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At least 721 records · Page 40Linked to original sources

USGS1999

Evaluation of waterfowl conservation under the North American Waterfowl Management Plan

In 1986, the North American Waterfowl Management Plan (Plan) was signed by the U.S. Secretary of the Interior and the Canadian Minister of the Environment, with a goal of restoring waterfowl populations to levels of the 1970s via habitat conservation. Central to the Plan is a set of ambitious continental population goals and habitat objectives to be met through broad-based public-private partnerships. Inadequate attention has been paid to evaluation of the Plan, despite the fact that Plan delivery can be enhanced via improved understanding of the effects of habitat conservation on waterfowl population dynamics. Several factors confound the effort to evaluate the Plan at regional and continental levels, including difficulties in accounting for national land-use policies. To date, evaluation has proceeded along 2 avenues of investigation: (1) the study of conservation actions at local-regional levels, and (2) statistical assessment of Plan assumptions. Among other things, results thus far indicate duck production from the U.S. Northern Great Plains has increased in recent years, and intensive treatments such as planted cover have had positive effects on local reproductive success. Many duck species currently exceed Plan population goals; however, population levels of some species, most notably northern pintail (Anas acuta), remain below expectations based on historic relationships with precipitation. Management implications include the need for ongoing and more carefully prioritized conservation efforts, broader partnerships, and improved understanding of the linkages between habitats and biological processes. Delivery of the Plan must involve collaboration among the Continental Evaluation Team, joint Venture partners, the Adaptive Management and Assessment Team of the U.S. Fish and Wildlife Service, and other conservation groups. Although the challenges and projected costs of Plan conservation efforts are considerable, the long-term potential benefits to waterfowl conservation are great.

Journal of Wildlife Management↗

USGS2015

Rafinesque’s names for western American mammals, including the earliest scientific name for the coyote ( Canis latrans Say, 1822), based on the apocryphal journal of Charles Le Raye

In 1817, the naturalist Constantine S. Rafinesque named nine new species of mammals from the American West, indicating the recently published journal of Charles Le Raye as the primary source for his descriptions. Le Raye was purported to be a French Canadian fur trader who, as a captive of the Sioux, had traveled across broad portions of the Missouri and Yellowstone river drainages a few years before the Lewis and Clark Expedition (1804-1806) traversed much of the same region. Le Raye's journal was relied upon by generations of scholars as a valuable source documenting the native peoples and natural history of the Upper Missouri river in the era just prior to European settlement. Subsequent research, however, has shown that Le Raye never existed, and his purported journal is fraudulent. Despite this, Rafinesque's creation of the names followed conventional and accepted practice at the time, and they are porentially available. Fortunately, much of the Le Raye journal was based on verifiable sources, such as Patrick Gass's published account of the Lewis and Clark Expedition. Identification of the original source materials makes it possible to establish the correct application of Rafinesque's names and to determine their current status. This process reveals that the earliest scientific name for the coyote ( Canis latrans Say, 1822) was Canis chlorops Rafinesque, 1817; this name is now a nomen oblitum , however, and is no longer available.

Proceedings of the Biological Society of Washingto↗

USGS2013

Sampling efficiency of the Moore egg collector

Quantitative studies focusing on the collection of semibuoyant fish eggs, which are associated with a pelagic broadcast-spawning reproductive strategy, are often conducted to evaluate reproductive success. Many of the fishes in this reproductive guild have suffered significant reductions in range and abundance. However, the efficiency of the sampling gear used to evaluate reproduction is often unknown and renders interpretation of the data from these studies difficult. Our objective was to assess the efficiency of a modified Moore egg collector (MEC) using field and laboratory trials. Gear efficiency was assessed by releasing a known quantity of gellan beads with a specific gravity similar to that of eggs from representatives of this reproductive guild (e.g., the Arkansas River Shiner Notropis girardi) into an outdoor flume and recording recaptures. We also used field trials to determine how discharge and release location influenced gear efficiency given current methodological approaches. The flume trials indicated that gear efficiency ranged between 0.0% and 9.5% (n = 57) in a simple 1.83-m-wide channel and was positively related to discharge. Efficiency in the field trials was lower, ranging between 0.0% and 3.6%, and was negatively related to bead release distance from the MEC and discharge. The flume trials indicated that the gellan beads were not distributed uniformly across the channel, although aggregation was reduced at higher discharges. This clustering of passively drifting particles should be considered when selecting placement sites for an MEC; further, the use of multiple devices may be warranted in channels with multiple areas of concentrated flow.

