Geology topics

Robert K. Al-Chokhachy

Publications and source records attributed to Robert K. Al-Chokhachy.

At least 37 records · Page 2Linked to original sources

USGS2016

Climate, invasive species and land use drive population dynamics of a cold-water specialist

Climate change is an additional stressor in a complex suite of threats facing freshwater biodiversity, particularly for cold-water fishes. Research addressing the consequences of climate change on cold-water fish has generally focused on temperature limits defining spatial distributions, largely ignoring how climatic variation influences population dynamics in the context of other existing stressors. We used long-term data from 92 populations of bull trout Salvelinus confluentus – one of North America's most cold-adapted fishes – to quantify additive and interactive effects of climate, invasive species and land use on population dynamics (abundance, variability and growth rate). Populations were generally depressed, more variable and declining where spawning and rearing stream habitat was limited, invasive species and land use were prevalent and stream temperatures were highest. Increasing stream temperature acted additively and independently, whereas land use and invasive species had additive and interactive effects (i.e. the impact of one stressor depended on exposure to the other stressor). Most (58%–78%) of the explained variation in population dynamics was attributed to the presence of invasive species, differences in life history and management actions in foraging habitats in rivers, lakes and reservoirs. Although invasive fishes had strong negative effects on populations in foraging habitats, proactive control programmes appeared to effectively temper their negative impact. Synthesis and applications . Long-term demographic data emphasize that climate warming will exacerbate imperilment of cold-water specialists like bull trout, yet other stressors – especially invasive fishes – are immediate threats that can be addressed by proactive management actions. Therefore, climate-adaptation strategies for freshwater biodiversity should consider existing abiotic and biotic stressors, some of which provide potential and realized opportunity for conservation of freshwater biodiversity in a warming world.

Journal of Applied Ecology↗

USGS2016

Influence of climate drivers on colonization and extinction dynamics of wetland-dependent species

Freshwater wetlands are particularly vulnerable to climate change. Specifically, changes in temperature, precipitation, and evapotranspiration (i.e., climate drivers) are likely to alter flooding regimes of wetlands and affect the vital rates, abundance, and distributions of wetland-dependent species. Amphibians may be among the most climate-sensitive wetland-dependent groups, as many species rely on shallow or intermittently flooded wetland habitats for breeding. Here, we integrated multiple years of high-resolution gridded climate and amphibian monitoring data from Grand Teton and Yellowstone National Parks to explicitly model how variations in climate drivers and habitat conditions affect the occurrence and breeding dynamics (i.e., annual extinction and colonization rates) of amphibians. Our results showed that models incorporating climate drivers outperformed models of amphibian breeding dynamics that were exclusively habitat based. Moreover, climate-driven variation in extinction rates, but not colonization rates, disproportionately influenced amphibian occupancy in monitored wetlands. Long-term monitoring from national parks coupled with high-resolution climate data sets will be crucial to describing population dynamics and characterizing the sensitivity of amphibians and other wetland-dependent species to climate change. Further, long-term monitoring of wetlands in national parks will help reduce uncertainty surrounding wetland resources and strengthen opportunities to make informed, science-based decisions that have far-reaching benefits.

Grand Teton National Park, Yellowstone National Pa↗

USGS2016

Physiological basis of climate change impacts on North American inland fishes

Global climate change is altering freshwater ecosystems and affecting fish populations and communities. Underpinning changes in fish distribution and assemblage-level responses to climate change are individual-level physiological constraints. In this review, we synthesize the mechanistic effects of climate change on neuroendocrine, cardiorespiratory, immune, osmoregulatory, and reproductive systems of freshwater and diadromous fishes. Observed climate change effects on physiological systems are varied and numerous, including exceedance of critical thermal tolerances, decreased cardiorespiratory performance, compromised immune function, and altered patterns of individual reproductive investment. However, effects vary widely among and within species because of species, population, and even sex-specific differences in sensitivity and resilience and because of habitat-specific variation in the magnitude of climate-related environmental change. Research on the interactive effects of climate change with other environmental stressors across a broader range of fish diversity is needed to further our understanding of climate change effects on fish physiology.

