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Many long-term genetic monitoring programmes began before next-generation sequencing became widely available. Older programmes can now transition to new marker systems usually consisting of 1000s of SNP loci, but there are still important questions about comparability, precision, and accuracy of key metrics estimated using SNPs. Ideally, transitioned programmes should capitalize on new information without sacrificing continuity of inference across the time series. We combined existing microsatellite-based genetic monitoring information with SNP-based microhaplotypes obtained from archived samples of Rio Grande silvery minnow (Hybognathus amarus) across a 20-year time series to evaluate point estimates and trajectories of key genetic metrics. Demographic and genetic monitoring bracketed multiple collapses of the wild population and included cases where captive-born repatriates comprised the majority of spawners in the wild. Even with smaller sample sizes, microhaplotypes yielded comparable and in some cases more precise estimates of variance genetic effective population size, multilocus heterozygosity and inbreeding compared to microsatellites because many more microhaplotype loci were available. Microhaplotypes also recorded shifts in allele frequencies associated with population bottlenecks. Trends in microhaplotype-based inbreeding metrics were associated with the fraction of hatchery-reared repatriates to the wild and should be incorporated into future genomic monitoring. Although differences in accuracy and precision of some metrics were observed between marker types, biological inferences and management recommendations were consistent.

Patterns of genetic diversity and effective size should be predicted by life history traits (intrinsic), landscape properties (extrinsic), and population dynamics. Theoretical models portray complicated relationships among population subdivision, rates of extirpation and recolonization, and metapopulation genetic effective size (

Many salmonid species exist in highly structured and isolated populations, and are susceptible to habitat fragmentation and disturbances. Gila Trout (Oncorhynchus gilae) is a threatened species found in the Southwestern United States, and is managed to preserve relict populations (i.e., lineages) distributed across a fragmented landscape. We evaluated genomic variation within and among remaining lineages of Gila Trout using RADseq to assess how drift and selection have structured populations using neutral and outlier loci. We also examined whether a signature of hybridization was evident in relict populations. Gila Trout lineages were significantly differentiated from one another and were characterized by low effective population sizes. However, most lineages maintained genomic diversity and are potentially adapted to local conditions. Hybridization with non-native Rainbow Trout (O. mykiss) was not detected in any lineage. All lineages have experienced population bottlenecks associated with mortality from drought and severe wildfires. Current management strategies should be reevaluated and adapted to better account for long-term effects of climate change. Specifically, we suggest reconnecting some populations via dendritic stream networks to facilitate natural dispersal in a metapopulation context. This would allow natural genetic mixing on the landscape and potentially increase adaptive potential. Furthermore, genetic rescue should be implemented to preserve integrity of the unique Spruce Creek lineage that is currently compromised by extremely low diversity.

Few studies have evaluated the effects of large wildfires on downstream non-salmonid fish assemblages. Using multi-year (2009–2015) data from fish assemblage surveys and high-frequency water quality monitoring, we analyzed within-site responses of a cypriniform-dominated fish assemblage at two sites located > 20 km downstream of a 633 km2 wildfire in 2011 in the Rio Grande watershed in New Mexico, USA. Season had a weak influence on fish assemblage (fish) catch rate, richness, and evenness at the upstream site, but it had a strong negative influence (during spring/winter) on fish catch rate and richness at the downstream site. Fish species richness and evenness at both sites were not strongly affected by the wildfire, despite numerous post-fire sags in dissolved oxygen (including short-lived hypoxia

The Sacramento Mountain salamander (Aneides hardii) is a fully terrestrial plethodontid endemic to mountains in south-central New Mexico. This species is of conservation concern but there is scant knowledge regarding the degree of genetic divergence among populations. This information is vital for developing an appropriate species management strategy. To address this issue, we generated sequence data from the mitochondrial cytochrome b gene and four nuclear loci to explore population demographic history. Cytochrome b data revealed three deeply divergent (2.3–2.8%) mitochondrial lineages corresponding to distinct mountains (Capitan, White, and Sacramento). Divergence dates suggest separation since the early Pleistocene, and signatures of population expansion in the mid to late Pleistocene. Of 25 haplotypes identified, none were shared among mountains, but genetic diversity differed among mitochondrial lineages and suggested different demographic histories within lineages. A single microsatellite locus identified private alleles in each of the three lineages. Other nuclear loci screened were invariant within and among populations, which corresponds to a lower mutation rate compared with mtDNA. Together these results indicate that each mountain population of A. hardii represents a demographically and genetically distinct management unit.

