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At least 901 records · Page 50Linked to original sources
USGS2014

Nearshore bathymetric mapping along a 7-mile reach of Lake Sharpe shoreline near Lower Brule, South Dakota, 2013

Shoreline erosion rates along Lake Sharpe, a Missouri River reservoir, near the community of Lower Brule, South Dakota, were studied previously during 2011–12 by the U.S. Geological Survey, the Lower Brule Sioux Tribe, and Oglala Lakota College. The rapid shoreline retreat has caused many detrimental effects along the shoreline of Lake Sharpe, including losses of cultural sites, recreation access points, wildlife habitat, irrigated cropland, and landmass. The Lower Brule Sioux Tribe is considering options to reduce or stop erosion. One such option for consideration is the placement of discontinuous rock breakwater structures in shallow water to reduce wave action at shore. Information on the depth of water and stability characteristics of bottom material in nearshore areas of Lake Sharpe is needed by the Lower Brule Sioux Tribe to develop structural mitigation alternatives. To help address this need, a bathymetric survey of nearshore areas of Lake Sharpe near Lower Brule, South Dakota, was completed in 2013 by the U.S. Geological Survey in cooperation with the Lower Brule Sioux Tribe. HYPACK® hydrographic survey software was used to plan data collection transects for a 7-mile reach of Lake Sharpe shoreline near Lower Brule, South Dakota. Regular data collection transects and oblique transects were planned to allow for quality-assurance/quality-control comparisons. Two methods of data collection were used in the bathymetric survey: (1) measurement from a boat using bathymetric instrumentation where water was more than 2 feet deep, and (2) wading using Real-Time Kinematic Global Navigation Satellite System equipment on shore and where water was shallower than 2 feet deep. A dual frequency, 24- or 200-kilohertz narrow beam, depth transducer was used in conjunction with a Teledyne Odom CV100 dual frequency echosounder for boat-based data collection. In water too shallow for boat navigation, the elevation and nature of the reservoir bottom were mapped using Real-Time Kinematic Global Navigation Satellite System equipment. Once the data collection effort was completed, data editing was performed in HYPACK® to remove erroneous data points and to apply water-surface elevations. Maps were developed separately for water depth and bottom elevation for the study area. Lines of equal water depth for 2, 3, 3.5, 4, and 5 feet from the water surface to the lake bottom were mapped in nearshore areas of Lake Sharpe. Overall, water depths stay shallow for quite a distance from shore. In the 288 transects that crossed a 2 foot depth line, this depth occurred an average of 88 feet from shore. Similarly, in the 317 transects that crossed a 3 foot depth line, this did not occur until an average of 343 feet from shore. Elevation contours of the lake bottom were mapped primarily for elevations ranging from 1,419 to 1,416 feet above North American Vertical Datum of 1988. Horizontal errors of the Real-Time Kinematic Global Navigation Satellite System equipment for the study area are essentially inconsequential because water depth and bottom elevation were determined to change relatively slowly. The estimated vertical error associated with the Real-Time Kinematic Global Navigation Satellite System equipment for the study area ranges from 0.6 to 0.9 inch. This vertical error is small relative to the accuracy of the bathymetric data. Accuracy assessments of the data collected for this study were computed according to the National Standard for Spatial Data Accuracy. The maps showing the lines of equal water depth and elevation contours of the lake bottom are able to support a 1-foot contour interval at National Standards for Spatial Data Accuracy vertical accuracy standards, which require a vertical root mean squared error of 0.30 foot or better and a fundamental vertical accuracy calculated at the 95-percent confidence level of 0.60 foot or better.

South Dakota↗
USGS2019

Relationships between wildfire burn severity, cavity-nesting bird assemblages and habitat in an eastern ponderosa pine forest

