Geology topics

Research about Idaho

Source-linked reports with geographic coverage including Idaho.

At least 217 records · Page 12Linked to original sources

USGS2018

Microhabitat use of native fishes in the Kootenai River: A fine‐scale evaluation of large‐scale habitat rehabilitation efforts

Fish and microhabitat data were collected at 542 prepositioned electrofishing sites (surface area of each site = 4 m 2 ) in the Kootenai River, Idaho, during 2014 and 2015 to evaluate small‐scale habitat use by fishes, as it relates to large‐scale habitat rehabilitation efforts. Samples were collected from a 12‐km braided segment of river that had received localized habitat rehabilitation treatments since 2011. Fish and microhabitat data were collected to investigate habitat drivers related to the occurrence and relative abundance of fishes. Each sampling location was selected at random and characterized as “treated” (i.e., rehabilitated) or “untreated” based on proximity to habitat treatments. Fishes sampled from backwaters composed 71% of the overall catch and 84% of the catch from locally untreated areas of the river. Species‐specific regression models suggested that water depth and current velocity influenced the occurrence and abundance of fishes. In particular, shallow habitats with low current velocities were important for small‐bodied native fishes and likely serve as important rearing areas for juvenile fish. These habitat conditions typically characterize backwater and channel‐margin habitats that are vulnerable to anthropogenic perturbation. Prioritizing process‐based rehabilitation of these areas in large, regulated rivers would allow natural channel‐forming processes for the benefit of native fishes.

Idaho↗

USGS2018

Spatial and temporal trends in selenium in the upper Blackfoot River watershed, southeastern Idaho, 2001–16

Phosphate mining in southeastern Idaho has been an important economic driver for the region and State for over 100 years, but weathering of mining waste rock has also released selenium into the Blackfoot River. This report analyzes and presents data from three separate but complementary studies monitoring selenium in streams in the region. The U.S. Geological Survey (USGS), in cooperation with the Bureau of Land Management, has been collecting streamflow and water-quality samples year-round on the Blackfoot River above reservoir near Henry, Idaho, (USGS streamgage 13063000) since 2001. Over the same period, the Idaho Department of Environmental Quality (IDEQ) has collected streamflow and water-quality samples from the Blackfoot River and tributaries during spring runoff. Data collected from 2001 to 2012 during these two studies were analyzed previously. This report extends the analysis using new data collected through 2016. This report also presents the results of a joint USGS and IDEQ seepage study conducted in June 2016 in the Blackfoot River near Dry Valley. Although limited in scope, this study explored the hypothesis that unaccounted selenium loading (loading in excess of tributary inputs) in this reach could be caused by groundwater inflow. USGS dissolved selenium concentration data from streamgage 13063000 on the Blackfoot River and IDEQ data from the mainstem and mining-affected tributaries are highest shortly after peak runoff and correlate with streamflow magnitude. Although earlier analyses indicated increasing selenium concentrations from 2001 to 2012, this study shows that runoff and baseflow dissolved selenium concentrations increased and then decreased during 2001–16. High median runoff concentrations from 2005 through 2011 are associated with high snowpack and streamflow. This result suggests that more snowmelt moving through selenium-bearing waste rock leads to increased instream concentrations. The time lag between peak runoff and then peak selenium concentrations suggests that selenium mobilization may occur as snowmelt percolates through waste rock rather than by faster surface runoff. However, variability in local snow accumulation and snowmelt conditions likely affects interannual variability in selenium concentrations in the mainstem Blackfoot River and tributaries. In contrast to runoff selenium concentrations, median baseflow (August to October) dissolved selenium concentrations were highest from 2009 to 2013. Aquatic plant senescence and release of selenium is an unlikely explanation for this trend because plants are still growing during this time of year. In addition, this trend is observed during and shortly after the observed period of high snowpack. Thus, increased baseflow selenium concentrations suggest that increased selenium loading to alluvial groundwater may occur during periods of high snowmelt and manifest in later years as higher instream concentrations during baseflows when the majority of streamflow is attributable to groundwater gains. Runoff-period streamflow and selenium loads were calculated for the tributaries and mainstem Blackfoot River. Selenium loads vary from year to year with mainstem loads greater than the total tributary contributions in some years and less than tributary contributions in other years. In general, East Mill Creek usually accounted for the largest proportion of the total Blackfoot River load, and unaccounted loads (loads in excess of tributary inputs) often occurred in the vicinity of Spring Creek and Dry Valley. The latter observation led the USGS and IDEQ to conduct a seepage study to further investigate groundwater and selenium loading to the Blackfoot River near Dry Valley. The seepage study results show consistent albeit small unaccounted increases in streamflow and dissolved selenium load in the Blackfoot River near Dry Valley. Field observation of a spring to the north of the river and independent groundwater monitoring data from Dry Valley to the south of the river suggest that alluvial groundwater may discharge to the river from both sides. However, the small unaccounted selenium load measured in the June 2016 study relative to loads measured during runoff suggest that groundwater loading in this reach may occur primarily during runoff. An improved understanding of alluvial groundwater extent, gradient, hydraulic conductivity, and quality would aid in interpreting unaccounted gains and losses in selenium loads in the Blackfoot River. Finally, State of Idaho selenium water-quality criteria have recently shifted to a hierarchical fish tissue and water concentration scheme. This report summarizes existing fish tissue and water-quality data in the mainstem and offers considerations for future selenium monitoring in the Blackfoot River.