North American Journal of Fisheries Management↗

USGS2002

Energy resource potential of natural gas hydrates

The discovery of large gas hydrate accumulations in terrestrial permafrost regions of the Arctic and beneath the sea along the outer continental margins of the world's oceans has heightened interest in gas hydrates as a possible energy resource. However, significant to potentially insurmountable technical issues must be resolved be fore gas hydrates can be considered a viable option for affordable supplies of natural gas. The combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors, known as bottom-simulating reflectors, that have been mapped at depths below the sea floor ranging from about 100 to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas hydrate accumulations are in rough accord at about 20,000 trillion m 3 . Disagreements over fundamental issues such as the volume of gas stored within delineated gas hydrate accumulations and the concentration of gas hydrates within hydrate-bearing strata have demonstrated that we know little about gas hydrates. Recently, however, several countries, including Japan, India, and the United States, have launched ambitious national projects to further examine the resource potential of gas hydrates. These projects may help answer key questions dealing with the properties of gas hydrate reservoirs, the design of production systems, and, most important, the costs and economics of gas hydrate production.

American Association of Petroleum Geologists Bulle↗

USGS2011

Distribution of lake sturgeon in New York: 11 years of restoration management

Lake sturgeon ( Acipenser fulvescens ) are native within the Lake Ontario drainage basin and listed as threatened by New York State. In 1995 the New York State Department of Environmental Conservation (NYSDEC) initiated restoration management of lake sturgeon. This management included both protection of extant populations and stocking of uninhabited historic waters with juvenile sturgeon. A list compiled by NYSDEC of observations of lake sturgeon from New York State waters for the period encompassing 1800–2005 was combined with recent observations through 2008 and formatted (Geographic Information System) to allow mapping of sturgeon geographical distribution. Distributions of pre- and post-restoration sturgeon were examined by occurrence and type of observation. Distribution patterns indicated lakes and rivers with current sturgeon presence have increased from five to eight, which was the first-phase goal of the New York Lake Sturgeon Recovery Plan. Lake sturgeon have started to expand into joining water to include the Indian R., Oneida R., Seneca R. and Oswego R. The protected historic populations in the Niagara R., Grasse R., St. Lawrence R., and Lakes Erie and Ontario continue to have low numbers of sturgeon observations. This summary of mapped lake sturgeon distribution information will help in guiding research assessments to waters containing substantial populations. These accessible reaches provide a generous advantage to the released juveniles as they move toward the next goal of restoration, spawning of sturgeon in targeted waters.

New York↗

USGS2024

Earthquake relocations delineate discrete a fault network and deformation corridor throughout Southeast Alaska and Southwest Yukon

Deformation in southeastern Alaska and southwest Yukon is governed by the subduction and translation of the Pacific-Yakutat plates relative to the North American plate in the St. Elias region. Despite notable historical seismicity and major regional faults, studies of the region between the Fairweather and Denali faults are complicated by glacial coverage and the remote setting. In the last decade, significant improvements have been made to the density of regional broadband seismometer networks. We relocate more than 5,000 earthquakes between 2010 and 2021 in the region of southeastern Alaska and southwestern Yukon utilizing these improved seismic networks. With reductions in catalog uncertainty, particularly in depth, we quantify the thickness of the seismogenic layer in the crust throughout the region and locate seismicity on a shallow network of upper-crustal faults. Relocated earthquakes, combined with an updated focal-mechanism catalog, permit estimating and classifying motion of active faults. This includes mapping the Totschunda-Fairweather “Connector” fault, which plays an important role in explaining regional deformation, and identifying new faults like the Kathleen Lake fault. We draw similarities between our seismic observations and simplified conceptual models of regional tectonics, which describe a dominant transpressional regime and localized slip partitioning. Our results support a hypothesis where current deformation is taking place on a well-defined and evolved network of shallow faults in the corridor between the Totschunda-Fairweather “Connector” and Denali faults.

