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Models that assess the vulnerability of freshwater species to shifting environmental conditions do not always account for short-duration extremes, which are increasingly common. Life cycle models for Pacific salmon ( Oncorhynchus spp.) generally focus on average conditions that fish experience during each life stage, yet many floods, low flows, and elevated water temperatures only last days to weeks. We developed a process-based life cycle model that links coho salmon ( Oncorhynchus kisutch) abundance to daily streamflow and thermal regimes to assess: (1) “How does salmon abundance respond to short-duration floods, low flows, and high temperatures in glacier-, snow-, and rain-fed streams?” and (2) “How does the temporal resolution of flow and temperature data influence these responses?”. Our simulations indicate that short-duration extremes can reduce salmon abundance in some contexts. However, after daily flow and temperature data were aggregated into weekly and monthly averages, the impact of extreme events on populations declined. Our analysis demonstrates that novel modeling frameworks that capture daily variability in flow and temperature are needed to examine impacts of extreme events on Pacific salmon.

Groundwater upwellings provide warmer, stable overwinter temperatures for developing salmon embryos, which may be particularly important in cold, braided, gravel-bed sub-Arctic rivers. We used a three-year time series of aerial counts and remote sensing to estimate the distribution of low and high aggregations of spawning fall chum salmon (Oncorhynchus keta), classify approximately 0.5 km long river segments by geomorphic channel type, and map thermal variability along a 25.4 km stretch of the Teedriinjik River, Alaska. We used a dynamic multistate occupancy model to estimate detectability, occupancy, and the dynamics of spawning aggregations among river segments. Detectability was higher for large (>150) relative to smaller aggregations. Unoccupied segments were likely to remain so from year to year; low abundance spawning segments were dynamic and rarely remained in that state for multiple years, while ∼20%–35% of high abundance segments remained stable, indicating the presence of high-quality spawning habitat. Spawning habitat use was associated with warmer water temperatures likely caused by groundwater upwellings. We identified spawning habitat characteristics and trends in usage by fall chum salmon, which will inform land management decisions and assist in evaluating impacts of shifting climate conditions and resource management on Arctic salmon populations.

Wildlife viewing within protected areas is an increasingly popular recreational activity. Management agencies are often tasked with providing these opportunities, yet quantitative analyses of factors influencing wildlife sightings are lacking. We analyzed locations of GPS-collared wolves and wolf sightings from 2945 trips in Denali National Park and Preserve, Alaska, USA, to provide a mechanistic understanding of how viewing opportunities are influenced by attributes of wolves and physical, biological, and harvest characteristics. We found that the presence of masking vegetation, den site proximity to the road, pack size, and presence of a wolf harvest closure adjacent to the park affected wolf sightings, and the influence of den proximity on sightings depended on harvest management. Wolf sightings increased with den site proximity to the road in years with a harvest closure adjacent to the park but not in the absence of the closure. The effect of the harvest closure on sightings was similar in magnitude to an increase in pack size by two wolves or a more than a two-fold decrease in masking vegetation. These findings were consistent across a 10-fold change in spatial resolution. Quantitative analysis of the factors influencing wildlife sightings provides valuable insight for agencies tasked with managing viewing opportunities.

One of the risks faced by habitat restoration practitioners is whether habitats included in restoration planning will be used by the target species or, conversely, whether habitats excluded from restoration planning would have benefited the target species. With the goal of providing a quantitative decision-making approach that represented varying levels of risk tolerance, we used multiple probability decision thresholds (PDT) to predict the range of occurrence for three anadromous fishes (Oncorhynchus spp.) in a watershed in southwestern Washington, USA. For each species, we compared the predicted range of occurrence to the distribution used for restoration planning and quantified the amount of habitat blocked by anthropogenic barriers. Coho salmon (O. kisutch) had the broadest predicted range of occurrence (3061.6-6357.9 km; 0.75-0.25 PDT), followed by steelhead trout (O. mykiss; 1828.8-2836.8 km) and chum salmon (O. keta; 1373.9-1629.1 km). For each species, the predicted range of occurrence was similar or greater than the distribution used for restoration planning, suggesting that the current plan may exclude habitats that would benefit each species. Coho salmon had the greatest percentage of habitat blocked by anthropogenic barriers, followed by steelhead trout and chum salmon, respectively. Modeling species distributions at multiple risk-tolerance scenarios acknowledges uncertainty in restoration planning and allows practitioners to weigh the ecological benefits and budgetary constraints when considering locations for restoration. To effectively communicate restoration science to support practitioners in decision-making, we developed an R Shiny application online user interface available at: https://shiny.wdfw-fish.us/ChehalisRiverBasinSalmonidRangeOfOccurence/.