Historically, eastern ponderosa pine ( Pinus ponderosa ) forests were described as sparse patches of old-growth trees maintained by frequent, low-severity fires; however, in recent decades, there have been a number of large mixed-severity wildfires throughout the range of these forests. Wildlife responses to severe fire disturbance in eastern ponderosa pine forests are not well understood. Our study investigates how cavity-nesting bird species in an eastern ponderosa pine forest are impacted by burn severity. The objectives of our study were to: (1) identify the community composition of cavity-nesting birds in a 27 y old burn of mixed severity, (2) assess how habitat variables important to cavity-nesting birds differ in the mixed-severity fire, and (3) determine what habitat variables best predict bird occurrence 27 y after mixed-severity fire. We surveyed 56 sites across four burn severity classes, ranging from unburned to severely burned forest, in the Pine Ridge region of Nebraska. We measured multiple habitat characteristics (tree and snag diameter at breast height (DBH), coarse woody debris (CWD), tree and snag density, shrub height, and shrub cover) in May–August 2016 and conducted bird count surveys between 25 May and 8 June 2016. Cavity-nesting bird species' occurrence varied among the burn severity variables. Burn severity class (unburned, low severity, moderate severity, high severity) was a significant predictor of habitat characteristics for cavity-nesting birds, including tree density, snag density, mean snag DBH, variance in DBH, and CWD, which also was the best indicator of cavity-nesting bird community composition. We report evidence that mixed-severity wildfires in eastern ponderosa pine forests create variation in habitat characteristics and cavity-nesting bird occurrence.

Nebraska↗
USGS2004

Organochlorine pesticides and thiamine in eggs of largemouth bass and American alligators and their relationship with early life-stage mortality

Thiamine deficiency has been linked to early mortality syndrome in salmonids in the Great Lakes. This study was conducted to compare thiamine concentrations in American alligators ( Alligator mississippiensis ) and Florida largemouth bass ( Micropterus salmoides floridanus ) eggs from sites with high embryo mortality and high exposure to organochlorine pesticides (OCPs) (Lakes Apopka and Griffin, and Emeralda Marsh, Florida, USA) to those from sites that have historically exhibited low embryo mortality and low OCPs (Lakes Woodruff and Orange, Florida). During June-July 2000, 20 alligator clutches were collected from these sites, artificially incubated, and monitored for embryo mortality. Thiamine and OCPs were measured in one egg/clutch. During February 2002, 10 adult female bass were collected from Emeralda Marsh and Lake Woodruff and mature ovaries analyzed for thiamine and OCP concentrations. Although ovaries from the Emeralda Marsh bass contained almost 1,000-fold more OCPs compared with the reference site, Lake Woodruff, there were no differences in thiamine concentrations between sites (11,710 vs. 11,857 pmol/g). In contrast, alligator eggs from the reference site had five times the amount of thiamine compared with the contaminated sites (3,123 vs. 617 pmol/g). Similarly, clutches with > 55% hatch rates had significantly higher concentrations of thiamine compared with clutches with <54% hatch rates (1,119 vs. 201 pmol/g). These results suggest that thiamine deficiency might be playing an important role in alligator embryo survival but not in reproductive failure and recruitment of largemouth bass. The cause(s) of this thiamine deficiency are unknown but might be related to differences in the nutritional value of prey items across the sites studied and/or to the presence of high concentration of contaminants in eggs.

Florida↗
USGS2022

Identifying translocation sites for a climate relict population of Finescale Dace

Translocation is a management strategy that seeks to address threats to fish and wildlife populations by establishing new populations in ecologically suitable areas. Populations of Finescale Dace Chrosomus neogaeus in the Great Plains may benefit from translocation, as they exhibit a climate relict natural history that has led to a disjunct distribution and minimal dispersal opportunities. We assessed the translocation suitability of sites for Finescale Dace in the Belle Fourche River basin, Wyoming–South Dakota, using a ranking approach for output from multiple analyses. We used multivariate analysis to evaluate dissimilarity in fish occurrence and habitat between sites with and without Finescale Dace in contemporary surveys (2018–2019; n = 68). We further evaluated the capacity for sites to support Finescale Dace under base case and future climate change scenarios using the predicted probability of occurrence ( P ) from species distribution models (SDMs) fitted with basinwide fish occurrence data from surveys conducted in 2008–2019 ( n = 124) and spatially continuous environmental variables, including forecasted stream temperature scenarios. Sites with Finescale Dace tended to occur close to standing waterbodies, contained emergent vegetation cover, and did not exhibit large overlap in species-space with either native or nonnative species. Predicted P of Finescale Dace exhibited nonlinear relationships with mean August stream temperature, channel slope, and base flow index. The amount of suitable habitat (i.e., high predicted P ) declined with forecasted stream warming scenarios in the SDMs. This study highlights the utility of using field observations, historical data, and forecasted climate change scenarios to assess translocation site suitability and inform management of at-risk native fish populations, and the results may be transferable to other populations with limited data or restricted distributions.