Alaska, Yukon↗

USGS2006

Diversity, composition, and geographical distribution of microbial communities in California salt marsh sediments

The Pacific Estuarine Ecosystem Indicators Research Consortium seeks to develop bioindicators of toxicant-induced stress and bioavailability for wetland biota. Within this framework, the effects of environmental and pollutant variables on microbial communities were studied at different spatial scales over a 2-year period. Six salt marshes along the California coastline were characterized using phospholipid fatty acid (PLFA) analysis and terminal restriction fragment length polymorphism (TRFLP) analysis. Additionally, 27 metals, six currently used pesticides, total polychlorinated biphenyls and polycyclic aromatic hydrocarbons, chlordanes, nonachlors, dichlorodiphenyldichloroethane, and dichlorodiphenyldichloroethylene were analyzed. Sampling was performed over large (between salt marshes), medium (stations within a marsh), and small (different channel depths) spatial scales. Regression and ordination analysis suggested that the spatial variation in microbial communities exceeded the variation attributable to pollutants. PLFA analysis and TRFLP canonical correspondence analysis (CCA) explained 74 and 43% of the variation, respectively, and both methods attributed 34% of the variation to tidal cycles, marsh, year, and latitude. After accounting for spatial variation using partial CCA, we found that metals had a greater effect on microbial community composition than organic pollutants had. Organic carbon and nitrogen contents were positively correlated with PLFA biomass, whereas total metal concentrations were positively correlated with biomass and diversity. Higher concentrations of heavy metals were negatively correlated with branched PLFAs and positively correlated with methyl- and cyclo-substituted PLFAs. The strong relationships observed between pollutant concentrations and some of the microbial indicators indicated the potential for using microbial community analyses in assessments of the ecosystem health of salt marshes. Copyright ?? 2006, American Society for Microbiology. All Rights Reserved.

Applied and Environmental Microbiology↗

USGS2012

History and progress of the North American Soil Geochemical Landscapes Project, 2001-2010

In 2007, the U.S. Geological Survey, the Geological Survey of Canada, and the Mexican Geological Survey initiated a low-density (1 site per 1600 km 2 , 13323 sites) geochemical and mineralogical survey of North American soils (North American Soil Geochemical Landscapes Project). Sampling and analytical protocols were developed at a series of workshops in 20032004 and pilot studies were conducted from 20042007. The ideal sampling protocol at each site includes a sample from 05 cm depth, a composite of the soil A horizon, and a sample from the soil C horizon. The <2-mm fraction of each sample is analyzed for Al, Ca, Fe, K, Mg, Na, S, Ti, Ag, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Ga, In, La, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Sn, Sr, Te, Th, Tl, U, V, W, Y, and Zn by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry following a near-total digestion in a mixture of HCl, HNO 3 , HClO 4 , and HF. Separate methods are used for As, Hg, Se, and total C on this same size fraction. The major mineralogical components are determined by a quantitative X-ray diffraction method. Sampling in the conterminous U.S. was completed in 2010 (c. 4800 sites) with chemical and mineralogical analysis currently underway. In Mexico, approximately 66% of the sampling (871 sites) had been done by the end of 2010 with completion expected in 2012. After completing sampling in the Maritime provinces and portions of other provinces (472 sites, 7.6% of the total), Canada withdrew from the project in 2010. Preliminary results for a swath from the central U.S. to Florida clearly show the effects of soil parent material and climate on the chemical and mineralogical composition of soils. A sample archive will be established and made available for future investigations.

