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At least 397 records · Page 22Linked to original sources

USGS2025

Seasonal movements of nonnative White Catfish in the Penobscot River estuary

Objective White Catfish Ameiurus catus has been introduced to coastal watersheds across the United States. In the Penobscot River, Maine, this species has become increasingly common in upstream habitats that have been made accessible by recent dam removals. We characterized the movements of White Catfish to understand the temporal variation in their movement patterns and contextualize these findings within the recent changes in watershed connectivity. Methods We captured and tagged 10 adult White Catfish (mean fork length = 271 mm) with acoustic transmitters in the lower Penobscot River in July 2022. The movements of the tagged fish were monitored through April 2023 with a large network of stationary receivers. Results The tagged catfish were detected up to 6 km upstream and 31 km downstream from the release site. The total distance that was traveled by individuals ranged from 0 to 154 km during the study. Fall and spring movements were associated with changes in river flow and water temperature, but fish were relatively stationary from December through March, when at least five individuals were assumed to have overwintered in lower river tributaries. Conclusion Our results show that individual White Catfish may move considerable distances within large river systems and that these movements are potentially facilitated by changing river conditions. Collectively, this study fills a long-standing knowledge gap about the movement ecology of this species, adds context to help explain a recent increase in observations within their introduced range, and shows how changes in river conditions may be used to predict when and where these fish will move within a tidal system.

Maine↗

USGS2003

Hydrological alteration along the Missouri River Basin: A time series approach

Human alteration of large rivers is common-place, often resulting in significant changes in flow characteristics. We used a time series approach to examine daily mean flow data from locations throughout the main-stem Missouri River. Data from a pre-alteration period (1925-1948) were compared with a post-alteration period (1967-1996), with separate analyses conducted using either data from the entire year or restricted to the spring fish spawning period (1 April-30 June). Daily mean flows were significantly higher during the post-alteration period at all locations. Flow variability was markedly reduced during the post-alteration period as a probable result of flow regulation and climatological shifts. Daily mean flow during the spring fish spawning period was significantly lower during the post-alteration period at the most highly altered locations in the middle portion of the river, but unchanged at the least altered locations in the upper and lower portions of the river. Our data also corroborate other analyses, using alternate statistical approaches, that suggest similar changes to the Missouri River system. Our results suggest human alterations on the Missouri River, particularly in the middle portion most strongly affected by impoundments and channelization, have resulted in changes to the natural flow regime.

Aquatic Sciences↗

USGS2005

Aqueous exposure to Aroclor 1254 modulates the mitogenic response of Atlantic salmon anterior kidney T-cells: Indications of short- and long-term immunomodulation

Polychlorinated biphenyls (PCBs) exist as persistent organic pollutants in numerous river systems in the United States. Unfortunately, some of these rivers are sites of active Atlantic salmon restoration programs, and polychlorinated biphenyls have been implicated as ancillary factors contributing to failed salmon restoration. Here, we investigate the immediate and chronic effects of intermediate duration aqueous PCB exposure (1 or 10 ??g L-1 Aroclor 1254) on the mitogen-stimulated lymphoproliferative response of Atlantic salmon anterior kidney leukocytes (AKLs). A short-term study was designed to examine immunomodulation in Atlantic salmon smolts immediately following 21 days of aqueous exposure, while a long-term study evaluated chronic impacts in the mitogen response in parr 15 months post-exposure as larvae. The proliferative response of AKLs to the mitogens concanavalin A (CON A), phytohemaglutinnin-P (PHA-P), pokeweed mitogen (PWM), and lipopolysaccharide were used as an indice of immunomodulation. The proliferative response to the T-cell mitogens CON A and PHA-P was significantly increased in the 10 ??g L-1 group (n = 10; P = 0.043 and 0.002, respectively) immediately following exposure of smolts. Additionally, The PHA-P response was significantly increased in the 1 ??g L-1 exposure group (n = 10, P = 0.036). In fish treated as larvae and tested 15 months later, the PHA-P sensitive populations exhibited elevated proliferation in the 1 and 10 ??g L-1 groups (n = 12, P < 0.04) relative to the vehicle control while the PWM response was significantly increased (n = 12, P = 0.036) only in the 10 ??g L-1 treated groups. These results demonstrate an immunomodulatory effect of PCBs on T-cell mitogen sensitive populations of lymphocytes in Atlantic salmon as well as long-term immunomodulation in PHA-P and PWM sensitive populations. ?? 2005 Elsevier B.V. All rights reserved.