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Studying the reproductive ecology of aggregate broadcast spawning fishes is difficult because it generally is not feasible to sample all potential parents and unambiguously assign their offspring. We used molecular-based parentage analysis to gain insights into the reproductive ecology of the endangered Bonytail, and to evaluate whether protected off-channel habitats could be used as an alternative to hatchery production. By genotyping adults and offspring stocked (n = 4130) into two experimental backwaters across three years, we determined that most adults (82–97%) contributed to progeny production across years and backwaters, with one exception. Both sexes mated multiply and the number of mates and family size were positively correlated. There was also a positive correlation between adult size and metrics of reproductive success. There were strong interactions between sample years and backwaters suggesting that environmental factors are the primary driver of variance in reproductive success. Knowledge of mating systems and sources of variance in reproductive success is important for management of endangered fish because high variance in reproductive success leads to substantial losses of genetic variation when few individuals reproduce successfully. Although variance in reproductive success was observed, most adults contributed to genetically diverse progeny in experimental backwaters. These results support the use of predator-free, but otherwise natural, backwaters as an effective conservation tool for reintroducing Bonytail to its native habitat.

Comparative transcriptomics can now be conducted on organisms in natural settings, which has greatly enhanced understanding of genome–environment interactions. Here, we demonstrate the utility and potential pitfalls of comparative transcriptomics of wild organisms, with an example from three cyprinid fish species (Teleostei:Cypriniformes). We present extensively filtered and annotated transcriptome assemblies that provide a valuable resource for studies of genome evolution (e.g. polyploidy), ecological and morphological diversification, speciation, and shared and unique responses to environmental variation in cyprinid fishes. Our results and analyses address the following points: (i) ‘essential developmental genes’ are shown to be ubiquitously expressed in a diverse suite of tissues across later ontogenetic stages (i.e. juveniles and adults), making these genes are useful for assessing the quality of transcriptome assemblies, (ii) the influence of microbiomes and other exogenous DNA, (iii) potentially novel, species-specific genes, and (iv) genomic rearrangements (e.g. whole genome duplication). The data we present provide a resource for future comparative work in cypriniform fishes and other taxa across a variety of sub-disciplines, including stress response, morphological diversification, community ecology, ecotoxicology, and climate change.

Public and private sectors promote increased use of recycled materials in asphalt pavement construction. However, concerns exist about possible premature pavement embrittlement and cracking because of these aged materials. Recycling agents, or rejuvenators, are used to offset these concerns. Rejuvenation mechanisms can be inferred depending on the type of recycling agent, yet there is a lack of supporting experimental evidence, especially related to the recycling agent–asphaltene interaction. This study provides insight on the effects and mechanisms of rejuvenation through extensive rheological and physicochemical characterization by considering experimental variables such as type of recycling agent, type/proportion of recycled materials, and binder type. Rejuvenation was effective based on restoration to PG 70-22, reduction in the Glover–Rowe parameter, and reduction in the glass transition temperature midpoint and end. Chemical characterization was not conclusive, yet the results were interpreted as str...

Summary Young-of-year (YOY) fishes are sometimes numerically dominant vertebrate consumers in many large river systems, but their effects as predators are not as well understood as those of adult fishes. We predicted that YOY fishes influence community composition and abundance of invertebrate prey. Predation effects could be especially important in recruitment-driven dryland river systems, where YOY fishes seasonally comprise a large portion of overall fish biomass. We conducted a mesocosm experiment to quantify effects of YOY fishes on trophic dynamics and interactions with environmental factors in a dryland river food web. We manipulated presence of YOY fishes (an assemblage of cypriniform species) and supplemental allochthonous carbon (LEAF treatments) in 24 mesocosms, and measured invertebrate abundance and diversity over 6 weeks. Experimental conditions mimicked a seasonal river drying regime that occurs during YOY fish growth. Seasonal drying in the Rio Grande frequently results in isolated pools with altered habitat complexity and riparian connectivity. Fishes exerted direct top-down control of invertebrate assemblage composition through differential prey selection, and indirect control mediated by non-lethal responses of invertebrates to predatory fishes. We observed enhanced water clarity in LEAF treatments associated with greater prey selectivity in fishes, presumably through enhanced visual feeding. Stable isotope analysis (C and N) was used to measure indirect impacts of YOY fishes on invertebrate prey items. YOY fishes caused a significant decrease in “isotopic niche breadth” among invertebrate taxa, suggesting that fish predators limit foraging opportunities for these consumers. However, allochthonous carbon sources were predominant in invertebrate diets in all LEAF treatments, suggesting consumer access to more biologically available autochthonous production is limited by factors other than fish predation. Although the roles of abiotic drivers and adult fishes in determining food web structure have received more attention, our results indicate that YOY fishes exert biologically relevant top-down control of invertebrate assemblage composition and trophic complexity in dryland river ecosystems against a backdrop of substantial changes in carbon availability and abiotic conditions (e.g. water quality and habitat volume) over the growing season.

