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At least 325 records · Page 18Linked to original sources
USGS2005

Managing water in the West: developing new tools for a critical resource

Rapid population growth in the Western United States over the last century has placed increasing strains on our water supplies and aquatic ecosystems. Historically, water rights have been used to determine the allocation of water in the West, but rules and regulations related to endangered species now often drive how water is released from reservoirs in large rivers such as the lower Colorado and the Columbia. In numerous smaller watersheds, communities are trying to balance the water necessary for human use, irrigation, and the conservation of ecosystems. To assist managers in the face of increasing complexity and uncertainty in water management decision-making, the Western Fisheries Research Center (WFRC) is involved in developing a new generation of integrative tools. Below are some examples of the types of tools that already exist within the WFRC.

Fact Sheet↗
USGS2018

Managing forest habitat for conservation-reliant species in a changing climate: The case of the endangered Kirtland’s Warbler

Conservation and recovery of species of concern necessitates evaluating forest habitat conditions under changing climate conditions, especially in the early stages of the delisting process. Managers must weigh implications of near-term habitat management activities within the context of changing environmental conditions and a species’ biological traits that may influence their vulnerability to changing conditions. Here we applied established population-habitat relationships based on decades of monitoring and research-management collaborations for the Kirtland’s Warbler ( Setophaga kirtlandii ) to project potential impacts of changing environmental conditions to breeding habitat distribution, quantity, and quality in the near future. Kirtland’s warblers are habitat-specialists that nest exclusively within dense jack pine ( Pinus banksiana ) forests between ca. 5–20 years of age. Using Random Forests to predict changes in distribution and growth rate of jack pine under future scenarios, results indicate the projected distribution of jack pine will contract considerably (ca. 75%) throughout the Lake States region, U.S.A. in response to projected environmental conditions in 2099 under RCP 4.5 and 8.5 climate scenarios regardless of climate model. Reduced suitability for jack pine regeneration across the Lake States may constrain management options, especially for creating high stem-density plantations nesting habitat. However, conditions remain suitable for jack pine regeneration within their historical and current core breeding range in northern Lower Michigan and several satellite breeding areas. Projected changes in jack pine growth rates varied within the core breeding area, but altered growth rates did not greatly alter the duration that habitat remained suitable for nesting by the Kirtland’s Warblers. These findings contribute to Kirtland’s Warbler conservation by informing habitat spatial planning of plantation management to provide a constant supply of nesting habitat based on the spatial variability of potential loss or gain of lands environmentally suitable for regenerating jack pine in the long-term.

Michigan, Wisconsin↗
USGS2022

Black Abalone surveys at Naval Base Ventura County, San Nicolas Island, California—2021, annual report

The U.S. Geological Survey monitors a suite of intertidal black abalone sites at San Nicolas Island, California, in cooperation with the U.S. Navy, which owns the island. The nine rocky intertidal sites were established in 1980 to study the potential effect of translocated sea otters on the intertidal black abalone population at the island. The sites were monitored from 1981 to 1997, usually annually or biennially. Monitoring resumed in 2001 and has been completed annually since then. Since 2018, the work has been carried out by the U.S. Geological Survey Western Ecological Research Center. The study sites became particularly important, from a management perspective, after a virulent disease decimated black abalone populations throughout southern California beginning in the mid-1980s. The disease, withering syndrome, was first observed on San Nicolas Island in 1992 and during the next few years, it reduced the population there by more than 99 percent. The species was subsequently listed as endangered under the Endangered Species Act in 2009. The subject of this report is the 2021 survey of the sites and how the measured population status compares to the long-term data (collected over several decades) at San Nicolas Island. During the last two decades, the total monitored black abalone population at the island has grown approximately ten-fold after the disease related decline, from about 200 to more than 2,000 abalone. Since it was first consistently measured in 2005, the mean distance between adjacent black abalone has decreased substantially from approximately 50 centimeters to less than 15 centimeters, indicating that abalone are close enough together at several of the sites to reproduce successfully. The 2021 counts were the first since 2016 to indicate a possible decline in the monitored population at San Nicolas Island. Although still more than ten times the population counted in 2001, counts on the transects dropped by 13.6 percent from the survey count in 2020. The most significant decline was the loss of 341 abalone, from the previous count of 547, on a transect that since 2002 had the highest count of all 44 transects. Between 2020 and 2021, there were increases and decreases at the sites and the transects at each site. Although the 2021 count was lower than the 2020 count, it was the second highest since 1997. Based on the number of small abalone counted, recruitment rates were similar to most years since 2008 and higher than the rates observed before the population declines resulting from withering syndrome.

