SEARCH · Geology Reports

Results for “Journal of Range Management”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources

USGS2016

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

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

Nevada↗

USGS2010

Estimating aboveground biomass for broadleaf woody plants and young conifers in Sierra Nevada, California forests

Quantification of biomass is fundamental to a wide range of research and natural resource management goals. An accurate estimation of plant biomass is essential to predict potential fire behavior, calculate carbon sequestration for global climate change research, assess critical wildlife habitat, and so forth. Reliable allometric equations from simple field measurements are necessary for efficient evaluation of plant biomass. However, allometric equations are not available for many common woody plant taxa in the Sierra Nevada. In this report, we present more than 200 regression equations for the Sierra Nevada western slope that relate crown diameter, plant height, crown volume, stem diameter, and both crown diameter and height to the dry weight of foliage, branches, and entire aboveground biomass. Destructive sampling methods resulted in regression equations that accurately predict biomass from one or two simple, nondestructive field measurements. The tables presented here will allow researchers and natural resource managers to easily choose the best equations to fit their biomass assessment needs.

California↗

USGS2020

Spatial ecology and resource selection of eastern box turtles

Eastern box turtles ( Terrapene carolina carolina ) are widely distributed throughout the eastern United States. Although once common throughout much of its distribution, the species has experienced declines in local populations. Understanding resource selection is important for the conservation of this species; however, few data exist on resource selection for eastern box turtles in the southeastern United States. We estimated home range and resource selection for 100 individual turtles in the Blue Ridge, Ridge and Valley, and Cumberland Plateau and Mountains physiographic regions in Tennessee, USA, from 2016 to 2018. We used step‐selection functions to investigate eastern box turtle resource selection during May–August 2017 and May–August 2018 at 2 spatial scales. We classified vegetation type, measured vegetation composition and structure, recorded time since fire, and measured coarse woody debris abundance at 1,225 used telemetry locations and 1,225 associated available points. Home range sizes averaged 9.3 ha ± 3.0 (SE) using minimum convex polygon analysis, 8.25 ha ± 2.88 using 95% kernel density analysis, and 1.50 ha ± 0.56 using 50% kernel density analysis. Box turtles selected areas with greater visual obstruction at the 0–0.25‐m level, greater amounts of 10‐hour and 100‐hour fuels (timelag categories used in fire‐danger ratings), and greater litter depths compared to available locations. Box turtles were more likely to select areas with greater cover of brambles and coarser woody debris and were less likely to select areas with less vegetation cover. Vegetation type and time since last fire did not affect selection. Our data suggest that management activities that encourage greater understory vegetation cover, greater visual obstruction at the 0–0.25‐m level, and greater bramble cover will enhance habitat quality for eastern box turtles.

Journal of Wildlife Management↗

USGS2022

Avian predation on juvenile and adult Lost River and Shortnose Suckers: An updated multi-predator species evaluation

Previous research suggests that predation by piscivorous colonial waterbirds may negatively influence the survival of Lost River Suckers (LRS) Deltistes luxatus and Shortnose Suckers (SNS) Chasmistes brevirostris in the Upper Klamath Basin (UKB), USA. However, estimates of predation from past studies, which were based on suckers with PIT tags, represent minimum estimates of sucker mortality because analyses did not account for the proportion of tags that were consumed by birds and deposited beyond their breeding colony. To address this uncertainty, we fed PIT-tagged suckers to American white pelicans Pelecanus erythrorhynchos to estimate deposition probabilities. A hierarchical Bayesian model was then used to estimate predation rates (percentage of available tagged fish that were consumed) on juvenile suckers that were released as part of the Sucker Assisted Rearing Program (SARP) and on wild juvenile and adult LRS and SNS during 2009–2020. Pelican deposition probabilities were estimated to be 0.47 (95% credible interval = 0.36–0.60), indicating that for every 100 tags consumed, 47 tags on average were deposited on breeding colonies by birds. Deposition-corrected estimates of predation rates were approximately two times greater than those previously reported and ranged annually from 4.3% (95% credible interval = 2.9–6.7%) to 8.5% (6.3–12.7%) on SARP juvenile suckers, from 4.3% (0.9–13.2%) to 10.5% (3.8–24.5%) on wild juvenile suckers, and from 0.1% (<0.1–0.3%) to 7.2% (2.8–16.4%) on adult suckers, depending on species and location. Results suggest that predation by colonial waterbirds, although not the original cause of sucker declines, was a substantial source of sucker mortality in some years. Future studies should consider models that jointly estimate both predation and survival and models that include environmental factors that potentially influence sucker susceptibility to avian predators in the UKB.