The energetic status of fishes represents energy stored as protein and lipids and reflects the ability of an individual to reproduce, migrate, and transition through life stages, ultimately influencing survival. However, traditional measurement methods, while highly accurate, are time consuming, expensive, and lethal, and nonlethal methods such as condition factor may not adequately characterize energetic status. We collected 161 Arctic grayling (Thymallus arcticus) from four interior Alaska river basins with varying hydrologic regimes during early summer and autumn seasons, and used multiple regression and model selection to evaluate the efficacy of bioelectrical impedance analysis (BIA), a nonlethal condition assessment method, to predict percent dry mass and percent lipid content estimated from proximate analysis. We found that Arctic grayling energetic status varied across seasons, by sex, and fish from sites with spawning runs of Pacific salmon had higher energy content than those from sites without salmon, potentially due to the influence of salmon-derived food subsidies. Electrical measurements explained 82% and 80% of the variability in percent dry mass and percent total lipids, respectively, and top models showed high predictive performance (observed vs. predicted root mean squared error ≤2.2%). Overall, we found the BIA approach to provide rapid, precise, and non-lethal estimates of Arctic grayling body condition. Such an approach may be useful for future work to characterize Arctic grayling bioenergetics and monitor fish condition under a rapidly changing Arctic environment.

Poor growth and survival in freshwater and marine environments have been implicated as responsible for Chinook salmon (Oncorhynchus tshawytscha) declines across Alaska. Lateral connectivity of river main stems with off‐channel habitats may play an integral role in sustaining Alaskan salmonid populations because off‐channel habitats commonly provide greater growth opportunities than main stem habitats through greater macroinvertebrate productivity and warmer water temperatures. However, off‐channel habitats may impose greater mortality risks to juvenile salmonids, as these habitats are typically more susceptible to drying and are often occupied by potential predators. We used a hierarchical Bayesian count model to describe juvenile Chinook salmon distributions throughout the Chena River, Alaska in main stem and off‐channel habitats and employed diet, prey availability, and bioenergetic analyses to explain these habitat selection decisions from data collected in the summer of 2015. We found salmon to be most abundant in off‐channel habitats as summer temperature increased, which suggested that salmon dispersed to off‐channel habitats to take advantage of energetically favourable growth conditions as indicated by the higher prey biomass in benthic and diet samples collected within off‐channel habitats. Our results could have significant implications for juvenile salmon under a warming Alaskan climate as access to productive off‐channel habitats may be important to offset increased energetic costs as temperature warms.

We applied an empirical model to predict hatching and emergence timing for 25 western Alaska sockeye salmon (Oncorhynchus nerka) populations in four lake-nursery systems to explore current patterns and potential responses of early life history phenology to warming water temperatures. Given the temperature regimes sockeye salmon experienced during development, we predicted hatching to occur in as few as 58 days to as many as 260 days depending on spawning timing and temperature. For a focal lake spawning population, our climate–lake temperature model predicted a water temperature increase of 0.7 to 1.4 °C from 2015 to 2099 during the incubation period, which translated to a hatching timing that was 16 to 30 days earlier. The most extreme warming scenarios shifted development to approximately 1 week earlier than historical minima and thus climatic warming may lead to only modest shifts in phenology during the early life history stage of this population. The marked variation in the predicted timing of hatching and emergence among populations in close proximity on the landscape may serve to buffer this metapopulation from climate change.

The relentless role of invasive species in the extinction of native biota requires predictions of ecosystem vulnerability to inform proactive management strategies. The worldwide invasion and range expansion of predatory northern pike (Esox lucius) has been linked to the decline of native fishes and tools are needed to predict the vulnerability of habitats to invasion over broad geographic scales. To address this need, we coupled an intrinsic potential habitat modelling approach with a Bayesian network to evaluate the vulnerability of five culturally and economically vital species of Pacific salmon (Oncorhynchusspp.) to invasion by northern pike. This study was conducted along 22,875 stream km in the Southcentral region of Alaska, USA. Pink salmon (O.gorbuscha) were the most vulnerable species, with 15.2% (2,458 km) of their calculated extent identified as “highly” vulnerable, followed closely by chum salmon (O.keta, 14.8%; 2,557 km) and coho salmon (O.kisutch, 14.7%; 2,536 km). Moreover, all five Pacific salmon species were highly vulnerable in 1,001 stream km of shared habitat. This simple to implement, adaptable, and cost-effective framework will allow prioritizing habitats for early detection and monitoring of invading northern pike.

