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Geology topics

William R. Gould

Publications and source records attributed to William R. Gould.

At least 19 recordsLinked to original sources
USGS2024

Diurnal habitat selection and survival of elk neonates

Natural selection should favor development of behaviors that increase survival, including juvenile survival. Habitat characteristics (e.g., hiding cover, forage quality and availability), maternal habitat selection, and microhabitat selection by the calf may influence elk ( Cervus canadensis ) calf survival and recruitment. We assessed diurnal microhabitat selection of bed sites by elk calves and calf-rearing areas selected by adult females to determine if these characteristics were associated with calf survival. We radio-tagged 33 elk calves in west-central New Mexico in 2011 and 55 calves in north-central New Mexico in 2012. We tracked calves daily to locate calf bedding sites and collected data on selected physical features and vegetation characteristics at used and paired random sites. The paired differences in these characteristics were then associated with calf fate. At the calf selection scale, for every 1-m difference in the distance to nearest concealment cover, the odds that a site was from a surviving calf increased by 7.8%. Habitat selection by adult females also was associated with calf survival. The odds of a bed site being from a surviving calf increased by 1.9% for every 1% difference in percentage of grass cover. High levels of concealment cover at the bed site were related to calf survival status. When we expanded selection to the adult level, females with surviving calves selected areas with higher grass cover, suggesting adult selection for higher forage availability while still providing high concealment cover for the calf.

Southwestern Naturalist↗
USGS2022

Multi-species amphibian monitoring across a protected landscape: Critical reflections on 15 years of wetland monitoring in Grand Teton and Yellowstone national parks

Widespread amphibian declines were well documented at the end of the 20th century, raising concerns about the need to identify individual and interactive contributors to this global trend. At the same time, there was growing interest in the use of amphibians as ecological indicators. In the United States, wetland and amphibian monitoring programs were launched in some national parks as a necessary first step to evaluating the status and trends of amphibian populations within some of North America’s most protected areas. In Grand Teton and Yellowstone national parks, a multi-species amphibian monitoring program was launched by many of the authors in 2006 and continues to this day. This Viewpoint Article serves as a self-evaluation of our journey from conception through implementation of an ongoing, long-term monitoring program. This self-evaluation should provide a framework and guidance for other monitoring programs. We address whether we are fulfilling the program’s main objective of describing status and trends of the four amphibian species, discuss how a one-size-fits-all monitoring approach does not serve all species equally, and describe opportunities to bolster our core work using emerging statistical approaches and thoughtful integration of remote sensing and molecular tools. We also describe how the data generated over the program’s first 15 years have been useful beyond our initial goal of characterizing status and trend. Notably, our integration of climate datasets has allowed us to describe wetland and species-specific amphibian responses to variations in climate drivers. Documenting climate links to amphibian occurrence and their primary habitats has allowed us to identify which species, habitat types, and subregions within this large, protected landscape are most vulnerable to anticipated climate change. Recognizing that tools and threats change over time, it will be important to adapt our original monitoring design to maximize opportunities and use of resulting information. Maintaining engagement by multiple stakeholders and expanding our funding portfolio will also be necessary to sustain our program into the future. Finally, collaboration has become standard for long-term, cross-jurisdictional, landscape-scale monitoring. We argue that collaborative monitoring facilitates resource sharing, leveraging of limited funds, completion of work, and mutual learning. Such collaboration also increases the efficacy of conservation.

Wyoming↗
USGS2019

Validating the performance of occupancy models for estimating habitat use and predicting the distribution of highly-mobile species: A case study using the American black bear