California, Oregon↗

USGS2021

Nutrient and suspended-sediment concentrations in the Maumee River and tributaries during 2019 rain-induced fallow conditions

Above average precipitation from October 2018 through July 2019 in the Maumee River (R.) Basin resulted in 29% of cropland left fallow, providing a glimpse of potential effects from decreased nutrient application. Ongoing monitoring at 15 water-quality sites on the Maumee R. upstream from Defiance enabled comparison with 2017, which was hydrologically similar to 2019 in precipitation and streamflow. In 2019, nitrate (as nitrogen; NO 3 -N) for March-July was significantly less than previous years (2015–2018), but the response for phosphorus (P) was more complicated. Relative to 2017, total P (TP) was lower at 7 of 15 sites, but higher at 7, reflecting higher suspended sediment (SS). Dissolved P (DP) was generally lower, but less different than NO 3 ; DP was higher at 3 sites. DP-P:NO 3 -N was generally higher in 2019, DP-P:TP was lower, and there was less TP relative to SS. Overall, less P was in the system in 2019. However smaller streams showed a large range of difference between 2019 and 2017 for all constituents, indicating variability in land management and physiography. In contrast, all constituents were lower in 2019 in larger (>5000 km 2 ) streams, including the Maumee R. near Defiance, where the difference in NO 3 (−37%) exceeded that for TP (−16%), DP (−10%), and SS (−20%). Differences in these relations among N, P, and SS indicate that P was available from legacy sources that are more difficult to distinguish during typical agricultural production years and that some material from 2019 was stored in the system upstream from the largest sites.

Indiana, Ohio↗

USGS2018

Golden Eagle Monitoring Plan for the Desert Renewable Energy Conservation Plan

This report describes options for monitoring the status and population trends of the golden eagle (Aquila chrysaetos) within the Desert Renewable Energy Conservation Plan (DRECP) area of Southern California in maintaining stable or increasing population in the planning area. The report profiles the ecology of golden eagles in the region and provides a range of potential sampling options to address monitoring needs and objectives. This approach also focused on links between changes in human land-use, golden eagle nesting and foraging habitat conditions, and population dynamics. The report outlines how monitoring data from demographic, prey, and habitat studies were used to develop a predictive demographic model for golden eagles in the DRECP area. Results from the model simulations suggest increases in renewable energy development could have negative consequences for population trajectories. Results also suggest site-specific conservation actions could reduce the magnitude of negative impacts to the local population of eagles. A monitoring framework is proposed including: (1) annual assessments of site-occupancy and reproduction by territorial pairs of golden eagles (including rates at which sites become colonized or vacated over time); (2) estimates of survival, movements, and intensity of use of landscapes by breeding and non-breeding golden eagles; (3) periodic (conducted every two to four years) assessments of nesting and foraging habitats, prey populations, and associations with land-use and management activities; and (4) updating the predictive demographic model with new information obtained on eagles and associated population stressors. The results of this research were published in the Journal of Rapture Research, Wiens, David,Inman, Rich D., Esque, Todd C., Longshore, Kathleen M. and Nussear, Kenneth (2017). Spatial Demographic Models to Inform Conservation Planning of Golden Eagles in Renewable Energy Landscapes. 51(3):234-257.