California↗
USGS2002

North American box turtles: A natural history

Once a familiar backyard visitor in many parts of the United States and Mexico, the box turtle is losing the battle against extinction. In North American Box Turtles, C. Kenneth Dodd, Jr., has written the first book-length natural history of the twelve species and subspecies of this endangered animal. This volume includes comprehensive information on the species’ evolution, behavior, courtship and reproduction, habitat use, diet, population structure, systematics, and disease. Special features include color photos of all species, subspecies, and their habitats; a simple identification guide to both living and fossil species; and a summary of information on fossil Terrapene and Native uses of box turtles. End-of-chapter sections highlight future research directions, including the need for long-term monitoring and observation of box turtles within their natural habitat and conservation applications. A glossary and a bibliography of literature on box turtles accompany the text.

Book↗
USGS2025

Local perceptions of marine conservation aquaculture for the restoration of native Atlantic salmon (Salmo salar) in Downeast, Maine

The entities responsible for the management of the endangered Gulf of Maine Distinct Population Segment of Atlantic salmon ( Salmo salar ) have partnered with a commercial aquaculture company to apply a novel conservation aquaculture program. This effort marks a major shift in management and has garnered mixed public reactions. Recent expansion of aquaculture in Maine has been a point of controversy as people and systems grapple with the social, environmental, and legal aspects of this burgeoning industry. Still, the use of aquaculture for conservation has shown some promise. In 2021, a questionnaire was administered to 850 households (response rate 27 %) in Maine via the Drop-off and Pick-up method. We examined differences and similarities in attitudes, beliefs, and knowledge about Atlantic salmon, hatcheries, and aquaculture between property owners in the town where the proposed net pens would be located (Cutler; n=73), and those in neighboring towns (n=152). The Potential for Conflict Index (PCI 2 ) was used to examine differences between the groups. Both groups held similar positive attitudes toward Atlantic salmon, endangered species conservation, freshwater hatcheries, and both commercial and conservation aquaculture. Both groups believe that “ Atlantic salmon should be protected, ” and that freshwater hatcheries and marine conservation aquaculture “ should be used for conservation. ” However, Cutler residents had less consensus and supported the use of freshwater hatcheries and marine conservation aquaculture less than other respondents. Community concerns have stalled efforts to move the project forward. Our research indicates there are several social concepts which may help to explain localized opposition to the project.

Maine↗
USGS1999

Restoration of bighorn sheep metapopulations in and near 15 national parks: Conservation of a severely fragmented species; Volume I, Planning, problem definition, findings, and restoration

Bighorn sheep ( Ovis canadensis ) were historically a ubiquitous species. Prior to the arrival of Europeans, they were seemingly widespread in nearly all steep habitats in the mountains, foothills, river breaks, and prairie badlands of the western United States. However, since catastrophic declines in the late 1800s and early 1900s, most extant populations have existed as small, isolated groups in a highly fragmented distribution. Stochastic events such as seasonal weather change or population fluctuations render these small populations more prone to extirpation than larger populations. Three different subspecies of bighorn sheep were eliminated from 14 of 18 National Park System (NPS) units in the 6-state Intermountain Region of the western United States (Singer 1994). In 1990, when this restoration was initiated, only 4 (18%) of 22 discrete park populations or metapopulations were considered large enough (300-500 animals) to be secure for long-term management. Five (23%) other populations numbered 100-299 animals and 3 (14%) populations numbered 75-99 animals. But, the remaining 10 populations (45%) were either extirpated (n = 2), remnant populations (n = 5, populations of 7-10 animals), or vulnerable to extirpation (n = 3, populations of less than 50 animals). Restoration prior to 1991-96 was largely completed in one NPS unit, but was incomplete in the remaining units. Most bighorn sheep are not federally listed as endangered or threatened species, although the California peninsular population of desert bighorn sheep was recently listed as endangered. The bighorn sheep is a rare or uncommon species that is declining in many parts of its range but is abundant in other areas and still relatively easy to study and manage. The Secretary of the Department of the Interior, Bruce Babbitt, directed the Biological Resources Division of the U.S. Geological Survey in 1993 (when this agency was still the National Biological Service) to research and recover species that were declining to avoid expensive and controversial federal listing. Because the capture and moving of the species are still relatively uncomplicated and because some source stocks are available, aggressive restoration in 15 National Park System units in the former Rocky Mountain Region was recommended in 1990. This report details the 7-year restoration of bighorn sheep to all currently suitable historic habitats in the national parks of the former Rocky Mountain Region (now the Intermountain and Midwest regions of the National Park Service). The purpose of the first phase of the restoration during 1991-93 was to conduct research and population surveys and to formulate the restoration plans. The purpose of the second phase of the initiative during 1994-97 was to conduct GIS-based habitat and biological assessments of prospective restoration sites, write restoration plans, and restore and monitor the released bighorn sheep.

