and Nass, in north-western British Columbia, Canada. We synthesized life-history information derived from scales collected from adult steelhead ( N = 7227) in these watersheds across a decade., These migratory fishes expressed 36 different manifestations of the anadromous life-history strategy, with 16 different combinations of freshwater and marine ages, 7·6% of fish performing multiple spawning migrations, and up to a maximum of four spawning migrations per lifetime. Furthermore, in the Nass watershed, various life histories were differently prevalent through time - three different life histories were the most prevalent in a given year, and no life history ever represented more than 45% of the population., These asynchronous dynamics among life histories decreased the variability of numerical abundance and biomass of the aggregated population so that it was > 20% more stable than the stability of the weighted average of specific life histories: evidence of a substantial portfolio effect. Year of ocean entry was a key driver of dynamics; the median correlation coefficient of abundance of life histories that entered the ocean the same year was 2·5 times higher than the median pairwise coefficient of life histories that entered the ocean at different times. Simulations illustrated how different elements of life-history diversity contribute to stability and persistence of populations., This study provides evidence that life-history diversity can dampen fluctuations in population abundances and biomass via portfolio effects. Conserving genetic integrity and habitat diversity in these and other large watersheds can enable a diversity of life histories that increases population and biomass stability in the face of environmental variability. [ABSTRACT FROM AUTHOR]

Restoration is an increasingly central theme in river ecology. Recent studies have highlighted the importance of the species pool in the surrounding river network for determining colonisation of restored river reaches by both invertebrates and fish., Using a comprehensive data set of 21 river restoration sites and 292 sites in the immediate surroundings, we tested the influence of distance to nearest colonist source on invertebrate colonisation based on a comparison of river network distances and Euclidean distances, expecting river network distances would better align with colonisation rates. We then assessed the importance of dispersal distance in relation to several other parameters, such as the number and intensity of barriers along the river network, surrounding taxon pool occupancy rate, physical characteristics of the restored sites and restoration techniques used in determining colonisation of commonly occurring benthic invertebrates., We hypothesised that (i) distance would be critical, with colonisation of restored sites declining with increasing distance; (ii) barriers between these sites would be a minor, but taxon-specific, influence on the colonisation; and (iii) the higher the regional pool occupancy rate of a certain taxon, the higher its probability of presence at a restored site., Overall, taxon pool occupancy rate was the most important driver of colonisation likelihood, followed by distance to nearest source, with the first kilometre particularly important. The effect of barriers was minor but significant, and taxon identity had no effect on the predictive ability of the model. Factors associated with the restoration projects such as techniques used and physical characteristics had minor influences, being completely outweighed by taxon pool and dispersal-related factors., To gauge the likelihood of successful outcomes of habitat restoration projects, we suggest it is important to assess regional taxon pools and ensure distances between healthy populations are minimised. These results clearly emphasise the importance of spatial planning for restoration projects. [ABSTRACT FROM AUTHOR]

For six fish species sampled from 86 lakes on the Arctic Coastal Plain, Alaska, we examined whether lake occupancy was related to variables representing lake size, colonisation potential and/or the presence of overwintering habitat., We found the relative importance of each factor for a given species could be related to its ecology and adult size. The three large-bodied migratory species, least cisco ( Coregonus sardinella), broad whitefish ( Coregonus nasus) and arctic grayling ( Thymallus arcticus), were influenced by factors associated with the likelihood of fish recolonising lakes, including whether the lakes had a stream connection. Of the large-bodied species, least cisco had the highest likelihood of occupancy (0.52 ± 0.05) and models provided evidence that least cisco exhibit both migratory and resident forms., Models for small-bodied fish differed among species, indicating different niches. Ninespine stickleback ( Pungitius pungitius) were the most widespread and ubiquitous of the species captured (occupancy probability = 0.97 ± 0.01); they were captured in lakes that freeze to the bottom, suggesting that they disperse widely and rapidly after the spring freshet, including colonisation of sink habitats. Alaska blackfish ( Dallia pectoralis) had a lower occupancy (occupancy probability = 0.76 ± 0.05) with a distribution that reflected tolerance to harsh conditions. Slimy sculpin ( Cottus cognatus) had an occupancy probability of 0.23 ± 0.06, with a distribution indicating its marine origin., Based on these patterns, we propose an overall model of primary controls on the distribution of fish on the Arctic Coastal Plain of Alaska. Harsh conditions, including lake freezing, limit occupancy in winter through extinction events while lake occupancy in spring and summer is driven by directional migration (large-bodied species) and undirected dispersal (small-bodied species). [ABSTRACT FROM AUTHOR]