Inland fishes provide important ecosystem services to communities worldwide and are especially vulnerable to the impacts of climate change. Fish respond to climate change in diverse and nuanced ways, which creates challenges for practitioners of fish conservation, climate change adaptation, and management. Although climate change is known to affect fish globally, a comprehensive online, public database of how climate change has impacted inland fishes worldwide and adaptation or management practices that may address these impacts does not exist. We conducted an extensive, systematic primary literature review to identify peer-reviewed journal publications describing projected and documented examples of climate change impacts on inland fishes. From this standardized Fish and Climate Change database, FiCli (pronounced fick-lee), researchers and managers can query fish families, species, response types, or geographic locations to obtain summary information on inland fish responses to climate change and recommended management actions. The FiCli database is updatable and provides access to comprehensive published information to inform inland fish conservation and adaptation planning in a changing climate., Measurement(s)Adaptation • response to climate change • freshwater fishes • management practicesTechnology Type(s)digital curationFactor Type(s)geographic location • date range of studySample Characteristic - OrganismfishSample Characteristic - Environmentclimate system • lake • stream • wetland ecosystem • freshwater biomeSample Characteristic - LocationEurope • Asia • Africa • North America • South America • Australia • Oceania Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12053385

We used spatially continuous field-measured and remotely sensed aquatic habitat characteristics paired with weekly ground-based telemetry tracking and snorkel surveys to describe movements and habitat occupancy of adult rainbow trout (Oncorhynchus mykiss) (N = 82) in a runoff-fed, salmon-influenced southcentral Alaska river system. We found that during the ice-free feeding season (June through September) rainbow trout occurrence was associated more with fine-scale (channel unit) characteristics relative to coarse-scale (stream reach) variables. The presence of Pacific salmon (Oncorhynchus spp., which provide an important seasonal food subsidy) and habitat size were particularly useful predictors. Weekly movement distance differed between pre- and postspawning salmon arrival, but did not vary by sex. Habitat quality, season, and the arrival of spawning salmon influenced the likelihood of rainbow trout movement, and fish moved farther to seek out higher-quality habitats. Because rainbow trout respond to habitat factors at multiple scales and seek out salmon-derived subsidies, it will be important to take a multiscale approach in protecting trout and salmon populations and managing the associated fisheries.

An important unresolved question is how populations of coldwater-dependent fishes will respond to rapidly warming water temperatures. For example, the culturally and economically important group, Pacific salmon (Oncorhynchus spp.), experience site-specific thermal regimes during early development that could be disrupted by warming. To test for thermal local adaptation and heritable phenotypic plasticity in Pacific salmon embryos, we measured the developmental rate, survival, and body size at hatching in two populations of sockeye salmon (Oncorhynchus nerka) that overlap in timing of spawning but incubate in contrasting natural thermal regimes. Using a split half-sibling design, we exposed embryos of 10 families from each of two populations to variable and constant thermal regimes. These represented both experienced temperatures by each population, and predicted temperatures under plausible future conditions based on a warming scenario from the downscaled global climate model (MIROC A1B scenario). We did not find evidence of thermal local adaptation during the embryonic stage for developmental rate or survival. Within treatments, populations hatched within 1 day of each other, on average, and among treatments, did not differ in survival in response to temperature. We did detect plasticity to temperature; embryos developed 2.5 times longer (189 days) in the coolest regime compared to the warmest regime (74 days). We also detected variation in developmental rates among families within and among temperature regimes, indicating heritable plasticity. Families exhibited a strong positive relationship between thermal variability and phenotypic variability in developmental rate but body length and mass at hatching were largely insensitive to temperature. Overall, our results indicated a lack of thermal local adaptation, but a presence of plasticity in populations experiencing contrasting conditions, as well as family-specific heritable plasticity that could facilitate adaptive change.

Although climate change is an important factor affecting inland fishes globally, a comprehensive review of how climate change has impacted and will continue to impact inland fishes worldwide does not currently exist. We conducted an extensive, systematic primary literature review to identify English-language, peer-reviewed journal publications with projected and documented examples of climate change impacts on inland fishes globally. Since the mid-1980s, scientists have projected the effects of climate change on inland fishes, and more recently, documentation of climate change impacts on inland fishes has increased. Of the thousands of title and abstracts reviewed, we selected 624 publications for a full text review: 63 of these publications documented an effect of climate change on inland fishes, while 116 publications projected inland fishes’ response to future climate change. Documented and projected impacts of climate change varied, but several trends emerged including differences between documented and projected impacts of climate change on salmonid abundance (P = 0.0002). Salmonid abundance decreased in 89.5% of documented effects compared to 35.7% of projected effects, where variable effects were more commonly reported (64.3%). Studies focused on responses of salmonids (61% of total) to climate change in North America and Europe, highlighting major gaps in the literature for taxonomic groups and geographic focus. Elucidating global patterns and identifying knowledge gaps of climate change effects on inland fishes will help managers better anticipate local changes in fish populations and assemblages, resulting in better development of management plans, particularly in systems with little information on climate change effects on fish.