Colorado, Montana, North Dakota, South Dakota, Uta↗
USGS2020

Abundance and productivity of marbled murrelets ( Brachyramphus marmoratus ) off central California during the 2019 breeding season

Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “endangered” by the State of California and “threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management, evaluation of conservation efficacy, and ultimately, to meet Federal and State recovery efforts for this species. During June–August 2019, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1996–2019), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (San Francisco Bay to Point Sur in central California). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 125 detections of 216 murrelets (mean group size, 1.72) observed on 8 surveys. The abundance estimated for the entire study area using all surveys in 2019 was 404 birds (95-percent confidence interval, 272–601 birds). Estimated abundance from 2019 is comparable to most prior years of study. In 2019, we estimated reproductive productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) using three detections of three HY murrelets observed on six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.025±0.020 standard error. We discuss changes in methodologies during 1996–2019 that could be addressed in re-analysis of this long-term dataset. We updated a synthesized database of all Zone 6 marbled murrelet survey data since 1999 with 2019 data to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates.

California↗
USGS2015

Plague bacterium as a transformer species in prairie dogs and the grasslands of western North America

Invasive transformer species change the character, condition, form, or nature of ecosystems and deserve considerable attention from conservation scientists. We applied the transformer species concept to the plague bacterium Yersinia pestis in western North America, where the pathogen was introduced around 1900. Y. pestis transforms grassland ecosystems by severely depleting the abundance of prairie dogs ( Cynomys spp. ) and thereby causing declines in native species abundance and diversity, including threatened and endangered species; altering food web connections; altering the import and export of nutrients; causing a loss of ecosystem resilience to encroaching invasive plants; and modifying prairie dog burrows. Y. pestis poses an important challenge to conservation biologists because it causes trophic-level perturbations that affect the stability of ecosystems. Unfortunately, understanding of the effects of Y. pestis on ecosystems is rudimentary, highlighting an acute need for continued research.

Conservation Biology↗
USGS2021

Using growth rates to estimate the minimum age and size at sexual maturity in a captive population of the critically endangered Central American river turtle Dermatemys mawii

The Central American river turtle Dermatemys mawii is a critically endangered species that has incurred substantial losses over the last several decades due to overhunting. This species is now being considered for head-starting programs (i.e. captive breeding of turtles for wild release). However, relatively little is known about their life history characteristics, especially with respect to growth and sexual maturation. A robust knowledge of D. mawii life history traits is important in developing conservation management plans. Our research is the first known study to maintain hatchlings, juveniles, and adults in captivity with regular morphometric data collection. We quantified growth rates (cm yr-1) and calculated growth parameters (e.g. growth coefficients) to estimate body size and age at onset of sexual maturity in a group of wild-caught but captive-held and captive-bred D. mawii in Belize. Sizes at the onset of sexual maturity were inferred by segmented linear regressions that identified changes in growth rate by body size. Asymptotic sizes and growth coefficients were calculated using the Fabens method and the Wang method. Parameters from these models were then applied to a modified von Bertalanffy growth equation to estimate age at the onset of sexual maturity. Male and female D. mawii begin sexual maturation at ca. 38.0 cm and 40.0 cm straight-line carapace length, respectively. We estimated ages associated with these sizes at 13.5-16.9 yrs (males) and 13.6-17.3 yrs (females). No previous literature on growth rates or age at maturation for wild or captive D. mawii has been reported, so our results serve as a starting point in conservation management. Given the life history trait of delayed sexual maturity (>10 years), D. mawii may be more sensitive to losses of the adult population. Therefore, the importance of captive breeding and head-starting programs may be concomitant with protecting wild, adult populations.