South Dakota, Wyoming↗
USGS2017

Diet composition, quality and overlap of sympatric American pronghorn and gemsbok

Species with a long evolutionary history of sympatry often have mechanisms for resource partitioning that reduce competition. However, introduced non-native ungulates often compete with native ungulates and competitive effects can be exacerbated in arid regions due to low primary productivity. Our objectives were to characterize diet composition, quality, and overlap between American pronghorn Antilocapra americana and introduced non-native gemsbok Oryx gazella in southcentral New Mexico, USA. Severe drought occurred between 2010 and 2011, which allowed us to evaluate drought impacts on diet composition, quality, and overlap. Using feces collected from each species, we assessed diet composition and overlap with microhistological analysis and diet quality using fecal nitrogen (FN) and fecal 2,6-diaminopimelic acid (FDAPA). Pronghorn diet was primarily composed of shrubs in the cool—dry season (64.5%) then shifted to forbs in the warm—dry (64.7%) and warm—wet (54.1%) seasons. Pronghorn diet also shifted to shrubs during drought (50.7%). Gemsbok diets were evenly distributed across forage types. Fifty-three percent of the species of plants consumed by pronghorn and gemsbok were shared; diet overlap averaged 0.44 ± 0.06 (SE) and 0.49 ± 0.06 during the warm—dry seasons of 2010 and 2011, respectively. During drought, key forage species shared between pronghorn and gemsbok included yucca Yucca spp., prickly pear Opuntia spp., globemallow Sphaeralcea coccinea and horsenettle Solanum elaeagnifolium, comprising 50% of the pronghorn and 40% of the gemsbok diets. Fecal nitrogen and FDAPA decreased in pronghorn by 26% and 27% between the warm—dry season of 2010 (non-drought) and the warm—dry season of 2011 (drought), respectively. Drought had little effect on dietary quality for gemsbok. Gemsbok can use forage with lower nutritional content giving them an advantage over pronghorn, particularly during drought periods. Pronghorn are more dependent upon precipitation, which may be important to consider in light of increasing drought frequency associated with climate change.

New Mexico↗
USGS1991

Wigeongrass ( Ruppia maritima ): a literature review

Wigeongrass (Ruppia maritima L.) is a submersed macrophyte of nearly cosmopolitan distribution and worldwide importance as a waterfowl food. Unfortunately, the plant no longer inhabits vast areas disturbed by human activities. Taxonomic status of the plant is uncertain, especially in North America. In mild climates, in habitats subject to environmental extremes, the plant behaves as an annual (vegetation perishes), or as a perennial in deeper, more stable habitats (some vegetative parts grow year round). Drupelets (seeds) provide a mechanism for wigeongrass to survive periods of drought and excessive water salinity. These sexual propagules can be washed ashore or carried by birds or fish for long distances.Wigeongrass mostly occurs in temporarily to permanently flooded mesohaline-hyperhaline estuarine wetlands, but it also occurs inland in fresh to hypersaline palustrine and lacustrine wetlands. Most populations inhabit warm, relatively unpolluted, and well lit waters <2.0 m deep where fetches and wave action are not great. The species is probably best adapted to stable water levels but can tolerate significant water level fluctuations, including periodic exposure in tidal areas. Robust growth occurs in areas of slow current. Wigeongrass is alone among the submersed North American angiosperms in tolerance to high salinity, but it is likely at a competitive disadvantage among specialist taxa in soft or acidic waters. The species grows in nearly all common bottom substrates, but growth is favored by aerobic and low H 2 S conditions. Turbidity frequently limits wigeongrass growth in waters overlying easily suspendible bottom substrates.Wigeongrass often occurs in monotypic stands, yet grows with many other submersed and emergent macrophytes. Dominance in certain wetlands sometimes alternates with dominance by other submersed macrophytes as salinities, seasonal temperature cycles, or other environmental factors change. The shading effect of metaphytic, planktonic, or epiphytic algae often reduces production.Wigeongrass and its detritus provide food and cover for a large invertebrate biota, although direct consumption of the living plants is minimal. Wigeongrass beds in coastal wetlands are heavily used by fish. The plant is recognized worldwide as an important food of migrant and wintering waterfowl, wading birds, and shorebirds. In subtropical climates, wintering waterfowl can quickly consume entire stands.Propagation and management of wigeongrass has occurred for nearly 60 years in the southern and eastern United States. During the seventies and eighties, sophisticated water level and salinity management techniques have been developed to encourage growth of the plant.Future research should concentrate on determining the means to reduce light-limiting turbidity in many wetland types; understanding the ways in which human activities on and near wetlands affect wigeongrass production; and developing reliable and predictable techniques to stimulate wigeongrass production by water level manipulations and other means in different environmental settings. Trophic interactions and the effects of biomanipulation of fish populations in managed wigeongrass habitat--now little understood--also require more study.