Occupancy models have become a valuable tool for estimating wildlife-habitat relationships and for predicting species distributions. Highly-mobile species often violate the assumption that sampling units are geographically closed shifting the probability of occupancy to be interpreted as the probability of use. We used occupancy models, in conjunction with noninvasive sampling, to estimate habitat use and predict the distribution of a highly-mobile carnivore, the American black bear ( Ursus americanus ) in New Mexico, USA. The top model indicated that black bears use areas with higher primary productivity and fewer roads. The predictive performance of such models is rarely validated with independent data, so we validated our model predictions with 2-independent datasets. We first assessed the correlation between predicted and observed habitat use for 28 telemetry-collared bears in the Jemez Mountains. Predicted habitat use was positively correlated with observed use for all 3 years (2012: ρ = 0.81; 2013: ρ = 0.87; 2014: ρ = 0.90). We then predicted the probability of use within a cell where a bear mortality was documented using 2043 mortality locations from sport harvest, depredation, and vehicle collisions. The probability of habitat use at a mortality location was also positively correlated with observed use by the species (2012: ρ = 0.74; 2013: ρ = 0.89; 2014: ρ = 0.93). Our validation procedure supports the notion that occupancy models can be an effective tool for estimating habitat use and predicting the distribution of highly-mobile species when the assumption of geographic closure has been violated. Our findings may be of interest to studies that are estimating habitat use for highly-mobile species that are secretive or rare, difficult to capture, or expensive to monitor with other more intensive methods.

New Mexico↗
USGS2018

Reproductive potential of captive Rio Grande Silvery Minnow

Captive propagation and augmentation of the Rio Grande Silvery Minnow Hybognathus amarus is necessary for continued persistence of the species until habitat can be restored. Augmentation occurs using captive fish within the first year (age 0) through age 2; however, older year‐classes (ages 3–4) have been released into the wild. We quantified fecundity and compared egg quality across four reproductive age‐classes (1–4) of hatchery‐reared Rio Grande Silvery Minnow. Batch fecundity (total number of spawned eggs) ranged from 2,029 eggs in age‐1 fish to 10,588 eggs in age‐4 fish. Standing stock of vitellogenic (i.e., yolked) oocytes remaining in ovaries after spawning increased from 988 oocytes at age 1 to 4,924 oocytes at age 4. Total fecundity (i.e., batch fecundity plus standing stock of yolked oocytes) increased from 3,017 eggs and yolked oocytes in age‐1 fish to 15,522 eggs and yolked oocytes in age‐4 fish. Of note, batch fecundity ranged from 57% to 68% across the four age‐classes indicating that over half of the total fecundity occurs in the first spawn. Average percent fertilization of eggs (63–82%) was not detectably different across the four age‐classes, while average egg diameter (4.1–5.5 mm) increased as age increased. Fecundity increased across all four reproductive age‐classes of Rio Grande Silvery Minnow, with the larger portion of total fecundity occurring in the first spawn across all age‐classes. The timing of spawning with optimal conditions in the Rio Grande is critical for survival and ultimately recruitment into the wild fish population.

North American Journal of Aquaculture↗
USGS2018

Survival and cause-specific mortality of desert bighorn sheep lambs

Juvenile recruitment in desert bighorn sheep (Ovis canadensis mexicana) is highly variable, yet the mechanisms driving neonate survival are not well understood for the species. Few studies have equipped desert bighorn sheep lambs with radiocollars. As a result, definitive data on cause-specific mortality and lamb survival estimates are lacking. Our objectives were to estimate lamb survival rates and determine cause-specific mortality for desert bighorn sheep lambs during a period of mountain lion (Puma concolor) and coyote (Canis latrans) removal in southwestern New Mexico. We captured pregnant adult females each fall and fitted them with a telemetry collar and a vaginal implant transmitter to aid with neonate captures. We captured and radiocollared 12 desert bighorn sheep lambs in 2012 and 14 in 2013 within 48 hrs of parturition in the Peloncillo Mountains, New Mexico. We used the nest survival model in program MARK to estimate lamb survival to 6 months of age. Across both years there were 14 mortalities, 12 (86%) of which were due to predation. Mountain lions killed 5 lambs (2 in 2012 and 3 in 2013), coyotes killed 4 lambs (all in 2013), a gray fox (Urocyon cinereoargenteus) killed 1 lamb in 2012; 2 lambs were killed by unknown predators in 2013. Staged-based survival estimates indicated the highest mortality rates occurred in the first week post birth; 33% to 36% of all lamb mortalities occurred before 7 days of age. Lamb survival was substantially lower in 2013 (0.20 ± 0.11 [SE]) than in 2012 (0.69 ± 0.16) with the differences in survival attributed to increased coyote predation in 2013. We did not detect differences in body mass, chest girth, or neck circumference between lambs that were killed by predators and those that survived. Coyotes, mountain lions and gray fox killed lambs <8 weeks of age, but only mountain lions killed lambs > 8 weeks old. Studies that fail to capture desert bighorn lambs near parturition will likely produce negatively biased survival estimates and inaccurate appraisals of primary causes of mortality due to early mortality of lambs.