Movement is necessary for re-colonization of habitats following disturbance, but methods to estimate dispersal of small-bodied fishes are limited. We evaluated the efficacy of otolith microchemistry in identifying habitat origin of longfin dace Agosia chrysogaster in the Gila River, NM, USA. Additionally, we used this method to determine the source population of speckled dace Rhinichthys osculus that re-colonized a tributary reach following wildfire-induced extirpation. We determined otolith microchemical analysis was possible after finding elevated ambient water concentrations of Mg, Mn, and Sr in the disturbed tributary both before and after wildfire relative to other source streams. These water chemistry differences allowed us to test if speckled dace were derived from downstream populations, or from those potentially persisting within refugia in the fire-affected tributary. We found that otolith signatures consistently reflected water chemistry patterns for Mn and Sr, allowing us to classify individuals to known capture locations 86% (range = 74–100%) of the time. Otolith microchemistry techniques then revealed that 88% of speckled dace that re-colonized the fire-affected tributary reach were derived from refuge populations within the tributary. Our results indicated that otolith microchemistry could be an important tool for characterizing re-colonization dynamics of fish populations residing in chemically heterogeneous stream networks.

A local hybrid swarm between Etheostoma radiosum and Etheostoma spectabile, found in June 1985 in a short reach of Little Glasses Creek, southern Oklahoma, consisted by eye of 35% phenotypic E. radiosum, 18% phenotypic E. spectabile, and 47% hybrids. In July 1985, investigation of an additional longer reach downstream of the initial discovery site showed that hybrids also were present there, although fewer. Thus, in 1985 both parental species, and substantial numbers of hybrids, were present in approximately a 300 m reach of the stream. No further collections were made until 2003, when sampling in the former hybrid reach and substantially further downstream showed E. radiosum to be the only species of Etheostoma present, and neither E. spectabile nor hybrids (by eye) were detected. From 2003 to 2013 the reach was surveyed 11 times, with a total of 363 darters identified phenotypically as E. radiosum, and none as E. spectabile or hybrids. Of 20 individuals sampled in December 2011 for molecular analyses, 1...

A peripheral population of mountain sucker, Pantosteus jordani, located in the Black Hills of South Dakota, USA, represents the eastern-most range of the species and is completely isolated from other populations. Over the last 50 years, mountain sucker populations have declined in the Black Hills, and now only occur in 40 % of the historic local range, with densities decreasing by more than 84 %.We used microsatellite DNA markers to estimate genetic diversity and to assess population structure across five streams where mountain suckers persist. We evaluated results in the context of recent ecological surveys to inform decisions about mountain sucker conservation. Significant allele frequency differences existed among sample streams (Global FST = 0.041) but there was no evidence of isolation by distance. Regionally, genetic effective size, Ne, was estimated to be at least 338 breeding individuals, but Ne within streams was expected to be less. Despite almost complete demographic isolation and reduced population size, there appears to be little evidence of inbreeding, but genetic drift and local isolation due to fragmentation probably best explains genetic structure in this peripheral mountain sucker population. Recommended strategies for population enhancement include restoration of stream connectivity and habitat improvement. Moreover, repatriation and assisted movement (i.e., gene flow) of fishes should maximize genetic diversity in stream fragments in the Black Hills region.