Fish and Wildlife Research↗
USGS2019

Public access for pheasant hunters: Understanding an emerging need

Ring-necked pheasant ( Phasianus colchicus ; i.e., pheasant) hunting participation is declining across North America, reflecting a larger downward trend in American hunting participation and threatening benefits to grassland conservation and rural economies. To stabilize and expand the pheasant hunting population, we must first identify factors that influence pheasant hunter participation. We used an extensive in-person hunter survey to test the hypothesis that hunter demographics interact with social-ecological traits of hunting locations to affect hunter decisions, outcomes, and perceptions. We built a series of Bayesian mixed effects models to parse variation in demographics, perceptions, and hunt outcomes of pheasant hunters interviewed at public access hunting sites across 3 regions in Nebraska, USA, that varied in pheasant abundance and proximity to urban population centers. Among pheasant hunters in Nebraska, access to private lands was negatively related to the human population density of a pheasant hunter's home ZIP code and the distance a hunter had traveled to reach a hunting location. Pheasant hunters interviewed closer to metropolitan areas tended to be more urban and travel shorter distances, and their parties were more likely to include youth but less likely to include dogs. Hunter satisfaction was positively associated with seeing and harvesting pheasants and hunting with youth. Whereas youth participation and the number of pheasants seen varied by study region, hunter satisfaction did not differ across regions, suggesting that hunters may calibrate their expectations and build their parties based on where they plan to hunt. The variation in hunter demographics across hunting locations and disconnects between social and ecological correlates of hunter satisfaction suggests that diverse pheasant hunting constituencies will be best served by diverse pheasant hunting opportunities.

Nebraska↗
USGS2016

Response of imperiled Okaloosa darters to stream restoration

The Okaloosa Darter Etheostoma okaloosae is a small percid endemic to six stream drainages in northwestern Florida. The U.S. Fish and Wildlife Service listed Okaloosa Darters as endangered in 1973 and downlisted them to threatened in 2011 because of habitat improvements and increasing abundance across much of their geographic range. Delisting is possible if remaining recovery criteria are met, including restoration of degraded stream reaches. Impounded reaches of Anderson Branch, Mill Creek, and Toms Creek were restored by removing impediments to water flow, draining impoundments, and reconstructing stream reaches. Restorations of Anderson Branch and Mill Creek were designed to rehabilitate populations of Okaloosa Darters without significantly affecting popular recreational activities at these locations. Restorations were evaluated from 2007 to 2013 by comparing counts of Okaloosa Darters and the composition of microhabitats in restored and nearby undisturbed reference sites. Okaloosa Darters were absent from degraded stream reaches at the beginning of the study, but they rapidly colonized once restorations were completed. Counts of Okaloosa Darters in reference and restoration sites in Anderson Branch were similar by the end of the study, whereas counts in restoration sites were significantly lower than nearby reference sites in Mill and Toms creeks. Restoration sites tended to have lower coverage of sand and root and higher coverage of macrophytes. As riparian vegetation surrounding restoration sites matures to a closed canopy that reduces excessive growth of macrophytes, stream microhabitats and numbers of darters will probably become similar to reference sites. Restoration of degraded stream sites increased abundance and distribution of Okaloosa Darters and reconnected formerly isolated upstream and downstream populations. These projects demonstrated that restoration is a useful conservation tool for imperiled fishes such as Okaloosa Darters and can be undertaken without interfering with popular recreational activities.

Florida↗
USGS1986

Dynamics of alewives in Lake Ontario following a mass mortality

The U.S. Fish and Wildlife Service and the New York Department of Environmental Conservation assessed the population of alewives Alosa pseudoharengus in U.S. waters of Lake Ontario during 1976–1982 with bottom trawls. Alewives were abundant in 1976 but a die-off greatly reduced their numbers during the winter of 1976–1977. The population quickly recovered, however, adult abundance increasing nearly sevenfold during 1978–1981. In spring 1981 the bottom population in southern Lake Ontario was estimated to be 5.25 × 10 9 fish weighing 128,500 t. Estimated average alewife biomass per hectare during 1978–1982 far exceeded the estimates for either Lake Michigan during 1967–1982 or western Lake Huron during 1973–1982. Recruitment of age-II fish to the population was affected by abundance of adults in two ways: (1) the number of yearlings produced was directly related to adult abundance at low population levels but inversely related at high population levels; and (2) survival of yearlings to age II was inversely related to adult abundance. Growth in 1977 was exceptional, leaving a wide, unmistakable band on scales of the previously slow-growing adults. This wide growth zone served as a marker to identify survivors of the 1976–1977 die-off and to show that each year after 1978 a successively larger proportion of survivors was failing to grow in length or to form an annulus (54% in 1979, 96% in 1980, and 100% in 1981). There was no marker on scales of alewives recruited after the die-off, but the apparent age composition of our catches strongly suggested that most of them also failed to grow in 1981.