Earth Science Frontiers↗

USGS2022

Landscape characteristics influence projected growth rates of stream-resident juvenile salmon in the face of climate change in the Kenai River watershed, south-central Alaska

Objective Climate change is affecting the distribution and productivity of Pacific salmon throughout their range. At high latitudes, warmer temperatures have been associated with increased freshwater growth of juvenile salmon, but it is not clear how long this trend will continue before further warming leads to reduced growth. To explore the potential influence of climate warming on juvenile Chinook and Coho Salmon summer growth rates in southcentral Alaska, we coupled bioenergetics models with temperature sensitivity models for streams across the Kenai River watershed. Methods We measured diet ( n = 772 stomachs) and growth ( n = 3,791 weight/length values) under current conditions and used published air temperature projections to model growth for the 2030–2039 and 2060–2069 decades. Result We estimated direct effects of climate warming on juvenile growth (body mass at the end of May–September study period) will be primarily negative, ranging from +5.1% to −22.8% relative to a 2010–2019 baseline. Estimated effects depended on age cohort, feeding rate, and climate scenario. However, an extended growing season from warming could mitigate or offset predicted reductions in growth during midsummer. Conclusion Our results illustrate how diverse habitats are expected to produce variation in the magnitude of climate effects throughout juvenile salmon rearing environments.

Alaska↗

USGS2025

Spatially explicit power analyses to inform occupancy‐based multi‐species wildlife monitoring programmes

1. Current and accurate information on wildlife populations is integral to successful biodiversity management and conservation globally. Nevertheless, many monitoring programs fail in their attempts to accurately monitor populations of interest due to interlinked issues including insufficient sample sizes, inappropriate duration, lack of reproducibility, and lack of clearly stated objectives. These common pitfalls could be avoided through the elicitation of explicit monitoring objectives and the a priori use of simulations to inform minimum sampling design requirements to meet said objectives. 2. Here, we provide a blueprint for using spatially explicit power analyses to inform the design and implementation of multi-species monitoring programs on landscape-scales. As a demonstration, we used spatially explicit simulations to devise a suitable sampling regime to meet clearly specified monitoring objectives in New York State: to use annual occupancy-based monitoring to be able to detect 25% and 50% changes in abundance of populations over five- and ten- year periods for all species of management interest in New York State, USA. We focused our simulation efforts on three challenging focal species (black bear, Ursus americanus, bobcat, Lynx rufus, and American marten, Martes americana) that differ notably in their morphology, life histories, space use, detection probability, habitat suitability, and population sizes/trajectories, and thus provide extremes in the challenges presented when it comes to sampling appropriately to detect changes in abundance. 3. Our simulations demonstrate variable context dependent trade-offs in sampling designs (i.e. number of sites [J] and number of sampling occasions [K]), and identify necessary minimum detection probabilities that must be attained to achieve statistical power to detect changes of varying magnitudes in populations of varying sizes in the three focal species. The simulations also highlight that monitoring population increases is likely beyond the reach of occupancy-based monitoring programs for wide-ranging or locally abundant species. 4. Synthesis and applications : We combine the results from the single-species simulations to produce a multi-species sampling design that meets the specified objectives for all three species. While the case study is centered on developing a multi-species sampling regime for New York State, it provides a reproducible step-by-step framework using established methods for wildlife managers and other practitioners to inform their own context- and objective- specific multi-species occupancy-based monitoring programs.