Report↗

USGS2000

Effects of forest management on density, survival, and population growth of wood thrushes

Loss and alteration of breeding habitat have been proposed as causes of declines in several Neotropical migrant bird populations. We conducted a 4-year study to determine the effects of winter prescribed burning and forest thinning on breeding wood thrush ( Hylocichla mustelina ) populations at the Piedmont National Wildlife Refuge (PNWR) in Georgia. We estimated density, adult and juvenile survival rates, and apparent annual survival using transect surveys, radiotelemetry, and mist netting. Burning and thinning did not cause lower densities ( P = 0.25); wood thrush density ranged from 0.15 to 1.30 pairs/10 ha. No radiomarked male wood thrushes ( n = 68) died during the 4 years, but female ( n = 63) weekly survival was 0.981 ± 0.014 (SE) for females ( n = 63) and 0.976 ± 0.010 for juveniles ( n = 38). Apparent annual adult survival was 0.579 (SE = 0.173). Thinning and prescribed burning did not reduce adult or juvenile survival during the breeding season or apparent annual adult survival. Annual population growth (lambda) at PNWR was 1.00 (95% confidence interval = 0.32-1.63), and the considerable uncertainty in this prediction underscores the need for long term monitoring to effectively manage Neotropical migrants. Population growth increased on experimental compartments after the burn and thin (95% CI before = 0.91-0.97, after = 0.98-1.05), while control compartment declined (before = 0.98-1.05, after = 0.87-0.92). We found no evidence that the current management regime at PNWR, designed to improve red-cockaded woodpecker ( Picoides borealis ) habitat, negatively affected wood thrushes.

Georgia↗

USGS2004

Injury and mortality of warmwater fishes immobilized by electrofishing

Most studies of injury associated with electrofishing have focused on salmonids: few have given attention to warmwater fishes. Under controlled laboratory conditions, we treated bluegill Lepomis macrochirus, channel catfish Ictalurus punctatus, and largemouth bass Micropterus salmoides of various sizes to duty cycles ranging from 1.5% to 100%. This range of duty cycles represented continuous DC and pulsed-DC frequencies ranging from 15 to 110 Hz and pulse durations of 1 to 6 ms. At each duty cycle, fish were exposed to power densities in excess of those required to immobilize them within 3 s, and we subsequently determined the incidence of hemorrhage, spinal injury, and mortality. Incidence of hemorrhage averaged 3% (range, 0-25%), differed among species, and was not related to duty cycle or fish size. Incidence of spinal injury averaged 3% (range, 0-22%) and mortality averaged 10% (range, 0-75%); both differed among species and were related to duty cycle, fish size, and interactions among these variables. Largemouth bass was the species most vulnerable to hemorrhage, spinal injury, and mortality, channel catfish the least vulnerable; bluegills exhibited effects that were intermediate. Small centrarchids were especially susceptible to mortality. Fish tetanized by the electrical treatment were more likely to experience injury and mortality than fish that were only narcotized. However, mortality was not related to the injuries studied because hemorrhage and spinal injuries were similar in fish that survived electroshock and in those that died. We suggest that electrofishing with intermediate to high duty cycles could reduce electrofishing-induced injury and mortality to warmwater fish. Additionally, the power output and electrode system should be managed to induce narcosis and prevent tetany and to avoid the large peak powers required to immobilize small individuals.

North American Journal of Fisheries Management↗

USGS2019

Black Carp in North America: A description of range, habitats, time of year, and methods of reported captures

Black Carp Mylopharyngodon piceus are considered invasive in North America. Since the first wild capture in 2003, collection records have increased, yet information summarizing successful collection methods is lacking. Reported capture methods throughout the Black Carp's native and introduced ranges vary providing minimal aid for determining control and monitoring methods. Here, we describe the current species range and the spatial and temporal variation among captures. The size of fish can affect capture; thus, we report captured fish and gear dimensions and recommend appropriate scientific collection methods. We focus on collection data from 302 Black Carp ranging from 410 to 1,607 mm total length received from 2011 to February 2019. The reported range of Black Carp has expanded in the Cumberland, Illinois, Mississippi, Missouri, Ohio, and Tennessee rivers. Captures most frequently occurred in channel (41%), side‐channel (24%), and backwater (22%) habitat types, with increased records in May, June, and July. Most records were commercial captures, of which hoop net (51%) and gill net (26%) were most common. Results suggest that standard scientific methods for sampling fish in large rivers and standing water by hoop net and gill net may be used to monitor Black Carp, but a robust study design needs to be applied to determine gear selectivity and to determine if catch rates are density dependent or incidental.