—Climatic variation is a key driver of freshwater physical processes that in turn control stream fish growth and population dynamics at fine spatial scales and species distributions across broad landscapes. A recent downturn in Chinook Salmon Oncorhynchus tshawytscha returns across the Yukon River basin, Alaska, USA and Yukon Territories, Canada has led to hardship among user groups and increased interest in understanding how freshwater processes affect population persistence within this important commercial, recreational, and subsistence fishery. Here, we present results for the Chena River basin, interior Alaska, where we used field observations and riverscape-scale spatially explicit models to assess the influence of stream temperature on juvenile Chinook Salmon growth potential among years (2003–2015) and across 438 stream kilometers. We ran bioenergetic simulations for warm and cool year scenarios and contrasted temperature model precision and growth among different habitat types (small and large tributaries, main stem, and side channels) based on field estimates of growth, size, diet, and measured stream temperatures. Stream temperature regimes predicted from remotely sensed land surface temperatures were precise during the open water season (R2 > 0.87; root-mean-squared error < 1.1°C), although the relationship was weakest in groundwater-mediated tributary habitats. Field observations revealed salmon were 67% larger by mass (g) in September during a warm year versus a cool year from main-stem sites. Bioenergetic simulations predicted that, on average, growth potential was 42% higher in warm years, although growth potential varied across the riverscape as much as 60% between cool upstream and warm downstream habitats. Climate variability is clearly an important driver of freshwater habitat conditions and has a large role in controlling freshwater growth of juvenile salmon. A better understanding of how climate influences growth conditions in different habitat types and across broad landscapes will be critical for conservation and management of Alaskan Chinook Salmon stocks under an expected warmer and more variable climate.

Potamodromous Rainbow Trout Oncorhynchus mykiss are an important ecological and recreational resource in freshwater ecosystems of Alaska, and increased human development, hydroelectric projects, and reduced escapement of Chinook Salmon Oncorhynchus tshawytscha may threaten their populations. We used aerial and on-the-ground telemetry tracking, a digital landscape model, and resource selection functions to characterize seasonal movements and habitat use of 232 adult (>400 mm FL) Rainbow Trout across the complex, large (31,221 km2) Susitna River basin of south-central Alaska during 2003–2004 and 2013–2014. We found that fish overwintered in main-stem habitats near tributary mouths from November to April. After ice-out in May, fish ascended tributaries up to 51 km to spawn and afterward moved downstream to lower tributary reaches, assumedly to intercept egg and flesh subsidies provided by spawning salmonids in July and August. Fish transitioned back to main-stem overwintering habitats at the onset of...

Climate is a critical driver of many fish populations, assemblages, and aquatic communities. However, direct observational studies of climate change impacts on North American inland fishes are rare. In this synthesis, we (1) summarize climate trends that may influence North American inland fish populations and assemblages, (2) compile 31 peer-reviewed studies of documented climate change effects on North American inland fish populations and assemblages, and (3) highlight four case studies representing a variety of observed responses ranging from warmwater systems in the southwestern and southeastern United States to coldwater systems along the Pacific Coast and Canadian Shield. We conclude by identifying key data gaps and research needs to inform adaptive, ecosystem-based approaches to managing North American inland fishes and fisheries in a changing climate.

We provide a simple framework for diagnosing the impairment of stream water temperature for coldwater fishes across broad spatial extents based on a weight-of-evidence approach that integrates biological criteria, species distribution models, and geostatistical models of stream temperature. As a test case, we applied our approach to identify stream reaches most likely to be thermally impaired for Lahontan Cutthroat Trout Oncorhynchus clarkii henshawi in the upper Reese River, located in the northern Great Basin, Nevada. We first evaluated the capability of stream thermal regime descriptors to explain variation across 170 sites, and we found that the 7-d moving average of daily maximum stream temperatures (7DADM) provided minimal among-descriptor redundancy and, based on an upper threshold of 20°C, was also a good indicator of acute and chronic thermal stress. Next, we quantified the range of Lahontan Cutthroat Trout within our study area using a geographic distribution model. Finally, we used a geostatistical model to assess spatial variation in 7DADM and predict potential thermal impairment at the stream reach scale. We found that whereas 38% of reaches in our study area exceeded a 7DADM of 20°C and 35% were significantly warmer than predicted, only 17% both exceeded the biological criterion and were significantly warmer than predicted. This filtering allowed us to identify locations where physical and biological impairment were most likely within the network and that would represent the highest management priorities. Although our approach lacks the precision of more comprehensive approaches, it provides a broader context for diagnosing impairment and is a useful means of identifying priorities for more detailed evaluations across broad and heterogeneous stream networks. Received July 8, 2014; accepted October 22, 2015