New Mexico↗
USGS2018

Temporal variation in breeding season survival and cause-specific mortality of lesser prairie-chickens

The lesser prairie-chicken Tympanuchus pallidicinctus has experienced significant declines in distribution and abundance since the early 1900s. A severe and prolonged drought from 2009 to 2013 resulted in further declines in population numbers and despite improved environmental and habitat conditions since 2013, populations of lesser prairie chickens have shown little improvement. To investigate whether breeding season survival of lesser prairie-chickens in eastern New Mexico could be driving this response, we developed the following objectives: 1) estimate male and female breeding-season survival; 2) determine whether male and female survival varies temporally among lekking, nesting, and brood-rearing periods; and 3) determine cause-specific mortality during the breeding season. We captured and radiocollared 76 lesser prairie-chickens (50 male, 26 female) during spring of 2014 and 2015 and estimated their survival throughout the breeding season (15 March–31 August). Male survival was nearly double that of females in both years (0.79–0.81 and 0.38–0.45, respectively). Males had similar survival across all periods (lekking, postlekking, late summer: 0.89–0.95). Females had the greatest period-specific survival during lekking and brood rearing (0.87 ± 0.08 and 0.85 ± 0.10, respectively) relative to the nesting period (0.58 ± 0.11). Mammalian predation was the primary cause of mortality in both years. Our results indicate that in New Mexico 1) lesser prairie-chicken breeding season survival was consistent with geographically similar studies, 2) females have lower survival during the nesting period, and 3) female lesser prairie-chicken survival was lower than male survival regardless of time period. Management actions that provide and protect high-quality nesting habitat may help ensure that female survival is maximized during the nesting period.

New Mexico↗
USGS2018

Density of American black bears in New Mexico

Considering advances in noninvasive genetic sampling and spatially explicit capture–recapture (SECR) models, the New Mexico Department of Game and Fish sought to update their density estimates for American black bear ( Ursus americanus ) populations in New Mexico, USA, to aide in setting sustainable harvest limits. We estimated black bear density in the Sangre de Cristo, Sandia, and Sacramento Mountains, New Mexico, 2012–2014. We collected hair samples from black bears using hair traps and bear rubs and used a sex marker and a suite of microsatellite loci to individually genotype hair samples. We then estimated density in a SECR framework using sex, elevation, land cover type, and time to model heterogeneity in detection probability and the spatial scale over which detection probability declines. We sampled the populations using 554 hair traps and 117 bear rubs and collected 4,083 hair samples. We identified 725 (367 male, 358 female) individuals. Our density estimates varied from 16.5 bears/100 km 2 (95% CI = 11.6–23.5) in the southern Sacramento Mountains to 25.7 bears/100 km 2 (95% CI = 13.2–50.1) in the Sandia Mountains. Overall, detection probability at the activity center (g0) was low across all study areas and ranged from 0.00001 to 0.02. The low values of g0 were primarily a result of half of all hair samples for which genotypes were attempted failing to produce a complete genotype. We speculate that the low success we had genotyping hair samples was due to exceedingly high levels of ultraviolet (UV) radiation that degraded the DNA in the hair. Despite sampling difficulties, we were able to produce density estimates with levels of precision comparable to those estimated for black bears elsewhere in the United States.

New Mexico↗
USGS2017

Impacts of mesquite distribution on seasonal space use of lesser prairie-chickens