New York↗

USGS2022

Water storage decisions and consumptive use may constrain ecosystem management under severe sustained drought

Drought has impacted the Colorado River basin for the past 20 years and is predicted to continue. In response, decisions about how much water should be stored in large reservoirs and how much water can be consumptively used will be necessary. These decisions have the potential to limit riverine ecosystem management options through the effect water-supply decisions have on reservoir elevations. We used projected hydrology and river temperatures to compare the outcome of combinations of water storage scenarios and consumptive use limits on metrics associated with ecosystem management of the Colorado River in Grand Canyon. Ecosystem management metrics included the ability to implement designer flows, temperature suitability for fishes, and fragmentation. We compared current water management operations to prioritizing storage in either Lake Mead or Lake Powell combined with three levels of consumptive use. Projected reservoir levels limited environmental flow delivery and increased fragmentation regardless of where water was stored if consumptive use was not limited. Warmer river temperatures associated with low reservoir levels are likely, creating suitable conditions for non-native species of concern, such as smallmouth bass. Water storage decisions provided variability and management flexibility, but water storage was less important when less water was available, highlighting the importance of keeping water in the system to provide flexibility for achieving ecosystem goals.

Arizona, Utah↗

USGS2005

An evaluation of the U.S. Geological Survey World Petroleum Assessment 2000

This study compares the additions to conventional crude oil and natural gas reserves as reported from January 1996 to December 2003 with the estimated undiscovered and reserve-growth volumes assessed in the U.S. Geological Survey World Petroleum Assessment 2000, which used data current through 1995. Approximately 28% of the estimated additions to oil reserves by reserve growth and approximately 11% of the estimated undiscovered oil volumes were realized in the 8 yr since the assessment (27% of the time frame for the assessment). Slightly more than half of the estimated additions to gas reserves by reserve growth and approximately 10% of the estimated undiscovered gas volumes were realized. Between 1995 and 2003, growth of oil reserves in previously discovered fields exceeded new-field discoveries as a source of global additions to reserves of conventional oil by a ratio of 3:1. The greatest amount of reserve growth for crude oil occurred in the Middle East and North Africa, whereas the greatest contribution from new-field discoveries occurred in sub-Saharan Africa. The greatest amount of reserve growth for natural gas occurred in the Middle East and North Africa, whereas the greatest contribution from new-field discoveries occurred in the Asia Pacific region. On an energy-equivalent basis, volumes of new gas-field discoveries exceeded new oil-field discoveries. Copyright ?? 2005. The American Association of Petroleum Geologists. All rights reserved.

American Association of Petroleum Geologists Bulle↗

USGS2009

Genetic conservation and paddlefish propagation

The conservation of genetic diversity of our natural resources is overwhelmingly one of the central foci of 21st century management practices. Three recommendations related to the conservation of paddlefish Polyodon spathula genetic diversity are to (1) identify genetic diversity at both nuclear and mitochondrial DNA loci using a suggested list of 20 sampling locations, (2) use genetic diversity estimates to develop genetic management units, and (3) identify broodstock sources to minimize effects of supplemental stocking on the genetic integrity of native paddlefish populations. We review previous genetic work on paddlefish and described key principles and concepts associated with maintaining genetic diversity within and among paddlefish populations and also present a genetic case study of current paddlefish propagation at the U.S. Fish and Wildlife Service Gavins Point National Fish Hatchery. This study confirmed that three potential sources of broodfish were genetically indistinguishable at the loci examined, allowing the management agencies cooperating on this program flexibility in sampling gametes. This study also showed significant bias in the hatchery occurred in terms of male reproductive contribution, which resulted in a shift in the genetic diversity of progeny compared to the broodfish. This shift was shown to result from differential male contributions, partially attributed to the mode of egg fertilization. Genetic insights enable implementation of a paddlefish propagation program within an adaptive management strategy that conserves inherent genetic diversity while achieving demographic goals.