Transactions of the American Fisheries Society↗
USGS2025

Silver Carp passage at three locks and dams on the Tennessee and Cumberland rivers from 2016–2019

Bigheaded carps (i.e., Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis ) are non-native species that continue to expand their ranges throughout North American river systems, including the Tennessee and Cumberland river systems in the southeastern United States. These species are known to have deleterious effects on native fishes. Management efforts have focused on reducing upstream passage at dams coupled with intensive removal of individuals occupying upstream reaches. Understanding mechanisms affecting the success of upstream fish passage through lock chambers is critical to determining immigration rates into upstream habitats, the likelihood of success for upstream removal efforts, and potential effects of upstream passage reduction using deterrents. We used acoustic telemetry to examine the timing of Silver Carp upstream and downstream dam passages, patterns of fish movement throughout the river systems, and the relationship between fish size and upstream passage through the lock chamber. During 2016–2019, 465 Silver Carp were surgically implanted with transmitters within the two river systems. We documented 37 upstream passages and 57 downstream passages of Barkley, Kentucky, and Pickwick dams. During the two years in which dam passages were observed, most upstream dam passages (89%) occurred during April–August when water temperature ranged from 12–31°C. Most downstream passages (89%) occurred from late-February through July. The relatively small portion of Silver Carp tagged in Pickwick Lake (11% of total tagged), the uppermost reach of the study area, accounted for nearly two-thirds of all dam passages. Our findings may help managers model Silver Carp populations and inform decisions regarding fish deterrent placement and operation.

Alabama, Arkansas, Illinois, Kentucky, Mississippi↗
USGS1998

Effect of restrictive harvest regulations on survival and recovery rates of American black ducks

Population management of waterfowl requires an understanding of the effects of changes in hunting regulations on harvest and survival rates. Mean survival and recovery rates of American black ducks (Anas rubripes) were estimated during 3 periods of increasingly restrictive harvest regulations: 1950-66, 1967-82, and 1983-93. From the first to the second period, direct recovery rates declined for at least 1 age class in 4 of 6 reference areas, with a mean decline of 14% for adult and 7% for immature black ducks. From the second to the third period, direct recovery rates declined in all areas, declines averaging 37% for adults and 27% for immatures. Estimated mean survival rates increased from the first to the second period, consistent with a model of additivity of hunting mortality. Limited evidence existed for increases in survival rates from the second to the third period for immature males. For adults, however, survival increased less between these periods than would be expected if hunting mortality were additive and changes in recovery rates were proportional to changes in hunting mortality. Changes in survival and recovery rates of black ducks banded postseason were similar to those of adults banded preseason. Comparisons among estimates by degree blocks of latitude and longitude indicate that, at least between 1967 and 1983, estimated survival rates of immature and adult black ducks were lower in areas with high direct recovery rates. Smaller samples of banded birds and changes in banding locations in recent years may be limiting ability to evaluate consequences of recent changes in harvest rates. These correlation-based studies are limited in their ability to explain causes of observed changes in survival rates, suggesting the need for alternative approaches such as adaptive harvest management to increase understanding of the effects of hunting on black duck populations.

Journal of Wildlife Management↗
USGS2021

Migration phenology and patterns of American woodcock in central North America derived using satellite telemetry

