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At least 1,549 records · Page 86Linked to original sources
USGS2016

The sensitivity of WRF downscaled precipitation in Puerto Rico to cumulus parameterization and interior grid nudging

The sensitivity of the Weather Research and Forecasting Model (WRF) simulated precipitation over Puerto Rico is evaluated using multiple combinations of cumulus parameterization (CP) schemes and interior grid nudging. NCEP-DOE AMIP-II reanalysis (R-2) is downscaled to 2- km horizontal grid spacing with both convective permitting simulations (CP active only in the 49 middle and outer domains) and CP schemes active in all domains. The results generally show lower simulated precipitation amounts compared to the observations, regardless of WRF configuration. However, activating the CP schemes in the inner domain improves the annual cycle, intensity, and placement of rainfall compared to the convective permitting simulations. Furthermore, the use of interior grid nudging techniques in the outer domains improves the placement and intensity of rainfall in the inner domain. Incorporating a CP scheme at convective permitting scales (< 4 km) and grid nudging at non-convective permitting scales (> 4 km) improves the island average correlation of precipitation by 0.05 to 0.2 and reduces the island average RMSE by up to 40 mm on average over relying on the explicit microphysics at convective permitting scales with grid nudging. Projected changes in summer precipitation between 2040-2042 and 1985-1987 using WRF to downscale CCSM4 ranges from a 2.6 mm average increase to 81.9 mm average decrease, depending on the choice of CP scheme. The differences are only associated with differences between WRF configurations, which indicates the importance of CP scheme for projected precipitation change as well as historical accuracy.

Puerto Rico↗
USGS2015

Implications of the methodological choices for hydrologic portrayals of climate change over the contiguous United States: Statistically downscaled forcing data and hydrologic models

Continental-domain assessments of climate change impacts on water resources typically rely on statistically downscaled climate model outputs to force hydrologic models at a finer spatial resolution. This study examines the effects of four statistical downscaling methods [bias-corrected constructed analog (BCCA), bias-corrected spatial disaggregation applied at daily (BCSDd) and monthly scales (BCSDm), and asynchronous regression (AR)] on retrospective hydrologic simulations using three hydrologic models with their default parameters (the Community Land Model, version 4.0; the Variable Infiltration Capacity model, version 4.1.2; and the Precipitation–Runoff Modeling System, version 3.0.4) over the contiguous United States (CONUS). Biases of hydrologic simulations forced by statistically downscaled climate data relative to the simulation with observation-based gridded data are presented. Each statistical downscaling method produces different meteorological portrayals including precipitation amount, wet-day frequency, and the energy input (i.e., shortwave radiation), and their interplay affects estimations of precipitation partitioning between evapotranspiration and runoff, extreme runoff, and hydrologic states (i.e., snow and soil moisture). The analyses show that BCCA underestimates annual precipitation by as much as −250 mm, leading to unreasonable hydrologic portrayals over the CONUS for all models. Although the other three statistical downscaling methods produce a comparable precipitation bias ranging from −10 to 8 mm across the CONUS, BCSDd severely overestimates the wet-day fraction by up to 0.25, leading to different precipitation partitioning compared to the simulations with other downscaled data. Overall, the choice of downscaling method contributes to less spread in runoff estimates (by a factor of 1.5–3) than the choice of hydrologic model with use of the default parameters if BCCA is excluded.

Journal of Hydrometeorology↗
USGS2003

Comparative hydraulics of two fishery research circular tanks and recommendations for control of experimental bias

Hydraulic characteristics inside two research circular tanks (1.5-m and 1.2-m diameter) with the same volume of water were studied to understand how they might affect experimental bias by influencing the behavior and development of juvenile fish. Water velocities inside each tank were documented extensively and flow behavior studied. Surface inflow to the 1.5-m tank created a highly turbulent and aerated surface, and produced unevenly distributed velocities within the tank. A low-flow velocity, or "dead" zone, persisted just upstream of the surface inflow. A single submerged nozzle in the 1.2-m tank created uniform flow and did not cause undue turbulence or introduce air. Flow behavior in the 1.5-m tank is believed to have negatively affected the feeding behavior and physiological development of a group of juvenile fall chinook salmon, Oncorhynchus tshawytscha. A new inflow nozzle design provided comparable flow behavior regardless of tank size and water depth. Maintaining similar hydraulic conditions inside tanks used for various biological purposes, including fish research, would minimize experimental bias caused by differences in flow behavior. Other sources of experimental bias are discussed and recommendations given for reporting and control of experimental conditions in fishery research tank experiments.

