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At least 811 records · Page 45Linked to original sources
USGS1989

Microcontaminants and reproductive impairment of the Forster's tern on Green Bay, Lake Michigan,1983

For the 1983 nesting season, Forster's tern ( Sterna forsteri ) reproductive success was significantly impaired on organochlorine contaminated Green Bay, Lake Michigan compared to a relatively uncontaminated inland location at Lake Poygan, Wisconsin. Compared with tern eggs from Lake Poygan, eggs from Green Bay had significantly higher median concentrations of 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD), other polychlorinated dibenzo- p -dioxins (PCDDs), total polychlorinated biphenyls (PCBs), total (three congeners) non-ortho, ortho' PCBs, five individual PCB congeners known to induce aryl hydrocarbon hydroxylase (AHH) and several other organochlorine contaminants. Conversions of analytical concentrations of TCDD and PCB congeners based on relative AHH induction potencies allowed for estimation of total 2,3,7,8-TCDD equivalents. Two PCB congeners, 2,3,3′,4,4′- and 3,3′,4,4′,5-pentachlorobiphenyl (PeCB) accounted for more than 90% of the median estimated TCDD equivalents at both Green Bay and Lake Poygan. The median estimated TCDD equivalents were almost 11-fold higher in tern eggs from Green Bay than in eggs from Lake Poygan (2175 and 201 pg/g). The hatching success of Green Bay sibling eggs from nests where eggs were collected for contaminant analyses was 75% lower at Green Bay than at Lake Poygan. Hatchability of eggs taken from other nests and artificially incubated was about 50% lower for Green Bay than for Lake Poygan. Among hatchlings from laboratory incubation, those from Green Bay weighed approximately 20% less and had a mean liver weight to body weight ratio 26% greater than those from Lake Poygan. In both field and laboratory, mean minimum incubation periods were significantly longer for eggs from Green Bay compared to Lake Poygan (8.25 and 4.58 days, respectively). Mean minimum incubation time for Green Bay eggs in the field was 4.37 days longer than in the laboratory. Hatchability was greatly improved when Green Bay eggs were incubated by Lake Poygan adults in an egg-exchange experiment, but was sharply decreased in Lake Poygan eggs incubated in Green Bay nests. Nest abandonment and egg disappearance were substantial at Green Bay but nil at Lake Poygan. Thus, not only factors intrinsic to the egg, but also extrinsic factors (parental attentiveness), impaired reproductive outcome at Green Bay. The epidemiological evidence from this study strongly suggested that contaminants were a causal factor. AHH-active PCB congeners (intrinsic effects) and PCBs in general (extrinsic effects) appeared to be the only contaminants at the concentrations measured in eggs, capable of producing the effects that were observed at Green Bay.

Wisconsin↗
USGS2015

Turbidity alters pre-mating social interactions between native and invasive stream fishes

Environmental degradation can result in the loss of aquatic biodiversity if impairment promotes hybridisation between non-native and native species. Although aquatic biological invasions involving hybridisation have been attributed to elevated water turbidity, the extent to which impaired clarity influences reproductive isolation among non-native and native species is poorly understood. We examined whether turbidity influences intraspecific and interspecific pre-mating social interactions between invasive red shiner ( Cyprinella lutrensis ) and native blacktail shiner ( Cyprinella venusta ) from the Upper Coosa River Basin (U.S.A.). We found that the number or duration of conspecific and heterospecific interactions increased under turbid conditions. Additionally, we found evidence indicating that native blacktail shiner females are especially likely to interact with invasive red shiner males due to species- and sex-specific responses to turbid conditions. These findings suggest that elevated turbidity can increase pre-mating social interactions between native and invasive species, which could result in greater hybridisation and promote the genetic assimilation of native species following species introductions. Thus, integrating knowledge of species behaviour into conservation and management planning can help deter the establishment and spread of invasive species.