Hatchery programs are critical for conservation and management of many imperiled fishes. Most traditional aquaculture programs negatively affect ecological performance, genetic, and phenotypic diversity of hatchery-origin fish compared with wild counterparts. Here, we synthesize outcomes of three conservation programs aimed at enhancing ‘wildness’. Each program focuses on a different species: lake sturgeon, razorback sucker, and Rio Grande silvery minnow. These species differ in key life history traits including size and age at sexual maturity, reproductive and migratory behavior, and habitat requirements. Threats to persistence of the focal taxa, however, exemplify common pressures experienced by freshwater fishes worldwide. Conservation hatchery programs for lake sturgeon, razorback sucker, and Rio Grande silvery minnow capitalize on natural spawning in the wild followed by collections of wild-fertilized eggs/larvae for hatchery rearing. Individuals are repatriated to the wild after rearing to body sizes less susceptible to mortality. Protocols include collections of eggs or larvae across the entire spawning period and at appropriate geographic scales to maximize retention of genetic diversity and, to increase the likelihood of preserving variation for heritable life history traits. Using direct and indirect evidence we show that hatchery programs that allow individuals to fulfill parts of the life-cycle in their native habitats can be conducted without compromising genetic diversity. Adoption of similar strategies in other imperiled fishes would improve understanding of species life history, and provide an incentive to protect native habitats so they may eventually support self-sustaining populations.

We report results from a 3-year field investigation to limit hybridization between native and nonnative suckers in 2 small tributaries of the Gunnison River basin, Delta County, Colorado. Upstream movement to spawning habitat was selectively impeded by picket weir in intermittent Cottonwood Creek. There, native suckers were identified based on morphological characters in the field and were transferred upstream of the weir, whereas nonnative fishes were excluded from upstream movement. Another stream, Potter Creek, was not impeded by weir. Genetic identification of adult fishes in both streams was consistent with morphological identification in the field. Larval genetic identification was consistent with probable spawning species in Potter Creek. However, in Cottonwood Creek, larval fish proportions differed significantly from likely spawners. Proportions of nonnative suckers were high in Cottonwood Creek because exclusion structures were compromised by flooding during the spawning season. Yet, instream control of spawning by nonnative fishes has potential for reducing the incidence of hybridization, but practical challenges remain for implementation in the field.

Coastal habitats in Chile are hypothesized to support a number of diadromous fish species. The objective of this study was to document migratory life histories of native galaxiids and introduced salmonids from a wide latitudinal range in Chilean Patagonia (39–48°S). Otolith microchemistry data were analysed using a recursive partitioning approach to test for diadromy. Based on annular analysis of Sr:Ca ratios, a diadromous life history was suggested for populations of native Aplochiton taeniatus, A. marinus, and Galaxias maculatus. Lifetime residency in freshwater was suggested for populations of A. zebra and G. platei. Among introduced salmonids, populations of Oncorhynchus tshawytscha and O. kisutch exhibited patterns consistent with anadromy, whereas the screened population of O. mykiss appeared restricted to freshwater. Salmo trutta exhibited variable patterns suggesting freshwater residency and possibly anadromy in one case. The capacity and geographic scope of hydropower development is increasing and may disrupt migratory routes of diadromous fishes. Identification of diadromous species is a critical first step for preventing their loss due to hydropower development.

Disruption of natural flow regimes, nutrient pollution, and other consequences of human population growth and development have impacted most major rivers of the world. Alarming losses of aquatic biodiversity coincide with human-caused river alteration, but effects of biotic homogenization on aquatic ecosystem processes are not as well documented. This is because unaltered systems for comparison are scarce, and some ecosystem-wide effects may take decades to manifest. We evaluated aquatic ecosystem responses to extensive river- floodplain engineering and nutrient addition in the Rio Grande of southwestern North America as revealed by changes in trophic structure of, and resource availability to, the fish community. Stable Isotope Analysis (SIA) was conducted on museum-preserved fishes collected over a 70-year period of intensive river management and exponential human population growth. Trophic complexity and resource heterogeneity for fish consumers (measured as "isotopic niche breadth") decreased following sediment deprivation and channelization, and these effects persist into the present. Increased nutrient inputs led to δ15N enrichment in the entire fish community at all affected sites, and a shift to autochthonous sources of carbon at the most proximal site downstream of wastewater release, probably via bottom-up transfer. Overall, retrospective SIA of apex consumers suggests radical change and functional impairment of a floodplain river ecosystem already marked by significant biodiversity loss.