Fisheries↗

USGS2016

Conservation of native Pacific trout diversity in western North America

Pacific trout Oncorhynchus spp. in western North America are strongly valued in ecological, socioeconomic, and cultural views, and have been the subject of substantial research and conservation efforts. Despite this, the understanding of their evolutionary histories, overall diversity, and challenges to their conservation is incomplete. We review the state of knowledge on these important issues, focusing on Pacific trout in the genus Oncorhynchus. Although most research on salmonid fishes emphasizes Pacific salmon, we focus on Pacific trout because they share a common evolutionary history, and many taxa in western North America have not been formally described, particularly in the southern extent of their ranges. Research in recent decades has led to the revision of many hypotheses concerning the origin and diversification of Pacific trout throughout their range. Although there has been significant success at addressing past threats to Pacific trout, contemporary and future threats represented by nonnative species, land and water use activities, and climate change pose challenges and uncertainties. Ultimately, conservation of Pacific trout depends on how well these issues are understood and addressed, and on solutions that allow these species to coexist with a growing scope of human influences.

Fisheries↗

USGS2016

Linkages between unpaved forest roads and streambed sediment: why context matters in directing road restoration

Unpaved forest roads remain a pervasive disturbance on public lands and mitigating sediment from road networks remains a priority for management agencies. Restoring roaded landscapes is becoming increasingly important for many native coldwater fishes that disproportionately rely on public lands for persistence. However, effectively targeting restoration opportunities requires a comprehensive understanding of the effects of roads across different ecosystems. Here, we combine a review and a field study to evaluate the status of knowledge supporting the conceptual framework linking unpaved forest roads with streambed sediment. Through our review, we specifically focused on those studies linking measures of the density of forest roads or sediment delivery with empirical streambed sediment measures. Our field study provides an example of a targeted effort of linking spatially explicit estimates of sediment production with measures of streambed sediment. Surprisingly, our review uncovered few studies ( n  = 8) that empirically tested the conceptual framework linking unpaved forest roads and streambed sediment, and the results varied considerably. Field results generally supported the conceptual model that unpaved forest roads can control streambed sediment quality, but demonstrated high-spatial variability in the effects of forest roads on streambed sediment and the need to address hotspots of sediment sources. The importance of context in the effects of forest roads is apparent in both our review and field data, suggesting the need for in situ studies to avoid misdirected restoration actions.

Pacific Northwest↗

USGS2016

Are brown trout replacing or displacing bull trout populations in a changing climate?

Understanding how climate change may facilitate species turnover is an important step in identifying potential conservation strategies. We used data from 33 sites in western Montana to quantify climate associations with native bull trout (Salvelinus confluentus) and non-native brown trout (Salmo trutta) abundance and population growth rates (λ). We estimated λ using exponential growth state space models and delineated study sites based on bull trout use for either Spawning and Rearing (SR) or Foraging, Migrating, and Overwintering (FMO) habitat. Bull trout abundance was negatively associated with mean August stream temperatures within SR habitat (r = -0.75). Brown trout abundance was generally highest at temperatures between 12 and 14°C. We found bull trout λ were generally stable at sites with mean August temperature below 10°C but significantly decreasing, rare, or extirpated at 58% of the sites with temperatures exceeding 10°C. Brown trout λ were highest in SR and sites with temperatures exceeding 12°C. Declining bull trout λs at sites where brown trout were absent suggests brown trout are likely replacing bull trout in a warming climate.

Idaho, Montana↗

USGS2015

The shifting climate portfolio of the Greater Yellowstone Area

Knowledge of climatic variability at small spatial extents (< 50 km) is needed to assess vulnerabilities of biological reserves to climate change. We used empirical and modeled weather station data to test if climate change has increased the synchrony of surface air temperatures among 50 sites within the Greater Yellowstone Area (GYA) of the interior western United States. This important biological reserve is the largest protected area in the Lower 48 states and provides critical habitat for some of the world’s most iconic wildlife. We focused our analyses on temporal shifts and shape changes in the annual distributions of seasonal minimum and maximum air temperatures among valley-bottom and higher elevation sites from 1948–2012. We documented consistent patterns of warming since 1948 at all 50 sites, with the most pronounced changes occurring during the Winter and Summer when minimum and maximum temperature distributions increased. These shifts indicate more hot temperatures and less cold temperatures would be expected across the GYA. Though the shifting statistical distributions indicate warming, little change in the shape of the temperature distributions across sites since 1948 suggest the GYA has maintained a diverse portfolio of temperatures within a year. Spatial heterogeneity in temperatures is likely maintained by the GYA’s physiographic complexity and its large size, which encompasses multiple climate zones that respond differently to synoptic drivers. Having a diverse portfolio of temperatures may help biological reserves spread the extinction risk posed by climate change.