Idaho↗

USGS2018

Coeur d’Alene Basin Environmental Monitoring Program, surface water, northern Idaho—Annual data summary, water year 2017

Streams within the Coeur d’Alene River drainage basin in northern Idaho have been extensively affected by historical mining activities and are subject to ongoing remedial actions as part of the Bunker Hill Mining & Metallurgical Complex Superfund Site. The U.S. Geological Survey (USGS) operates 12 real-time streamgages and collects surface-water-quality samples two to four times annually at 20 sites in the Spokane River and Coeur d’Alene River drainage basins. These data are used by the U.S. Environmental Protection Agency (USEPA) to monitor cleanup progress and to support decisions related to implementing remedial actions throughout the basin. USGS data collection highlights from water year 2017 include: • A rain-on-snow event in March 2017 produced high streamflows and flooding in the basin. • The March event mobilized high concentrations of total metals (cadmium, lead, zinc, and others) in the Coeur d’Alene River near Cataldo, at Rose Lake, and near Harrison; these concentrations were among the highest that have been measured at these sites during flood events sampled by the USGS. • Total lead and dissolved zinc and cadmium concentrations decreased in Canyon Creek in 2017 when compared with water years 2007–16; in contrast, concentrations of dissolved zi

Idaho↗

USGS2018

Idaho water use, 2015

The ability to quantify water resources hinges on the understanding of water use by the population. The demand humans place on the water cycle varies across the United States, driven by both need and availability. The U.S. Geological Survey quantifies water use nationally, at the county scale, with estimates of water withdrawals and deliveries, by category of use (for example, irrigation, thermoelectric power, industrial, public supply, including domestic deliveries and self-supply domestic, livestock, mining, and aquaculture) and source (fresh and saline groundwater or surface water) every 5 years. Estimates of water use are an important component of the water budget to help manage water supplies and plan for the future. Understanding water use in Idaho is important not only at the local (county) and State scales, but also at the National level because Idaho ranked third in the Nation for total water use in 2015. This fact sheet describes calendar year 2015 freshwater withdrawals by source and by each Idaho county. An associated data release provides the data discussed herein. Freshwater withdrawals totaled 17,737 million gallons per day during 2015. Surface water accounted for 70 percent of total withdrawals for all categories of use, mostly for irrigation of crops and aquaculture production. Withdrawals for mining activities were mostly from surface water, whereas the remaining categories of use—public supply, domestic, industrial, livestock, irrigation of golf courses, and thermoelectric power—relied largely on groundwater withdrawals. Most withdrawals occurred in southern Idaho counties to support irrigated agriculture.

Idaho↗

USGS2018

Thresholds and hotspots for shrub restoration following a heterogeneous megafire

Context Reestablishing foundational plant species through aerial seeding is an essential yet challenging step for restoring the vast semiarid landscapes impacted by plant invasions and wildfire-regime shifts. A key component of the challenge stems from landscape variability and its effects on plant recovery. Objectives We assessed landscape correlates, thresholds, and tipping points for sagebrush presence from fine-scale sampling across a large, heterogeneous area burned the previous year, where we were able to quantify soil surface features that are typically occluded yet can strongly affect recovery patterns. Methods Hypothesis testing and binary-decision trees were used to evaluate factors affecting initial sagebrush establishment, using 2171 field plots (totaling ~ 2,000,000 m 2 sampled) over a 113,000-ha region. Results Sagebrush established in 50% of plots where it was seeded, a > 12-fold greater establishment frequency than in unseeded areas. Sagebrush establishment was enhanced in threshold-like ways by elevation (> 1200 m ASL), topographic features that alter heatload and soil water, and by soil-surface features such as “fertile islands” that bore the imprint of pre-fire sagebrush. Sagebrush occupancy had a negative, linear relationship with exotic-annual grass cover and parabolic relationship with perennial bunchgrasses (optimal at 40% cover). Conclusions Our approach revealed interactive, ecological relationships such as novel soil-surface effects on first year establishment of sagebrush across the burned landscape, and identified “hot spots” for recovery. The approach could be expanded across sites and years to provide the information needed to explain past seeding successes or failures, and in designing treatments at the landscape scale.