Aquatic Toxicology↗

USGS2012

Sex difference in polybrominated diphenyl ether concentrations of walleyes

Polybrominated diphenyl ether (PBDE) concentrations were determined for mature male and mature female walleyes ( Sander vitreus ) sampled from the Saginaw Bay population during 2007. PBDE concentrations in prey fish caught in the Saginaw River, the primary tributary to Saginaw Bay, and in Saginaw Bay during 2005 and 2007 also were determined. Mature male and mature female walleyes averaged 70.3 ng/g and 24.8 ng/g, respectively, in ΣPBDE, which was equal to the sum of concentrations of six PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, and BDE-154). This sex difference was likely due to males spending more time in the Saginaw River system than females. Prey fish captured in the Saginaw River were roughly ten times higher in ΣPBDE than those caught in Saginaw Bay. BDE-47 was the predominant congener in both walleyes and prey fish, and this congener contributed about 50%, on average, to ΣPBDE. Congener profiles differed significantly between the two sexes of walleyes. In contrast, congener profiles of the prey fish did not differ significantly between the river-caught fish and the bay-caught fish. One plausible explanation for these congener profile results was that net trophic transfer efficiencies of PBDEs to walleyes from their prey were similar for all congeners except BDE-28, and that diet composition differed between the two sexes of walleyes.

Michigan↗

USGS2018

Application of a luminescence‐based sediment transport model

Quantifying the transport history of sand is a challenging but important goal in geomorphology. In this paper, we take a simple idea that luminescence is bleached during transport and regenerates during storage, and use this as a basis to re‐envision luminescence as a sediment tracer. We apply a mathematical model describing luminescence through an idealized channel and reservoir system and then compare this idealized model to real rivers to see if luminescence can reproduce known sediment transport data. We provide results from application of this luminescence method in three rivers from the mid‐Atlantic region of the United States. This method appears promising. However, as a river system diverges from idealized conditions of the mathematical model, the luminescence data diverge from model predictions. We suggest that spatial variation in the delivery of sediment from hillslopes can be reflected in the channel sediment luminescence and that luminescence acts as a function of landscape dynamics.

Geophysical Research Letters↗

USGS2001

Life in the fast lane: Fish and foodweb structure in the main channel of large rivers

We studied the main channel of the lower Illinois River and of the Mississippi River just upstream and downstream of its confluence with the Illinois River to describe the abundance, composition, and/or seasonal appearance of components of the main-channel community. Abundance of fishes in the main channel was high, especially adults. Most adult fishes were present in the main channel for either 3 or 4 seasons/y, indicating that fishes regularly reside in the main channel. We documented abundant zooplankton and benthic invertebrates in the main channel, and the presence of these food types in the diets of channel catfish and freshwater drum. All trophic levels were well represented in the main channel, indicating that the main channel supports a unique food web. The main channel also serves as an important energetic link with other riverine habitats (e.g., floodplains, secondary channels, backwater lakes) because of the mobility of resident fishes and because of the varied energy sources supplying this food web. It may be more realistic to view energy flow in large-river systems as a combination of 3 existing concepts, the river continuum concept (downstream transport), the flood pulse concept (lateral transport to the floodplain), and the riverine productivity model (autochthonous production). We urge additional research to quantify the links between the main channel and other habitat types in large rivers because of the apparent importance of main-channel processes in the overall structure and function of large-river ecosystems.

Illinois↗

USGS2012

Biological assessment of environmental flows for Oklahoma

Large-scale patterns in fish assemblage structure and functional groups are influenced by alterations in streamflow regime. In this study, we defined an objective threshold for alteration for Oklahoma streams using a combination of the expected range of 27 flow indices and a discriminant analysis to predict flow regime group. We found that fish functional groups in reference flow conditions had species that were more intolerant to flow alterations and preferences for stream habitat and faster flowing water. In contrast, altered sites had more tolerant species that preferred lentic habitat and slower water velocity. Ordination graphs of the presence and functional groups of species revealed an underlying geographical pattern roughly conforming to ecoregions, although there was separation between reference and altered sites within the larger geographical framework. Additionally, we found that reservoir construction and operation significantly altered fish assemblages in two different systems, Bird Creek in central Oklahoma and the Kiamichi River in southeastern Oklahoma. The Bird Creek flow regime shifted from a historically intermittent stream to one with stable perennial flows, and changes in fish assemblage structure covaried with changes in all five components of the flow regime. In contrast, the Kiamichi River flow regime did not change significantly for most flow components despite shifts in fish assemblage structure; however, most of the species associated with shifts in assemblage structure in the Kiamichi River system were characteristic of lentic environments and were likely related more to proximity of reservoirs in the drainage system than changes in flow. The spatial patterns in fish assemblage response to flow alteration, combined with different temporal responses of hydrology and fish assemblage structure at sites downstream of reservoirs, indicate that interactions between flow regime and aquatic biota vary depending on ecological setting. This supports the notion that regional variation in natural flow regimes could affect the development of flow recommendations.