American Fisheries Society Symposium↗

USGS2024

Sod farms drive habitat selection of a migratory grassland shorebird during a critical stopover period

Migratory shorebirds are one of the fastest declining groups of North American avifauna. Yet, relatively little is known about how these species select habitat during migration. We explored the habitat selection of Buff-breasted Sandpipers ( Calidris subruficollis ) during spring and fall migration through the Texas Coastal Plain, a major stopover region for this species. Using tracking data from 118 birds compiled over 4 years, we found Buff-breasted Sandpipers selected intensively managed crops such as sod and short-stature crop fields, but generally avoided rangeland and areas near trees and shrubs. This work supports prior studies that also indicate the importance of short-stature vegetation for this species. Use of sod and corn varied by season, with birds preferring sod in spring, and avoiding corn when it is tall, but selecting for corn in fall after harvest. This dependence on cropland in the Texas Coastal Plain is contrary to habitat use observed in other parts of their non-breeding range, where rangelands are used extensively. The species' almost complete reliance on a highly specialized crop, sod, at this critical stopover site raises concerns about potential exposure to contaminants as well as questions about whether current management practices are providing suitable conditions for migratory grassland birds.

Texas↗

USGS2000

Landscape associations of frog and toad species in Iowa and Wisconsin, U.S.A

Landscape habitat associations of frogs and toads in Iowa and Wisconsin were tested to determine whether they support or refute previous general habitat classifications. We examined which Midwestern species shared similar habitats to see if these associations were consistent across large geographic areas (states). Rana sylvatica (wood frog), Hyla versicolor (eastern gray treefrog), Pseudacris crucifer (spring peeper), and Acris crepitans (cricket frog) were identified as forest species, P. triseriata (chorus frog), H. chrysoscelis (Cope's gray treefrog), R. pipiens (leopard frog), and Bufo americanus (American toad) as grassland species, and R. catesbeiana (bullfrog), R. clamitans (green frog), R. palustris (pickerel frog), and R. septentrionalis (mink frog) as lake or stream species. The best candidates to serve as bioindicators of habitat quality were the forest species R. sylvatica, H. versicolor, and P. crucifer, the grassland species R. pipiens and P. triseriata, and a cold water wetland species, R. palustris. Declines of P. crucifer, R. pipiens, and R. palustris populations in one or both states may reflect changes in habitat quality. Habitat and community associations of some species differed between states, indicating that these relationships may change across the range of a species. Acris crepitans may have shifted its habitat affinities from open habitats, recorded historically, to the more forested habitat associations we recorded. We suggest contaminants deserve more investigation regarding the abrupt and widespread declines of this species. Interspersion of different habitat types was positively associated with several species. A larger number of wetland patches may increase breeding opportunities and increase the probability of at least one site being suitable. We noted consistently negative associations between anuran species and urban development. Given the current trend of urban growth and increasing density of the human population, declines of amphibian populations are likely to continue.

Book chapter↗

USGS2003

Boll weevil eradication: a model for sea lamprey control?

Invasions of boll weevil ( Anthonomus grandis ) into the United States and sea lamprey ( Petromyzon marinus ) into the Great Lakes were similar in many ways. Important species (American cotton, Gossypium hirsutum , and lake trout, Salvelinus namaycush ) and the industries they supported were negatively affected. Initial control efforts were unsuccessful until pesticides and application technologies were developed. For boll weevils, controls relying on pesticides evolved into an integrated program that included recommended farming practices and poisoned baits. However, the discovery of a boll weevil sex pheromone in 1964 allowed adoption of an ongoing program of eradication. Despite opposition over concept and cost, insecticides, pheromone traps, poisoned baits, and approved farming practices were used to eradicate boll weevils from Virginia, North Carolina, South Carolina, Georgia, Florida, and Alabama by 1999. Using the working back approach along the path of the original invasion, eradication was nearly completed by 2002 in Mississippi and eradication programs were underway in Arkansas, Tennessee, Oklahoma, Louisiana, and parts of Texas. Insecticide use for cotton production decreased 50 to 90%, and cotton yields and farm income increased an average of 78 kg/ha and $190 U.S./ha in areas where boll weevils were eradicated. For sea lampreys, integrated management uses lampricides, barriers to migration, trapping, and release of sterilized males. Although sea lamprey eradication is not currently feasible, recent research on larval and sex pheromones might provide the tools to make it possible. A successful eradication program for sea lampreys starting in Lake Superior and expanding to the lower Great Lakes would ultimately provide huge ecological and economic benefits by eliminating lampricide applications, removing barriers that block teleost fishes, and facilitating the recovery of lake trout. Should the opportunity arise, the concept of sea lamprey eradication should not be rejected out of hand. The successful boll weevil eradication program shows that sea lamprey eradication might be achievable.