Pacific Northwest salmonids are adapted to natural disturbance regimes that create dynamic habitat patterns over space and through time. However, human land use, particularly long-term fire suppression, has altered the intensity and frequency of wildfire in forested upland and riparian areas. To examine the potential impacts of wildfire on aquatic systems, we developed stream-reach-scale models of freshwater habitat for three life stages (adult, egg/fry, and juvenile) of spring Chinook salmon (Oncorhynchus tshawytscha) in the Wenatchee River subbasin, Washington. We used variables representing pre- and post-fire habitat conditions and employed novel techniques to capture changes in in-stream fine sediment, wood, and water temperature. Watershed-scale comparisons of high-quality habitat for each life stage of spring Chinook salmon habitat suggested that there are smaller quantities of high-quality juvenile overwinter habitat as compared to habitat for other life stages. We found that wildfire has the potential to increase quality of adult and overwintering juvenile habitat through increased delivery of wood, while decreasing the quality of egg and fry habitat due to the introduction of fine sediments. Model results showed the largest effect of fire on habitat quality associated with the juvenile life stage, resulting in increases in high-quality habitat in all watersheds. Due to the limited availability of pre-fire high-quality juvenile habitat, and increased habitat quality for this life stage post-fire, occurrence of characteristic wildfires would likely create a positive effect on spring Chinook salmon habitat in the Wenatchee River subbasin. We also compared pre- and post-fire model results of freshwater habitat for each life stage, and for the geometric mean of habitat quality across all life stages, using current compared to the historic distribution of spring Chinook salmon. We found that spring Chinook salmon are currently distributed in stream channels in which in-stream habitat for most life stages has a consistently positive response to fire. This compares to the historic distribution of spring Chinook, in which in-stream habitat exhibited a variable response to fire, including decreases in habitat quality overall or for specific life stages. This suggests that as the distribution of spring Chinook has decreased, they now occupy those areas with the most positive potential response to fire. Our work shows the potentially positive link between wildfire and aquatic habitat that supports forest managers in setting broader goals for fire management, perhaps leading to less fire suppression in some situations.

In Arctic ecosystems, freshwater fish migrate seasonally between productive shallow water habitats that freeze in winter and deep overwinter refuge in rivers and lakes. How these movements relate to seasonal hydrology is not well understood. We used passive integrated transponder tags and stream wide antennae to track 1035 Arctic grayling in Crea Creek, a seasonally flowing beaded stream on the Arctic Coastal Plain, Alaska. Migration of juvenile and adult fish into Crea Creek peaked in June immediately after ice break-up in the stream. Fish that entered the stream during periods of high flow and cold stream temperature traveled farther upstream than those entering during periods of lower flow and warmer temperature. We used generalized linear models to relate migration of adult and juvenile fish out of Crea Creek to hydrology. Most adults migrated in late June – early July, and there was best support (Akaike weight = 0.46; w i ) for a model indicating that the rate of migration increased with decreasing discharge. Juvenile migration occurred in two peaks; the early peak consisted of larger juveniles and coincided with adult migration, while the later peak occurred shortly before freeze-up in September and included smaller juveniles. A model that included discharge, minimum stream temperature, year, season, and mean size of potential migrants was most strongly supported (w i = 0.86). Juvenile migration rate increased sharply as daily minimum stream temperature decreased, suggesting fish respond to impending freeze-up. We found fish movements to be intimately tied to the strong seasonality of discharge and temperature, and demonstrate the importance of small stream connectivity for migratory Arctic grayling during the entire open-water period. The ongoing and anticipated effects of climate change and petroleum development on Arctic hydrology (e.g. reduced stream connectivity, earlier peak flows, increased evapotranspiration) have important implications for Arctic freshwater ecosystems.

Linked atmospheric and wildfire changes will complicate future management of native coldwater fishes in fire-prone landscapes, and new approaches to management that incorporate uncertainty are needed to address this challenge. We used a Bayesian network (BN) approach to evaluate population vulnerability of bull trout (Salvelinus confluentus) in the Wenatchee River basin, Washington, USA, under current and future climate and fire scenarios. The BN was based on modeled estimates of wildfire, water temperature, and physical habitat prior to, and following, simulated fires throughout the basin. We found that bull trout population vulnerability depended on the extent to which climate effects can be at least partially offset by managing factors such as habitat connectivity and fire size. Moreover, our analysis showed that local management can significantly reduce the vulnerability of bull trout to climate change given appropriate management actions. Tools such as our BN that explicitly integrate the linked nature of climate and wildfire, and incorporate uncertainty in both input data and vulnerability estimates, will be vital in effective future management to conserve native coldwater fishes.