Loss of native grasslands by anthropogenic disturbances has reduced availability and connectivity of habitat for many grassland species. A primary threat to contiguous grasslands is the encroachment of woody vegetation, which is spurred by disturbances that take on many forms from energy development, fire suppression, and grazing. These disturbances are exacerbated by natural- and human-driven cycles of changes in climate punctuated by drought and desertification conditions. Encroachment of honey mesquite (Prosopis glandulosa) into the prairies of southeastern New Mexico has potentially limited habitat for numerous grassland species, including lesser prairie-chickens (Tympanuchus pallidicinctus) . To determine the magnitude of impacts of distribution of mesquite and how lesser prairie-chickens respond to mesquite presence on the landscape in southeastern New Mexico, we evaluated seasonal space use of lesser prairie-chickens in the breeding and nonbreeding seasons. We derived several remotely sensed spatial metrics to characterize the distribution of mesquite. We then used these data to create population-level resource utilization functions and predict intensity of use of lesser prairie-chickens across our study area. Home ranges were smaller in the breeding season compared with the nonbreeding season; however, habitat use was similar across seasons. During both seasons, lesser prairie-chickens used areas closer to leks and largely avoided areas with mesquite. Relative to the breeding season, during the nonbreeding season habitat use suggested a marginal increase in mesquite within areas of low intensity of use, yet aversion to mesquite was strong in areas of medium to high intensity of use. To our knowledge, our study is the first to demonstrate a negative behavioral response by lesser prairie-chickens to woody encroachment in native grasslands. To mitigate one of the possible limiting factors for lesser prairie-chickens, we suggest future conservation strategies be employed by land managersto reduce mesquite abundance in the southern portion of their current range.

New Mexico↗
USGS2016

Influence of climate drivers on colonization and extinction dynamics of wetland-dependent species

Freshwater wetlands are particularly vulnerable to climate change. Specifically, changes in temperature, precipitation, and evapotranspiration (i.e., climate drivers) are likely to alter flooding regimes of wetlands and affect the vital rates, abundance, and distributions of wetland-dependent species. Amphibians may be among the most climate-sensitive wetland-dependent groups, as many species rely on shallow or intermittently flooded wetland habitats for breeding. Here, we integrated multiple years of high-resolution gridded climate and amphibian monitoring data from Grand Teton and Yellowstone National Parks to explicitly model how variations in climate drivers and habitat conditions affect the occurrence and breeding dynamics (i.e., annual extinction and colonization rates) of amphibians. Our results showed that models incorporating climate drivers outperformed models of amphibian breeding dynamics that were exclusively habitat based. Moreover, climate-driven variation in extinction rates, but not colonization rates, disproportionately influenced amphibian occupancy in monitored wetlands. Long-term monitoring from national parks coupled with high-resolution climate data sets will be crucial to describing population dynamics and characterizing the sensitivity of amphibians and other wetland-dependent species to climate change. Further, long-term monitoring of wetlands in national parks will help reduce uncertainty surrounding wetland resources and strengthen opportunities to make informed, science-based decisions that have far-reaching benefits.

Grand Teton National Park, Yellowstone National Pa↗
USGS2016

Estimating black bear density in New Mexico using noninvasive genetic sampling coupled with spatially explicit capture-recapture methods

