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At least 343 records · Page 19Linked to original sources
USGS2003

Response of benthic invertebrate assemblages to metal exposure and bioaccumulation associated with hard-rock mining in northwestern streams, USA

Benthic macroinvertebrate assemblages, environmental variables, and associated mine density were evaluated during the summer of 2000 at 18 reference and test sites in the Coeur d'Alene and St. Regis River basins, northwestern USA as part of the US Geological Survey's National Water-Quality Assessment Program. Concentrations of Cd, Pb, and Zn in water and (or) streambed sediment at test sites in basins where production mine density was ???0.2 mines/km2 (in a 500-m stream buffer) were significantly higher than concentrations at reference sites. Zn and Pb were identified as the primary contaminants in water and streambed sediment, respectively. These metal concentrations often exceeded acute Ambient Water Quality Criteria for aquatic life and the National Oceanic and Atmospheric Administration Probable Effect Level for streambed sediment. Regression analysis identified significant correlations between production mine density in each basin and Zn concentrations in water and Pb in streambed sediment (r2 = 0.69 and 0.65, p < 0.01). Metal concentrations in caddisfly tissue, used to verify site-specific exposures of benthos, also were highest at sites downstream from intensive mining. Benthic invertebrate taxa richness and densities were lower at sites downstream than upstream of areas of intensive hard-rock mining and associated metal enrichment. Benthic invertebrate metrics that were most effective in discriminating changes in assemblage structure between reference and mining sites were total number of taxa, number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa, and densities of total individuals, EPT individuals, and metal-sensitive Ephemeroptera individuals.

Journal of the North American Benthological Societ↗
USGS2020

Validation of laboratory tests for infectious diseases in wild mammals: Review and recommendations

Evaluation of the diagnostic sensitivity (DSe) and specificity (DSp) of tests for infectious diseases in wild animals is challenging, and some of the limitations may affect compliance with the OIE-recommended test validation pathway. We conducted a methodologic review of test validation studies for OIE-listed diseases in wild mammals published between 2008 and 2017 and focused on study design, statistical analysis, and reporting of results. Most published papers addressed Mycobacterium bovis infection in one or more wildlife species. Our review revealed limitations or missing information about sampled animals, identification criteria for positive and negative samples (case definition), representativeness of source and target populations, and species in the study, as well as information identifying animals sampled for calculations of DSe and DSp as naturally infected captive, free-ranging, or experimentally challenged animals. The deficiencies may have reflected omissions in reporting rather than design flaws, although lack of random sampling might have induced bias in estimates of DSe and DSp. We used case studies of validation of tests for hemorrhagic diseases in deer and white-nose syndrome in hibernating bats to demonstrate approaches for validation when new pathogen serotypes or genotypes are detected and diagnostic algorithms are changed, and how purposes of tests evolve together with the evolution of the pathogen after identification. We describe potential benefits of experimental challenge studies for obtaining DSe and DSp estimates, methods to maintain sample integrity, and Bayesian latent class models for statistical analysis. We make recommendations for improvements in future studies of detection test accuracy in wild mammals.

Journal of Veterinary Diagnostic Investigation↗
USGS2016

A simple prioritization tool to diagnose impairment of stream temperature for coldwater fishes in the Great Basin

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

Nevada↗
USGS2012

Spring onset variations and trends in the continental United States: past and regional assessment using temperature-based indices

Phenological data are simple yet sensitive indicators of climate change impacts on ecosystems, but observations have not been made routinely or extensively enough to evaluate spatial and temporal patterns across most continents, including North America. As an alternative, many studies use weather-based algorithms to simulate specific phenological responses. Spring Indices (SI) are a set of complex phenological models that have been successfully applied to evaluate variations and trends in the onset of spring across the Northern Hemisphere’s temperate regions. To date, SI models have been limited by only producing output in locations where both the plants’ chilling and warmth requirements are met. Here, we develop an extended form of the SI (abbreviated SI-x) that expands their application into the subtropics by ignoring chilling requirements while still retaining the utility and accuracy of the original SI (now abbreviated SI-o). The validity of the new indices is tested, and regional SI anomalies are explored across the data-rich continental United States. SI-x variations from 1900 to 2010 show an abrupt and sustained delay in spring onset of about 4–8 d (around 1958) in parts of the Southeast and southern Great Plains, and a comparable advance of 4–8 d (around 1984) in parts of the northern Great Plains and the West. Atmospheric circulation anomalies, linked to large-scale modes of variability, exert modest but significant roles in the timing of spring onset across the United States on interannual and longer timescales. The SI-x are promising metrics for tracking spring onset variations and trends in mid-latitudes, relating them to relevant ecological, hydrological, and socioeconomic phenomena, and exploring connections between atmospheric drivers and seasonal timing.