Freshwater Biology↗
USGS2007

The distribution of nuclear genetic variation and historical demography of sea otters

The amount and distribution of population genetic variation is crucial information for the design of effective conservation strategies for endangered species and can also be used to provide inference about demographic processes and patterns of migration. Here, we describe variation at a large number of nuclear genes in sea otters Enhydra lutris ssp. We surveyed 14 variable microsatellite loci and two genes of the major histocompatibility complex (MHC) in up to 350 California sea otters Enhydra lutris nereis , which represents ∼10% of the subspecies' population, and 46 otters from two Alaskan sites. We utilized methods for detecting past reductions in effective population size to examine the effects of near extinction from the fur trade. Summary statistic tests largely failed to find a signal of a recent population size reduction (within the past 200 years), but a Bayesian method found a signal of a strong reduction over a longer time scale (up to 500 years ago). These results indicate that the reduction in size began long enough ago that much genetic variation was lost before the 19th century fur trade. A comparison of geographic distance and pairwise relatedness for individual otters found no evidence of kin-based spatial clustering for either gender. This indicates that there is no population structure, due to extended family groups, within the California population. A survey of population genetic variation found that two of the MHC genes, DQB and DRB, had two alleles present and one of the genes, DRA, was monomorphic in otters. This contrasts with other mammals, where they are often the most variable coding genes known. Genetic variation in the sea otter is among the lowest observed for a mammal and raises concerns about the long-term viability of the species, particularly in the face of future environmental changes.

Animal Conservation↗
USGS2008

Landscape-scale evaluation of genetic structure among barrier-isolated populations of coastal cutthroat trout, Oncorhynchus clarkii clarkii

Relationships among landscape structure, stochastic disturbance, and genetic diversity were assessed by examining interactions between watershed-scale environmental factors and genetic diversity of coastal cutthroat trout (Oncorhynchus clarkii clarkii) in 27 barrier-isolated watersheds from western Oregon, USA. Headwater populations of coastal cutthroat trout were genetically differentiated (mean FST = 0.33) using data from seven microsatellite loci (2232 individuals), but intrapopulation microsatellite genetic diversity (mean number of alleles per locus = 5, mean He = 0.60) was only moderate. Genetic diversity of coastal cutthroat trout was greater (P = 0.02) in the Coast Range ecoregion (mean alleles = 47) than in the Cascades ecoregion (mean alleles = 30), and differences coincided with indices of regional within-watershed complexity and connectivity. Furthermore, regional patterns of diversity evident from isolation-by-distance plots suggested that retention of within-population genetic diversity in the Coast Range ecoregion is higher than that in the Cascades, where genetic drift is the dominant factor influencing genetic patterns. Thus, it appears that physical landscape features have influenced genetic patterns in these populations isolated from short-term immigration. ?? 2008 NRC.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS2001

Effects of dissolved carbon dioxide on the physiology and behavior of fish artificial streams

A new technology for treating waters contaminated with acid mine drainage involves the dissolution of limestone particles using carbon dioxide at pressures above ambient. Because of the fish health risks associated with episodes of high carbon dioxide levels in treated waters, we subjected three species of fish, brook trout ( Salvelinus fontinalis ), slimy sculpin ( Cottus cognatus ), and blacknose dace ( Rhinichthys atratulus ), to 24 h exposures of elevated dissolved carbon dioxide (CO 2 ) at three levels, ranging from 1.0 (low) to 6.3 (high)%, under laboratory conditions. We measured blood physiological variables as well as behavior, including feeding responses, before, during, and after exposure. Physiological responses differed by species, but all species had elevated hematocrits after 1 h of exposure. Brook trout hematocrits were higher at medium and high levels of CO 2 than in a control group (0.0% CO 2 ) after 24 h of exposure. Slimy sculpin hematocrits were higher in medium- and high-level exposure groups than in controls after 1 h, but not after 24 h, of exposure. Blacknose dace hematocrits were higher in all three exposure groups than in controls after 1 h but only in medium-level exposure groups after 24 h. Brook trout plasma glucose was significantly higher in medium- and high-level exposure groups after 1 h, and in the high-level group after 24 h, than in controls. Slimy sculpin plasma glucose was not significantly different in elevated CO 2 exposure groups from that of controls throughout exposure. Branchial ventilation was significantly greater in all species at elevated CO 2 during exposure, indicating stress; however, no difference was observed between treatment and control groups of blacknose dace after 24 h, indicating acclimation. Pectoral fin beats and cough rates were not consistently related to CO 2 exposure throughout the study. Brook trout had the longest lasting reaction to stress at lower levels of CO 2 among the three species tested. Many of the 11 observed behavioral variables, related to swimming, feeding, social, and illness factors, were affected by elevations of dissolved CO 2 . Two to seven behavioral variables (18–64% of those measured) were affected by treatment level of dissolved CO 2 with a trend by species for the number of variables affected: brook trout>blacknose dace>slimy sculpin. However, behavioral sensitivity to treatment level was greatest in blacknose dace. Recovery to pre-treatment activity rates for most behavior patterns (including feeding) was observed 24 h after cessation of exposure in all three species. Recovery was independent of treatment level, was most rapid in blacknose dace, and was slowest in brook trout. Overall, slimy sculpin was least affected behaviorally by elevated CO 2 . Although all three species showed stress response and changes in behavior at moderate levels of CO 2 (≥2%), brook trout and blacknose dace showed evidence of ability to avoid harmful CO 2 levels by swimming out of affected waters, whereas the slimy sculpin showed minimal behavioral changes despite remaining in place during exposure. Thus, predation risk and other sources of mortality seem minimal in the event of technological malfunction at a stream treatment site involving the use of CO 2 under pressure.