Oklahoma↗

USGS2024

Aboveground carbon stocks across a hydrological gradient: Ghost forests to non-tidal freshwater forested wetlands

Upper estuarine forested wetlands (UEFWs) play an important role in the sequestration of atmospheric carbon (C), which is facilitated by their position at the boundary of terrestrial and maritime environments but threatened by sea level rise. This study assessed the change in aboveground C stocks along the estuarine–riverine hydrogeomorphic gradient spanning salt-impacted freshwater tidal forested wetlands to freshwater forested wetlands in seasonally tidal and nontidal landscape positions. Standing stocks of C in forested wetlands were measured along two major coastal river systems, the Winyah Bay in South Carolina and the Savannah River in Georgia (USA), replicating and expanding a previous study to allow the assessment of change over time. Aboveground C stocks on these systems averaged 172.9 Mg C ha −1 , comparable to those found in UEFWs across the globe and distinct from the terrestrial forested ecosystems they are often considered to be a part of during large-scale C inventory efforts. Groundwater salinity conditions as low as 1.3 ppt were observed in conjunction with losses of aboveground C. When viewed in context alongside expected sea level rise and corresponding saltwater intrusion estimates, these data suggest a marked decrease in aboveground C stocks in forested wetlands situated in and around tidal estuaries.

Georgia, South Carolina↗

USGS2001

Flow and habitat effects on juvenile fish abundance in natural and altered flow regimes

Conserving biological resources native to large river systems increasingly depends on how flow-regulated segments of these rivers are managed. Improving management will require a better understanding of linkages between river biota and temporal variability of flow and instream habitat. However, few studies have quantified responses of native fish populations to multiyear (>2 yr) patterns of hydrologic or habitat variability in flow-regulated systems. To provide these data, we quantified young-of-year (YOY) fish abundance during four years in relation to hydrologic and habitat variability in two segments of the Tallapoosa River in the southeastern United States. One segment had an unregulated flow regime, whereas the other was flow-regulated by a peak-load generating hydropower dam. We sampled fishes annually and explored how continuously recorded flow data and physical habitat simulation models (PHABSIM) for spring (April-June) and summer (July-August) preceding each sample explained fish abundances. Patterns of YOY abundance in relation to habitat availability (median area) and habitat persistence (longest period with habitat area continuously above the long-term median area) differed between unregulated and flow-regulated sites. At the unregulated site, YOY abundances were most frequently correlated with availability of shallow-slow habitat in summer (10 species) and persistence of shallow-slow and shallow-fast habitat in spring (nine species). Additionally, abundances were negatively correlated with 1-h maximum flow in summer (five species). At the flow-regulated site, YOY abundances were more frequently correlated with persistence of shallow-water habitats (four species in spring; six species in summer) than with habitat availability or magnitude of flow extremes. The associations of YOY with habitat persistence at the flow-regulated site corresponded to the effects of flow regulation on habitat patterns. Flow regulation reduced median flows during spring and summer, which resulted in median availability of shallow-water habitats comparable to the unregulated site. However, habitat persistence was severely reduced by flow fluctuations resulting from pulsed water releases for peak-load power generation. Habitat persistence, comparable to levels in the unregulated site, only occurred during summer when low rainfall or other factors occasionally curtailed power generation. As a consequence, summer-spawning species numerically dominated the fish assemblage at the flow-regulated site; five of six spring-spawning species occurring at both study sites were significantly less abundant at the flow-regulated site. Persistence of native fishes in flow-regulated systems depends, in part, on the seasonal occurrence of stable habitat conditions that facilitate reproduction and YOY survival.