International Journal of Climatology↗
USGS1996

Calculation and evaluation of sediment effect concentrations for the amphipod Hyalella azteca and the midge Chironomus riparius

Procedures are described for calculating and evaluating sediment effect concentrations (SECs) using laboratory data on the toxicity of contaminants associated with field-collected sediment to the amphipod Hyalella azteca and the midge Chironomus riparius . SECs are defined as the concentrations of individual contaminants in sediment below which toxicity is rarely observed and above which toxicity is frequently observed. The objective of the present study was to develop SECs to classify toxicity data for Great Lake sediment samples tested with Hyalella azteca and Chironomus riparius . This SEC database included samples from additional sites across the United States in order to make the database as robust as possible. Three types of SECs were calculated from these data: (1) Effect Range Low (ERL) and Effect Range Median (ERM), (2) Threshold Effect Level (TEL) and Probable Effect Level (PEL), and (3) No Effect Concentration (NEC). We were able to calculate SECs primarily for total metals, simultaneously extracted metals, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The ranges of concentrations in sediment were too narrow in our database to adequately evaluate SECs for butyltins, methyl mercury, polychlorinated dioxins and furans, or chlorinated pesticides. About 60 to 80% of the sediment samples in the database are correctly classified as toxic or not toxic depending on type of SEC evaluated. ERMs and ERLs are generally as reliable as paired PELs and TELs at classifying both toxic and non-toxic samples in our database. Reliability of the SECs in terms of correctly classifying sediment samples is similar between ERMs and NECs; however, ERMs minimize Type I error (false positives) relative to ERLs and minimize Type II error (false negatives) relative to NECs. Correct classification of samples can be improved by using only the most reliable individual SECs for chemicals (i.e., those with a higher percentage of correct classification). SECs calculated using sediment concentrations normalized to total organic carbon (TOC) concentrations did not improve the reliability compared to SECs calculated using dry-weight concentrations. The range of TOC concentrations in our database was relatively narrow compared to the ranges of contaminant concentrations. Therefore, normalizing dry-weight concentrations to a relatively narrow range of TOC concentrations had little influence on relative concentra of contaminants among samples. When SECs are used to conduct a preliminary screening to predict the potential for toxicity in the absence of actual toxicity testing, a low number of SEC exceedances should be used to minimize the potential for false negatives; however, the risk of accepting higher false positives is increased.

Journal of Great Lakes Research↗
USGS2024

Estimating migration timing and abundance in partial migratory systems by integrating continuous antenna detections with physical captures

Many populations migrate between two different habitats (e.g. wintering/foraging to breeding area, mainstem–tributary, river–lake, river–ocean, river–side channel) as part of their life history. Detection technologies, such as passive integrated transponder (PIT) antennas or sonic receivers, can be placed at boundaries between habitats (e.g. near the confluence of rivers) to detect migratory movements of marked animals. Often, these detection systems have high detection probabilities and detect many individuals but are limited in their ability to make inferences about abundance because only marked individuals can be detected. Here, we introduce a mark–recapture modelling approach that uses detections from a double-array PIT antenna system to imply movement directionality from arrays and estimate migration timing. Additionally, when combined with physical captures, the model can be used to estimate abundances for both migratory and non-migratory groups and help quantify partial migration. We first test our approach using simulation, and results indicate our approach displayed negligible bias for total abundance (less than ±1%) and slight biases for state-specific abundance estimates (±1%–6%). We fit our model to array detections and physical captures of three native fishes (humpback chub [ Gila cypha ], flannelmouth sucker [ Catostomus latipinnis ] and bluehead sucker [ Catostomus discobolus ]) in the Little Colorado River (LCR) in Grand Canyon, AZ, a system that exhibits partial migration (i.e. includes residents and migrants). Abundance estimates from our model confirm that, for all three species, migratory individuals are much more numerous than residents. There was little difference in movement timing between 2021 (a year without preceding winter/spring floods) and 2022 (a year with a small flood occurring in early April). In both years, flannelmouth sucker arrived in mid-March whereas humpback chub and bluehead sucker arrivals occurred early- to mid-April. With humpback chub and flannelmouth sucker, movement timing was influenced by body size so that large individuals were more likely to arrive early compared to smaller individuals. With more years of data, this model framework could be used to evaluate ecological questions pertaining to flow cues and movement timing or intensity, relative trends in migrants versus residents and ecological drivers of skipped spawning.