Environmental Toxicology↗
USGS1985

Effects of a Kentucky flood-control reservoir on macroinvertebrates in the tailwater

The effects of a flood-control reservoir on downstream macroinvertebrates were assessed by comparing the tailwater community with that of a natural stream. Samples were collected 1.6 and 21.1 km below Barren River Lake dam in 1979, 1980, and 1981 and in a reservoir tributary in 1980 and 1981. An indication of environmental stress in the macroinvertebrate community was observed at both tailwater stations, whereas macroinvertebrates in the natural tributary stream had the characteristics commonly associated with a ‘healthy’ community. Densities of macroinvertebrates in tailwaters were highest during periods of low-stable flows and lowest during fluctuating and high-stable flows. Changes in temperature cycles and water quality were also considered factors in reducing macroinvertebrate abundance in the tailwater. Dominant macroinvertebrate taxa in tailwaters were primarily small organisms with a high tolerance for dynamic living conditions. Of these, aquatic Diptera, Oligochaeta, Caenis, Cheumatopsyche , and Planariidae were most common. The effects of reservoir discharge were most evident near the dam, where macroinvertebrate densities were relatively high and taxonomic diversity was low. Downstream, the impact of the reservoir was moderated, but recovery was judged incomplete.

Kentucky↗
USGS2025

Cell penetrating peptide-mediated delivery of gene-silencing nucleic acids to the invasive common reed Phragmites australis via foliar application

As a popular tool for gene function characterization and gene therapy, RNA interference (RNAi)-based gene silencing has been increasingly explored for potential applications to control invasive species. At least two major hurdles exist when applying this approach to invasive plants: (1) the design and screening of species- and gene-specific biomacromolecules (i.e., gene-silencing agents or GSAs) made of DNA, RNA, or peptides that can suppress the expression of target genes efficiently, and (2) the delivery vehicle needed to penetrate plant cell walls and other physical barriers (e.g., leaf cuticles). In this study, we investigated the cell-penetrating peptide (CPP)-mediated delivery of multiple types of GSAs (e.g., double-stranded RNA (dsRNA), artificial microRNA (amiRNA), and antisense oligonucleotide (ASO)) to knock down a putative phytoene desaturase ( PDS ) gene in the invasive common reed ( Phragmites australis spp. australis ). Both microscopic and quantitative gene expression evidence demonstrated the CPP-mediated internalization of GSA cargos and transient suppression of PDS expression in both treated and systemic leaves up to 7 days post foliar application. Although various GSA combinations and application rates and frequencies were tested, we observed limitations, including low gene-silencing efficiency and a lack of physiological trait alteration, likely owing to low CPP payload capacity and the incomplete characterization of the PDS-coding genes (e.g., the recent discovery of two PDS paralogs) in P. australis . Our work lays a foundation to support further research toward the development of convenient, cost-effective, field-deployable, and environmentally benign gene-silencing technologies for invasive P. australis management.