Toledo↗
USGS2000

Breeding season ecology: Chapter 6 in Status, ecology and conservation of the Southwestern Willow Flycatcher (RMRS-GTR-60)

The willow flycatcher ( Empidonax traillii ) breeds across much of the conterminous United States and in portions of extreme southern Canada. As might be expected in such a wide-ranging species, willow fly- catchers in different portions of the range exhibit differences in appearance, song, and ecological characteristics. The intent of this chapter is to provide information on the breeding-season ecology of the southwestern subspecies, E.t. extimus . However, most ecological studies to date have dealt with other willow flycatcher subspecies. Relatively few studies have been published on E.t. extimus , and much of what is currently known is presented in unpublished literature (e.g., agency and consulting firm reports); these sources are relied upon heavily in this chapter. This chapter does not address habitat characteristics in depth, other than for nest sites (refer to A Survey of Current Breeding Habitats for additional details). Although southwestern willow flycatchers are frequent victims of nest parasitism by brown-headed cowbirds ( Molothrus ater ), this chapter will not address the topic of parasitism and its effect on breeding ecology (refer to The Ecology of Brown-headed Cowbirds and their Effects on Southwestern Willow Flycatchers for details). Readers interested in more details of willow flycatcher biology and ecology are encouraged to read McCabe’s (1991) treatise, which is based on over a decade of willow flycatchers research in Wisconsin and includes comparisons with other populations and subspecies.

General Technical Report↗
USGS2019

Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2018 breeding season

Executive Summary Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “endangered” by the State of California and “threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management, evaluation of conservation efficacy, and ultimately, to meet Federal- and State-mandated recovery efforts for this species. During June–August 2018, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–2018), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (San Francisco Bay to Point Sur in central California). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 137 detections of 227 individuals observed on 9 surveys. The abundance estimated for the entire study area using all surveys in 2018 was 370 birds (95-percent confidence interval, 250–546 birds). Estimated abundance from 2018 is comparable to most prior years of study, except for 2001–03, when greater abundances were estimated. In 2018, we estimated reproductive productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) using four detections of four HY individuals observed on six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.047 ± 0.024 standard error. We updated a synthesized database of all Zone 6 marbled murrelet survey data since 1999 with 2018 data to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates.

California↗
USGS2018

Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2017 breeding season

Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “Endangered” by the State of California and “Threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management and evaluation of conservation efficacy, and ultimately to meet Federal- and State-mandated recovery efforts for this species. During June–August 2017, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–2016), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (central California—San Francisco Bay to Monterey Bay). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 189 detections of 321 individuals observed on nine unique surveys. The abundance estimated for the entire study area using all surveys in 2017 was 530 birds (95-percent confidence interval, 384–732 birds). Estimated abundance from 2017 is comparable to most prior years of study, except for 2008 and 2015, which had anomalously low abundances. We estimated productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) in 2017 using three detections of three individuals observed in six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.022 ± 0.014 standard error. We created a synthesized database of all marbled murrelet survey data from 1999 to 2017 to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates. Future modifications of survey design could help reduce variance in abundance estimation.

California↗
USGS1983

Supporting data for Environmental Trends

Information has been compiled as a companion document to ' Environmental Trends ' to provide analysts and researchers with statistical data to understand better how natural and man-made environments were changing. Subjects include land and climate; wetlands; wild areas; historic places; risk zones; settlement patterns; housing units; housing conditions; neighborhood conditions; transportation systems, including use and impacts on the environment such as noise, energy consumption; material use and solid waste; toxic substances, including radiation; cropland , forests and rangeland; wildlife, including extinct, threatened and endangered species; energy; water resources, water quality and air quality; and the biosphere. Statistics in the tables were taken from various published and unpublished sources. Therefore, the number of significant figures for the same information may differ. (Author 's abstract)

Open-File Report↗
USGS2006

Ecology of bonytail and razorback sucker and the role of off-channel habitats in their recovery