Journal of Animal Ecology↗
USGS2023

Efficacy of hydrogen peroxide to reduce Gyrodactylus species infestation density on four fish species

Objective The ability to effectively treat parasitic infestations of fish is of high importance for fish culture facilities. However, tools or approved therapies for treating infestations on fish are limited. This paper summarizes results from four separate clinical field studies that evaluated the efficacy of hydrogen peroxide (H 2 O 2 ; 35% PEROX-AID) for reducing Gyrodactylus spp. infestation density. Methods Three species of Gyrodactylus were studied ( G. salmonis , hosts: Brook Trout Salvelinus fontinalis and Lake Trout S. namaycush ; G. freemani , host: Yellow Perch Perca flavescens ; G. hoffmani , host: Fathead Minnow Pimephales promelas ) before and after the application of immersion H 2 O 2 therapy. Result Parasite density was significantly reduced for each parasite × host combination to which H 2 O 2 therapy was applied. Two clinical field studies in salmonids were found to demonstrate substantial effectiveness that enabled 35% PEROX-AID approval. Conclusion Further assessments of Gyrodactylus spp. could expand the use of H 2 O 2 for controlling these parasites in aquaculture. Specifically, H 2 O 2 was effective at all levels tested (50 or 75 mg H 2 O 2 /L for 60 min for the Yellow Perch and Fathead Minnow clinical field studies; 100 or 150 mg H 2 O 2 /L for 30 min regardless of salt pre-treatment for the Brook Trout study; and 100 mg H 2 O 2 /L for 30 min or 50 mg H 2 O 2 /L for 60 min for the Lake Trout study).

Journal of Aquatic Animal Health↗
USGS2011

The effects of myxobolus cerebralis on the physiological performance of whirling disease resistant and susceptible strains of rainbow trout

The development of rainbow trout Oncorhynchus mykiss strains that are resistant to whirling disease has shown promise as amanagement tool for populationsin areas where Myxobolus cerebralisis present. However, the physiological effects of the disease on characteristics necessary for fish survival in natural river conditions have not been tested in many of these strains. Five rainbow trout strains were evaluated for their swimming ability and growth characteristics in relation to M. cerebralis exposure: the resistant German rainbow trout (GR) strain (Hofer strain), the susceptible Colorado River rainbow trout (CRR) strain, and three intermediate (hybrid) strains (F1 = GR ?? CRR; F2 = F1 ?? F1; B2 = backcross of F1 ?? CRR). Three broad response patterns among strain and exposure were evident in our study. First, exposure metrics, growth performance, and swimming ability differed among strains. Second, exposure to the parasite did not necessarily produce differences in growth or swimming ability. Exposure to M. cerebralis did not affect batch weight for any strain, and critical swimming velocity did not differ between exposed and unexposed families. Third, although exposure did not necessarily affect growth or swimming ability, individuals that exhibited clinical deformities did show reduced growth and swimming performance; fish with clinical deformities were significantly smaller and had lower critical swimming velocities than exposed fish without clinical deformities. Research and management have focused on GR ?? CRR hybrid strains; however, given the performance of the GR strain in our study, it should not be discounted as a potential broodstock. Additional field trials comparing the GR and F1 strains should be conducted before wholesale adoption of the GR strain to reestablish rainbow trout populations in Colorado. ?? American Fisheries Society 2011.