North American Journal of Fisheries Management↗

USGS2010

Dispersal of smallmouth bass from a simulated tournament weigh-in site

Simulated smallmouth bass Micropterus dolomieu fishing tournaments were staged in Dale Hollow Lake, a 12,400-ha reservoir in Tennessee, between March 2004 and February 2005 to investigate posttournament dispersal. Smallmouth bass (n = 54) were captured with conventional hook-and-line tackle and artificial lures, placed in live wells, and subjected to a weigh-in procedure before being externally tagged with an ultrasonic transmitter and released. Water temperatures ranged from 7.4°C to 29.3°C (mean [SE] = 17.6°C [2.5]), fish ranged in total length from 330 to 572 mm (mean = 452 [8.3]), and no fish were dead at the weigh-ins. Smallmouth bass dispersed rapidly away from the release site, which was located at the head of a 68-ha embayment. After 3-5d, survivors (n = 44) traversed an average distance of 1,475 m [213]. Most (72%) fish swam uplake and out of the 385-ha study area after 6 d. The rapid dispersal of smallmouth bass may be relevant in systems that experience heavy tournament activity. The smallmouth bass caught and subjected to simulated tournament conditions on Dale Hollow Lake did not stockpile near the release site.

North American Journal of Fisheries Management↗

USGS2026

Decadal-scale characteristics of natural and anthropogenic dune morphology along North Carolina Barrier Islands (SE Atlantic Coast)

Dunes offer protection to coastal communities from storms, yet quantitative research characterizing human influences on dune systems across decades and 10–100 km spatial scales constitutes a known data gap. This study analyzed a multidecadal archive of dune crest elevations and positions to map mesoscale spatiotemporal trends in foredune morphology across the barrier island coastline of North Carolina, SE Atlantic coast. Results are summarized within four categories of coastline representing a range of coastal management intensities, integrating beach width and dune lateral accommodation space to assess the comparative influence of differing intensities of anthropogenic intervention on dune morphology. These categories account for the presence of structures, roads, and alongshore connectivity to anthropogenic sediment sources (beach nourishment). These categories show distinct dune and beach system characteristics. Dunes are largest in the areas with the longest legacy of coastal management. As categories decrease in development intensity, dune and beach system characteristics generally depart from the large, static dunes and narrow beaches consistent with hold-the-line management. Where small or transgressive dunes exist on heavily developed coasts, they coincide with relatively strong hydrodynamic forcing or sediment-limiting geology. There is evidence of indirect coastal management influence on undeveloped barrier islands with alongshore connectivity to developed barriers. While this analysis was conducted at the mesoscale, the results provide researchers with the framework to make insights at smaller scales than those demonstrated in this study.

North Carolina↗

USGS2014

Migratory behavior of Chinook salmon microjacks reared in artificial and natural environments

Emigration was evaluated for hatchery Chinook salmon ( Oncorhynchus tshawytscha ) microjacks (age-1 mature males) and immature parr (age-1 juveniles, both sexes) released from both a hatchery and a natural stream (fish released as fry). In the hatchery, volitional releases (&sim;14 to 15 months post-fertilization) to an adjacent river occurred during October–November. The hatchery release was monitored by using an experimental volitional release that diverted fish to a neighboring raceway. Fish captured during the experimental release (range 361–4,321 volitional migrants) were made up of microjacks and immature parr. Microjacks were found only in the migrant samples, averaged 18% (range 0–52%) of all migrants, and were rarely found in non-migrant samples. In comparison, immature parr were common in both the migrant and non-migrant samples. Microjacks were significantly longer (9%), heavier (36%), and had a greater condition factor (16%) than migrant immature parr (P<0.01). In addition, they differed significantly (P<0.01) from non-migrant immature parr; 10% longer, 44% heavier and 14% greater condition factor. In natural streams, microjacks were captured significantly earlier (P<0.01) than immature parr during the late-summer/fall migration and comprised 9–89% of all fish captured. Microjacks have the potential to contribute to natural spawning populations but can also represent a loss of productivity to hatchery programs or create negative effects by introducing non-native genes to wild populations and should be monitored by fishery managers.