Montana, Wyoming↗

USGS2015

Impacts of climatic variation on trout: A global synthesis and path forward

Despite increasing concern that climate change may negatively impact trout—a globally distributed group of fish with major economic, ecological, and cultural value—a synthetic assessment of empirical data quantifying relationships between climatic variation and trout ecology does not exist. We conducted a systematic review to describe how temporal variation in temperature and streamflow influences trout ecology in freshwater ecosystems. Few studies ( n = 42) have quantified relationships between temperature or streamflow and trout demography, growth, or phenology, and nearly all estimates (96 %) were for Salvelinus fontinalis and Salmo trutta . Only seven studies used temporal data to quantify climate-driven changes in trout ecology. Results from these studies were beset with limitations that prohibited quantitatively rigorous meta-analysis, a concerning inadequacy given major investment in trout conservation and management worldwide. Nevertheless, consistent patterns emerged from our synthesis, particularly a positive effect of summer streamflow on trout demography and growth; 64 % of estimates were positive and significant across studies, age classes, species, and locations, highlighting that climate-induced changes in hydrology may have numerous consequences for trout. To a lesser degree, summer and fall temperatures were negatively related to population demography (51 and 53 % of estimates, respectively), but temperature was rarely related to growth. To address limitations and uncertainties, we recommend: (1) systematically improving data collection, description, and sharing; (2) appropriately integrating climate impacts with other intrinsic and extrinsic drivers over the entire lifecycle; (3) describing indirect consequences of climate change; and (4) acknowledging and describing intrinsic resiliency.

Reviews in Fish Biology and Fisheries↗

USGS2015

Consequences of actively managing a small Bull Trout population in a fragmented landscape

Habitat fragmentation, which affects many native salmonid species, is one of the major factors contributing to the declines in distribution and abundance of Bull Trout Salvelinus confluentus . Increasingly, managers are considering options to maintain and enhance the persistence of isolated local populations through active management strategies. Understanding the ecological consequences of such actions is a necessary step in conservation planning. We used an individual-based model to evaluate the consequences of an ongoing management program aimed at mitigating the anthropogenic fragmentation of the lower Clark Fork River in Montana. Under this program juvenile Bull Trout are trapped and transported from small, headwater source populations to Lake Pend Oreille, Idaho, for rearing, and adults are subsequently recaptured in their upstream migration and returned to the natal population for spawning. We examined one of these populations and integrated empirical estimates of demographic parameters to simulate different management scenarios where moderate ( n = 4) and high ( n = 8) numbers of age-2, age-3, or age-4 Bull Trout were removed for transport with variable return rates under both demographic stochasticity and environmental perturbations. Our results indicated the risks from removal with no returns increased substantially when removal totals and age of Bull Trout removed from the simulated population increased. Specifically, removing eight age-3 or age-4 individuals resulted in 26% and 62% reductions in average adult population size, respectively, across simulations. We found the risks of transport were not likely alleviated with low (3%) or moderate (6%) return rates, and there were considerable risks of declines for the source population even when return rates were extremely high (>12%). Our simulations indicated little risk of declines for the source population with removals of age-2 Bull Trout, and any risks were alleviated with low return rates. However, we found higher return rates were particularly beneficial in the presence of large, density-independent perturbations.