American woodcock Scolopax minor (hereafter woodcock) migration ecology is poorly understood, but has implications for population ecology and management, especially related to harvest. To describe woodcock migration patterns and phenology, we captured and equipped 73 woodcock with satellite tracking devices in the Central Management Region (analogous to the Mississippi Flyway) of North America and documented migration paths of 60 individual woodcock and 87 autumn or spring woodcock migrations during 2014–2016. Woodcock migration at the scale of the Central Management Region was more synchronous in spring than in autumn, but unlike most other migratory birds, average duration of autumn migration (31 days) was shorter than duration of spring migration (53 days). This difference in migration duration resulted from woodcock making more close-together migratory stopovers during spring migration, not because woodcock had individual stopovers of longer duration. During autumn migration, the number of days, the number of stopovers, migration end date and net migration displacement were negatively related to initiation date and rate of migration, and the number of stopovers and the net migration displacement were negatively related with migration end date. Spring migration duration, end date, the number of stopovers and net migration displacement were negatively related to migration rate and initiation date was positively related to migration rate, suggesting that woodcock that initiated spring migration later had faster migration rates. Juvenile female woodcock began spring migration later than adult female woodcock. Our results provide a basis for comparing current harvest seasons with presence of migrating woodcock during autumn and provide insight into differential harvest of migratory versus local woodcock on breeding areas.

central North America↗
USGS2013

U.S. Geological Survey environmental health science strategy — Providing environmental health science for a changing world

Executive Summary America has an abundance of natural resources. We have bountiful clean water, fertile soil, and unrivaled national parks, wildlife refuges, and public lands. These resources enrich our lives and preserve our health and wellbeing. These resources have been maintained because of our history of respect for their value and an enduring commitment to their vigilant protection. Awareness of the social, economic, and personal value of the health of our environment is increasing. The emergence of environmentally driven diseases caused by exposure to contaminants and pathogens is a growing concern worldwide. New health threats and patterns of established threats are affected by both natural and anthropogenic changes to the environment. Human activities are key drivers of emerging (new and re-emerging) health threats. Societal demands for land and natural resources, quality of life, and economic prosperity lead to environmental change. Natural earth processes, climate trends, and related climatic events will compound the environmental impact of human activities. These environmental drivers will influence exposure to disease agents, including viral, bacterial, prion, and fungal pathogens, parasites, synthetic chemicals and substances, natural earth materials, toxins, and other biogenic compounds. The U.S. Geological Survey (USGS) defines environmental health science broadly as the interdisciplinary study of relations among the quality of the physical environment, the health of the living environment, and human health. The interactions among these three spheres are driven by human activities, ecological processes, and natural earth processes; the interactions affect exposure to contaminants and pathogens and the severity of environmentally driven diseases in animals and people. This definition provides USGS with a framework for synthesizing natural science information from across the Bureau and providing it to environmental, natural resource, agricultural, and public health managers. USGS specializes in science at the environment-health interface, by characterizing the processes that affect the interaction among the physical environment, the living environment, and people, and the resulting factors that affect ecological and human exposure to disease agents. The USGS is a Federal science agency with a broad range of natural science expertise relevant to environmental health. USGS provides scientific information and tools as a scientific basis for management and policy decisionmaking. This report describes a 10-year strategy that encompasses the portfolio of USGS environmental health science. It summarizes national environmental health priorities that USGS is best suited to address, and will serve as a strategic framework for USGS environmental health science goals, actions, and outcomes for the next decade. Implementation of this strategy is intended to aid coordination of USGS environmental health activities and to provide a focal point for disseminating information to stakeholders. The “One Health” paradigm advocated by the World Health Organization (WHO; World Health Organization, 2011), and the American Veterinary Medical Association (AVMA; American Veterinary Medical Association, 2008), among others, is based on a general recognition that the health of humans, animals, and the environment are inextricably linked. Thus, successful efforts to protect that health will require increased interdisciplinary research and increased communication and collaboration among the broader scientific and health community. This strategy is built upon that paradigm.

Circular↗
USGS2003

Use of North American Breeding Bird Survey data to estimate population change for bird conservation regions

Conservation planning requires information at a variety of geographic scales, and it is often unclear whether surveys designed for other purposes will provide appropriate information for management at various scales. We evaluated the use of the North American Breeding Bird Survey (BBS) to meet information needs for conservation planning in Bird Conservation Regions (BCRs). The BBS originally was developed to provide regional estimates for states, provinces, physiographic regions, and larger areas. Many analyses have used physiographic regions within states/provinces as strata. We evaluated potential consequences of using BCRs instead of the BBS physiographic regions, testing for spatial differences in sample intensity within states and provinces. We reclassified the BBS survey routes to BCRs and conducted route regression trend (interval-specific population change) analyses for a variety of regions and time intervals. Our results were similar to those based on traditional BBS regions and suggest minimal consequences of the reclassification for the BBS sample. We summarized population change within BCRs and assessed the efficiency of the BBS in estimating population change for 421 species surveyed. As would be expected from an omnibus survey, many species appeared to be poorly monitored by the BBS, with 42% of species encountered at <1 bird per route from the survey, and 28% of trend estimates too imprecise to detect a 3% per year change over 35 years. Our results indicated that the quality of the survey for estimation of population change varied among BCRs. Population trends of species were heterogeneous over space and time, varying among BCRs for 76% of species and over time for 39% of species. Regional heterogeneity also existed in trends of species groups from the BBS. While 49% of all species in the survey had increasing populations, grassland breeding birds showed consistent declines, with only 18% of species having positive trend estimates. Bird Conservation Regions appear to provide reasonable strata for summary of BBS data.