Journal of Aquatic Animal Health↗
USGS2015

Groundwater recharge assessment at local and episodic scale in a soil mantled perched karst aquifer in southern Italy

Groundwater recharge assessment of karst aquifers, at various spatial and temporal scales, is a major scientific topic of current importance, since these aquifers play an essential role for both socio-economic development and fluvial ecosystems. In this study, groundwater recharge was estimated at local and episodic scales in a representative perched karst aquifer in a region of southern Italy with a Mediterranean climate. The research utilized measurements of precipitation, air temperature, soil water content, and water-table depth, obtained in 2008 at the Acqua della Madonna test area (Terminio Mount karst aquifer, Campania region). At this location the aquifer is overlain by ash-fall pyroclastic soils. The Episodic Master Recession (EMR) method, an improved version of the Water Table Fluctuation (WTF) method, was applied to estimate the amount of recharge generated episodically by individual rainfall events. The method also quantifies the amount of precipitation generating each recharge episode, thus permitting calculation of the Recharge to the Precipitation Ratio (RPR) on a storm-by-storm basis. Depending on the seasonally varying air temperature, evapotranspiration, and precipitation patterns, calculated values of RPR varied between 35% and 97% among the individual episodes. A multiple linear correlation of the RPR with both the average intensity of recharging rainfall events and the antecedent soil water content was calculated. Given the relatively easy measurability of precipitation and soil water content, such an empirical model would have great hydrogeological and practical utility. It would facilitate short-term forecasting of recharge in karst aquifers of the Mediterranean region and other aquifers with similar hydrogeological characteristics. By establishing relationships between the RPR and climate-dependent variables such as average storm intensity, it would facilitate prediction of climate-change effects on groundwater recharge. The EMR methodology could further be applied to other aquifers for evaluating the relationship of recharge to various hydrometeorological and hydrogeological processes.

Journal of Hydrology↗
USGS2008

Magnetic fabric of sheared till: A strain indicator for evaluating the bed deformation model of glacier flow

Wet-based portions of ice sheets may move primarily by shearing their till beds, resting in high sediment fluxes and the development of subglacial landforms. This model of glacier movement, which requires high bed shear strains, can be tested using till microstructural characteristics that evolve during till deformation. Here we examine the development of magnetic fabric using a ring shear device to defom two Wisconsin-age basal tills to shear strains as high as 70. Hysteresis experiments and the dependence of magnetic susceptibility of these tills on temperature demonstrate that anisotropy of magnetic susceptibility (AMS) develops during shear due to the rotation of primarily magnetite particles that are silt sized or smaller. At moderate shear strains (???6-25), principal axes of maximum magnetic susceptibility develop a strong fabric (S1 eignevalues of 0.83-0.96), without further strengthening at higher strains, During deformation, directions of maximum susceptibility cluster strongly in the direction of shear and plunge 'up-glacier,' consistent with the behavior of pebbles and sand particles studied in earlier experiments. In contrast, the magnitude of AMS does not vary systematically with strain and is small relative to its variability among samples; this is because most magnetite grains are contained as inclusions in larger particles and hence do not align during shear. Although processes other than pervasive bed deformation may result in strong flow parallel fabrics, AMS fabrics provide a rapid and objective means of identifying basal tills that have not been sheared sufficiently to be compatible with the bed deformation model. Copyright 2008 by the American Geophysical Union.

Journal of Geophysical Research F: Earth Surface↗
USGS2013

Serum chemistry, hematologic, and post-mortem findings in free-ranging bobcats ( Lynx rufus ) with notoedric mange

Notoedric mange was responsible for a population decline of bobcats ( Lynx rufus ) in 2 Southern California counties from 2002–2006 and is now reported to affect bobcats in Northern and Southern California. With this study we document clinical laboratory and necropsy findings for bobcats with mange. Bobcats in this study included free-ranging bobcats with mange (n = 34), a control group of free-ranging bobcats without mange (n = 11), and a captive control group of bobcats without mange (n = 19). We used 2 control groups to evaluate potential anomalies due to capture stress or diet. Free-ranging healthy and mange-infected bobcats were trapped or salvaged. Animals were tested by serum biochemistry, complete blood count, urine protein and creatinine, body weight, necropsy, and assessment for anticoagulant rodenticide residues in liver tissue. Bobcats with severe mange were emaciated, dehydrated, and anemic with low serum creatinine, hyperphosphatemia, hypoglycemia, hypernatremia, and hyperchloremia, and sometimes septicemic when compared to control groups. Liver enzymes and leukocyte counts were elevated in free-ranging, recently captured bobcats whether or not they were infested with mange, suggesting capture stress. Bobcats with mange had lower levels of serum cholesterol, albumin, globulin, and total protein due to protein loss likely secondary to severe dermatopathy. Renal insufficiency was unlikely in most cases, as urine protein:creatinine ratios were within normal limits. A primary gastrointestinal loss of protein or blood was possible in a few cases, as evidenced by elevated blood urea nitrogen, anemia, intestinal parasitism, colitis, gastric hemorrhage, and melena. The prevalence of exposure to anticoagulant rodenticides was 100% (n = 15) in bobcats with mange. These findings paint a picture of debilitating, multisystemic disease with infectious and toxic contributing factors that can progress to death in individuals and potential decline in populations.