Montana↗

USGS2015

Genetic diversity is related to climatic variation and vulnerability in threatened bull trout

Understanding how climatic variation influences ecological and evolutionary processes is crucial for informed conservation decision-making. Nevertheless, few studies have measured how climatic variation influences genetic diversity within populations or how genetic diversity is distributed across space relative to future climatic stress. Here, we tested whether patterns of genetic diversity (allelic richness) were related to climatic variation and habitat features in 130 bull trout ( Salvelinus confluentus ) populations from 24 watersheds (i.e., ~4–7th order river subbasins) across the Columbia River Basin, USA. We then determined whether bull trout genetic diversity was related to climate vulnerability at the watershed scale, which we quantified on the basis of exposure to future climatic conditions (projected scenarios for the 2040s) and existing habitat complexity. We found a strong gradient in genetic diversity in bull trout populations across the Columbia River Basin, where populations located in the most upstream headwater areas had the greatest genetic diversity. After accounting for spatial patterns with linear mixed models, allelic richness in bull trout populations was positively related to habitat patch size and complexity, and negatively related to maximum summer temperature and the frequency of winter flooding. These relationships strongly suggest that climatic variation influences evolutionary processes in this threatened species and that genetic diversity will likely decrease due to future climate change. Vulnerability at a watershed scale was negatively correlated with average genetic diversity ( r = −0.77; P < 0.001); watersheds containing populations with lower average genetic diversity generally had the lowest habitat complexity, warmest stream temperatures, and greatest frequency of winter flooding. Together, these findings have important conservation implications for bull trout and other imperiled species. Genetic diversity is already depressed where climatic vulnerability is highest; it will likely erode further in the very places where diversity may be most needed for future persistence.

Global Change Biology↗

USGS2015

Empirical evaluation of the conceptual model underpinning a regional aquatic long-term monitoring program using causal modelling

Conceptual models are an integral facet of long-term monitoring programs. Proposed linkages between drivers, stressors, and ecological indicators are identified within the conceptual model of most mandated programs. We empirically evaluate a conceptual model developed for a regional aquatic and riparian monitoring program using causal models (i.e., Bayesian path analysis). We assess whether data gathered for regional status and trend estimation can also provide insights on why a stream may deviate from reference conditions. We target the hypothesized causal pathways for how anthropogenic drivers of road density, percent grazing, and percent forest within a catchment affect instream biological condition. We found instream temperature and fine sediments in arid sites and only fine sediments in mesic sites accounted for a significant portion of the maximum possible variation explainable in biological condition among managed sites. However, the biological significance of the direct effects of anthropogenic drivers on instream temperature and fine sediments were minimal or not detected. Consequently, there was weak to no biological support for causal pathways related to anthropogenic drivers’ impact on biological condition. With weak biological and statistical effect sizes, ignoring environmental contextual variables and covariates that explain natural heterogeneity would have resulted in no evidence of human impacts on biological integrity in some instances. For programs targeting the effects of anthropogenic activities, it is imperative to identify both land use practices and mechanisms that have led to degraded conditions (i.e., moving beyond simple status and trend estimation). Our empirical evaluation of the conceptual model underpinning the long-term monitoring program provided an opportunity for learning and, consequently, we discuss survey design elements that require modification to achieve question driven monitoring, a necessary step in the practice of adaptive monitoring. We suspect our situation is not unique and many programs may suffer from the same inferential disconnect. Commonly, the survey design is optimized for robust estimates of regional status and trend detection and not necessarily to provide statistical inferences on the causal mechanisms outlined in the conceptual model, even though these relationships are typically used to justify and promote the long-term monitoring of a chosen ecological indicator. Our application demonstrates a process for empirical evaluation of conceptual models and exemplifies the need for such interim assessments in order for programs to evolve and persist.

California, Colorado, Idaho, Montana, Nevada, Oreg↗

USGS2015

Monitoring Greater Yellowstone Ecosystem wetlands: Can long-term monitoring help us understand their future?

In the Greater Yellowstone Ecosystem (GYE), changes in the drying cycles of wetlands have been documented. Wetlands are areas where the water table is at or near the land surface and standing shallow water is present for much or all of the growing season. We discuss how monitoring data can be used to document variation in annual flooding and drying patterns of wetlands monitored across Yellowstone and Grand Teton national parks, investigate how these patterns are related to a changing climate, and explore how drying of wetlands may impact amphibians. The documented declines of some amphibian species are of growing concern to scientists and land managers alike, in part because disappearances have occurred in some of the most protected places. These disappearances are a recognized component of what is being described as Earth’s sixth mass extinction.