Idaho↗

USGS2018

Geochemistry of groundwater in the eastern Snake River Plain aquifer, Idaho National Laboratory and vicinity, eastern Idaho

Nuclear research activities at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) in eastern Idaho produced radiochemical and chemical wastes that were discharged to the subsurface, resulting in detectable concentrations of some waste constituents in the eastern Snake River Plain (ESRP) aquifer. These waste constituents may pose risks to the water quality of the aquifer. In order to understand these risks to water quality the U.S. Geological Survey, in cooperation with the DOE, conducted a study of groundwater geochemistry to improve the understanding of hydrologic and chemical processes in the ESRP aquifer at and near the INL and to understand how these processes affect waste constituents in the aquifer. Geochemistry data were used to identify sources of recharge, mixing of water, and directions of groundwater flow in the ESRP aquifer at the INL. The geochemistry data were analyzed from 167 sample sites at and near the INL. The sites included 150 groundwater, 13 surface-water, and 4 geothermal-water sites. The data were collected between 1952 and 2012, although most data collected at the INL were collected from 1989 to 1996. Water samples were analyzed for all or most of the following: field parameters, dissolved gases, major ions, dissolved metals, isotope ratios, and environmental tracers. Sources of recharge identified at the INL were regional groundwater, groundwater from the Little Lost River (LLR) and Birch Creek (BC) valleys, groundwater from the Lost River Range, geothermal water, and surface water from the Big Lost River (BLR), LLR, and BC. Recharge from the BLR that may have occurred during the last glacial epoch, or paleorecharge, may be present at several wells in the southwestern part of the INL. Mixing of water at the INL primarily included mixing of surface water with groundwater from the tributary valleys and mixing of geothermal water with regional groundwater. Additionally, a zone of mixing between tributary valley water and regional groundwater, trending southwesterly, extended from near the northeastern boundary of the INL to the southern boundary of the INL. Groundwater flow directions for regional groundwater were southwesterly, and flow directions for tributary groundwater were southeasterly upon entering the ESRP, but eventually began to flow southwesterly in a direction parallel with regional groundwater. Several discrepancies were identified from comparison of sources of recharge determined from geochemistry data and backward particle tracking with a groundwater-flow model. Some discrepancies observed in the particle tracking results included representation of recharge from BC near the north INL boundary, groundwater from the BC valley not extending far enough south, regional groundwater that extends too far west in the southern part of the INL, and no representation of recharge from geothermal water in model layer 1 or recharge from the BLR in the southwestern part of the INL.

Idaho↗

USGS2018

Effects of summer air exposure on the survival of caught-and-released salmonids

Despite the success of catch‐and‐release regulations, exposing fish to air during release has emerged as a growing concern over the past two decades. We evaluated the effect of air exposure during midsummer on survival of Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri , Bull Trout Salvelinus confluentus , and Rainbow Trout O. mykiss exposed to catch‐and‐release angling. Fish were sampled by angling on Palisades Creek (August 2016), Sawmill Creek, and the Main Fork of the Little Lost River, Idaho (July−August 2017). After capture, fish were kept underwater while they were measured and individually tagged. Anglers, in groups of two to four, caught study fish and gave them an air exposure treatment of 0, 30, or 60 s. Single‐pass backpack electrofishing was then used to recapture tagged fish and estimate relative survival. In total, 328 Yellowstone Cutthroat Trout were sampled (0 s: n = 110; 30 s: n = 110; 60 s: n = 108), 278 Bull Trout (0 s: n = 92; 30 s: n = 94; 60 s: n = 92), and 322 Rainbow Trout (0 s: n = 103; 30 s: n = 106; 60 s: n = 113). The majority of fish were caught using artificial flies (≥92%) and were hooked in the corner of the mouth, lower jaw, or upper jaw (≥78%) in all three species. No difference in survival was observed among air exposure treatments for all three species. Results from the present study along with those from prior field studies of air exposure times during angling suggest that mortality from exposing fish to air for ≤60 s is not likely a population‐level concern in catch‐and‐release fisheries for these species.