The bonytail and razorback sucker are two of four endangered mainstem fishes found in the Colorado River. Unlike the Colorado pikeminnow and humpback chub, wild populations of the bonytail and razorback sucker are either extirpated from the mainstem river or are nearly so. Agencies are aggressively stocking these fish and while repatriated fish spawn, their young are rapidly eaten by introduced predators. A decade of predator removal efforts has proved ineffective in restoring natural recruitment. Today, the presence of these species is totally dependent on stocking, suggesting both species are worse off today than when recovery efforts began nearly two decades ago. In contrast, both species readily produce young in ponds where nonnative predators are absent. Evidence shows they evolved with the ability to spawn in both flowing and standing water, which suggests isolated oxbow communities may have been an essential feature in their evolution and survival strategy. Sustainable populations during the past few decades have only occurred in isolated ponds devoid of predatory nonnative fish. Efforts to force recovery in the main channel river continue to fail due to the presence of nonnative predators that may be economically important recreational species. Off-channel sanctuaries provide research and management opportunities on a scale that are both biologically and economically realistic. Effective management of these species in small habitats appears to be the most logical approach to advance recovery in larger river reaches. This report presents new findings, updates existing information, and describes what may well represent the only practical approach to these species’ conservation and recovery. Chapter 1 provides an overview of the Colorado River system from its origin to the Gulf of California and includes a description of propagation and stocking programs which have not been described elsewhere. The report also updates what is known or suspected on the life history and ecology of these two endangered fishes. Chapter 2 describes the successful recruitment of both species at an oxbow pond on the Cibola National Wildlife Refuge in Arizona, discusses factors that contribute to completion of the life cycle of both fishes, and provides recommendations for future management of the impoundment. Chapter 3 provides historical evidence that oxbow habitats were formed historically in years of high runoff and the importance of these habitats for survival and evolution of native fishes. It also summarizes key features of habitats that can serve as sanctuaries that enhance early survival of the endangered fishes and allow the fish to complete their entire life cycles.

Scientific Investigations Report↗
USGS2022

Abundance and productivity of Marbled Murrelets ( Brachyramphus marmoratus ) off central California during the 2020 and 2021 breeding seasons

Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “endangered” by the State of California and “threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management, evaluation of conservation efficacy, and ultimately, to meet federal- and state-mandated recovery efforts for this species. During June–August 2020 and 2021, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–present), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (San Francisco Bay to Point Sur in central California). The abundance estimated for the entire study area was 470 birds (95-percent confidence interval, 313–707 birds) in 2020 and 402 birds (95-percent confidence interval, 219–737 birds) in 2021. Estimated abundances for both years are comparable with most prior years of study. We estimated reproductive productivity (calculated as the hatch-year to after-hatch-year ratio) after date-correcting hatch-year and after-hatch-year counts to account for birds expected to be absent from the water while inland at nests. The date-corrected juvenile ratio was 0.018±0.011 standard error in 2020 and 0.041±0.024 standard error in 2021. We updated a comprehensive database of all Zone 6 marbled murrelet survey data since 1999 with 2020–21 data to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates.

California↗
USGS2005

Technical review of the status of Northern Goshawks in the western United States

The U.S. Fish and Wildlife Service (FWS) was petitioned in 1997 to consider listing Northern Goshawks (Accipiter gentilis atricapillus) under the Endangered Species Act of 1973, west of the 100th meridian of the contiguous United States. In their 12-mo finding issued in June 1998, the FWS determined that listing this population as threatened or endangered was not warranted and based that decision on review existing population and habitat information. Because the status of goshawks in the western U.S. continues to be contentious and the FWS finding has been challenged, the Raptor Research Foundation, Inc. and The Wildlife Society jointly formed a committee to review information regarding the status of the goshawk population in the contiguous U.S. west of the 100th meridian. The committee was requested to: (1) determine if there is evidence of a population trend in goshawks in the western U.S., excluding Alaska; (2) determine if there is evidence that goshawks nesting in the eastern and western U.S. represent distinctive, genetically unique populations; and (3) evaluate evidence for goshawk-habitat relations, including any association with large, mostly-unbroken tracts of old growth and mature forests. Based on existing information, the committee concluded: (1) existing data are not adequate to assess population trend in goshawks west of the 100th meridian; (2) existing analyses of phylogeography have not provided evidence of genetic differences among recognized (atricapillus, laingi) or putative (apache) subspecies, and the genetic distinctness of atricapillus goshawks in western and eastern North America is not known; and (3) at present, assessing the status of goshawks solely using distribution of late-successional forests is not appropriate, based on the current understanding of goshawk-habitat relations, although goshawks clearly use and often select late-successional forests for nesting and foraging. We provide recommendations on information needs to assess status and population trend of goshawks in the western U.S. ?? 2005 The Raptor Research Foundation, Inc.