Climate change and fire suppression have altered fire regimes globally, leading to larger, more frequent, and more severe wildfires. Responses of coldwater stream biota to single wildfires are well studied, but measured responses to consecutive wildfires in warmwater systems that often include mixed assemblages of native and nonnative taxa are lacking. We quantified changes in physical habitat, resource availability, and biomass of cold- and warmwater oligochaetes, insects, crayfish, fishes, and tadpoles following consecutive megafires (covering >100 km2) in the upper Gila River, New Mexico, USA. We were particularly interested in comparing responses of native and nonnative fishes that might have evolved under different disturbance regimes. Changes in habitat and resource availability were related to cumulative fire effects, fire size, and postfire precipitation. The 2nd of 2 consecutive wildfires in the basin was larger and, coupled with moderate postfire discharge, resulted in increased siltatio...

Thorough sampling is necessary to delineate lineage diversity for polytypic "species" such as Cyprinella lutrensis. We conducted extensive mtDNA sampling (cytochrome b and ND4) from the Pecos River, Rio Grande, and South Canadian River, New Mexico. Our study emphasized the Pecos River due to its complex geological history and potential to harbor multiple lineages. We used geometric-morphometric, morphometric, and meristic analyses to test for phenotypic divergence and combined nucDNA with mtDNA to test for cytonuclear disequilibrium and combined our sequences with published data to conduct a phylogenetic re-assessment of the entire C. lutrensis clade. We detected five co-occurring mtDNA lineages in the Pecos River, but no evidence for cytonuclear disequilibrium or phenotypic divergence. Recognized species were interspersed amongst divergent lineages of "C. lutrensis". Allopatric divergence among drainages isolated in the Late Miocene and Pliocene apparently produced several recognized species and major divisions within "C. lutrensis". Pleistocene re-expansion and subsequent re-fragmentation of a centralized lineage founded younger, divergent lineages throughout the Rio Grande basin and Edwards Plateau. There is also evidence of recent introductions to the Rio Grande, Pecos and South Canadian Rivers. Nonetheless, deeply divergent lineages have coexisted since the Pleistocene.

The Cuatro Cienegas killifish Lucania interioris is an endemic fundulid in the Chihuahuan Desert valley of Cuatro Cienegas, Coahuila, Mexico. It occurs in 3 major drainage regions of the basin and is limited primarily to naturally fragmented and physicochemically severe habitats of the valley floor. We assessed mitochondrial DNA variation and population genetic structure in L. interioris from 8 populations representative of the entire geographic range of this species, including its distribution within and among major drainage regions (western, central, and southeastern) of the valley. Five populations were invariant, including both populations in the western region (Haplotype A only), whereas 2 haplotypes were observed in each of the remaining populations. Haplotype diversity was low in the central basin (HD = 0.10 and HD = 0.19) and moderate in the southeastern basin (HD = 0.52). Low levels of divergence among haplotypes (0.3%–0.9%), together with high levels of genetic differentiation among re...

Razorback Sucker Xyrauchen texanus is iconic of the plight of native “big-river” fishes of the Colorado River system of western North America. The species was historically widespread and abundant throughout the basin but has suffered substantial range reductions and population declines now characteristic of Western fishes. By the 1960s the largest remaining population was in Lake Mohave, a lower Colorado River reservoir where casual monitoring began in the mid-1950s and intensified to focus on Razorback Sucker in the late 1970s. The population then was comprised of several hundred thousand large adults, but recruitment past the larval stage was nil presumably because of predation by non-native fishes and potentially worsened by nutritional limitation. Remnant adults began to dwindle in the 1980s and were virtually gone within twenty years. An ad-hoc “Lake Mohave Native Fishes Work Group” initiated investigations to identify and understand the reasons for recruitment failure and launched an informal progra...

Conservation genetic studies are challenged by the fact that populations of many imperiled species have experienced declines and fragmentation to the degree they no longer exhibit natural, self-sustaining metapopulation processes; characteristics of great importance to managers charged with their protection. Genetic patterns of species from minimally impacted systems can inform management practices for populations in more modified and fragmented systems. We assessed spatial and temporal patterns of intraspecific genetic diversity and differentiation using microsatellites for three imperiled fishes of the unfragmented upper Gila River, New Mexico, USA. Estimates of contemporary effective size were low for these species, but we observed little genetic evidence of inbreeding. Overall genetic structure was low (all species FST

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.