Idaho↗

USGS2018

Groundwater-quality data from the eastern Snake River Plain Aquifer, Jerome and Gooding Counties, south-central Idaho, 2017

Groundwater-quality samples and water-level data were collected from 36 wells in the Jerome/Gooding County area of the eastern Snake River Plain aquifer during June 2017. The wells included 30 wells sampled for the U.S. Geological Survey’s National Water-Quality Assessment project, plus an additional 6 wells were selected to increase spatial distribution. The data provide water managers with the ability for an improved understanding of groundwater quality and flow directions in the area. Groundwater-quality samples were analyzed for nutrients, major ions, trace elements, and stable isotopes of water. Quality-assurance and quality-control measures consisted of multiple blank samples and a sequential replicate sample. All data are available online at the USGS National Water Information System.

Idaho↗

USGS2018

Seismicity in the Challis, Idaho region, January 2014 - May 2017: Late aftershocks of the 1983 Ms 7.3 Borah Peak earthquake

In April 2014, after about 20 yrs of relatively low seismicity, an energetic earthquake sequence (maximum M L "> M L 4.8) began 25–30 km northwest of the 1983 M s "> M s 7.3 Borah Peak earthquake rupture area near the town of Challis, Idaho. This sequence ended in the fall of 2014, but in January 2015, a second energetic sequence (maximum M L "> M L 5.0) began about 20 km to the southeast. Modest seismicity has continued in both regions with ∼ 1000 "> ∼ 1000 earthquakes detected and located through May 2017. To better characterize the seismicity in the area, we deployed a seven‐station local seismometer network during April–October 2014; one of the stations remained active until July 2015. Here, we report updated locations for earthquakes in the Challis area for 1 January 2014–31 May 2017. Using a combination of absolute and differential arrival times, we generated a catalog of high‐accuracy relocations. The earthquakes clustered into four primary groups, three of them with strikes similar to the Lost River fault—the fault responsible for the 1983 Borah Peak event. We used a modified cut‐and‐paste method to determine moment tensors for 15 of the largest events. All of the moment tensors showed normal faulting with nodal plane strikes consistent with the trend of the relocated seismicity and the regional stress field. We suggest that the recent seismicity near Challis is best interpreted as a continuation of the 1983 M s "> M s Ms 7.3 Borah Peak aftershock sequence, which is unusually long compared to plate boundary aftershock sequences because of the lower regional strain rate.

Idaho↗

USGS2018

Compilation and analysis of multiple groundwater-quality datasets for Idaho

Groundwater is an important source of drinking and irrigation water throughout Idaho, and groundwater quality is monitored by various Federal, State, and local agencies. The historical, multi-agency records of groundwater quality include a valuable dataset that has yet to be compiled or analyzed on a statewide level. The purpose of this study is to combine groundwater-quality data from multiple sources into a single database, to summarize this dataset, and to perform bulk analyses to reveal spatial and temporal patterns of water quality throughout Idaho. Data were retrieved from the Water Quality Portal ( https://www.waterqualitydata.us/ ), the Idaho Department of Environmental Quality, and the Idaho Department of Water Resources. Analyses included counting the number of times a sample location had concentrations above Maximum Contaminant Levels (MCL), performing trends tests, and calculating correlations between water-quality analytes. The water-quality database and the analysis results are available through USGS ScienceBase ( https://doi.org/10.5066/F72V2FBG ).

Idaho↗

USGS2018

Spatial, road geometric, and biotic factors associated with Barn Owl mortality along an interstate highway