Groundwater pumping for agriculture is a major driver causing declines of global freshwater ecosystems, yet the ecological consequences for stream fish assemblages are rarely quantified. We combined retrospective (1950–2010) and prospective (2011–2060) modeling approaches within a multiscale framework to predict change in Great Plains stream fish assemblages associated with groundwater pumping from the United States High Plains Aquifer. We modeled the relationship between the length of stream receiving water from the High Plains Aquifer and the occurrence of fishes characteristic of small and large streams in the western Great Plains at a regional scale and for six subwatersheds nested within the region. Water development at the regional scale was associated with construction of 154 barriers that fragment stream habitats, increased depth to groundwater and loss of 558 km of stream, and transformation of fish assemblage structure from dominance by large-stream to small-stream fishes. Scaling down to subwatersheds revealed consistent transformations in fish assemblage structure among western subwatersheds with increasing depths to groundwater. Although transformations occurred in the absence of barriers, barriers along mainstem rivers isolate depauperate western fish assemblages from relatively intact eastern fish assemblages. Projections to 2060 indicate loss of an additional 286 km of stream across the region, as well as continued replacement of large-stream fishes by small-stream fishes where groundwater pumping has increased depth to groundwater. Our work illustrates the shrinking of streams and homogenization of Great Plains stream fish assemblages related to groundwater pumping, and we predict similar transformations worldwide where local and regional aquifer depletions occur.

Methods to sample fishes in stream ecosystems and to analyze the raw data, focusing primarily on assemblage-level (all fish species combined) analyses, are presented in this chapter. We begin with guidance on sample site selection, permitting for fish collection, and information-gathering steps to be completed prior to conducting fieldwork. Basic sampling methods (visual surveying, electrofishing, and seining) are presented with specific instructions for estimating population sizes via visual, capture-recapture, and depletion surveys, in addition to new guidance on environmental DNA (eDNA) methods. Steps to process fish specimens in the field including the use of anesthesia and preservation of whole specimens or tissue samples (for genetic or stable isotope analysis) are also presented. Data analysis methods include characterization of size-structure within populations, estimation of species richness and diversity, and application of fish functional traits. We conclude with three advanced topics in assemblage-level analysis: multidimensional scaling (MDS), ecological networks, and loop analysis.

Reproductive tactics and migratory strat- egies in Pacific and Atlantic salmonines are inextri- cably linked through the effects of migration (or lack thereof) on age and size at maturity. In this review, we focus on the ecological and evolutionary patterns of freshwater maturation in salmonines, a key process resulting in the diversification of their life histories. We demonstrate that the energetics of maturation and reproduction provides a unifying theme for under- standing both the proximate and ultimate causes of variation in reproductive schedules among species, populations, and the sexes. We use probabilistic maturation reaction norms to illustrate how variation in individual condition, in terms of body size, growth rate, and lipid storage, influences the timing of maturation. This useful framework integrates both genetic and environmental contributions to condi- tional strategies for maturation and, in doing so, demonstrates how flexible life histories can be both heritable and subject to strong environmental influ- ences. We review evidence that the propensity for freshwater maturation in partially anadromous species is predictable across environmental gradients at geo- graphic and local spatial scales. We note that growth is commonly associated with the propensity for fresh- water maturation, but that life-history responses to changes in growth caused by temperature may be strikingly different than changes caused by differences in food availability. We conclude by exploring how contemporary management actions can constrain or

Streams and rivers host a significant portion of Earth's biodiversity and provide important ecosystem services for human populations. Accurate information regarding the status and trends of stream resources is vital for their effective conservation and management. Most statistical techniques applied to data measured on stream networks were developed for terrestrial applications and are not optimized for streams. A new class of spatial statistical model, based on valid covariance structures for stream networks, can be used with many common types of stream data (e.g., water quality attributes, habitat conditions, biological surveys) through application of appropriate distributions (e.g., Gaussian, binomial, Poisson). The spatial statistical network models account for spatial autocorrelation (i.e., nonindependence) among measurements, which allows their application to databases with clustered measurement locations. Large amounts of stream data exist in many areas where spatial statistical analyses could be used to develop novel insights, improve predictions at unsampled sites, and aid in the design of efficient monitoring strategies at relatively low cost. We review the topic of spatial autocorrelation and its effects on statistical inference, demonstrate the use of spatial statistics with stream datasets relevant to common research and management questions, and discuss additional applications and development potential for spatial statistics on stream networks. Free software for implementing the spatial statistical network models has been developed that enables custom applications with many stream databases.

Unfortunately, one of the co-author’s affiliations has been misspelled in the original article and the correct affiliation is ‘‘U.S. Geological Survey.’’ The ‘‘acknowledgment section’’ in the original publication should have included the following disclaimer: ‘‘Use of trade or firm names here is for reader information only and does not imply endorsement of any product or service by the U.S. Government.’’ Figures 1, 2, and 3 have been published incorrectly in the original publication of the article. The corrected version of these figures is provided below.