During the 2004–2005 to 2015–2016 hunting seasons, the New Mexico Department of Game and Fish (NMDGF) estimated black bear abundance (Ursus americanus) across the state by coupling density estimates with the distribution of primary habitat generated by Costello et al. (2001). These estimates have been used to set harvest limits. For example, a density of 17 bears/100 km2 for the Sangre de Cristo and Sacramento Mountains and 13.2 bears/100 km2 for the Sandia Mountains were used to set harvest levels. The advancement and widespread acceptance of non-invasive sampling and mark-recapture methods, prompted the NMDGF to collaborate with the New Mexico Cooperative Fish and Wildlife Research Unit and New Mexico State University to update their density estimates for black bear populations in select mountain ranges across the state. We established 5 study areas in 3 mountain ranges: the northern (NSC; sampled in 2012) and southern Sangre de Cristo Mountains (SSC; sampled in 2013), the Sandia Mountains (Sandias; sampled in 2014), and the northern (NSacs) and southern Sacramento Mountains (SSacs; both sampled in 2014). We collected hair samples from black bears using two concurrent non-invasive sampling methods, hair traps and bear rubs. We used a gender marker and a suite of microsatellite loci to determine the individual identification of hair samples that were suitable for genetic analysis. We used these data to generate mark-recapture encounter histories for each bear and estimated density in a spatially explicit capture-recapture framework (SECR). We constructed a suite of SECR candidate models using sex, elevation, land cover type, and time to model heterogeneity in detection probability and the spatial scale over which detection probability declines. We used Akaike’s Information Criterion corrected for small sample size (AICc) to rank and select the most supported model from which we estimated density. We set 554 hair traps, 117 bear rubs and collected 4,083 hair samples. We identified 725 (367 M, 358 F) individuals; the sex ratio for each study area was approximately equal. Our density estimates varied within and among mountain ranges with an estimated density of 21.86 bears/100 km2 (95% CI: 17.83 – 26.80) for the NSC, 19.74 bears/100 km2 (95% CI: 13.77 – 28.30) in the SSC, 25.75 bears/100 km2 (95% CI: 13.22 – 50.14) in the Sandias, 21.86 bears/100 km2 (95% CI: 17.83 – 26.80) in the NSacs, and 16.55 bears/100 km2 (95% CI: 11.64 – 23.53) in the SSacs. Overall detection probability for hair traps and bear rubs, combined, was low across all study areas and ranged from 0.00001 to 0.02. We speculate that detection probabilities were affected by failure of some hair samples to produce a complete genotype due to UV degradation of DNA, and our inability to set and check some sampling devices due to wildfires in the SSC. Ultraviolet radiation levels are particularly high in New Mexico compared to other states where NGS methods have been used because New Mexico receives substantial amounts of sunshine, is relatively high in elevation (1,200 m – 4,000 m), and is at a lower latitude. Despite these sampling difficulties, we were able to produce density estimates for New Mexico black bear populations with levels of precision comparable to estimated black bear densities made elsewhere in the U.S. Our ability to generate reliable black bear density estimates for 3 New Mexico mountain ranges is attributable to our use of a statistically robust study design and analytical method. There are multiple factors that need to be considered when developing future SECR-based density estimation projects. First, the spatial extent of the population of interest and the smallest average home range size must be determined; these will dictate size of the trapping array and spacing necessary between hair traps. The number of technicians needed and access to the study areas will also influence configuration of the trapping array. We believe shorter sampling occasions could be implemented to reduce degradation of DNA due to UV radiation; this might help increase amplification rates and thereby increase both the number of unique individuals identified and the number of recaptures, improving the precision of the density estimates. A pilot study may be useful to determine the length of time hair samples can remain in the field prior to collection. In addition, researchers may consider setting hair traps and bear rubs in more shaded areas (e.g., north facing slopes) to help reduce exposure to UV radiation. To reduce the sampling interval it will be necessary to either hire more field personnel or decrease the number of hair traps per sampling session. Both of these will enhance detection of long-range movement events by individual bears, increase initial capture and recapture rates, and improve precision of the parameter estimates. We recognize that all studies are constrained by limited resources, however, increasing field personnel would also allow a larger study area to be sampled or enable higher trap density. In conclusion, we estimated the density of black bears in 5 study areas within 3 mountains ranges of New Mexico. Our estimates will aid the NMDGF in setting sustainable harvest limits. Along with estimates of density, information on additional demographic rates (e.g., survival rates and reproduction) and the potential effects that climate change and future land use may have on the demography of black bears may also help inform management of black bears in New Mexico, and may be considered as future areas for research.

New Mexico↗
USGS2015

Trends in Rocky Mountain amphibians and the role of beaver as a keystone species

Despite prevalent awareness of global amphibian declines, there is still little information on trends for many widespread species. To inform land managers of trends on protected landscapes and identify potential conservation strategies, we collected occurrence data for five wetland-breeding amphibian species in four national parks in the U.S. Rocky Mountains during 2002&ndash;2011. We used explicit dynamics models to estimate variation in annual occupancy, extinction, and colonization of wetlands according to summer drought and several biophysical characteristics (e.g., wetland size, elevation), including the influence of North American beaver ( Castor canadensis ). We found more declines in occupancy than increases, especially in Yellowstone and Grand Teton national parks (NP), where three of four species declined since 2002. However, most species in Rocky Mountain NP were too rare to include in our analysis, which likely reflects significant historical declines. Although beaver were uncommon, their creation or modification of wetlands was associated with higher colonization rates for 4 of 5 amphibian species, producing a 34% increase in occupancy in beaver-influenced wetlands compared to wetlands without beaver influence. Also, colonization rates and occupancy of boreal toads ( Anaxyrus boreas ) and Columbia spotted frogs ( Rana luteiventris ) were ⩾2 times higher in beaver-influenced wetlands. These strong relationships suggest management for beaver that fosters amphibian recovery could counter declines in some areas. Our data reinforce reports of widespread declines of formerly and currently common species, even in areas assumed to be protected from most forms of human disturbance, and demonstrate the close ecological association between beaver and wetland-dependent species.