Mississippi, Ohio↗
USGS2018

Evaluating the conservation potential of tributaries for native fishes in the Upper Colorado River Basin

We explored the conservation potential of tributaries in the upper Colorado River basin by modeling native fish species richness as a function of river discharge, temperature, barrier‐free length, and distance to nearest free‐flowing main‐stem section. We investigated a historic period prior to large‐scale water development and a contemporary period. In the historic period, species richness was log‐linearly correlated to variables capturing flow magnitude, particularly mean annual discharge. In the contemporary period, the log‐linear relationship between discharge and species richness was still evident but weaker. Tributaries with lower average temperature and separated from free‐flowing main‐stem sections often had fewer native species compared to tributaries with similar discharge but with warmer temperature and directly connected to free‐flowing main stems. Thus, tributaries containing only a small proportion of main‐stem discharge, especially those at lower elevations with warmer temperatures and connected to free‐flowing main stems, can support a relatively high species richness. Tributaries can help maintain viable populations by providing ecological processes disrupted on large regulated rivers, such as natural flow and temperature regimes, and may present unique conservation opportunities. Efforts to improve fish passage, secure environmental flows, and restore habitat in these tributaries could greatly contribute to conservation of native fish richness throughout the watershed.

Upper Colorado River Basin↗
USGS2021

Genetic structure and diversity of the mustard hill coral Porites astreoides along the Florida Keys reef tract

Increases in local and global stressors have led to major declines in coral populations throughout the western Atlantic. While abundances of other species have declined, however, the relative abundance of the mustard hill coral, Porites astreoides , has increased. Porites astreoides is relatively resilient to some stressors, and because of its mixed reproductive strategies, its populations often recover quickly following disturbances. The ability for P. astreoides to continue as a potential “winner” in western Atlantic reefs relies on maintaining sufficient genetic variation within populations to support acclimatization and adaptation to current and future environmental change. Without high genetic diversity and gene flow within the population, it would have limited capacity for adaptation and the species’ competitive advantages could be short-lived. In this study, we determined the genetic relatedness of 37 P. astreoides colonies at four shallow reefs along the offshore Florida Keys Reef Tract (FKRT), a region particularly hard-hit by recent disturbances. Using previously designed microsatellite markers, we determined the genetic diversity and connectivity of individuals among and between sites. Our results suggest that the FKRT likely contains a single, well-mixed genetic population of P. astreoides , with high levels of gene flow and evidence for larval migration throughout the region. This suggests that regional populations of P. astreoides likely have a higher chance of maintaining resilience than many other western Atlantic species as they face current and future disturbances.

Florida↗
USGS2021

Modern Mars' geomorphological activity, driven by wind, frost, and gravity

Extensive evidence of landform-scale martian geomorphic changes has been acquired in the last decade, and the number and range of examples of surface activity have increased as more high-resolution imagery has been acquired. Within the present-day Mars climate, wind and frost/ice are the dominant drivers, resulting in large avalanches of material down icy, rocky, or sandy slopes; sediment transport leading to many scales of aeolian bedforms and erosion; pits of various forms and patterned ground; and substrate material carved out from under subliming ice slabs. Due to the ability to collect correlated observations of surface activity and new landforms with relevant environmental conditions with spacecraft on or around Mars, studies of martian geomorphologic activity are uniquely positioned to directly test surface-atmosphere interaction and landform formation/evolution models outside of Earth. In this paper, we outline currently observed and interpreted surface activity occurring within the modern Mars environment, and tie this activity to wind, seasonal surface CO2 frost/ice, sublimation of subsurface water ice, and/or gravity drivers. Open questions regarding these processes are outlined, and then measurements needed for answering these questions are identified. In the final sections, we discuss how many of these martian processes and landforms may provide useful analogs for conditions and processes active on other planetary surfaces, with an emphasis on those that stretch the bounds of terrestrial-based models or that lack terrestrial analogs. In these ways, modern Mars presents a natural and powerful comparative planetology base case for studies of Solar System surface processes, beyond or instead of Earth.