Journal of Applied Aquaculture↗
USGS1982

Cyclic deposits and hummocky cross-stratification of probable storm origins in Upper Cretaceous rocks of the Cape Sebastian area, southwestern Oregon

Cyclic deposits containing hummocky cross-stratification occur in the upper part of the Cape Sebastian Sandstone of Bourgeois (1980), a shallow marine transgressive sandstone of Late Cetaceous age on the southern Oregon coast. The cycles average 1.6 m in thickness and consist, where complete, of a lower hummocky cross-stratified sandstone, a middle planar and ripple bedded sandstone with a shale bed in its middle part, and an upper bioturbated sandstone. Noteworthy features of the hummocky cross-stratification include the presence of depositional domes in addition to scoured depressions, the absence of significant bedform migration, and the presence of a small proportion of dip angles greater than the angle of repose (>34 degrees ) in addition to the large proportion of low (<15 degrees ) dip angles. The lower, stratified, fining-upward part of the cycle (up to the top of the shale bed) is interpreted as having accumulated under conditions of initially great but gradually decreasing current velocity and deposition rate. The currents probably had a strong oscillatory component, and the depositional event is inferred to have been a storm. The part of the planar- and ripple-bedded sandstone above the shale bed was probably deposited during relatively fair weather after the storm but before re-establishment of a normal benthic fauna. The bioturbated sandstone is interpreted to have been deposited during fair weather or during minor storms separated by long intervals of fair weather.

Journal of Sedimentary Petrology↗
USGS1985

The role of erosion by fish in shaping topography around Hudson submarine canyon.

An 800-km 2 area of rough topography around the head of Hudson Canyon off the eastern United States is attributed to erosion by tilefish ( Lopholatilus chamaeleonticeps ) and associated species of crustaceans. The rough topography has a relief of 1-10 m, occurs in water depths of 120-500 m, and has been cut into a semilithified, silty clay substrate since the onset of the Holocene transgression. Commercial fishing activity indicates that a large population of tilefish, which dig burrows in the sea floor, occupy the area of the rough topography. Average tilefish burrows are 1.6 m in diameter and 1.7 m in depth. They have a clustered, not uniform, distribution, and their average density is 2,500 per km 2 . The close match of areas of rough topography and high tilefish populations, the active burrowing of the sea floor, and the clustered distribution of the burrows suggest that the hummocky topography in this area may be the result of continuous erosion by tilefish and associated crustaceans during the Holocene. An erosion rate of 13 cm per 1,000 years is necessary to create this topography during the past 13,000 years--and 18 cm per 1,000 years if(as is more likely based on the depths at which tilefish presently are found) the erosion started 9,000 years ago.