Journal of Fish and Wildlife Management↗

USGS2013

Predicting the planform configuration of the braided Toklat River, AK with a suite of rule-based models

An ensemble of rule-based models was constructed to assess possible future braided river planform configurations for the Toklat River in Denali National Park and Preserve, Alaska. This approach combined an analysis of large-scale influences on stability with several reduced-complexity models to produce the predictions at a practical level for managers concerned about the persistence of bank erosion while acknowledging the great uncertainty in any landscape prediction. First, a model of confluence angles reproduced observed angles of a major confluence, but showed limited susceptibility to a major rearrangement of the channel planform downstream. Second, a probabilistic map of channel locations was created with a two-parameter channel avulsion model. The predicted channel belt location was concentrated in the same area as the current channel belt. Finally, a suite of valley-scale channel and braid plain characteristics were extracted from a light detection and ranging (LiDAR)-derived surface. The characteristics demonstrated large-scale stabilizing topographic influences on channel planform. The combination of independent analyses increased confidence in the conclusion that the Toklat River braided planform is a dynamically stable system due to large and persistent valley-scale influences, and that a range of avulsive perturbations are likely to result in a relatively unchanged planform configuration in the short term.

Alaska↗

USGS2016

Temporal variation in survival and recovery rates of lesser scaup

Management of lesser scaup (Aythya affinis) has been hindered by access to reliable data on population trajectories and vital rates. We conducted a Bayesian analysis of historical (1951–2011) band-recovery data throughout North America to estimate annual survival and recovery rates for juvenile and adult male and female lesser scaup to determine if increasing harvest or declining survival rates have contributed to population changes and to determine if harvest has been primarily additive or compensatory. Annual recovery rates were low, ranging from 1% to 4% for adults and 2% to 10% for juveniles during most years, with trend models indicating that recovery rates have declined through time for all age–sex classes. Annual survival (mid-Aug to mid-Aug) averaged 0.402 (σ ̂ 0.043) for juvenile males, 0.416 (σ ̂ 0.067) for juvenile females, 0.689 (σ ̂ 0.109) for adult males, and 0.602 (σ ̂ 0.115) for adult females, where σ ̂ represents an estimate of annual process variation in each survival rate. Annual survival rates exhibited no evidence of long-term declines or negative correlations with annual recovery rates (i.e., an index of harvest intensity) for any age–sex class, suggesting that declining fecundity was the most likely explanation for population declines during 1975–2005. We conclude that hunting mortality played a minor role in affecting population dynamics of lesser scaup and waterfowl managers could take a less cautious approach in managing harvest, especially if recruiting or maintaining waterfowl hunters are viewed as important management objectives.

Journal of Wildlife Management↗

USGS1992

Evaluation of aerial transects for counting winter mallards

Winter waterfowl surveys rarely use sampling methods, and little is known about the precision and biases of their population estimates. Consequently, we developed aerial transect surveys (n=5) in 4 strata comprising 16 substrata in the lower Mississippi Alluvial Valley during winters 1987-88 through 1989-90 to estimate mallard ( Anas platyrhynchos ) population indices and determine regional patterns of habitat use. Mallard population indices ranged from 1,147,628 (SE=192,341) in December 1988 to 1,790,708 (SE=179,406) in January 1988. Coefficients of variation (CV's) for early winter surveys averaged 0.15 and those for late winter surveys averaged 0.10. During early winter, 59-69% of mallards were on wetlands with water regimes managed for waterfowl; whereas in late winter, 52-79% used wetlands with unmanaged water regimes. Late winter was wet during 1987-88 and 1988-89, and most mallards (62-68%) were on naturally flooded croplands. Use of forested wetlands (3-11%) and moist-soil habitats (3-29%) varied among surveys but was not correlated with water conditions. The number of mallards using naturally flooded croplands (e.g., >1,100,000 in Jan 1988) illustrated the extent of habitat use on private lands. We recommend transect surveys (e.g., 5-yr intervals) for evaluating responses of mallard populations to management programs and as a sampling framework for integrating regional waterfowl research and management data.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗

USGS2021

Environmental factors predicting the orientation of sea turtle hatchlings on a naturally lighted beach: A baseline for light-management goals