Knowledge of basic life-history attributes, paired with unbiased estimates of species distribution, is critical for the effective conservation of sensitive fish species. We quantified the spawning phenology, habitat use, and detectability for larvae of an assemblage of threatened Great Plains, USA, stream fishes using new occupancy estimation methods. Spawning by six Great Plains fish species occurred from April through July, and was likely initiated by changes in water temperature and photoperiod. Habitat size and type were important factors influencing the occupancy of larvae in spawn- ing habitats. Detectability of larvae differed among species and over time, and was influenced by habitat depth and fish size. Our models indicated that multiple samples from individual habitats within a season are needed to adequately detect and predict occupancy by stream fish larvae. Conservation efforts for imperiled Great Plains fish assemblages should focus on sustaining flows that maintain a sufficient density and size of habitats needed for successful spawning and recruitment. The occupancy estimation and modeling methods employed here will be useful in developing comprehensive, unbiased programs to monitor the reproductive success of Great Plains stream fishes. Resume´ : La conservation efficace des especes sensibles de poissons requiert une connaissance des caracteristiques fonda- mentales de leur cycle biologique, de meme que des estimations non faussees de leur repartition. Nous avons determinela phenologie de la reproduction, l'utilisation de l'habitat et la detectabilitedes larves dans des peuplements de poissons me- naces des Grandes Plaines, E ´ .-U., a l'aide de nouvelles methodes d'estimation de l'occupation. La fraie de six especes de poissons des plaines a lieu d'avril ala fin de juillet et est vraisemblablement declenchee par la temperature de l'eau et la photoperiode. La taille et le type de l'habitat sont des facteurs importants qui influencent l'occupation des habitats de fraie par les larves. La detection des larves varie d'une espece al'autre dans le temps et est influencee par la profondeur de l'habitat et la taille des poissons. Notre modelisation indique qu'il faut de multiples echantillons provenant de chaque habi- tat au cours d'une saison pour detecter adequatement et predire l'occupation du cours d'eau par les larves de poissons. Les efforts de conservation des peuplements de poissons menaces des Grandes Plaines devraient se concentrer sur le maintien de debits qui assurent une densiteet une taille d'habitats suffisantes pour une fraie et un recrutement reussis. Les methodes d'estimation de l'occupation et de modelisation que nous avons employees pourront servir amettre sur pied des program- mes complets et non fausses de surveillance du succes reproductif des poissons des eaux courantes dans les plaines. (Traduit par la Redaction)

Flow alterations caused by reservoir storage, groundwater pumping, diversions, and drought are widespread in North American Great Plains streams and have altered and fragmented habitats and reduced native fish biodiversity. Early life stages of fish are particularly sensitive to altered flow regimes, and reduced growth and survival may negatively affect the persistence of native species and assemblages. We investigated how growth and survival of brassy minnow Hybognathus hankinsoni larvae in the Arikaree River, Colorado, varied among three 6.4-km river segments that differed in hydrology and how climate influenced drying rates of spawning and rearing habitats in these segments over 3 years. We found that brassy minnow spawned in backwater habitats within a discrete period from mid-April to late May, based on otolith increment analysis. The timing of spawning and growth of larvae were influenced by climate and the hydrologic context of the river segment. Brassy minnow spawned 2 weeks earlier under...

SUMMARY 1. Understanding factors that regulate the assembly of communities is a main focus of ecology. Human-engineered habitats, such as reservoirs, may provide insight into these assembly processes because they represent novel habitats that are subjected to colonization by fishes from the surrounding river basin or transported by humans. By contrasting community similarity within and among reservoirs from different drainage basins to nearby stream communities, we can test the relative constraints of reservoir habitats and regional species pools in determining species composition of reservoirs. 2. We used a large spatial database that included intensive collections from 143 stream and 28 reservoir sites within three major river basins in the Great Plains, U.S.A., to compare patterns of species diversity and community structure between streams and reservoirs and to characterize variation in fish community structure within and among major drainage basins. We expected reservoir fish faunas to reflect the regional species pool, but would be more homogeneous that stream communities because similar species are stocked and thrive in reservoirs (e.g. planktivores and piscivores), and they lack obligate stream organisms that are not shared among regional species pools. 3. We found that fish communities from reservoirs were a subset of fishes collected from streams and dominant taxa had ecological traits that would be favoured in lentic environments. Although there were regional differences in reservoir fish communities, species richness, patterns of rank abundance and community structure in reservoir communities were more homogonous across three major drainage basins than for stream communities. 4. The general pattern of convergence of reservoir fish community structure suggests their assembly is constrained by local factors such as habitat and biotic interactions, and facilitated by the introduction of species among basins. Because there is a reciprocal transfer of biota between reservoirs and streams, understanding factors structuring both habitats is necessary to evaluate the long-term dynamics of impounded river networks.

We determined the relative benefits for eight categories of ecosystem goods and services associated with native and restored lands across the conterminous United States. Less than 10% of most native US ecosystems remain, and the proportion that is restored varies widely by biome. Restored lands offer 31% to 93% of native land benefits within a decade after restoration, with restored wetlands providing the most economic value and deserts providing the least. Restored ecosystems that recover rapidly and produce valuable commodities return a higher proportion of total value. The relative values of the benefits provided by restoration vary both by biome and by the ecosystem goods and services of interest. Our analysis confirms that conservation should be the first priority, but that restoration programs across broad geographic regions can have substantial value. “No net loss” policies should recognize that restored lands are not necessarily equivalent to native areas with regard to estimated ecosyste...