New York↗
USGS1986

An experimental study of subaqueous slipface deposition

A flume study indicates that grainflow on slipfaces accounts for most cross-strata formed in unidirectional, shallow-water flows. The slipfaces studied were on small megaripples and delta-like steps (0.06-0.28 m high). During intermittent avalanching, at relatively low flow velocities, periods between avalanches were marked by grainfall onto the slipface, the intensity of which was greatest near the brink of the slipface and increased with current velocity. Nearly all grainfall deposits, however, were incorporated into subsequent grainflows. Grain flow cross-strata were made up of relatively distinct layers, at least near the base of the slipface. Continuous avalanching at high flow velocity was marked by a steady stream of grains forming more poorly defined cross-strata. Although the fundamental cause of grain flow is the gradual buildup of sediment on the upper slipface to the angle of initial yield, four other processes were recognized as promoting avalanching: 1) migration of superimposed bedforms to the brink, 2) generation of turbulent pulses upstream of the brink, 3) lee-eddy impingement on the lower slipface, and 4) extension of the lee eddy above the brink. The lee eddy proved very significant in slipface processes by redistributing grainfall sediments and both promoting and impeding grainflow. Regression analyses showed that the slipface advance per avalanche, S a , is strongly correlated with the slipface height, H, expressed approximately by S a = 0.060H. In addition, S a is a direct function of the rate of slipface advance, V b . The relationship among S a , H, and V b can be expressed as S a /H = 0.0385[1 - 0.134 (min/cm) V b ] (super -1) . Cross-strata dip angles between 28 degrees and 34 degrees show no systematic relation to H and V b , but dip angles greater than 34 degrees occurred only when both H and V b were small, and dip angles less than 28 degrees occurred only when both H and V b were large.

Journal of Sedimentary Petrology↗
USGS1991

Hatchery efficacy trials with chloramine-T for control of bacterial kidney disease

Three hatchery trials were carried out to determine the efficacy of chloramine-T for the control of bacterial gill disease in rainbow trout Oncorhynchus mykiss , ranging in weight from 2.5 to 54 g. In each trial, we used a single flow-through treatment of 8.5 mg chloramine-T/L. The single treatment provided effective control in all three trials; however, results were best when treatment was begun in the early stages of an outbreak. A second or third treatment may be required if an outbreak is in an advanced stage or if fish are under stress.

Journal of Aquatic Animal Health↗
USGS1999

Nonlethal gill biopsy does not affect juvenile chinook salmon implanted with radio transmitters

Using gastric and surgical transmitter implantation, we compared radio-tagged juvenile chinook salmon Oncorhynchus tshawytscha (T(O)) with tagged fish also having a gill biopsy (T(B)) to determine biopsy effects on fish implanted with radio transmitters. We found no evidence during the 21-d period to suggest that a gill biopsy reduced survival, growth, or gross condition of the tagged-biopsy group, regardless of transmitter implantation technique. We recorded 100% survival of all treatment groups. Relative growth rates of T(O) and T(B) fish did not differ significantly. Leukocrit and lysozyme levels were not significantly different among groups, suggesting that no signs of infection were present. Our findings suggest that small chinook salmon can tolerate the combination of transmitter implantation and gill biopsy without compromising condition relative to fish receiving only the transmitter. We believe a gill biopsy can be used in field telemetry studies, especially when physiological data are needed in addition to behavioral data.

North American Journal of Fisheries Management↗
USGS2003

An evaluation of selective feeding by three age-groups of the rainbow mussel Villosa iris

A tri-algal diet was fed to three age-groups of the rainbow mussel Villosa iris: ages 2-3 d, 50-53 d, and 3-6 years. Changes in the relative abundance of each algal species were determined in 5-h feeding trials from feeding chambers and by gut content analyses. All age-groups rejected Scenedesmus quadricauda and preferentially selected Nannochloropsis oculata and Selenastrum capricornutum, principally on the basis of size. Changes in the relative abundance of algae in feeding chambers did not differ significantly among age-groups. Observed differences in the ingested quantities of the similar-sized N. oculata and S. capricornutum were attributed to other particle-related characteristics. Results indicate that the rainbow mussel can be fed similar-sized algae at ali ages in captive propagation facilities. When developing a suitable algal diet for rearing juvenile mussels, one probably need not investigate different species at each stage of development if the algae used are in the 2.8-8.5-??m size range.

North American Journal of Aquaculture↗
USGS2004

Prevalence of the parasitic copepod Haemobaphes intermedius on juvenile buffalo sculpins from Washington State

The parasitic copepod, Haemobaphes intermedius, was detected in 62% of juvenile buffalo sculpins Enophrys bison, a previously unreported host, from the San Juan Islands archipelago in Washington State. Most infestations were characterized by the presence of a single female copepod infestations with multiple H. intermedius occurred either unilaterally or bilaterally in 29% of parasitized individuals. Impaired condition of parasitized hosts was indicated by significantly lower total lengths and weights (34.9 mm; 1.6 g) than in unparasitized cohorts (38.9 mm; 2.1 g). Host specificity was indicated by the failure to detect H. intermedius in 43 sympatric great sculpins Myoxocephalus polyacanthocephalus from the same location.