Journal of Wildlife Management↗
USGS2008

A double-observer method to estimate detection rate during aerial waterfowl surveys

We evaluated double-observer methods for aerial surveys as a means to adjust counts of waterfowl for incomplete detection. We conducted our study in eastern Canada and the northeast United States utilizing 3 aerial-survey crews flying 3 different types of fixed-wing aircraft. We reconciled counts of front- and rear-seat observers immediately following an observation by the rear-seat observer (i.e., on-the-fly reconciliation). We evaluated 6 a priori models containing a combination of several factors thought to influence detection probability including observer, seat position, aircraft type, and group size. We analyzed data for American black ducks (Anas rubripes) and mallards (A. platyrhynchos), which are among the most abundant duck species in this region. The best-supported model for both black ducks and mallards included observer effects. Sample sizes of black ducks were sufficient to estimate observer-specific detection rates for each crew. Estimated detection rates for black ducks were 0.62 (SE = 0.10), 0.63 (SE = 0.06), and 0.74 (SE = 0.07) for pilot-observers, 0.61 (SE = 0.08), 0.62 (SE = 0.06), and 0.81 (SE = 0.07) for other front-seat observers, and 0.43 (SE = 0.05), 0.58 (SE = 0.06), and 0.73 (SE = 0.04) for rear-seat observers. For mallards, sample sizes were adequate to generate stable maximum-likelihood estimates of observer-specific detection rates for only one aerial crew. Estimated observer-specific detection rates for that crew were 0.84 (SE = 0.04) for the pilot-observer, 0.74 (SE = 0.05) for the other front-seat observer, and 0.47 (SE = 0.03) for the rear-seat observer. Estimated observer detection rates were confounded by the position of the seat occupied by an observer, because observers did not switch seats, and by land-cover because vegetation and landform varied among crew areas. Double-observer methods with on-the-fly reconciliation, although not without challenges, offer one viable option to account for detection bias in aerial waterfowl surveys where birds are distributed at low density in remote areas that are inaccessible by ground crews. Double-observer methods, however, estimate only detection rate of animals that are potentially observable given the survey method applied. Auxiliary data and methods must be considered to estimate overall detection rate.

Journal of Wildlife Management↗
USGS2023

Population dynamics of the threatened Oregon spotted frog before and after drought mitigation

Amphibians are among the most sensitive taxa to climate change, and species inhabiting arid and semiarid landscapes at the extremes of their range are especially vulnerable to drought. The Jack Creek, Oregon, USA, population of Oregon spotted frogs ( Rana pretiosa ) faces unique challenges because it occupies the highest elevation site in the species' extant range and one that has been transformed by loss of American beavers ( Castor canadensis ), which historically maintained open water. We evaluated the effects of drought mitigation (addition of excavated ponds) on relationships between local and regional water availability, inactive legacy beaver dams, and Oregon spotted frog population dynamics in the Jack Creek system. We conducted egg mass surveys and capture-mark-recapture sampling at a treatment reach with excavated ponds and 3 reference reaches over 13 years; surveys spanned a period before and after pond excavation at the treatment and 1 primary comparison reference reach. We analyzed data using a combination of robust design capture-mark-recapture estimators and generalized linear mixed models to characterize population dynamics. Adult Oregon spotted frog survival was approximately 19.5% higher at the treatment reach than the primary reference reach during the study period. Annual survival was most strongly associated with late summer vegetation greenness, a proxy for water availability, and males had higher survival than females. Among the 4 study reaches, the treatment reach consistently had higher late summer vegetation greenness, and the hydrology functioned more independently of regional precipitation patterns relative to the reference reaches; however, these dynamics were not linked to pond excavation. Breeding was concentrated in 2 legacy beaver ponds that were deepened by excavation during the study compared to an unexcavated beaver pond, 2 excavated ponds without legacy beaver dams, and 9 reference ponds. These results point to the benefit of enhancing existing beaver structures and indicate that management actions aimed at maintaining surface water for breeding in spring and saturated soils and ponded water for adults in late summer would benefit this unique population of Oregon spotted frogs in the face of drought.