The upstream effects of reservoirs on stream fish assemblages were highly localized in 3rd- through 5th-order streams in the Great Plains, USA. Streams that differed in connectivity to reservoirs were sampled at their confluences with a river or reservoir and between the confluence and the stream's origin. Sites at confluences had higher total, nonnative, and reservoir species richness than middle sites. Variability in fish assemblage structure upstream of reservoirs was influenced by catchment area, stream size, gradient, and reservoir connectivity. Confluence sites connected to reservoirs were correctly classified based on the presence of red shiners (Cyprinella lutrensis) and bluntnose minnows (Pimephales notatus) and the absence of sand shiners (Notropis stramineus); middle sites on connected streams were classified by the absence of redfin shiners (Lythrurus umbratilis). Intensive sampling across pool habitats within two streams isolated by a reservoir indicated that abundance of common reservoir species was related to pool size, turbidity, and canopy cover, but not proximity to the reservoir. These data suggest that streams connected to reservoirs can maintain diverse native fish communities with minimal invasions by reservoir-dwelling species, but a fraction of the community either has been lost or occurs at low abundance (e.g., sand shiners and redfin shiners).

Predicting species distributions has important implications for the conservation and management of freshwater fishes, particularly in areas such as the Great Plains, USA where human impacts have resulted in extirpations and declines for numerous native species. There are a number of statistical approaches for constructing distributional models; the accuracy of each is likely dependent on the nature of the environmental gradients, species responses to those gradients and the spatial extent of the modelling. Thus, it is important to compare multiple approaches across species and habitats to identify the most effective modelling approach. Using geographical information system (GIS) derived characteristics of stream segments as predictors, we tested the model performance of three methodologies - linear discriminant function analysis, classification trees and artificial neural networks (ANN) - for predicting the occurrence of 38 fish species in a Great Plains river basin. Results showed that all approaches predicted species occurrences with relatively high success. ANN generally were the best models, in that they generated the most significant models (35 of 38 species) and most accurately predicted species presence for the greatest number of species (average correct classification ¼ 81.1%). The importance of GIS variables for predicting stream fish occurrences varied among species and modelling techniques, but were generally strong predictors of species distributions, including the federally endangered Topeka shiner Notropis topeka. In summary, predictive models should be viewed as both competitive and complementary methodologies for establishing quantitative linkages between fish species and their environment. Our study demonstrates the potential utility of such an approach for guiding conservation efforts for stream fishes of the Great Plains, USA.

Reservoirs are important components of modern aquatic ecosystems that have negative impacts on native aquatic biota both up- and downstream. We used a landscape-scale geographic information system (GIS) approach to quantify the spatial effects of 19 large reservoirs on upstream prairie fish assemblages at 219 sites in Kansas, USA. We hypothesized that fish assemblage structure would vary with increasing distance from a reservoir and that the abundance of reservoir fishes in upstream reaches would decline with distance from a reservoir. Ordination of sample sites showed variation in fish assemblage structure occurred primarily across river basins and with stream size. Variance partitioning of a canonical ordination revealed that the pure effect of reservoir distance explained a small but significant (6%; F = 4.90, P = 0.002) amount of variability in fish assemblage structure in upstream reaches. Moreover, reservoir species catch per unit of effort (CPUE) significantly declined with distance from a reservoir, but only in fourth- and fifth- order streams (r2 = 0.32, P

Density-dependent (DD) and density-independent (DI) habitat selection is strongly linked to a species' evolutionary history. Determining the relative importance of each is necessary because declining populations are not always the result of altered DI mechanisms but can often be the result of DD via a reduced carrying capacity. We developed spatially and temporally explicit models throughout the Chena River, Alaska to predict important DI mechanisms that influence Chinook salmon spawning success. We used resource-selection functions to predict suitable spawning habitat based on geomorphic characteristics, a semi-distributed water-and-energy balance hydrologic model to generate stream flow metrics, and modeled stream temperature as a function of climatic variables. Spawner counts were predicted throughout the core and periphery spawning sections of the Chena River from escapement estimates (DD) and DI variables. Additionally, we used isodar analysis to identify whether spawners actively defend spawning habitat or follow an ideal free distribution along the riverscape. Aerial counts were best explained by escapement and reference to the core or periphery, while no models with DI variables were supported in the candidate set. Furthermore, isodar plots indicated habitat selection was best explained by ideal free distributions, although there was strong evidence for active defense of core spawning habitat. Our results are surprising, given salmon commonly defend spawning resources, and are likely due to competition occurring at finer spatial scales than addressed in this study.