Washington↗
USGS2006

An isolate of Piscirickettsia salmonis from white seabass is fully virulent for coho salmon

The virulence of the WSB-98 isolate of Piscirickettsia salmonis from white seabass Atractoscion nobilis was compared with that of the American Type Culture Collection type strain LF-89, which was originally isolated from coho salmon Oncorhynchus kisutch in Chile. In controlled laboratory challenges of juvenile coho salmon, the isolate from white seabass exhibited virulence that was equal to or greater than that of LF-89. The cumulative percent mortality (CPM) was similar between groups of coho salmon receiving an intraperitoneal injection of WSB-98 at 104.5 tissue culture infectious dose with 50% endpoint (TCID50)/fish (CPM = 98%) or an injection of LF-89 at 104.8 TCID50/fish (CPM = 95%). The mean day to death of 9.3 d for WSB-98 and 18.6 d for LF-89, however, differed significantly (P < 0.0001) between the two isolates. The virulence of an isolate of P. salmonis from white seabass for a salmonid species is consistent with the hypothesis that nonsalmonids can serve as natural marine hosts for the bacterium and potential sources for infection of salmonids. ?? Copyright by the American Fisheries Society 2006.

Journal of Aquatic Animal Health↗
USGS2006

Survival and growth of age-0 steelhead after surgical implantation of 23-mm passive integrated transponders

Little information is available on the effects of implanting 23-mm passive integrated transponder (PIT) tags in salmonids less than 90 mm fork length (FL). Using juvenile steelhead Oncorhynchus mykiss (range, 73&ndash;97 mm FL), we compared instantaneous growth rates and survival among three experimental groups: control, surgery with no tag, and surgery with tag. Survival rate was lower for tagged fish (86%) than for control and surgery&minus;no tag fish (virtually 100% in each group). Approximately 90% of the mortalities occurred during days 1&ndash;3. Growth rate for the tagged group was lower for the first two 10-d measurement intervals; however, during the third 10-d interval, growth rates for tagged fish equaled or exceeded values for the other groups. These results suggest that tagged fish recovered by day 20. Growth rates for the control and surgery&minus;no tag groups did not differ from one another during any measurement interval. Tag retention rate was 97% over the 30-d period of the study. It appears that the combination of fish length and tag size in this study resulted in short-term negative effects on growth rate and survival; however, 23-mm PIT tags may still be useful for studies of salmonids 80&ndash;90 mm FL when survival is not the parameter of interest.

North American Journal of Fisheries Management↗
USGS2009

Hatch Timing Variations Among Reservoir Gizzard Shad Populations: Implications for Stocked Sander spp. Fingerlings

Growth and survival of stocked Sander spp. fingerlings can be influenced by timing of stocking in relation to the peak in density of larval gizzard shad Dorosoma cepedianum. However, coordinating stockings to coincide with peaks in gizzard shad density is difficult due to temporal variation in spawn timing among reservoirs. We used weekly estimates of larval gizzard shad density and length distributions to identify dates of peak hatching and peak total density in Ohio reservoirs and to explore the influence of spring water temperature regimes on timing of peak larval density. Gizzard shad density peaked over 21–32 d among reservoirs but generally varied by 12 d or less among years for any given population. Density peaks were driven by hatching, as larvae smaller than 10 mm accounted for a majority of the gizzard shad collected on the peak date. Peaks in gizzard shad density corresponded to water temperatures of 17–22°C and occurred most frequently when water temperatures had been stable or rising. Reservoirs in the southern portion of the state were 2–5°C warmer than northern reservoirs throughout the spring; thus, gizzard shad spawning and date of peak larval density were earliest in southern reservoirs and became progressively later for populations in more northerly reservoirs. Historical stocking dates for fingerling walleyes S. vitreus and saugeyes (sauger S. canadensis × walleye) in Ohio reservoirs indicated that southern reservoirs were often stocked after the expected peak in gizzard shad density and northern reservoirs were stocked before the peak. A statewide approach to stocking that incorporates latitudinal variations in gizzard shad hatch timing whereby southern reservoirs are stocked earliest would better align stockings with peak gizzard shad density, potentially improving survival of fingerling walleyes and saugeyes.