Oregon↗
USGS2020

Carbon dioxide-induced mortality of four species of North American fishes

Fisheries managers have a growing interest in the use of carbon dioxide (CO 2 ) as a tool for controlling invasive fishes. However, limited published data exist on susceptibility of many commonly encountered species to elevated CO 2 concentrations. Our objective was to estimate the 24-h 50% lethal concentration (LC 50 ) and 95% lethal concentration (LC 95 ) of CO 2 for four fishes (Rainbow Trout Oncorhynchus mykiss , Common Carp Cyprinus carpio , Channel Catfish Ictalurus punctatus , and Westslope Cutthroat Trout Oncorhynchus clarkii lewisi ). In the laboratory, we exposed juvenile fish to a range of CO 2 concentrations for 24 h in unpressurized, flow-through tanks. We developed a Bayesian hierarchical model to estimate the dose-response relationship for each fish species with associated uncertainty, and estimated 24-h LC 50 and LC 95 values based on laboratory trials for each species. The minimum concentration inducing mortality differed among cold water–adapted species and warm water–adapted species groups: 150 mg CO 2 /L for Westslope Cutthroat Trout and Rainbow Trout and 225 mg CO 2 /L for Common Carp and Channel Catfish. We observed complete mortality at 275 mg CO 2 /L (38,672 microatmospheres [μatm]), 225 mg CO 2 /L (30,711 μatm), and 495 mg CO 2 /L (65,708 μatm [Common Carp]; 77,213 μatm [Channel Catfish]) for Westslope Cutthroat Trout, Rainbow Trout, and both Common Carp and Channel Catfish, respectively. There was evidence of a statistical difference between the 24-h LC 95 values of Westslope Cutthroat Trout and Rainbow Trout (245.0 [222.2–272.2] and 190.6 [177.2–207.8] mg CO 2 /L, respectively). Additionally, these values were almost half the estimated 24-h LC 95 values for Common Carp and Channel Catfish (422.5 [374.7–474.5] and 434.2 [377.2–492.2] mg CO 2 /L, respectively). Although the experimental findings show strong relationships between increased CO 2 concentration and higher mortality, additional work is required to assess the efficacy and feasibility of a CO 2 application in a field setting.

Journal of Fish and Wildlife Management↗
USGS2022

Dispersal limitations increase vulnerability under climate change for reptiles and amphibians in the southwestern United States

Species conservation plans frequently rely on information that spans political and administrative boundaries, especially when predictions are needed of future habitat under climate change; however, most species conservation plans and their requisite predictions of future habitat are often limited in geographical scope. Moreover, dispersal constraints for species of concern are not often incorporated into distribution models, which can result in overly optimistic predictions of future habitat. We used a standard modeling approach across a suite of 23 taxa of amphibians and reptiles in the North American deserts (560,024 km 2 across 13 ecoregions) to assess impacts of climate change on habitat and combined landscape population dispersal simulations with species distribution modeling to reduce the risk of predicting future habitat in areas that are not available to species given their dispersal abilities. We used 3 general circulation models and 2 representative concentration pathways (RCPs) to represent multiple scenarios of future habitat potential and assess which study species may be most vulnerable to changes forecasted under each climate scenario. Amphibians were the most vulnerable taxa, but the most vulnerable species tended to be those with the lowest dispersal ability rather than those with the most specialized niches. Under the most optimistic climate scenario considered (RCP 2.6; a stringent scenario requiring declining emissions from 2020 to near zero emissions by 2100), 76% of the study area may experience a loss of >20% of the species examined, while up to 87% of the species currently present may be lost in some areas under the most pessimistic climate scenario (RCP 8.5; a scenario wherein greenhouse gases continue to increase through 2100 based on trajectories from the mid-century). Most areas with high losses were concentrated in the Arizona and New Mexico Plateau ecoregion, the Edwards Plateau in Texas, and the Southwestern Tablelands in New Mexico and Texas, USA. Under the most pessimistic climate scenario, all species are predicted to lose some existing habitat, with an average of 34% loss of extant habitat across all species. Even under the most optimistic scenario, we detected an average loss of 24% of extant habitat across all species, suggesting that changing climates may influence the ranges of reptiles and amphibians in the Southwest.

Arizona, California, Nevada, New Mexico, Texas, Ut↗