Journal of Great Lakes Research↗

USGS2015

Status and conservation of interior Redband Trout in the western United States

In this article we describe the current status and conservation of interior (potamodromous) Redband Trout Oncorhynchus mykiss sspp. throughout its range in the western United States using extant data and expert opinion provided by fish managers. Redband Trout historically occupied 60,295 km of stream habitat and 152 natural lakes. Currently, Redband Trout occupy 25,417 km of stream habitat (42% of their historical range) and 124 lakes or reservoirs. Nonhybridized populations are assumed to occupy 11,695 km (46%) of currently occupied streams; however, fish from only 4,473 km (18%) have been genetically tested. Approximately 47% of the streams occupied by Redband Trout occur on private land, 45% on government lands, and 8% in protected areas. A total of 210 Redband Trout populations, occupying 15,252 km of stream habitat (60% of the current distribution) and 95,158 ha of lake habitat (52%), are being managed as “conservation populations.” Most conservation populations have been designated as weakly to strongly connected metapopulations (125; 60%) and occupy much more stream length (14,112 km; 93%) than isolated conservation populations (1,141 km; 7%). The primary threats to Redband Trout include invasive species, habitat degradation and fragmentation, and climate change. Although the historical distribution of interior Redband Trout has declined dramatically, we conclude that the species is not currently at imminent risk of extinction because it is still widely distributed with many populations isolated by physical barriers and active conservation efforts are occurring for many populations. However, the hybridization status of many populations has not been well quantified, and introgression may be more prevalent than documented here. We recommend (1) collecting additional genetic data and estimating distribution and abundance by means of a more rigorous spatial sampling design to reduce uncertainties, (2) collecting additional information to assess and predict the impacts of climate on populations, and (3) continuing to use this database to evaluate the status of Redband Trout and inform conservation efforts through time.

North American Journal of Fisheries Management↗

USGS2010

Estimation and modeling of electrofishing capture efficiency for fishes in wadeable warmwater streams

Stream fish managers often use fish sample data to inform management decisions affecting fish populations. Fish sample data, however, can be biased by the same factors affecting fish populations. To minimize the effect of sample biases on decision making, biologists need information on the effectiveness of fish sampling methods. We evaluated single-pass backpack electrofishing and seining combined with electrofishing by following a dual-gear, mark–recapture approach in 61 blocknetted sample units within first- to third-order streams. We also estimated fish movement out of unblocked units during sampling. Capture efficiency and fish abundances were modeled for 50 fish species by use of conditional multinomial capture–recapture models. The best-approximating models indicated that capture efficiencies were generally low and differed among species groups based on family or genus. Efficiencies of single-pass electrofishing and seining combined with electrofishing were greatest for Catostomidae and lowest for Ictaluridae. Fish body length and stream habitat characteristics (mean cross-sectional area, wood density, mean current velocity, and turbidity) also were related to capture efficiency of both methods, but the effects differed among species groups. We estimated that, on average, 23% of fish left the unblocked sample units, but net movement varied among species. Our results suggest that (1) common warmwater stream fish sampling methods have low capture efficiency and (2) failure to adjust for incomplete capture may bias estimates of fish abundance. We suggest that managers minimize bias from incomplete capture by adjusting data for site- and species-specific capture efficiency and by choosing sampling gear that provide estimates with minimal bias and variance. Furthermore, if block nets are not used, we recommend that managers adjust the data based on unconditional capture efficiency.

North American Journal of Fisheries Management↗