Wyoming↗

USGS2014

Annual variation of spawning Cutthroat Trout in a small Western USA stream: A case study with implications for the conservation of potamodromous trout life history diversity

Little is known about the variability in the spatial and temporal distribution of spawning potamodromous trout despite decades of research directed at salmonid spawning ecology and the increased awareness that conserving life history diversity should be a focus of management. We monitored a population of fluvial–resident Bonneville Cutthroat Trout Oncorhynchus clarkii utah in a tributary to the Logan River, Utah, from 2006 to 2012 to gain insight into the distribution and timing of spawning and what factors may influence these spawning activities. We monitored Bonneville Cutthroat Trout using redd surveys with multiple observers and georeferenced redd locations. We documented an extended spawning period that lasted from late April to mid‐July. The onset, median, and end of spawning was best predicted by the mean maximum water temperature during the first 13 weeks of the year ( F = 130. 4, df = 5, R 2 = 0.96, P < 0.0001) with spawning beginning and ending earlier in years that had warmer water temperatures prior to spawning. The distribution of redds was clumped each year and the relative density of redds was greater in a reach dominated by dams constructed by beavers Castor canadensis . Both dam failure and construction appeared to be responsible for creating new spawning habitat that was quickly occupied, demonstrating rapid temporal response to local habitat changes. Bonneville Cutthroat Trout appeared to establish and defend a redd for up to 2 d, and spawning most often occurred between similar‐sized individuals. Spawning surveys for potamodromous trout are an underutilized tool that could be used to better understand the distribution and timing of spawning as well as determine the size and trends of the reproducing portion of populations of management concern. Without efforts to document the diversity of this important aspect of potamodromous trout life history, prioritization of conservation will be problematic.

Utah↗

USGS2014

Invasive hybridization in a threatened species is accelerated by climate change

Climate change will decrease worldwide biodiversity through a number of potential pathways 1 , including invasive hybridization 2 (cross-breeding between invasive and native species). How climate warming influences the spread of hybridization and loss of native genomes poses difficult ecological and evolutionary questions with little empirical information to guide conservation management decisions 3 . Here we combine long-term genetic monitoring data with high-resolution climate and stream temperature predictions to evaluate how recent climate warming has influenced the spatio-temporal spread of human-mediated hybridization between threatened native westslope cutthroat trout ( Oncorhynchus clarkii lewisi ) and non-native rainbow trout ( Oncorhynchus mykiss ), the world’s most widely introduced invasive fish 4 . Despite widespread release of millions of rainbow trout over the past century within the Flathead River system 5 , a large relatively pristine watershed in western North America, historical samples revealed that hybridization was prevalent only in one (source) population. During a subsequent 30-year period of accelerated warming, hybridization spread rapidly and was strongly linked to interactions between climatic drivers—precipitation and temperature—and distance to the source population. Specifically, decreases in spring precipitation and increases in summer stream temperature probably promoted upstream expansion of hybridization throughout the system. This study shows that rapid climate warming can exacerbate interactions between native and non-native species through invasive hybridization, which could spell genomic extinction for many species.

Alberta, Idaho, Montana↗

USGS2014

Aquatic invasive species: Lessons from cancer research

Aquatic invasive species are disrupting ecosystems with increasing frequency. Successful control of these invasions has been rare: Biologists and managers have few tools for fighting aquatic invaders. In contrast, the medical community has long worked to develop tools for preventing and fighting cancer. Its successes are marked by a coordinated research approach with multiple steps: prevention, early detection, diagnosis, treatment options and rehabilitation. The authors discuss how these steps can be applied to aquatic invasive species, such as the American bullfrog (Lithobates catesbeianus), in the Northern Rocky Mountain region of the United States, to expedite tool development and implementation along with achievement of biodiversity conservation goals.