North American Journal of Fisheries Management↗
USGS2009

Effects of open marsh water management on numbers of larval salt marsh mosquitoes

Open marsh water management (OMWM) is a commonly used approach to manage salt marsh mosquitoes than can obviate the need for pesticide application and at the same time, partially restore natural functions of grid-ditched marshes. OMWM includes a variety of hydrologic manipulations, often tailored to the specific conditions on individual marshes, so the overall effectiveness of this approach is difficult to assess. Here, we report the results of controlled field trials to assess the effects of two approaches to OMWM on larval mosquito production at National Wildlife Refuges (NWR). A traditional OMWM approach, using pond construction and radial ditches was used at Edwin B. Forsythe NWR in New Jersey, and a ditch-plugging approach was used at Parker River NWR in Massachusetts. Mosquito larvae were sampled from randomly placed stations on paired treatment and control marshes at each refuge. The proportion of sampling stations that were wet declined after OMWM at the Forsythe site, but not at the Parker River site. The proportion of samples with larvae present and mean larval densities, declined significantly at the treatment sites on both refuges relative to the control marshes. Percentage of control for the 2 yr posttreatment, compared with the 2 yr pretreatment, was >90% at both treatment sites.

New Jersey;Massachusetts↗
USGS2007

Assessing small mammal abundance with track-tube indices and mark-recapture population estimates

We compared track-tube sampling with mark–recapture livetrapping and evaluated a track-tube index, defined as the number of track tubes with identifiable small mammal tracks during a 4-night period, as a predictor of small mammal abundance estimates in North Dakota grasslands. Meadow voles ( Microtus pennsylvanicus ) were the most commonly recorded species by both methods, but were underrepresented in track-tube sampling, whereas 13-lined ground squirrels ( Spermophilus tridecemlineatus ) and Franklin's ground squirrels ( S. franklinii ) were overrepresented in track-tube sampling. Estimates of average species richness were lower from track tubes than from livetrapping. Regression models revealed that the track-tube index was at best a moderately good predictor of small mammal population estimates because both the form (linear versus curvilinear) and slope of the relationship varied between years. In addition, 95% prediction intervals indicated low precision when predicting population estimates from new track-tube index observations. Track tubes required less time and expense than mark–recapture and eliminated handling of small mammals. Using track tubes along with mark–recapture in a double sampling for regression framework would have potential value when attempting to estimate abundance of small mammals over large areas.

Journal of Mammalogy↗
USGS2007

Selection of den sites by black bears in the southern Appalachians

We evaluated selection of den sites by American black bears (Ursus americanus) in the Pisgah Bear Sanctuary, western North Carolina, by comparing characteristics of dens at 53 den sites with availability of habitat characteristics in annual home ranges of bears and in the study area. We also tested whether den-site selection differed by sex, age, and reproductive status of bears. In addition, we evaluated whether the den component of an existing habitat model for black bears predicted where bears would select den sites. We found bears selected den sites far from gravel roads, on steep slopes, and at high elevations relative to what was available in both annual home ranges and in the study area. Den-site selection did not differ by sex or age, but it differed by reproductive status. Adult females with cubs preferred to den in areas that were relatively far from gravel roads, but adult females without cubs did not. The habitat model overestimated the value of areas near gravel roads, underestimated the value of moderately steep areas, and did not include elevation as a predictor variable. Our results highlight the importance of evaluating den selection in terms of both use and availability of den characteristics. ?? 2007 American Society of Mammalogists.

Journal of Mammalogy↗