Biodiversity in stream networks is threatened globally by interactions between habitat fragmentation and altered hydrologic regimes. In the Great Plains of North America, stream networks are fragmented by >19 000 anthropogenic barriers, and flow regimes are altered by surface water retention and groundwater extraction. We documented the distribution of anthropogenic barriers and dry stream segments in five basins covering the central Great Plains to assess effects of broad-scale environmental change on stream fish community structure and distribution of reproductive guilds. We used an information-theoretic approach to rank competing models in which fragmentation, discharge magnitude, and percentage of time streams had zero flow (a measure of desiccation) were included to predict effects of environmental alterations on the distribution of fishes belonging to different reproductive guilds. Fragmentation caused by anthropogenic barriers was most common in the eastern Great Plains, but stream desiccation beca...

Aridland rivers can present several logistical challenges for invertebrate sampling due to shifting substrate and low invertebrate densities. We compared 4 sampling methods for col- lecting both meiofauna and macroinvertebrates in an aridland river (Rio Grande, New Mexico): a water column sampling method, an epibenthic core, a throwtrap, and a stovepipe sampling method. The objective of this study was to find the most efficient combination of sampling meth- ods with which to collect the entire assemblage. Differences were tested among sampling meth- ods in terms of abundance, taxonomic richness, assemblage composition, and invertebrate body size. No single sampling method was able to provide accurate estimates of both abundance and taxonomic richness across the range of body sizes of taxa collected in this study. Invertebrates were concentrated in the epibenthos, and thus using the water column sampling method was not necessary. Samples from the epibenthic core and stovepipe sampling methods contained rela- tively high densities of small-bodied meiofauna, while throwtrap samples included both meio- fauna and macroinvertebrates. Throwtrap and epibenthic core sampling methods together pro- vided the most accurate estimates of taxonomic richness, density, abundance, and invertebrate assemblage composition, and were processed relatively efficiently in the laboratory. Sampling methods that performed well in the Rio Grande are likely to work well in other higher-order (>4) rivers with shifting substrates.

Compliance with Ethical StandardsOtolith analysis was funded by a RAC grant from the University of New Mexico, USA. The Government of Chile supported the drafting of this document with a CONICYT Doctoral Fellowship to D. Alò in 2015 and to C. Correa through grants CONICYT-PAI N°82130009, and FONDECYT-Iniciación en la Investigación N°11150990.All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. Specimens were collected under permits No. 3587, 29 December 2006, and No. 2886, 4 November 2008 (amendment No. 602, 12 February 2009) granted by the Chilean Subsecretary of Fishing to C. Correa. The McGill University Animal Care Committee (UACC), Animal Use Protocol No. 5291, approved use and handling of animals.AbstractCoastal habitats in Chile are hypothesized to support a number of diadromous fishes. The objective of this study was to document migratory life histories of native galaxiids and introduced salmonids from a wide latitudinal range in Chilean Patagonia (39-48°S). Otolith microchemistry data were analysed using a recursive partitioning approach to test for diadromy. Based on annular analysis of Sr:Ca ratios, a diadromous life history was detected for populations of native Aplochiton taeniatus, A. marinus, and Galaxias maculatus. Lifetime residency in freshwater was suggested for populations of A. zebra and G. platei. Among introduced salmonids, populations of Oncorhynchus tshawytscha and O. kisutch exhibited anadromous migratory patterns, whereas the population of O. mykiss screened appeared restricted to freshwater. Salmo trutta exhibited variable habitat use consistent with establishment of an ocean-type life history in some populations. The capacity and geographic scope of hydropower development is increasing and may disrupt migratory routes of diadromous fishes. Identification of diadromous species is a critical first step for preventing their loss due to hydropower development.