Journal of Parasitology↗
USGS2018

Spatial sampling bias in the Neotoma paleoecological archives affects species paleo-distribution models

The ability to infer paleo-distributions with limited knowledge of absence makes species distribution modeling (SDM) a useful tool for exploring paleobiogeographic questions. Spatial sampling bias is a known issue when modeling extant species. Here we quantify the spatial sampling bias in a North American packrat midden archive and explore its impact on estimating paleo-distributions. We test whether (1) spatial sampling bias inherent in this macrofossil record can influence estimates of paleo-distributions, (2) this bias can alter the ability to measure shifts in distributions and climatic niche breadth from the Northgrippian subdivision of the Holocene (8.3 ka – 4.2 ka) to present day (1950–2000 yr), and (3) bias correction methods can improve estimates of paleo-distributions and analyses of range shifts and niche breadth. We estimate spatial sampling bias for the mid-Holocene period with a three-stage statistical model, each representing a hypothesized source of bias: fossil site availability, preservation and accessibility. This approach enables the use of SDM to evaluate three separate paleo-distributions calibrated on the packrat midden archive: those without bias correction (σ-naïve), those created with a standard method (σ-standard), and those created with a novel alternative (σ-modeled) incorporating the three-stage model of bias. We find that paleo-distributions modeled for the mid-Holocene without bias correction (σ-naïve) provided poor estimates of hindcast paleo-distributions, and that the σ-modeled correction method improved paleo-distributions for our six species with, on average, 50% higher overlap to hindcast distributions than σ-naïve paleo-distributions (σ-standard results fell between σ-naïve and σ-modeled).

Journal of Quaternary Science Reviews↗
USGS2006

General circulation model simulations of winter and summer sea-level pressures over North America

Temporal variability of synoptic-scale circulation is a dominant factor in regional temporal climate variations. In the midlatitudes, temporal variability of synoptic-scale circulation has been found to be related to temporal variations in regional air temperature and precipitation. General circulation model (GCM) simulations of long-term changes in synoptic-scale circulation may be useful in assessing the effects of climate change on regional air temperature and precipitation. Atmospheric pressure is an important component of synoptic-scale circulation. In this paper, observed sea-level pressures were used to evaluate winter and summer sea-level pressures over North America simulated by the Goddard Institute for Space Studies (GISS) and the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation models. The objective of the study is to determine how similar the spatial and temporal distributions of GCM-simulated daily sea-level pressures over North America are to observed distributions. Overall, both models are better at reproducing observed within-season variance of winter and summer sea-level pressures than they are at simulating the magnitude of mean winter and summer sea-level pressures. Results indicate that winter sea-level pressures are better simulated by the GISS model than by the GFDL model. The GFDL model simulates anomalously high winter sea-level pressures over north-eastern North America. In summer, the GISS model underestimates sea-level pressures, whereas the GFDL model overestimates sea-level pressures over most of North America. Kolmogorov-Smirnov tests indicate that much of the error in model simulations can be attributed to differences between simulated and observed means. Comparisons of spatial correlation matrices of observed and simulated sea-level pressures indicate that GCMs simulate spatial variability of sea-level pressures that is similar to observed. These results suggest that GCMs are able to simulate major components of synoptic-scale circulation over North America, especially for winter.