Colorado pikeminnow ( Ptychocheilus lucius) has been extirpated from a large portion of its historical range in the Colorado River basin, USA. A repatriation effort via stocking of juvenile P. lucius in the San Juan River, NM, CO and UT has resulted in limited recruitment of individuals into an adult population. Understanding biotic and abiotic factors that limit their persistence in the Colorado River basin will be a critical step in providing for their recovery. To elucidate potential recruitment barriers in the San Juan River, we assessed relationships between the numbers of two age classes of P. lucius and prey, competitors and predators collected at a 1.6 km reach scale between 2003 and 2012. We used an information theoretical approach to rank candidate models testing the relative importance of these biotic conditions in predicting the spatial distribution of P. lucius. We found positive relationships between the numbers of P. lucius ≤200 mm total length (TL) collected and catch per unit effort ( CPUE) of native prey among reaches. For P. lucius >200 mm TL (individuals that are likely completely piscivorous), we found positive associations between the numbers of P. lucius collected and CPUE of total prey and CPUE of potential non-native competitors in each reach. Our data suggest size-specific affinities of P. lucius for native and non-native prey as well as the potential for negative interactions between P. lucius and non-native competitors may contribute to limited recruitment of juvenile P. lucius into an adult population in the San Juan River. [ABSTRACT FROM AUTHOR]

To understand the interplay between habitat use and contemporary anadromous Pacific salmon, Oncorhynchus spp., distributions we explored the habitat associations of three species, pink ( O. gorbuscha), chum ( O. keta) and Chinook salmon ( O. tshawytscha) in streams of the Wood River system of Bristol Bay, Alaska, where sockeye salmon ( O. nerka) are numerically dominant. We developed models to investigate the occurrence of nondominant salmon in relation to habitat characteristics and sockeye salmon density, using four decades of salmon presence and abundance data. The frequency of occurrence and abundance of nondominant species increased with watershed drainage area and stream depth and decreased with sockeye salmon density. The range of occurrence varied from nonexistent to perennial for the other species in sockeye-dominated streams. Increasing watershed area resulted in larger stream habitat area and deeper habitats, allowing for the sympatric occurrence and persistence of all salmon species. The relationships between habitat and the presence of these Pacific salmon help define their requirements but also remind us that the patterns of presence and absence, within the overall ranges of salmon species, have yet to be fully understood. [ABSTRACT FROM AUTHOR]

The umbrella species approach, where conservation actions targeted for one or a group of species should benefit the broader community, may provide an effective framework to guide habitat restoration. This requires congruence in the response of umbrella and co-occurring species to environmental stress and recovery, and the identification of potential mechanisms by which co-occurring species benefit from conservation of an umbrella species., Past evaluations of this approach have considered only the presence/absence of umbrella species. In addition to the presence/absence, we quantified abundance and biomass of both umbrella and co-occurring species to support a more quantitative evaluation of species co-occurrence. Floodplain ponds are restored in British Columbia and the Pacific Northwest to benefit coho salmon Oncorhynchus kisutch, a presumptive umbrella species. To test its effectiveness as an umbrella species, we assessed the relationships between species richness, abundance and biomass of aquatic vertebrates, including vertebrates of conservation concern ('listed'), and benthic invertebrates and the abundance and biomass of juvenile coho. We used ordination to evaluate relationships between species' abundance and biomass and environmental attributes., Positive relationships were identified between coho abundance and biomass and species richness, abundance and biomass of fish and listed species. These relationships were negative for benthic invertebrates. Listed species were located close to coho in ordinations, suggesting they respond to similar environmental features while benthic invertebrates clustered away from coho., Synthesis and applications. We found that where our umbrella species coho is most productive, so are other listed species and fish in general, a relationship that would not have been evident had evaluated species richness alone. We also reported strong relationships between some environmental features manipulated in the habitat restoration and the presence and productivity of coho and co-occurring species. Our study demonstrates the umbrella species approach has potential to guide habitat restoration when there is congruence in the response of umbrella and co-occurring species to environmental attributes that can be manipulated in the restoration. Where this is possible, one can use restoration designed for one or several umbrella species and successfully restore habitats that are viable for other species, including listed species. [ABSTRACT FROM AUTHOR]