Geomorphology↗
USGS2020

Hydrogeomorphological controls on reach‐scale distributions of cichlid nest sites in a small neotropical river

The Cichlidae are among the most diversified families of fish in the Neotropics and represent an important component of aquatic biodiversity. Understanding cichlid nest‐site selection is important for assemblages facing uncertain futures due to species invasions and environmental change. This information could be used to predict how inter‐ and intraspecific competition for reproductive space may affect populations with changing community dynamics or to identify areas as targets for conservation. We investigated which hydrogeomorphological factors correlated to preferred nest sites of four native cichlid species in the Bladen River, Belize. We recorded the locations of nest sites and collected habitat data through the study reach, including flow velocity, depth, sediment type, fish cover type richness and distance to the bank. Nest locations and physical habitat data were used to construct spatially explicit habitat models using boosted regression trees (BRTs). The models provided statistically significant evidence that physical habitat variables influence the distribution of the nest sites. We found that all species except Archocentrus spilurus were associated with substrate, specifically sand. Thorichthys meeki was also associated with lower water velocities, whereas Cichlasoma salvini was influenced by all five variables. Vieja maculicauda and Archocentrus spilurus were both influenced by flow velocity, distance to bank and depth, although A. spilurus preferred deeper, slightly faster locations about the same distance to the bank. This study suggests that the spatial distribution of nest sites within this cichlid community is significantly different than random and is at least partially governed by physical controls.

Monkey River Basin↗
USGS2016

Historical habitat barriers prevent ring-like genetic continuity throughout the distribution of threatened Alameda Striped Racers ( Coluber lateralis euryxanthus )

We used microsatellites and mtDNA sequences to examine the mixed effects of geophysical, habitat, and contemporary urban barriers on the genetics of threatened Alameda Striped Racers (Coluber lateralis euryxanthus), a species with close ties to declining coastal scrub and chaparral habitat in the eastern San Francisco Bay area of California. We used cluster assignments to characterize population genetic structuring with respect to land management units and approximate Bayesian analysis to rank the ability of five alternative evolutionary hypotheses to explain the inferred structure. Then, we estimated rates of contemporary and historical migration among the major clusters and measured the fit of different historical migration models to better understand the formation of the current population structure. Our results reveal a ring-like pattern of historical connectivity around the Tri-Valley area of the East Bay (i.e., San Ramon, Amador, and Livermore valleys), with clusters largely corresponding to different management units. We found no evidence of continuous gene flow throughout the ring, however, and that the main gap in continuity is centered across the Livermore Valley. Historical migration models support higher rates of gene flow away from the terminal ends of the ring on the north and south sides of the Valley, compared with rates into those areas from western sites that border the interior San Francisco Bay. We attribute the break in ring-like connectivity to the presence of unsuitable habitat within the Livermore Valley that has been reinforced by 20th century urbanization, and the asymmetry in gene flow rates to spatial constraints on movement and east–west environmental gradients influenced by the proximity of the San Francisco Bay.

California↗
USGS2019

Monitoring breeding and survival of ring-necked pheasant (Phasianus colchicus) in the Sacramento Valley, Sacramento-San Joaquin River Delta, and Klamath Basin, northern California—Five-year summary, 2013–17

The U.S. Geological Survey Western Ecological Research Center, Pheasants Forever, Mandeville Island Duck Club, and the California Department of Fish and Wildlife collaborated in a reconnaissance study to monitor populations of ring-necked pheasant ( Phasianus colchicus ) using radio-telemetry in the Sacramento Valley, Sacramento-San Joaquin River Delta, and Klamath Basin of northern California. The purpose of this study was to provide agencies and private landowners with a framework of decision-support tools to help manage pheasant populations in California. During winter, spring, and autumn of 2013–17, we radio- or Global Positioning System-marked 227 female pheasant across six study sites. Data collection was focused on investigating nest-site and brood-rearing habitat selection, examining avian predator composition, and estimating population vital rates to improve our understanding of pheasant population dynamics and to identify factors that may contribute to decreases in pheasant populations in California. The cumulative annual adult survival probability across all sites during 2013–17 was 27.6 percent (95-percent confidence interval [CI], 21.9–33.6), and the cumulative nest and brood survival probabilities were 34.5 percent (95-percent CI, 27.0–42.2) and 54.2 percent (95-percent CI, 43.7–63.5), respectively. Evidence from microhabitat surveys completed at nest-sites, brood locations, and random locations suggested that marked female pheasant tended to select increasing vertical cover and residual vegetation cover and tended to avoid areas of increasing bare ground cover regardless of life-history stage. However, females at nest-sites selected increasing grass cover and height, whereas brood-rearing females tended to select increasing forb cover and height. Only perennial grass cover and perennial grass height were shown to have a positive influence on nest survival, which suggests that increasing perennial grass cover in areas occupied by pheasant may increase nest survival. Analysis of environmental factors linked to vital rate information are ongoing and will continue with investigations at increased spatial scales (that is, macro-habitat) to develop integrated population models that can incorporate abundance estimates from crow count data with vital rates from telemetry data. This report includes results from 5 years of data collection and should be interpreted with caution, as these findings are preliminary.

