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At least 1,045 records · Page 58Linked to original sources
USGS2011

Regional skew for California, and flood frequency for selected sites in the Sacramento-San Joaquin River Basin, based on data through water year 2006

Improved flood-frequency information is important throughout California in general and in the Sacramento-San Joaquin River Basin in particular, because of an extensive network of flood-control levees and the risk of catastrophic flooding. A key first step in updating flood-frequency information is determining regional skew. A Bayesian generalized least squares (GLS) regression method was used to derive a regional-skew model based on annual peak-discharge data for 158 long-term (30 or more years of record) stations throughout most of California. The desert areas in southeastern California had too few long-term stations to reliably determine regional skew for that hydrologically distinct region; therefore, the desert areas were excluded from the regional skew analysis for California. Of the 158 long-term stations used to determine regional skew, 145 have minimally regulated annual-peak discharges, and 13 stations are dam sites for which unregulated peak discharges were estimated from unregulated daily maximum discharge data furnished by the U.S. Army Corp of Engineers. Station skew was determined by using an expected moments algorithm (EMA) program for fitting the Pearson Type 3 flood-frequency distribution to the logarithms of annual peak-discharge data. The Bayesian GLS regression method previously developed was modified because of the large cross correlations among concurrent recorded peak discharges in California and the use of censored data and historical flood information with the new expected moments algorithm. In particular, to properly account for these cross-correlation problems and develop a suitable regression model and regression diagnostics, a combination of Bayesian weighted least squares and generalized least squares regression was adopted. This new methodology identified a nonlinear function relating regional skew to mean basin elevation. The regional skew values ranged from -0.62 for a mean basin elevation of zero to 0.61 for a mean basin elevation of 11,000 feet. This relation between skew and elevation reflects the interaction of snow with rain, which increases with increased elevation. The equivalent record length for the new regional skew ranges from 52 to 65 years of record, depending upon mean basin elevation. The old regional skew map in Bulletin 17B, published by the Hydrology Subcommittee of the Interagency Advisory Committee on Water Data (1982), reported an equivalent record length of only 17 years. The newly developed regional skew relation for California was used to update flood frequency for the 158 sites used in the regional skew analysis as well as 206 selected sites in the Sacramento-San Joaquin River Basin. For these sites, annual-peak discharges having recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years were determined on the basis of data through water year 2006. The expected moments algorithm was used for determining the magnitude and frequency of floods at gaged sites by using regional skew values and using the basic approach outlined in Bulletin

Scientific Investigations Report↗
USGS1986

Applications of U.S. Geological Survey digital cartographic products, 1979-1983

The U.S. Geological Survey prepares and distributes fundamental, multipurpose cartographic data to a wide range of users throughout the United States. Recognizing that traditional cartographic procedures will eventually be replaced by digital techniques, the USGS is now actively developing computer-based methods to produce digital cartographic products. The digital cartographic products currently being developed parallel the traditional map-based information but have the advantage that they can be used in a computer environment. The digital cartographic products include: 1) digital elevation models (DEM's), 2) digital land use and land cover data, and 3) digital line graphs (DLG's). In addition, digital terrain tapes (DTT's) that were developed by the Defense Mapping Agency are currently available through the USGS. As with conventional map products, the digital products are suitable for efficient application to a variety of problems.

Bulletin↗
USGS2005

Growth history of oil reserves in major California oil fields during the twentieth century

Oil reserves in 12 of California's 52 giant fields (fields with estimated recovery > 100 million barrels of oil) have continued to appreciate well past the age range at which most fields cease to show significant increases in ultimate recovery. Most of these fields were discovered between 1890 and 1920 and grew to volumes greater than 500 million barrels in their first two decades. Growth of reserves in these fields accelerated in th e1950s and 1960s and is mostly explained by application of secondary and tertiary recovery technicques, primarily waterflooding and thermal recovery. The remaining three-fourths of California's giant fields show a pattern of growth in which fields cease to grow significantly by 20-30 years following recovery. virtually all of these fields have estimated ultimate recoveries less than about 500 million barrels and most are in the 100-200 million barrel range. Three of six offshore giant fields, all discovered between 1966 and 1981, have shown decreases in their estimated ultimate sizes within about the first decade after production began, presumably because production volumes ailed to match initial projections. The data suggest that: 1. Only fields that attain an estimated ultimate size of several hundred million barrels shortly after discovery and have geologic characterisics that make them suceptible to advanced recovery techniques are likely to show substantial late growth. 2. Offshore fields are less likely to show significant growth, probably because projections based on modern seismic reflection and reservoir test data are unlikely to underestimate the volume of oil in the field. 3. Secondary and tertiary recovery programs rather than field extensions or new pool discoveries are responsible for most of the significant growth of reserves in California. 4. field size data collected ove rmany decades provide a more comprehensive context for inferring reasons for reserve appreciation than shorter data series such as the Oil and Gas Integrated Field file (OGIFF) from the U.S. Department of Energy's Energy Information Administration (EIA). 5. Efforts to project future growth in California fields, and perhaps fields in other regions, should focus on evaulating the potential for enhanced recovery in fields with current estimated ultimate recoveries of about 250-500 million barrels. 6. By analogy with oil, attempts to project growth in gas reservoirs, in California and perhaps elsewhere, should focus on larger fields with lower permeability reservoirs where advances in recovery technology, such as perhaps horizontal drilling, are more likely to add substantial reserves.