We used comparative landscape genetics to examine the relative roles of historical events, intrinsic traits and landscape factors in determining the distribution of genetic diversity of river fishes across the North American Great Plains. Spatial patterns of diversity were overlaid on a patch-based graphical model and then compared within and among three species that co-occurred across five Great Plains watersheds. Species differing in reproductive strategy (benthic vs. pelagic-spawning) were hypothesized to have different patterns of genetic diversity, but the overriding factor shaping contemporary patterns of diversity was the signature of past climates and geological history. Allelic diversity was significantly higher at southern latitudes for Cyprinella lutrensis and Hybognathus placitus, consistent with northward expansion from southern Pleistocene refugia. Within the historical context, all species exhibited lowered occupancy and abundance in heavily fragmented and drier upstream reaches, particularly H. placitus; a pelagic-spawning species, suggesting rates of extirpation have outpaced losses of genetic diversity in this species. Within most tributary basins, genetically diverse populations of each species persisted. Hence, reconnecting genetically diverse populations with those characterized by reduced diversity (regardless of their position within the riverine network) would provide populations with greater genetic and demographic resilience. We discuss cases where cross-basin transfer may be appropriate to enhance genetic diversity and mitigate negative effects of climate change. Overall, striking similarities in genetic patterns and in response to fragmentation and dewatering suggest a common strategy for genetic resource management in this unique riverine fish assemblage.

In desert streams, fishes and other organisms that depend on surface water are predicted to inhabit smaller and more isolated wetted reaches, while the frequency and severity of disturbance is expected to increase under most climate change models. Together, these factors should reduce population genetic diversity and persistence probabilities. In this study, our goal was to understand genetic responses of stream fish populations to disturbance in an intermittent stream network. This network is occupied by Rio Grande sucker (Pantosteus plebeius) that is native to highland desert streams in North America. Sample localities in upland perennial reaches were connected by moderate to high levels of gene flow even when separated by up to a 30-km intermittent reach. However, drier and lower-elevation reaches were significant barriers to gene flow. Effects of genetic drift (lower allelic diversity and higher levels of inbreeding) were more pronounced in the watershed with fewest wetted reaches. Temporal analysis of genetic diversity indicated that streams with several spatially distinct wetted reaches were more genetically resistant to wildfire-induced demographic bottlenecks than a stream with only one wetted reach. Maintenance of multiple wetted reaches within streams and facilitated gene flow among watersheds could slow losses of genetic diversity in upland desert stream fishes, and will be important strategies for conserving stream biodiversity in the face of habitat fragmentation and disturbance related to climate change.

A study involving two rolling-thin-film-oven–aged asphalts and their blends with 15 and 50% of extracted reclaimed asphalt pavement (RAP) binders was conducted to investigate the effect of RAP content and properties on the long-term aging characteristics of asphalt binders. The results from rheological analyses of aged, blended binders indicate that the aging characteristics of blended binders are dependent on fresh asphalt binders. The results show that the crossover frequency decreases at an exponential form as RAP concentrations increase, and the rheological index increases as RAP concentration increases. The pattern for stiffness increase as a function of aging times for RAP-blended binders is similar to that of a typical chemical-aging kinetic model, in which the stiffness increases substantially initially and then levels off at longer aging times. The results demonstrate that there is a linear relationship between the logarithm of G* and the phase angle for RAP-blended binders at all aging t...

SUMMARY 1. Freshwater fish commonly exhibit differences in reproductive seasonality within assemblages. However, the extent of variation in reproductive timing among years is less well understood, particularly in relation to environmental variation. Phenological shifts in response to environmental variation, including climate change, can differ among species and thereby change temporal resource partitioning (e.g. in the use of nursery habitat, dietary items, etc.) and potentially the strength of biotic interactions such as competition. 2. To assess interannual variation in reproductive phenology and temporal resource partitioning in an arid-land river, we collected a data set on young-of-year fish in four years within an overall span of 16 years, from 1995 to 2010. Fish species spawned in a consistent order across years; however, the onset of spawning was between 4 and 28 days earlier in 2008–2010 than in 1995. Spawning onset advanced more for later-spawning species, resulting in reduced temporal partitioning across the assemblage. 3. Based on these observations, we developed four alternate models of assemblage-level responses to alteration of flow regime based on the magnitude of phenological shifts and corresponding temporal partitioning among species. Phenological data are consistent with only one of these models. 4. Convergence and overlap in spawning time among species may decrease resource partitioning at a critical life stage and alter assemblage composition in recruitment-driven systems like arid-land rivers. Understanding factors driving convergence and overlap in spawning time among species is key to predicting effects of ongoing climate change and alteration of flow regimes on fish assemblages.

In the late 1940s, Rio Grande Sucker Pantosteus plebeius was reported in tributaries of the Gila River in the Colorado Basin and presumed to be introduced because of its absence in mid-19th century...