Biological Conservation↗
USGS2015

Movement patterns and dispersal potential of Pecos bluntnose shiner ( Notropis simus pecosensis ) revealed using otolith microchemistry

Natal origin and dispersal potential of the federally threatened Pecos bluntnose shiner ( Notropis simus pecosensis ) were successfully characterized using otolith microchemistry and swimming performance trials. Strontium isotope ratios ( 87 Sr: 86 Sr) of otoliths within the resident plains killifish ( Fundulus zebrinus ) were successfully used as a surrogate for strontium isotope ratios in water and revealed three isotopically distinct reaches throughout 297 km of the Pecos River, New Mexico, USA. Two different life history movement patterns were revealed in Pecos bluntnose shiner. Eggs and fry were either retained in upper river reaches or passively dispersed downriver followed by upriver movement during the first year of life, with some fish achieving a minimum movement of 56 km. Swimming ability of Pecos bluntnose shiner confirmed upper critical swimming speeds ( U crit ) as high as 43.8 cm&middot;s &minus;1 and 20.6 body lengths&middot;s &minus;1 in 30 days posthatch fish. Strong swimming ability early in life supports our observations of upriver movement using otolith microchemistry and confirms movement patterns that were previously unknown for the species. Understanding patterns of dispersal of this and other small-bodied fishes using otolith microchemistry may help redirect conservation and management efforts for Great Plains fishes.

New Mexico↗
USGS2014

Post-parturition habitat selection by elk calves and adult female elk in New Mexico

Neonatal survival and juvenile recruitment are crucial to maintaining viable elk ( Cervus elaphus ) populations. Neonate survival is known to be influenced by many factors, including bed-site selection. Although neonates select the actual bed-site location, they must do so within the larger calf-rearing area selected by the mother. As calves age, habitat selection should change to meet the changing needs of the growing calf. Our main objectives were to characterize habitat selection at 2 spatial scales and in areas with different predator assemblages in New Mexico. We evaluated bed-site selection by calves and calf-rearing area selection by adult females. We captured 108 elk calves by hand and fitted them with ear tag transmitters in two areas in New Mexico: the Valle Vidal and Blue Range Wolf Recovery Area. In both study areas, we found that concealing cover structure and distance to that cover influenced bed-site selection of young calves (i.e., <2 weeks of age). Older calves (i.e., 3&ndash;10 weeks of age) still selected areas in relation to distance to cover, but also preferred areas with higher visibility. At the larger spatial scale of calf-rearing habitat selection by the adult female, concealing cover (e.g., rocks, shrubs, and logs) and other variables important to the hiding calves were still in the most supported models, but selection was also influenced by forage availability and indices of forage quality. Studies that seek to obtain insight into microhabitat selection of ungulate neonates should consider selection by the neonate and selection by the adult female, changes in selection as neonates age, and potential selection differences in areas of differing predation risk. By considering these influences together and at multiple scales, studies can achieve a broader understanding of neonatal ungulate habitat requirements.

New Mexico↗
USGS2013

Prescribed-fire effects on an aquatic community of a southwest montane grassland system

The use of prescription fire has long been recognized as a reliable management tool to suppress vegetative succession processes and to reduce fuel loading to prevent catastrophic wildfires, but very little attention has been paid to the effects on aquatic systems. A late-fall prescribed burn was implemented to characterize effects on an aquatic community within a montane grassland system in north-central New Mexico. The fire treatment was consistent with protocols of a managed burn except that the fire was allowed to burn through the riparian area to the treatment stream to replicate natural fire behavior. In addition to summer and fall preburn assessment of the treatment and reference stream, we characterized immediate postfire effects (within a week for macroinvertebrates and within 6 months for fish) and seasonal effects over a 2-year period. Responses within the treatment stream were compared with an unburned reference stream adjacent to the prescription burn. During the burn, the diel range in air temperature increased by 5°C while diel range in water temperature did not change. Carbon–nitrogen ratios did not differ between treatment and reference streams, indicating the contribution of ash from the surrounding grassland was negligible. Although total taxa and species richness of aquatic macroinvertebrates were not altered, qualitative indices revealed departure from preburn condition due to loss of sensitive taxa (mayflies [order Ephemeroptera] and stoneflies [order Plecoptera]) and an increase in tolerant taxa (midges [order Chironomidae]) following the burn. Within 1 year of the burn, these attributes returned to preburn conditions. The density and recruitment of adult Brown Trout Salmo trutta did not differ between pre- and postburn collections, nor did fish condition differ. Fire is rarely truly replicated within a given study. Although our study represents one replication, the results will inform managers about the importance in timing (seasonality) of prescription burn and anticipated effects on aquatic communities.