On sea turtle nesting beaches, artificial lighting associated with human development interferes with hatchling orientation from nest to sea. Although hatchling disorientation has been documented for many beaches, data that managers can use in understanding, predicting, and managing the issue are of limited detail. The present study provides baseline hatchling orientation data that can be compared to those from beaches with artificial lighting to prioritize light-management efforts there. In 2014, the precision of hatchling orientation was quantified for 87 nests on a naturally lighted beach that had little to no artificial lighting. Precision of hatchling orientation was regressed against seven environmental variables: beach slope, distance from nest to dune, dune height, apparent dune silhouette height relative to nest site, moon illumination percentage, cloud cover percentage, and relative humidity. Results favored a regression model that included distance from nest to dune, with shorter distances from the dune predicting a narrower angular range (i.e., greater precision) of hatchling orientation. The study confirmed findings of an earlier laboratory experiment that highlighted the importance to accurate hatchling orientation of a dark silhouette (dune) on the side of the nest site opposite the ocean side. Reducing artificial light and promoting the planting of pioneer plants that assist dune formation can increase hatchling survival.

Florida↗

USGS2016

Dispersal limitation does not control high elevational distribution of alien plant species in the southern Sierra Nevada, California

Patterns of elevational distribution of alien plant species in the southern Sierra Nevada of California were used to test the hypothesis that alien plant species invading high elevations around the world are typically climate generalists capable of growing across a wide elevational range. The Sierra Nevada has been heavily impacted for more than a century and a half, first by heavy grazing up into high elevation meadows, followed by major logging, and finally, by impacts associated with recreational use. The comparative elevational patterns of distribution and growth form were compared for native and alien plant species in the four families (Asteraceae, Brassicaceae, Fabaceae, and Poaceae) that contribute the majority of naturalized aliens in the study area. The distribution of realized climatic niche breadth, as measured by elevational range of occurrence, was virtually identical for alien and native species, with both groups showing a roughly Gaussian distribution peaking with species whose range covers a span of 1500–1999 m. In contrast to alien species, which only rarely occurred at higher elevations, native species showed a distribution of upper elevation limits peaking at 3000–3499 m, an elevation that corresponds to the zone of upper montane and subalpine forests. Consistent with a hypothesis of abiotic limitations, only a few alien species have been ecologically successful invaders at subalpine and alpine elevations above 2500 m. The low diversity of aliens able to become established in these habitats is unlikely due to dispersal limitations, given the long history of heavy grazing pressure at high elevations across this region. Instead, this low diversity is hypothesized to be a function of life history traits and multiple abiotic stresses that include extremes of cold air and soil temperature, heavy snowfall, short growing seasons, and low resource availability. These findings have significant implications for resource managers.

California↗

USGS2018

Genetic population structure of Shoal Bass within their native range

Endemic to the Apalachicola River basin of the southeastern USA, the Shoal Bass Micropterus cataractae is a fluvial‐specialist sport fish that is imperiled because of anthropogenic habitat alteration. To counter population declines, restorative stocking efforts are becoming an increasingly relevant management strategy. However, population genetic structure within the species is currently unknown, but it could influence management decisions, such as brood source location. Leveraging a collaborative effort to collect and genotype specimens with 16 microsatellite loci, our objective was to characterize hierarchical population structure and genetic differentiation of the Shoal Bass across its native range, including an examination of structuring mechanisms, such as relatedness and inbreeding levels. Specimens identified as Shoal Bass were collected from 13 distinct sites ( N ranged from 17 to 209 per location) and were then taxonomically screened to remove nonnative congeners and hybrids (pure Shoal Bass N ranged from 13 to 183 per location). Our results revealed appreciable population structure, with five distinct Shoal Bass populations identifiable at the uppermost hierarchical level that generally corresponded with natural geographic features and anthropogenic barriers. Substructure was recovered within several of these populations, wherein differences appeared related to spatial isolation and local population dynamics. An analysis of molecular variance revealed that 3.6% of the variation in our data set was accounted for among three larger river drainages, but substructure within each river drainage also explained an additional 8.9% of genetic variation, demonstrating that management at a scale lower than the river drainage level would likely best conserve genetic diversity. Results provide a population genetic framework that can inform future management decisions, such as brood source location, so that genetic diversity within and among populations is conserved and overall adaptability of the species is maintained.

Apalachicola–Chattahoochee–Flint River Basin↗