California↗
USGS2021

Resistance, resilience, and recovery of dryland soil bacterial communities across multiple disturbances

Dryland ecosystems are sensitive to perturbations and generally slow to recover post disturbance. The microorganisms residing in dryland soils are especially important as they contribute to soil structure and nutrient cycling. Disturbance can have particularly strong effects on dryland soil structure and function, yet the natural resistance and recovery of the microbial components of dryland soils has not been well documented. In this study, the recovery of surface soil bacterial communities from multiple physical and environmental disturbances is assessed. Samples were collected from three field sites in the vicinity of Moab, UT, United States, 6 to 7 years after physical and climate disturbance manipulations had been terminated, allowing for the assessment of community recovery. Additionally, samples were collected in a transect that included three habitat patches: the canopy zone soils under the dominant shrubs, the interspace soils that are colonized by biological soil crusts, and edge soils at the plot borders. Field site and habitat patch were significant factors structuring the bacterial communities, illustrating that sites and habitats harbored unique soil microbiomes. Across the different sites and disturbance treatments, there was evidence of significant bacterial community recovery, as bacterial biomass and diversity were not significantly different than control plots. There was, however, a small number of 16S rRNA gene amplicon sequence variants that distinguished particular treatments, suggesting that legacy effects of the disturbances still remained. Taken together, these data suggest that dryland bacterial communities may possess a previously unappreciated potential to recover within years of the original disturbance.

Frontiers in Microbiology↗
USGS1997

Population genetic studies of the polar bear ( Ursus maritimus ): A summary of available data and interpretation of results

A summary of existing population genetics literature is presented for polar bears ( Ursus maritimus ) and interpreted in the context of the species' life-history characteristics and regional heterogeneity in environmental regimes and movement patterns. Several nongenetic data sets including morphology, contaminant levels, geographic variation in reproductive characteristics, and the location and distribution of open-water foraging habitat suggest some degree of spatial structuring. Eleven populations are recognized by the IUCN Polar Bear Specialist Group. Few genetics studies exist for polar bears. Interpretation and generalizations of regional variation in intra- and interpopulation levels of genetic variability are confounded by the paucity of data from many regions and by the fact that no single informative genetic marker has been employed in multiple regions. Early allozyme studies revealed comparatively low levels of genetic variability and no compelling evidence of spatial structuring. Studies employing mitochondrial DNA (mtDNA) also found low levels of genetic variation, a lack of phylogenetic structure, and no significant evidence for spatial variation in haplotype frequency. In contrast, microsatellite variable number of tandem repeat (VNTR) loci have revealed significant heterogeneity in allele frequency among populations in the Canadian Arctic. These regions are characterized by archipelgic patterns of sea-ice movements. Further studies using highly polymorphic loci are needed in regions characterized by greater polar bear dependency on pelagic sea-ice movements and in regions for which no data currently exist (i.e., Laptev and Novaya Zemlya/Franz Josef).