New Mexico↗
USGS2013

Abundance: Population size and density estimation

Estimates of population size (total number of individuals) or density (number of individuals per unit area) are some of the most basic requirements for wildlife research and management. This article provides a brief overview of approaches for wildlife population estimation. These include habitat‐based approaches such as quadrat, line intercept, distance, and repeated count methods, as well as animal‐based approaches such as capture–recapture and harvest methods. In contrast to methods that only index changes in these parameters, estimates of size or density must account for the probability that an individual will be included in the sample used for estimation. The essential differences in the approaches are in how the samples are obtained and how the sampling probabilities are estimated.

Book chapter↗
USGS2013

Capture-recapture methodology

Capture-recapture methods were initially developed to estimate human population abundance, but since that time have seen widespread use for fish and wildlife populations to estimate and model various parameters of population, metapopulation, and disease dynamics. Repeated sampling of marked animals provides information for estimating abundance and tracking the fate of individuals in the face of imperfect detection. Mark types have evolved from clipping or tagging to use of noninvasive methods such as photography of natural markings and DNA collection from feces. Survival estimation has been emphasized more recently as have transition probabilities between life history states and/or geographical locations, even where some states are unobservable or uncertain. Sophisticated software has been developed to handle highly parameterized models, including environmental and individual covariates, to conduct model selection, and to employ various estimation approaches such as maximum likelihood and Bayesian approaches. With these user-friendly tools, complex statistical models for studying population dynamics have been made available to ecologists. The future will include a continuing trend toward integrating data types, both for tagged and untagged individuals, to produce more precise and robust population models.

Book chapter↗
USGS2011

Physiological effects of potassium chloride, formalin and handling stress on bonytail

We characterized the sublethal physiological changes in bonytail Gila elegans subjected to consecutive 750-mg/L potassium chloride (KCl) and 25-mg/L formalin treatments for the removal of zebra mussel Dreissena polymorpha and quagga mussel D. bugensis veligers. Plasma cortisol, glucose, and osmolality were measured over 24 h and at 14 d posthandling after exposing bonytail to KCl and one net stressor (capture with a net), KCl plus formalin and two net stressors, and one or two net stressors without chemicals. Elevated plasma cortisol (322–440 ng/mL) and glucose (254–399 mg/dL) concentrations were observed in all treatments compared with the concentrations in control fish (plasma cortisol, 56 ng/mL; glucose, 43 mg/dL). While there were no detectable differences in plasma osmolality among the treatment and control fish, a difference was observed between fish that were handled once versus twice. Chemical effects of stress were not observed in any of the physiological responses when the KCl treatment was compared with the one-net stressor treatment or when the KCl plus formalin treatment was compared with the two-net stressor treatment. Cumulative responses, however, were observed between one net stressor and two net stressors for plasma glucose and osmolality but not for plasma cortisol. Plasma cortisol and glucose levels remained elevated at 24 h posthandling, indicating that bonytail had not completely recovered from the handling stressors and would benefit from a recovery period in protected refugia before being released.

North American Journal of Fisheries Management↗
USGS2006

Abundance: Population size and density estimation

Estimates of population size (total number of individuals) or density (number of individuals per unit area) are some of the most basic requirements for wildlife research and management. This article provides a brief overview of approaches for wildlife population estimation. These include habitat-based approaches such as quadrat, line intercept, distance, and repeated count methods, as well as animal-based approaches such as capture–recapture and harvest methods. In contrast to methods that only index changes in these parameters, estimates of size or density must account for the probability that an individual will be included in the sample used for estimation. The essential differences in the approaches are in how the samples are obtained and how the sampling probabilities are estimated.

Book chapter↗