Alabama, Georgia↗

USGS1999

Chesapeake Bay habitat criteria scores and the distribution of submersed aquatic vegetation in the tidal Potomac River and Potomac Estuary, 1983-1997

The Chesapeake Bay Program has identified habitat requirements for the restoration of submersed aquatic vegetation (SAV) in the Chesapeake Bay estuary and tidal reaches of contributing river systems conditioned on the salinity regime of a specific location. The tidal Potomac River and Potomac Estuary is an important component of the Chesapeake Bay system to which these requirements can be applied. The SAV habitat requirements are formulated as threshold criteria that certain critical water-quality characteristics must satisfy during the SAV growing season. A multivariate scoring system based on these criteria was developed in order to synopsize water quality conditions during the 1983-1997 SAV growing seasons. Chesapeake Bay habitat criteria scores are displayed relative to annual SAV coverage for each Potomac River and Potomac Estuary segment. It is seen that although there is some correspondence in the inter-annual expansion or contraction of SAV coverage and compliance with Chesapeake Bay SAV habitat criteria, individual criteria provide neither necessary nor sufficient conditions to explain inter-annual dynamics of SAV coverage, especially in the Potomac Estuary.

Open-File Report↗

USGS2024

Gulf killifish (Fundulus grandis) in the Pecos River: Unique life history traits in a nonnative, island population

Nonnative species may display unique life history traits when established in habitats with distinctive environmental and biotic contexts compared with their native ecosystems. Gulf killifish ( Fundulus grandis ), native to coastal habitats of the Gulf of Mexico, are established in several inland river systems where they pose a potential threat to native fishes. In the Pecos River, Texas, nonnative Gulf killifish have shown a high rate of piscivory compared with native coastal populations; otherwise, little is known about the ecology of the species in inland systems. We examined reproductive characteristics, size, and age of Gulf killifish in the Pecos River. We found that reproduction takes place approximately between late March and September, with the gonadosomatic index of females showing a large and extended peak in spring and a second minor peak in late August–September. Our age estimations indicate that this population consists mostly of fish <2 years old, similarly to that reported for coastal populations. Total length ranged 11.9–143.4 mm for males and 32.3–162.5 mm for females, indicating a sexually dimorphic size structure with Pecos River individuals reaching larger sizes compared with coastal populations. The relatively large size and piscivorous nature of Gulf killifish, along with tolerance for a wide range of environmental conditions, are attributes in nonnative species hypothesized to promote invasion success and replacement of native species.

New Mexico, Texas↗

USGS2025

Smallmouth bass (Micropterus dolomieu) and chain pickerel (Esox niger) identified as Atlantic salmon (Salmo salar) smolt predators in a reservoir system

Reservoir predation has been identified as a leading mortality source for smolts migrating through impounded river systems. We investigated smolt predation risk for an endangered Atlantic salmon ( Salmo salar ) population in the Weldon Dam reservoir in the Penobscot River, Maine, USA. In spring 2022, we characterized the fates of 390 tethered smolts. Smolts were exclusively predated by two predator species not native to the study area: chain pickerel ( Esox niger , n = 43) and smallmouth bass ( Micropterus dolomieu , n = 42). Using Cox-proportional hazard analysis, we estimated that 23% (95% CI = 15%–29%) of tethered smolts were expected to be predated within a one-hour deployment. Water temperature was the primary driver of predation risk as predation probability increased from 10% to 33% when temperature increased from 5 to 15 °C. Smolts also incurred above-average predation risk when they were within 40 m of shore. We demonstrate that non-native fish predation may drive patterns of high impoundment mortality and that risk is spatially and temporally heterogeneous within these systems. Collectively, this study offers direct evidence of species-specific predation on Atlantic salmon smolts and illuminates potential strategies to mitigate predation risk during reservoir migration.

Maine↗

USGS2012

Spatial patterns of aquatic habitat richness in the Upper Mississippi River floodplain, USA

Interactions among hydrology and geomorphology create shifting mosaics of aquatic habitat patches in large river floodplains (e.g., main and side channels, floodplain lakes, and shallow backwater areas) and the connectivity among these habitat patches underpins high levels of biotic diversity and productivity. However, the diversity and connectivity among the habitats of most floodplain rivers have been negatively impacted by hydrologic and structural modifications that support commercial navigation and control flooding. We therefore tested the hypothesis that the rate of increase in patch richness (# of types) with increasing scale reflects anthropogenic modifications to habitat diversity and connectivity in a large floodplain river, the Upper Mississippi River (UMR). To do this, we calculated the number of aquatic habitat patch types within neighborhoods surrounding each of the ≈19 million 5-m aquatic pixels of the UMR for multiple neighborhood sizes (1–100 ha). For all of the 87 river-reach focal areas we examined, changes in habitat richness ( R ) with increasing neighborhood length ( L , # pixels) were characterized by a fractal-like power function R = L z ( R 2 > 0.92 ( P < 0.05)). The scaling exponent ( z ) measures the rate of increase in habitat richness with neighborhood size and is related to a fractal dimension. Variation in z reflected fundamental changes to spatial patterns of aquatic habitat richness in this river system. With only a few exceptions, z exceeded the river-wide average of 0.18 in focal areas where side channels, contiguous floodplain lakes, and contiguous shallow-water areas exceeded 5%, 5%, and 10% of the floodplain respectively. In contrast, z was always less than 0.18 for focal areas where impounded water exceeded 40% of floodplain area. Our results suggest that rehabilitation efforts that target areas with <5% of the floodplain in side channels, <5% in floodplain lakes, and/or <10% in shallow-water areas could improve habitat diversity across multiple scales in the UMR.