Highway programs typically focus on reducing vehicle collisions with large mammals because of economic or safety reasons while overlooking the millions of birds that die annually from traffic. We studied wildlife‐vehicle collisions along an interstate highway in southern Idaho, USA, with among the highest reported rates of American Barn Owl Tyto furcata road mortality. Carcass data from systematic and ad hoc surveys conducted in 2004–2006 and 2013–2015 were used to explore the extent to which spatial, road geometric, and biotic factors explained Barn Owl‐vehicle collisions. Barn Owls outnumbered all other identified vertebrate species of roadkill and represented > 25% of individuals and 73.6% of road‐killed birds. At a 1‐km highway segment scale, the number of dead Barn Owls decreased with increasing numbers of human structures, cumulative length of secondary roads near the highway, and width of the highway median. Number of dead Barn Owls increased with higher commercial average annual daily traffic (CAADT), small mammal abundance index, and with grass rather than shrubs in the roadside verge. The small mammal abundance index was also greater in roadsides with grass versus mixed shrubs, suggesting that Barn Owls may be attracted to grassy portions of the highway with more abundant small mammals for hunting prey. When assessed at a 3‐km highway segment scale, the number of dead Barn Owls again increased with higher CAADT as well as with greater numbers of dairy farms. At a 5‐km scale, number of dead Barn Owls increased with greater percentage of cropland near the highway. While human conversion of the environment from natural shrub‐steppe to irrigated agriculture in this region of Idaho has likely enhanced habitat for Barns Owls, it simultaneously has increased risk for owl‐vehicle collisions where an interstate highway traverses the altered landscape. We review some approaches for highway mitigation and suggest that reducing wildlife‐vehicle collisions involving Barn Owls may contribute to the persistence of this species.

Idaho↗

USGS2018

Deglaciation and postglacial vegetation history of the West Mountains, west-central Idaho, U.S.A.

The West Mountains, west-central Idaho, were deglaciated before ca. 11,500 BP, as indicated by radiocarbon ages and Glacier Peak tephra, at several sites in cirques. Pollen analysis of a sediment core, and plant macrofossils from sediments recovered from the cirque at the head of Van Wyck Creek, indicate that a closed spruce-pine forest surrounded the site from ca. 11,500 to 9800 BP. Early in this period, spruce (probably krummholz) was already growing near the present-day altitudinal limit of large upright spruce. Hence, the climate during this period was significantly warmer than before 11,500 BP. Between ca. 9800 and 3200 BP the climate was warmer and drier than present. Pollen data indicate that from ca. 9300 to the time of Mazama tephra deposition (ca. 6700 BP), the climate was warmer and drier than at any time since 11,500 BP. From ca. 6700 to 3200 BP there was a small decrease in temperature with a minor increase in effective moisture. Beginning ca. 3200 BP, the climate was characterized by cooler temperatures and more mesic conditions. Modern plant communities were established by ca. 1500 BP.

Idaho↗

USGS2018

Geologic map of the Lower Valley quadrangle, Caribou County, Idaho

The Lower Valley 7.5-minute quadrangle, located in the core of the Southeast Idaho Phosphate Resource Area, includes Mississippian to Triassic marine sedimentary rocks, Pliocene to Pleistocene basalt, and Tertiary to Holocene surficial deposits. The Mississippian to Triassic marine sedimentary sequence was deposited on a shallow shelf between an emergent craton to the east and the Antler orogenic belt to the west. The Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation hosts high-grade deposits of phosphate that were the subject of geologic studies through much of the 20th century. Open-pit mining of the phosphate has been underway within and near the Lower Valley quadrangle for several decades.

Idaho↗

USGS2018

Using genetic and phenotypic comparisons to evaluate apparent segregation among Kokanee spawning groups

Genetic and phenotypic traits of spatially and temporally segregated kokanee Oncorhynchus nerka spawning groups in Lake Pend Oreille, Idaho, were compared to test for evidence of divergence on the basis of ecotype (stream spawners versus shoreline spawners) and spawn timing and to describe morphological, life history, and reproductive variation within and among groups. Early and late spawning runs were found to be reproductively isolated; however, there was no clear evidence of genetic differentiation between ecotypes. Spawning groups within the same ecotype differed in length, age distribution, mean length at age, fecundity, and egg size. Variation in reproductive attributes was due primarily to differences in length distributions. Larger‐bodied shore‐spawning kokanee were located in areas where egg survival is known to be enhanced by downwelling, suggesting that the distribution of shore‐spawning kokanee may be partly structured by competition for spawning habitats with groundwater influence. This study contributes to other research indicating that introduced kokanee populations are unlikely to undergo adaptive divergence if they have a history of population fluctuations and are supplemented regularly.