International Journal of Climatology↗
USGS2008

Effects of disturbance on germination and seedling establishment in a coastal prairie grassland: A test of the competitive release hypothesis

1. We evaluated the responses of native grassland sods to a variety of types of disturbance in order to assess hypotheses about the competitive effects of established vegetation on seed germination and seedling establishment. In particular, we consider whether germination is more responsive to the magnitude and duration of vegetation removal (competitive release) or to individual disturbance types (specific effects). 2. Field-collected sods of coastal tallgrass prairie were subjected to no manipulation, cutting with clippings left, cutting with clippings removed (hayed), burning, and complete destruction of established vegetation under greenhouse conditions. The emergence and fate of seedlings, as well as light penetration through the canopy, were followed for a period of 4.5 months. 3. Total seedling emergence increased from cut to control, hayed, burned and plants-removed treatments. Several periods of increased seedling emergence suggested responses to both light penetration and seasonal change. 4. Species richness was lowest in cut sods and highest in sods that had plants removed or were burned. Rarefaction analysis showed that these differences were largely those expected from differences in seedling number, except for the cut treatment, which produced fewer species per seedling than other treatments. 5. Indicator species analysis and ordination methods revealed that seedling community composition overlapped strongly across all treatments, although the area of ordination space did increase with increasing numbers of seedlings. 6. Overall, most of the effects of disturbance could be explained by cumulative light penetration to the soil surface, an indicator of total competitive release, although a few specific effects could be found (particularly for the cutting treatment). Thus, these results generally support the competitive release hypothesis.

Journal of Ecology↗
USGS2012

Relying on fin erosion to identify hatchery-reared brown trout in a Tennessee river

Hatchery-induced fin erosion can be used to identify recently stocked catchable-size brown trout Salmo trutta during annual surveys to qualitatively estimate contributions to a fishery. However, little is known about the longevity of this mark and its effectiveness as a short-term (&le; 1 year) mass-marking technique. We evaluated hatchery-induced pectoral fin erosion as a mass-marking technique for short-term stocking evaluations by stocking microtagged brown trout in a tailwater and repeatedly sampling those fish to observe and measure their pectoral fins. At Dale Hollow National Fish Hatchery, 99.1% (228 of 230) of microtagged brown trout in outdoor concrete raceways had eroded pectoral fins 1 d prior to stocking. Between 34 and 68 microtagged and 26-35 wild brown trout were collected during eight subsequent electrofishing samples. In a blind test based on visual examination of pectoral fins at up to 322 d poststocking, one observer correctly identified 91.7% to 100.0% (mean of 96.9%) of microtagged brown trout prior to checking for microtags. In the laboratory, pectoral fin length and width measurements were recorded to statistically compare the fin measurements of wild and microtagged hatchery brown trout. With only one exception, all pectoral fin measurements on each date averaged significantly larger for wild trout than for microtagged brown trout. Based on the number of pectoral fin measurements falling below 95% prediction intervals, 93.7% (148 of 158) of microtagged trout were correctly identified as hatchery fish based on regression models up to 160 d poststocking. Only 72.2% (70 of 97) of microtagged trout were identified correctly after 160 d based on pectoral fin measurements and the regression models. We concluded that visual examination of pectoral fin erosion was a very effective way to identify stocked brown trout for up to 322 d poststocking.

North American Journal of Fisheries Management↗
USGS2023

Is chemical control for crayfish in hatchery fish shipments practical?

Invasive crayfish (family Cambaridae) displace native crayfish species and alter aquatic habitat, community structure, and ecosystem function. We evaluated whether chemical control can be a reliable control agent for crayfish to ensure that shipments from fish hatcheries did not result in new infestations of invasive crayfish. A series of acute (≤1 h) toxicity tests were conducted to evaluate the toxicity of cypermethrin and pyrethrin to crayfish, freshwater mussels, and fish; chemical concentrations in test organisms; effectiveness of carbon-block filters to remove cypermethrin from test waters; and the cost of chemical control relative to extra handling of fish. Cypermethrin dosed at 75 μg/L for 15 min resulted in 100% mortality of adult white river crawfish Procambarus acutus and virile crayfish Faxonius virilis but did not cause >20% mortality in adult pondmussel Ligumia subrostrata , juvenile fatmucket Lampsilis siliquoidea , fingerling Bluegill Lepomis macrochirus , hybrid sunfish (Bluegill × Green Sunfish L. cyanellus ), hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis ), yearling Paddlefish Polyodon spathula, or ready-to-eat Bluegill, hybrid sunfish, and Channel Catfish Ictalurus punctatus . Behavioral effects, such as loss of equilibrium or head shaking, were generally limited to 1 h postexposure. Mean concentrations of cypermethrin increased in fish fillets (4–26 μg/g) and whole fish (5–1,770 μg/g); therefore, regulations limiting harvest for up to 7 d following stocking may be required. A carbon-block filtration system was effective in reducing (<90%) cypermethrin concentrations and thus reducing potential effects to nontarget species in receiving waters. Extra handling of fish was more cost-effective for all fish tested except for Paddlefish, where the cost of chemical control was half that for extra handling. For all other fish tested, chemical control was 4–10 times more expensive than extra handling. Special use permits or chemical registration are needed before chemical control for crayfish could be routinely used at fish hatcheries.