Bulletin↗
USGS2003

Sediment-hosted copper deposits of the world: Deposit models and database

Introduction This publication contains four descriptive models and four grade-tonnage models for sediment hosted copper deposits. Descriptive models are useful in exploration planning and resource assessment because they enable the user to identify deposits in the field and to identify areas on geologic and geophysical maps where deposits could occur. Grade and tonnage models are used in resource assessment to predict the likelihood of different combinations of grades and tonnages that could occur in undiscovered deposits in a specific area. They are also useful in exploration in deciding what deposit types meet the economic objectives of the exploration company. The models in this report supersede the sediment-hosted copper models in USGS Bulletin 1693 (Cox, 1986, and Mosier and others, 1986) and are subdivided into a general type and three subtypes. The general model is useful in classifying deposits whose features are obscured by metamorphism or are otherwise poorly described, and for assessing regions in which the geologic environments are poorly understood. The three subtypes are based on differences in deposit form and environments of deposition. These differences are described under subtypes in the general model. Deposit models are based on the descriptions of geologic environments and physical characteristics, and on metal grades and tonnages of many individual deposits. Data used in this study are presented in a database representing 785 deposits in nine continents. This database was derived partly from data published by Kirkham and others (1994) and from new information in recent publications. To facilitate the construction of grade and tonnage models, the information, presented by Kirkham in disaggregated form, was brought together to provide a single grade and a single tonnage for each deposit. Throughout the report individual deposits are defined as being more than 2,000 meters from the nearest adjacent deposit. The deposit models are presented here as a PDF file. The database can be most conveniently read in FileMaker Pro. For those who do not have the FileMaker application, Microsoft-Excel, tab-delimited-ASCII and comma-separated-value files are included. The reader may be interested in a similar publication on porphyry copper deposits (Singer and others, 2005) also available online. The Google Earth image is not intended to be viewed at the highest possible magnification because the resolution of the database is plus or minus two kilometers. At extreme zoom settings, the deposit locations may not coincide with the Google-Earth images of the mine workings.

Open-File Report↗
USGS1999

Obtaining environmental measures to facilitate vertebrate habitat modeling

Published literature generally lacks habitat information needed to adequately model the habitats of most wildlife species at large scales (>1:100,000). We searched in primary and secondary literature for occurrence of several potentially useful habitat measures for 20 species of interest to the Idaho Department of Fish and Game. We found adequate information for modeling only the habitats of certain game species and species of special interest. We suggest that many more researchers could collect simple habitat information regarding vegetation composition and structure, topographic features, soils, temperature, and distance to special landscape features such that current research expenses would not be increased significantly. We recommend that habitat data be consistently reported in peer-reviewed literature or deposited into a central data repository. This will not only help fill the gaps in our current knowledge of wildlife but also place it in a format that is readily accessible by the scientific community.

Wildlife Society Bulletin↗
USGS2009

Gap Analysis -A geographic approach to planning for biological diversity

The Mission of the Gap Analysis Project (GAP) is to promote conservation by providing broad geographic information on biological diversity to resource managers, planners, and policy makers who can use the information to make informed decisions. As part of the National Biological Information Infrastructure (NBII) —a collaborative program to provide increased access to data and information on the nation’s biological resources--GAP data and analytical tools have been used in hundreds of applications: from basic research to comprehensive state wildlife plans; from educational projects in schools to ecoregional assessments of biodiversity. The challenge: keeping common species common means protecting them BEFORE they become threatened. To do this on a state or regional basis requires key information such as land cover descriptions, predicted distribution maps for native animals, and an assessment of the level of protection currently given to those plants and animals. GAP works cooperatively with Federal, state, and local natural resource professionals and academics to provide this kind of information. GAP activities focus on the creation of state and regional databases and maps that depict patterns of land management, land cover, and biodiversity. These data can be used to identify “gaps” in conservation--instances where an animal or plant community is not adequately represented on the existing network of conservation lands. GAP is administered through the U.S. Geological Survey. Through building partnerships among disparate groups, GAP hopes to foster the kind of collaboration that is needed to address conservation issues on a broad scale.