Upper Mississippi River↗

USGS2020

Water temperature controls for regulated canyon-bound rivers

Many canyon‐bound rivers have been dammed and downstream flow and water temperatures modified. Climate change is expected to cause lower storage in reservoirs and warmer release temperatures, which may further alter downstream flow and thermal regimes. To anticipate potential future changes, we first need to understand the dominant heat transfer mechanisms in canyon‐bound river systems. Towards this end, we adapt a dynamic process‐based river routing and temperature model to account for complex shading and radiation characteristics found in canyon‐bound rivers. We apply the model to a 362 km segment of the Colorado River in Grand Canyon National Park, USA to simulate temperature over an 18‐year period. Extensive temperature and flow datasets from within the canyon were used to assess model performance. At the most downstream gaging location, root mean square errors of hourly flow routing and temperature predictions were 11.5 m 3 /s and 0.93 °C, respectively. We found that heat fluxes controlling temperatures were highly variable over space and time, primarily due to shortwave radiation dynamics and hydropeaking flow conditions. Additionally, the large differences between air and water temperature during summer periods resulted in high sensible and latent heat fluxes. Sensitivity analyses indicate that reservoir release temperatures are most influential above the RM88 gage (141 kilometers below Glen Canyon Dam), while a combination of discharge, shortwave radiation, and air temperature become more important farther downstream. This study illustrates the importance of understanding the spatial and temporal variability of topographic shading when predicting water temperatures in canyon‐bound rivers.

Colorado↗

USGS2010

A likelihood framework for joint estimation of salmon abundance and migratory timing using telemetric mark-recapture

Many fisheries for Pacific salmon Oncorhynchus spp. are actively managed to meet escapement goal objectives. In fisheries where the demand for surplus production is high, an extensive assessment program is needed to achieve the opposing objectives of allowing adequate escapement and fully exploiting the available surplus. Knowledge of abundance is a critical element of such assessment programs. Abundance estimation using mark—recapture experiments in combination with telemetry has become common in recent years, particularly within Alaskan river systems. Fish are typically captured and marked in the lower river while migrating in aggregations of individuals from multiple populations. Recapture data are obtained using telemetry receivers that are co-located with abundance assessment projects near spawning areas, which provide large sample sizes and information on population-specific mark rates. When recapture data are obtained from multiple populations, unequal mark rates may reflect a violation of the assumption of homogeneous capture probabilities. A common analytical strategy is to test the hypothesis that mark rates are homogeneous and combine all recapture data if the test is not significant. However, mark rates are often low, and a test of homogeneity may lack sufficient power to detect meaningful differences among populations. In addition, differences among mark rates may provide information that could be exploited during parameter estimation. We present a temporally stratified mark—recapture model that permits capture probabilities and migratory timing through the capture area to vary among strata. Abundance information obtained from a subset of populations after the populations have segregated for spawning is jointly modeled with telemetry distribution data by use of a likelihood function. Maximization of the likelihood produces estimates of the abundance and timing of individual populations migrating through the capture area, thus yielding substantially more information than the total abundance estimate provided by the conventional approach. The utility of the model is illustrated with data for coho salmon O. kisutch from the Kasilof River in south-central Alaska.