American Scientist↗

USGS2014

Quantifying the effectiveness of conservation measures to control the spread of anthropogenic hybridization in stream salmonids: A climate adaptation case study

Quantifying the effectiveness of management actions to mitigate the effects of changing climatic conditions (i.e., climate adaptation) can be difficult, yet critical for conservation. We used population genetic data from 1984 to 2011 to assess the degree to which ambient climatic conditions and targeted suppression of sources of nonnative Rainbow Trout Oncorhynchus mykiss have influenced the spread of introgressive hybridization in native populations of Westslope Cutthroat Trout O. clarkii lewisi . We found rapid expansion in the spatial distribution and proportion of nonnative genetic admixture in hybridized populations from 1984 to 2004, but minimal change since 2004. The spread of hybridization was negatively correlated with the number of streamflow events in May that exceeded the 75th percentile of historic flows ( r = −0.98) and positively correlated with August stream temperatures ( r = 0.89). Concomitantly, suppression data showed a 60% decline in catch per unit effort for fish with a high proportion of Rainbow Trout admixture, rendering some uncertainty as to the relative strength of factors controlling the spread of hybridization. Our results illustrate the importance of initiating management actions to mitigate the potential effects of climate change, even where data describing the effectiveness of such actions are initially limited but the risks are severe.

Montana↗

USGS2013

Thermal controls of Yellowstone cutthroat trout and invasive fishes under climate change

We combine large observed data sets and dynamically downscaled climate data to explore historic and future (2050–2069) stream temperature changes over the topographically diverse Greater Yellowstone Ecosystem (elevation range = 824–4017 m). We link future stream temperatures with fish growth models to investigate how changing thermal regimes could influence the future distribution and persistence of native Yellowstone cutthroat trout (YCT) and competing invasive species. We find that stream temperatures during the recent decade (2000–2009) surpass the anomalously warm period of the 1930s. Climate simulations indicate air temperatures will warm by 1 °C to >3 °C over the Greater Yellowstone by mid-21st century, resulting in concomitant increases in 2050–2069 peak stream temperatures and protracted periods of warming from May to September (MJJAS). Projected changes in thermal regimes during the MJJAS growing season modify the trajectories of daily growth rates at all elevations with pronounced growth during early and late summer. For high-elevation populations, we find considerable increases in fish body mass attributable both to warming of cold-water temperatures and to extended growing seasons. During peak July to August warming, mid-21st century temperatures will cause periods of increased thermal stress, rendering some low-elevation streams less suitable for YCT. The majority (80%) of sites currently inhabited by YCT, however, display minimal loss (<10%) or positive changes in total body mass by midcentury; we attribute this response to the fact that many low-elevation populations of YCT have already been extirpated by historical changes in land use and invasions of non-native species. Our results further suggest that benefits to YCT populations due to warmer stream temperatures at currently cold sites could be offset by the interspecific effects of corresponding growth of sympatric, non-native species, underscoring the importance of developing climate adaptation strategies that reduce limiting factors such as non-native species and habitat degradation.

Global Change Biology↗

USGS2013

Characterizing the thermal suitability of instream habitat for salmonids: A cautionary example from the Rocky Mountains

Understanding a species’ thermal niche is becoming increasingly important for management and conservation within the context of global climate change, yet there have been surprisingly few efforts to compare assessments of a species’ thermal niche across methods. To address this uncertainty, we evaluated the differences in model performance and interpretations of a species’ thermal niche when using different measures of stream temperature and surrogates for stream temperature. Specifically, we used a logistic regression modeling framework with three different indicators of stream thermal conditions (elevation, air temperature, and stream temperature) referenced to a common set of Brook Trout Salvelinus fontinalis distribution data from the Boise River basin, Idaho. We hypothesized that stream temperature predictions that were contemporaneous with fish distribution data would have stronger predictive performance than composite measures of stream temperature or any surrogates for stream temperature. Across the different indicators of thermal conditions, the highest measure of accuracy was found for the model based on stream temperature predictions that were contemporaneous with fish distribution data (percent correctly classified = 71%). We found considerable differences in inferences across models, with up to 43% disagreement in the amount of stream habitat that was predicted to be suitable. The differences in performance between models support the growing efforts in many areas to develop accurate stream temperature models for investigations of species’ thermal niches.

Idaho↗