Journal of Raptor Research↗
USGS2005

Captive breeding and reintroduction of the endangered masked bobwhite

Efforts to restore the endangered masked bobwhite ( Colinus virginianus ridgwayi ) to its former range have required 1) habitat acquisition, restoration, and preservation; 2) captive propagation; and 3) reintroduction of captive-bred stock. In its role to recover the masked bobwhite, the Patuxent Wildlife Research Center (U.S. Fish and Wildlife Service) has refined captive breeding techniques; provided captive-produced stock for release; conducted field research on the distribution, limiting factors, and habitat characteristics of this species; and developed release methods. Techniques for the husbandry and captive management, breeding, artificial incubation and hatching of eggs, and rearing of young of the masked bobwhite have been developed. Successful reintroduction techniques for the masked bobwhite have included prerelease conditioning and/or cross-fostering of captive-reared masked bobwhite chicks to a wild-caught, related, vasectomized bobwhite species and their release to the wild as family units. In addition, the establishment by the U.S. Fish and Wildlife Service of the Buenos Aires National Wildlife Refuge in 1985 has further enhanced the potential for establishing a self-sustaining population of the masked bobwhite in the U.S. Through continued releases and active management of habitat, therefore, it is believed that the masked bobwhite can become permanently established at the refuge to ensure its continued survival in the wild.

Zoo Biology↗
USGS2008

Abundance Trends and Status of the Little Colorado River Population of Humpback Chub: An Update Considering 1989-2006 Data

EXECUTIVE SUMMARY In 1967, the humpback chub (Gila cypha) (HBC) was added to the federal list of endangered species and is today protected under the Endangered Species Act of 1973. Only six populations of humpback chub are currently known to exist, five in the Colorado River Basin above Lees Ferry, Arizona, and one in Grand Canyon, Arizona. The majority of Grand Canyon humpback chub are found in the Little Colorado River (LCR)-the largest tributary to the Colorado River in Grand Canyon-and the Colorado River near its confluence with the Little Colorado River. Monitoring and research of the Grand Canyon humpback chub population is overseen by the U.S. Geological Survey's (USGS) Grand Canyon Monitoring and Research Center (GCMRC) under the auspices of the Glen Canyon Dam Adaptive Management Program (GCDAMP), a Federal initiative to protect and improve resources downstream of Glen Canyon Dam. This report provides updated information on the status and trends of the LCR population in light of new information and refined assessment methodology. An earlier assessment of the LCR population (Coggins and others, 2006a) used data collected during 1989?2002; the assessment provided here includes that data and additional data collected through 2006. Catch-rate indices, closed population mark-recapture model abundance estimates, results from the original age-structured mark recapture (ASMR) model (Coggins and others, 2006b), and a newly refined ASMR model are presented. This report also seeks to (1) formally evaluate alternative stock assessment models using Pearson residual analyses and information theoretic procedures, (2) use mark-recapture data to estimate the relationship between HBC age and length, (3) translate uncertainty in the assignment of individual fish age to resulting estimates of recruitment and abundance from the ASMR model, and (4) evaluate past and present stock assessments considering the available data sources and analyses, recognizing the limitations inherent in both. A major task of this study was to improve the overall methodology used to conduct HBC stock assessment by addressing concerns identified in an independent review conducted in 2003 (Kitchell and others, 2003). The review report identified that the current technique of assigning age to individual fish based on length was a potential source of bias in ASMR estimates of abundance and recruitment, and called for a more complete examination of this potential error source. Additionally, the review suggested that further work to develop procedures to better arbitrate among alternative assessment models (e.g., ASMR 1?3) would be beneficial. To address the first of the concerns identified by the independent review, this study uses mark-recapture data to develop a temperature-dependent growth model to characterize the relationship between HBC age and length. This model attempts to account for temperature differences resulting from both ontogenetic habitat shifts between the Little Colorado and the mainstem Colorado Rivers as well as seasonal variation in water temperature within the LCR. The resulting growth model is then used to characterize the error in assigning age to individual fish based on length. Results presented in this study suggest that ageing error does not result in large bias in either abundance or recruitment estimates from the ASMR model. However, incorporating ageing error into the assessment does result in less precise estimates, particularly for recruitment. To address the second concern brought forward in the review report related to model selection procedures, this study arbitrated among the competing models by both examining model fit using Pearson residual analyses and considering information theoretic measures. Although adult abundance estimates and trend varied little among all models considered, these procedures identified ASMR 3 as the model whose underlying assumptions were most consistent with the data. Because ASMR 3 is

Open-File Report↗