GAP Bulletin↗
USGS2024

Real-time lava flow forecasting during the 2022 Mauna Loa eruption response

On November 27, 2022, Mauna Loa (Hawai‘i) erupted for the first time in 38 years, initially producing lava flows that covered the floor of its summit caldera, Moku‘āweoweo. Over the first 12 h following the summit eruption, four main fissures opened on Mauna Loa’s Northeast Rift Zone, with “fissure 3” quickly becoming the dominant source of lava flows. For the next 12 days, fissure 3 produced a 19-km-long lava flow to the north, crossing the Mauna Loa Weather Observatory access road and coming within 2.8 km of inundating the Daniel K. Inouye Highway (Saddle Road). Within 40 min of fissure 3 opening, inundation modeling efforts had begun. For the duration of the eruption, the computational fluid dynamics model Lava2d was run in real time, using flow front locations and other field observations to make sequential forecast improvements, eventually producing a set of models which accurately predicted the routing and arrival times of lava from fissure 3. These models were used to inform timing estimates of possible future inundation of the Saddle Road. As the eruption progressed, almost 4000 Lava2d models were made using high-performance computing resources, providing critical information on uncertainty in multi-week forecasts. To our knowledge, this was the first ever real-time physics-based ensemble lava flow modeling and forecasting effort. Here, we present a chronology of these real-time efforts, focusing on the successes and limitations of this approach.

Hawaii↗
USGS1982

Applications of Landsat imagery to problems of petroleum exploration in Qaidam Basin, China

Tertiary and Quaternary nonmarine, petroleum-bearing sedimentary rocks in the Qaidam basin of remote western China have been extensively deformed by compressive forces. These forces created many folds which are current targets of Chinese exploration programs. Manual techniques of image analysis and interpretation were applied to computer-enhanced Landsat images of the western part of the Qaidam basin in an effort to evaluate the contributions of Landsat imagery in defining the geologic conditions of the basin and to determine its usefulness as an exploration tool in the region. Most success was realized in defining the structural geologic setting of the region. Image-derived interpretations of folds, strike-slip faults, thrust faults, normal or reverse faults, and fractures compared very favorably, in terms of locations and numbers mapped, with Chinese data compiled from years of extensive field mapping. The image studies resulted in the identification of at least one subsurface fold that had not been detected by field mapping. The results of this study have direct exploration significance. Many potential hydrocarbon trapping structures were precisely located and information was obtained that may have significant implications with respect to fluid migration or attempts to locate offset reservoirs and buried folds. In addition, the orientations of major structural trends defined from Landsat imagery correlate well with those predicted for the area based on global tectonic theory. These correlations suggest that similar orientations exist in the eastern half of the basin where folded rocks are mostly obscured by unconsolidated surface sediments and where limited exploration has occurred.

Qaidam Basin↗
USGS1978

Understanding natural systems; a perspective for land-use planning in Appalachian Kentucky

An eight-county area at the headwaters of the Kentucky River has been designated the Kentucky River Area Development District (KRADD) by the Appalachian Regional Commission. The objective of the project described in this report has been to provide materials to KRADD planners in a format and containing terminology usable by local people untrained in earth science. Experimental maps (not included in this report) have been prepared largely from preexisting data. Time and cost limitations required a regional analysis as well as somewhat more detailed examples of selected localities. Most of the maps produced to meet these needs show the abundance and distribution of naturally occurring materials and the areas affected by various geomorphic processes. Three types of maps, showing current land use, slope, and flood-prone areas, present both basic and derived data directly applicable to specific land-use decisions. Basic map information on quality and quantity of surface and ground water, bedrock and surficial geology, and mineral fuels can be interpreted for a wide variety of current and potential uses. Texts accompanying the maps explain bedrock control of geomorphic processes, distribution and significance of surficial deposits, and hydrologic characteristics of the intricately dissected eastern Kentucky terrain. Within this conceptual framework, geomorphic processes and the landscape may be evaluated in humanly significant terms of low to high potential risk, thereby indicating both opportunities and limitations for land use.