North American Journal of Aquaculture↗
USGS2011

Assessment of clinical pathology and pathogen exposure in sea otters (Enhydra lutris) bordering the threatened population in Alaska

Northern sea otter ( Enhydra lutris kenyoni ) abundance has decreased dramatically over portions of southwest Alaska, USA, since the mid-1980s, and this stock is currently listed as threatened under the Endangered Species Act. In contrast, adjacent populations in south central Alaska, USA, and Russia have been stable to increasing during the same period. Sea otters bordering the area classified in the recent decline were live-captured during 2004–2006 at Bering Island, Russia, and the Kodiak Archipelago, Alaska, USA, to evaluate differences in general health and current exposure status to marine and terrestrial pathogens. Although body condition was lower in animals captured at Bering Island, Russia, than it was at Kodiak, USA, clinical pathology values did not reveal differences in general health between the two regions. Low prevalences of antibodies (>5%) were found in Kodiak, USA, and on Bering Island, Russia, to Toxoplasma gondii , Sarcocystis neurona , and Leptospira interrogans . Exposure to phocine herpesvirus-1 was found in both Kodiak, USA (15.2%), and Bering Island, Russia (2.3%). Antibodies to Brucella spp. were found in 28% of the otters tested on Bering Island, Russia, compared with only 2.7% of the samples from Kodiak, USA. Prevalence of exposure to Phocine distemper virus (PDV) was 41% in Kodiak, USA, but 0% on Bering Island, Russia. Archived sera from southwest and south-central Alaska dating back to 1989 were negative for PDV, indicating exposure occurred in sea otters in Kodiak, USA, in recent years. Because PDV can be highly pathogenic in naïve and susceptible marine mammal populations, tissues should be examined to explore the contribution of this virus to otter deaths. Our results reveal an increase in exposure to pathogens in sea otters in Kodiak, Alaska, USA, since the 1990s.

Journal of Wildlife Diseases↗
USGS2008

Differential exposure, duration, and sensitivity of unionoidean bivalve life stages to environmental contaminants

Freshwater mussels (superfamily Unionoidea) are in serious global decline and in urgent need of protection and conservation. The declines have been attributed to a wide array of human activities resulting in pollution and water-quality degradation, and habitat destruction and alteration. Linkages among poor water quality, pollutant sources, and mussel decline in rivers and streams have been associated with results of laboratory-based tests of specific pollutants. However, uncertainties remain about the relationship of laboratory data to actual contaminant exposure routes for various mussel species, life stages, and in the habitats occupied during these exposures. We evaluated the pathways of exposure to environmental pollutants for all 4 life stages (free glochidia, encysted glochidia, juveniles, adults) of unionoidean mussels and found that each life stage has both common and unique characteristics that contribute to observed differences in exposure and sensitivity. Free glochidia typically are exposed only briefly (e.g., seconds to days) through surface water, whereas adults sustain exposure over years to decades through surface water, pore water, sediment, and diet. Juveniles live largely burrowed in the sediment for the first 0 to 4 y of life. Thus, sediment, pore water, and diet are the predominant exposure routes for this life stage, but surface water also might contribute to exposure during certain periods and environmental conditions. The obligate parasitic stage (encysted glochidia stage) on a host fish might be exposed from surface water while partially encysted or from toxicants in host-fish tissue while fully encysted. Laboratory methods for testing for acute and chronic exposures in water have advanced, and toxicant-specific information has increased in recent years. However, additional research is needed to understand interactions of life history, habitat, and long-term exposure to contaminants through water, pore water, sediment, and diet so that the risks of environmental exposures can be properly assessed and managed. ?? 2008 by The North American Benthological Society.

Journal of the North American Benthological Societ↗