Book chapter↗
USGS1988

Effects of krenite® brush control agent (fosamine ammonium) on embryonic development in mallards and bobwhite

Fosamine ammonium (Krenite®) is a highly water-soluble carbamoylphosphonate herbicide used to control woody brush. It has been reported to be teratogenic to avian embryos following spray application of the eggs. The embryotoxic and teratogenic potential of Krenite was examined in mallards ( Anas platyrhynchos ) and bobwhite ( Colinus virginianus ). At 96 h of development, eggs were briefly immersed in distilled water or in Krenite formulation in distilled water at concentrations of 1.5, 6.5, or 30% fosamine ammonium. At 6.5% active ingredient (a.i.), Krenite reduced hatching success in bobwhite and mallards to 85 and 33% of that in the distilled-water controls. At 30% a.i., Krenite caused 95 to 100% mortality in both species by the time of hatching. Early embryonic growth was impaired by 30% Krenite in both species. There was no evidence of teratogenesis of the axial skeleton, as reported previously in chickens and Japanese quail ( Coturnix japonica ). Most abnormal embryos had severe edema and some stunting. Mallard hatchlings from the 1.5 and 6.5% Krenite groups weighed significantly less than controls and had lower plasma alanine aminotransferase and aspartate aminotransferase activities, with elevated plasma glucose and cholesterol concentrations. Brain acetylcholinesterase activity was unaffected by Krenite in embryos and hatchlings.

Environmental Toxicology and Chemistry↗
USGS2026

The effect of temperature, flow, density and disease on smallmouth bass (Micropterus dolomieu) early life growth rate

Individual growth rates of fish are influenced by gradually changing environmental conditions and rapid-onset events. However, there is a paucity of information on drivers of spatiotemporal variability in growth rates of fishes across large spatial extents. Using a 36-year dataset of smallmouth bass ( Micropterus dolomieu ) length-at-age data across 10 river reaches in Pennsylvania, USA ( n = 54,068 individuals), we estimated annual early life growth rates (mm year −1 ) and assessed the effects of relative abundance, summer temperature, summer streamflow rate and a disease outbreak on growth rate. We found that temperature had a positive effect on growth rate, varied spatially, and had a stronger effect in diseased reaches. There was also evidence for an impact of disease on early life growth through density-dependent mechanisms, with growth rates increasing from ∼85 to 101 mm·year −1 following disease-related decreases in abundance. This study adds to our understanding of the factors that shape early life growth, including rapid-onset events like disease which can have immediate and lasting effects on growth rate trajectory.

Pennsylvania↗
USGS2021

Factors influencing distributional shifts and abundance at the range core of a climate-sensitive mammal

Species are frequently responding to contemporary climate change by shifting to higher elevations and poleward to track suitable climate space. However, depending on local conditions and species’ sensitivity, the nature of these shifts can be highly variable and difficult to predict. Here, we examine how the American pika ( Ochotona princeps ), a philopatric, montane lagomorph, responds to climatic gradients at three spatial scales. Using mixed-effects modeling in an information-theoretic approach, we evaluated a priori model suites regarding predictors of site occupancy, relative abundance, and elevational-range retraction across 760 talus patches, nested within 64 watersheds across the Northern Rocky Mountains of North America, during 2017–2020. The top environmental predictors differed across these response metrics. Warmer temperatures in summer and winter were associated with lower occupancy, lower relative abundances, and greater elevational retraction across watersheds. Occupancy was also strongly influenced by habitat patch size, but only when combined with climate metrics such as actual evapotranspiration. Using a second analytical approach, acute heat stress and summer precipitation best explained retraction residuals (i.e., the relative extent of retraction given the original elevational range of occupancy). Despite the study domain occurring near the species’ geographic-range center, where populations might have higher abundances and be at lower risk of climate-related stress, 33.9% of patches showed evidence of recent extirpations. Pika-extirpated sites averaged 1.44℃ warmer in summer than did occupied sites. Additionally, the minimum elevation of pika occupancy has retracted upslope in 69% of watersheds (mean: 281 m). Our results emphasize the nuance associated with evaluating species’ range dynamics in response to climate gradients, variability, and temperature exceedances, especially in regions where species occupy gradients of conditions that may constitute multiple range edges. Furthermore, this study highlights the importance of evaluating diverse drivers across response metrics to improve the predictive accuracy of widely used, correlative models.

Idaho, Montana↗