Etheostoma cyanorum, endemic to the Blue River drainage of southern Oklahoma, is redescribed and recognized as a distinct species within the Etheostoma whipplei–Etheostoma radiosum complex, separating it from E. radiosum. Originally described as Poecilichthys radiosus cyanorum, it was one of three putative subspecies of E. radiosum (with E. r. radiosum and E. r. paludosum) considered valid until now, defined in part by drainage-specific allopatry. Two separate mtDNA gene trees show that E. cyanorum forms a distinct and strongly supported lineage. Ten meristic and 16 morphometric traits are reexamined and new information included, confirming traits separating E. cyanorum from E. radiosum, and clarifying ambiguities about “bluntness of the snout” as diagnostic for P. r. cyanorum. Etheostoma cyanorum differs from E. radiosum by lower counts of unpored lateral line scales, higher counts of pored lateral line scales, and greater interorbital width. Large adult E. cyanorum have a deep body and blunt snout per earlier studies, but those traits are not diagnostic due to allometry. Head depth and head width can separate E. cyanorum from most populations of E. radiosum, but they overlap with some populations of E. radiosum in southwest Arkansas. All evidence supports recognition of E. cyanorum as a valid species. A broad geographic, molecular assessment to supplement existing morphological information is needed to assess validity of the two remaining subspecies of E. radiosum.

We developed microsatellite loci for the Julimes pupfish, Cyprinodon julimes. Twenty-five loci were screened across 19 individuals from Julimes Spring, Chihuahua, Mexico. The number of alleles per locus ranged from 2 to 14, observed heterozygosity ranged from 0.105 to 0.947, and the probability of identity values ranged from 0.022 to 0.588. We then tested for cross-amplification in the bighead pupfish, C. pachycephalus; twenty-three individuals from San Diego de Alcala, Chihuahua, Mexico, were screened across the 20 loci that amplified cleanly. These new loci will be used for long-term genetic monitoring of these critically endangered species.

Pupfishes (genus Cyprinodon) are iconic of biodiversity and endemism in the desert southwest of North America. Most of these species are imperiled, primarily because of excessive exploitation of water resources in this arid region. The critically endangered Julimes pupfish, Cyprinodon julimes, is restricted to a small, isolated, and highly modified desert spring in Chihuahua, Mexico. We evaluated effective population size (microsatellites) and genetic variation (microsatellites and mitochondrial DNA) to determine the conservation genetic status of this species. The effective population size was critically low and indicated that this pupfish is at genetic risk of extinction through loss of adaptive variance and, potentially, from inbreeding depression. Mitochondrial variation was also extremely low, and haplotype frequency was biased heavily in favor of one of two variants. The uncommon haplotype was derived from a past hybridization event with the closely related C. eximius; whether cessation of introgressive hybridization is relevant to conservation management of Julimes pupfish is unknown but may be important to consider. Minimally, C. julimes is compromised genetically. Baseline population genetic information provided by this study will be vital to long-term monitoring of this highly imperiled species.

Pelagic-broadcast spawning is a dominant mode of fish reproduction in the oceans and is associated with Fundamental Triad (i.e. nutrient enrichment, nutrient concentration, propagule retention) and Loophole (i.e. disruption of larval competition and predation) processes that are mediated by water currents. Pelagic-broadcast spawning is uncommon in freshwater, but is employed by an evolutionarily convergent spawning guild in rivers on the Great Plains, North America. We reviewed ecological studies of pelagic-broadcast spawning minnows to evaluate whether Fundamental Triad and Loophole concepts explain the adaptive significance of this behaviour. Pelagic-broadcast spawning minnows exhibit spawning periodicity dependent on floods. Nutrient enrichment, nutrient concentration and propagule retention are enhanced during flood recession. Retention is also enhanced by high fecundity and rapid development of pelagic-broadcast propagules. Predation and competition threats are relatively low in temporary, patchily distributed nurseries present during flood recession. Extended spawning periods and diffusive spread of juveniles and adults ensure annual recruitment despite the unpredictable and often harsh conditions in rivers on the plains. Over the last century, pelagic-broadcast spawners have suffered declines due to dewatering, flood control and sediment deprivation that disrupt natural Fundamental Triad and Loophole processes. We propose that restoration of conditions necessary for Fundamental Triad and Loophole processes to operate will be most successful at stopping decline and extinction of pelagic-broadcast spawning minnows of the Great Plains.