Idaho↗

USGS2018

Estimating vegetation biomass and cover across large plots in shrub and grass dominated drylands using terrestrial lidar and machine learning

Terrestrial laser scanning (TLS) has been shown to enable an efficient, precise, and non-destructive inventory of vegetation structure at ranges up to hundreds of meters. We developed a method that leverages TLS collections with machine learning techniques to model and map canopy cover and biomass of several classes of short-stature vegetation across large plots. We collected high-definition TLS scans of 26 1-ha plots in desert grasslands and big sagebrush shrublands in southwest Idaho, USA. We used the Random Forests machine learning algorithm to develop decision tree models predicting the biomass and canopy cover of several vegetation classes from statistical descriptors of the aboveground heights of TLS points. Manual measurements of vegetation characteristics collected within each plot served as training and validation data. Models based on five or fewer TLS descriptors of vegetation heights were developed to predict the canopy cover fraction of shrubs (R 2 = 0.77, RMSE = 7%), annual grasses (R 2 = 0.70, RMSE = 21%), perennial grasses (R 2 = 0.36, RMSE = 12%), forbs (R 2 = 0.52, RMSE = 6%), bare earth or litter (R 2 = 0.49, RMSE = 19%), and the biomass of shrubs (R 2 = 0.71, RMSE = 175 g) and herbaceous vegetation (R 2 = 0.61, RMSE = 99 g) (all values reported are out-of-bag). Our models explained much of the variability between predictions and manual measurements, and yet we expect that future applications could produce even better results by reducing some of the methodological sources of error that we encountered. Our work demonstrates how TLS can be used efficiently to extend manual measurement of vegetation characteristics from small to large plots in grasslands and shrublands, with potential application to other similarly structured ecosystems. Our method shows that vegetation structural characteristics can be modeled without classifying and delineating individual plants, a challenging and time-consuming step common in previous methods applying TLS to vegetation inventory. Improving application of TLS to studies of shrub-steppe ecosystems will serve immediate management needs by enhancing vegetation inventories, environmental modeling studies, and the ability to train broader datasets collected from air and space.

Idaho↗

USGS2018

Fight and air exposure times of caught and released salmonids from the South Fork Snake River

Catch-and-release regulations are among the most common types of fishing regulations. In recent years, concerns have arisen regarding the exposure of fish to air during catch-and-release angling. The purpose of our study was to quantify the length of time angled fish were exposed to air by anglers in a typical catch-and-release fishery and relate it to the lengths of time reported to produce negative effects. In total, 312 individual anglers were observed on the South Fork Snake River, Idaho, from May through August 2016. Fight time varied from 1.1 s to 230.0 s, and average fight time was 40.0 s (SD = 36.8). Total air exposure times varied from 0.0 s to 91.8 s and averaged 19.3 s (SD = 15.0). Though not statistically significant, a trend in reduced fight times was observed when anglers were guided and increased air exposure times when a net was used and a picture was taken. Results of the current study suggest that anglers expose fish to air for periods that are much less than those reported to cause mortality.

Idaho↗

USGS2018

Patterns in fish assemblage structure in a small western stream

Knowledge of how patterns in fish assemblages are spatially structured is important for guiding management and conservation actions. However, most studies have taken place in the eastern and midwestern U.S., resulting in a poor understanding of factors influencing western stream fishes. The objectives of this study were to evaluate habitat and species associations of fishes in Deep Creek, a small tributary of the Kootenai River in Idaho. Fishes and habitat were sampled from 58 reaches in Deep Creek. In total, 7,129 individual fishes representing 18 species were sampled. Patterns in species richness were largely a function of channel gradient and associated habitat characteristics. Species richness decreased with increased channel gradient. Species-specific habitat relationships for native and nonnative fishes in Deep Creek provided specific insights into the ecology of each species. Predicted probability of occurrence and relative abundance varied by species and were related to a broad suite of environmental characteristics. This study provides insight on patterns of fish assemblage structure, as well as important information on the ecology of native and nonnative fishes in a western stream system.

Idaho↗

USGS2018

Effects of water-level management and hatchery supplementation on kokanee recruitment in Lake Pend Oreille, Idaho

Resource managers have been attempting to recover the kokanee ( Oncorhynchus nerka ) population in Lake Pend Oreille, Idaho for more than three decades using an annual stocking program and an experimental water-level management strategy. This study evaluated the effect of both management actions on kokanee recruitment. A bootstrap-based generalized Ricker model was used to test if wild kokanee recruitment was significantly influenced by water-level management, while accounting for error due to sampling variability and differential survival of wild- and hatchery-origin fish within age-classes. Wild kokanee exhibited a compensatory stock-recruitment relationship, whereas hatchery recruitment was positively and linearly related to stocking. The model did not identify a significant relationship between water level and wild kokanee recruitment. Density dependence and variable stocking appeared to explain the synchronized and cyclic recruitment of wild and hatchery fry.

Idaho↗