North American Journal of Fisheries Management↗

USGS1989

Trace elements in bed sediments of the San Joaquin River and its tributary streams, California, 1985

Bed sediments were sampled at 24 sites on the San Joaquin River, California and its tributaries in October 1985 to assess the distribution of trace elements and factors affecting their concentrations. The proportion of less than 62-micrometer sediment was significantly (alpha=0.05) correlated with organic-carbon concentrations. Bed sediments from tributaries originating in the Sierra Nevada were much coarser than sediments in streams draining the Coast Range and western valley. Selenium concentrations in water have been measured. Interrelations among trace elements were examined using principal component analysis. 57% of the variance was accounted for in the first two principal components, which together show a distinct separation between sites dominated by Coast Range sediments and sites dominated by Sierra Nevada sediments. The third and fourth components accounted for 21% of the variance and distinguished the mixed-source sediments of the intermittent upper San Joaquin River from other parts of the river system. Generally, elements in bed sediments of the San Joaquin River and its tributaries were similar in concentration to elements in San Joaquin Valley soils, and concentrations were far below hazardous waste criteria. Concentrations were lower than in sediments from some polluted urban rivers and water more comparable to other rural agricultural rivers. (USGS)

Water-Resources Investigations Report↗

USGS2013

Status and trends monitoring of the mainstem Columbia River: sample frame development and review of programs relevant to the development of an integrated approach to monitoring

Implementing an Integrated Status and Trends Monitoring program (ISTM) for the mainstem Columbia River will help identify trends in important natural resources and help us understand the long-term collective effects of management actions. In this report, we present progress towards the completion of a stepwise process that will facilitate the development of an ISTM for the mainstem Columbia River. We discuss planning and regulatory documents that can be used to identify monitoring goals and objectives and present existing monitoring and research activities that should be considered as the development of a Columbia River ISTM proceeds. We also report progress towards the development of sample frames for the Columbia and Snake Rivers and their floodplains. The sample frames were formulated using Digital Elevation Models (DEM’s) of the river channel and upland areas and a Generalized Random-Tessellation Stratified (GRTS) algorithm for an area based resource to generate “master sample(s).” Working with the Pacific Northwest Aquatic Monitoring Partnership (PNAMP) we facilitated the transfer of the sample frames to the PNAMP “Monitoring Sample Designer” tool. We then discuss aspects of response and survey designs as they pertain to the formulation of a mainstem Columbia River ISTM. As efforts to formulate an ISTM for the mainstem Columbia River proceed, practitioners should utilize the extensive literature describing the planning and implementation of fish and wildlife mitigation and recovery efforts in the Columbia River Basin. While we make progress towards establishing an ISTM framework, considerable work needs to be done to formulate an ISTM program for the mainstem Columbia River. Long-term monitoring programs have been established for other large rivers systems; scientists that have experience planning, implementing, and maintaining large river monitoring efforts such as those in the Colorado, Illinois, and Mississippi Rivers should be consulted and involved as efforts proceed.

Idaho;Oregon;Washington↗

USGS1982

Habitat suitability index models: Cutthroat trout

Cutthroat trout, Salmo clarki, are a polytypic species consisting of several geographically distinct forms with a broad distribution and a great amount of genetic diversity (Hickman 1978; Behnke 1979). Behnke (1979) recognized 13 extant subspecies: Coastal cutthroat (S. c. clarki) in coastal streams from Prince William Sound, Alaska to the Eel Rlver in California; mountain cutthroat (~. ~. alpestris) in upper Columbia and F~Dser River drainages of British Columbia; west slope cutthroat (S. c. lewisi) in the upper Columbia, Salmon, Clearwater, South Saskatchewan and upper Missouri drainages of Montana and Idaho; an undescribed subspecies in the Alvord basin, Oregon; Lahonton cutthroat (S. c ..henshawi), Pauite cutthroat (S. c. seleniris), and an undescribed- subspecies in the Humboldt River drafnage of the Lahontan basin of Nevada and California; Yellowstone cutthroat (S. c. bouvieri) in the Yellowstone drainage of Wyoming and Montana and the Snake River drainage of Wyoming, Idaho, and Nevada; an undescribed subspecies (fine spotted) in the upper Snake River, Wyoming; Bonneville cutthroat (S. c. utah) in the Bonneville basin in Utah, Nevada, Idaho, and Wyoming; Colorado River cutthroat (~. ~. pleuriticus) in the Colorado River drainage in Wyoming, Utah, New Mexico, and Colorado; greenback cutthroat (S. c. stomias) in the South Platte and Arkansas River systems; and Rio Grande cutthroat (~. ~. virginalis) in the Rio Grande River drainage of Colorado and New Mexico. Many of these 13 subspecies are included on Federal or State endangered or threatened species lists. Temperature and chemical preferences, migration, and other ecological and life history attributes vary among cutthroat subspecies (Behnke 1979). Differences in growth rate (Carlander 1969; Scott and Crossman 1973; Behnke 1979) and food preferences have also been reported (Trojnar and Behnke 1974) between some subspecies.

FWS/OBS↗