Kentucky↗
USGS2023

Magnitude and frequency of floods on Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi, based on data through water year 2020

Accurate estimates of flood magnitude and frequency are needed to (1) optimize the design and location of infrastructure, including dams, culverts, bridges, industrial buildings, and highways, and (2) inform flood-zoning and flood-insurance studies. The U.S. Geological Survey (USGS), in cooperation with the State of Hawaiʻi Department of Transportation, estimated flood magnitudes for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEP) for unregulated streamgages in Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi, using data through water year 2020. Regression equations were developed to estimate flood magnitude and associated frequency at ungaged streams. This study improves upon a previous USGS flood-frequency report (Oki and others, 2010) by including more peak-flow data, implementing new statistical methods in flood-frequency analysis, and using updated techniques to estimate the regional-skewness coefficient (regional skew). Flood magnitude and frequency at 238 streamgages were estimated—following national guidelines established in Bulletin 17C (England and others, 2019)—by fitting annual peak-flow data to the Log-Pearson Type III distribution using the expected moments algorithm and the PeakFQ flood-frequency software. Potentially influential low outliers in the data were identified and removed using the Multiple Grubbs-Beck Test. An updated regional skew for Hawaiʻi was estimated using the Bayesian weighted least squares/Bayesian generalized least squares method. The updated regional skew employs a constant model for the five islands in the study area and has a value of −0.157 (mean square error of 0.212). Multiple linear regression techniques were used to develop regression equations that relate basin and climatic characteristics to peak flows at streamgages. The regression equations can be applied to estimate flood magnitude and frequency at ungaged sites. The study area was split into 10 regions—2 regions per island, generally following a leeward/windward division—containing from 9 to 49 streamgages each. The final regression equations for each region were determined with generalized least-squares analysis using the USGS weighted-multiple-linear regression (WREG) program. The standard error of prediction at the 1-percent AEP for the regression equations ranged from 18 to 164 percent; the pseudo coefficient of determination (pseudo-R2) at the 1-percent AEP ranged from 46 to 100 percent. The regression equations performed well for all regions except leeward Molokaʻi and southern Island of Hawaiʻi; for all other regions, the pseudo-R2 values ranged from about 75 to 100 percent. Compared to the regression equations developed by Oki and others (2010), the regression equations in this study generally showed modest improvements, although the magnitude of differences varied for each region. Peak-flow estimates at the 238 streamgages included in this study are improved by weighting the at-site statistics computed with PeakFQ and the predicted flows based on the regression equations. Results of this study—including the final peak-flow estimates at streamgages and the regional regression equations—are implemented in the USGS StreamStats web application (U.S. Geological Survey, 2023, StreamStats: https://streamstats.usgs.gov/ss/ ). StreamStats provides a consistent approach for obtaining peak-flow estimates at streamgages and for applying the regional regression equations for estimating peak flows at ungaged locations.

Hawaii↗
USGS1999

A comparison of sampling techniques to estimate number of wetlands

Service use annual estimates of the number of ponded wetlands to estimate duck production and establish duck hunting regulations. Sampling techniques that minimize bias may provide more reliable estimates of annual duck production. Using a wetland geographic information system (GIS), we estimated number of wetlands using standard counting protocol with belt transects and samples of square plots. Estimates were compared to the known number of wetlands in the GIS to determine bias. Bias in transect-derived estimates ranged from +67-87% of the known number of wetlands, compared to bias of +3-6% in estimates from samples of 10.24-km2 plots. We recommend using samples of 10.24-km2 plots stratified by wetland density to decrease bias.

Wildlife Society Bulletin↗
USGS2017

Polar bear attacks on humans: Implications of a changing climate

Understanding causes of polar bear (Ursus maritimus) attacks on humans is critical to ensuring both human safety and polar bear conservation. Although considerable attention has been focused on understanding black (U. americanus) and grizzly (U. arctos) bear conflicts with humans, there have been few attempts to systematically collect, analyze, and interpret available information on human-polar bear conflicts across their range. To help fill this knowledge gap, a database was developed (Polar Bear-Human Information Management System [PBHIMS]) to facilitate the range-wide collection and analysis of human-polar bear conflict data. We populated the PBHIMS with data collected throughout the polar bear range, analyzed polar bear attacks on people, and found that reported attacks have been extremely rare. From 1870–2014, we documented 73 attacks by wild polar bears, distributed among the 5 polar bear Range States (Canada, Greenland, Norway, Russia, and United States), which resulted in 20 human fatalities and 63 human injuries. We found that nutritionally stressed adult male polar bears were the most likely to pose threats to human safety. Attacks by adult females were rare, and most were attributed to defense of cubs. We judged that bears acted as a predator in most attacks, and that nearly all attacks involved ≤2 people. Increased concern for both human and bear safety is warranted in light of predictions of increased numbers of nutritionally stressed bears spending longer amounts of time on land near people because of the loss of their sea ice habitat. Improved conflict investigation is needed to collect accurate and relevant data and communicate accurate bear safety messages and mitigation strategies to the public. With better information, people can take proactive measures in polar bear habitat to ensure their safety and prevent conflicts with polar bears. This work represents an important first step towards improving our understanding of factors influencing human-polar bear conflicts. Continued collection and analysis of range-wide data on interactions and conflicts will help increase human safety and ensure the conservation of polar bears for future generations.

Wildlife Society Bulletin↗
USGS2000

Assessing factors that may predispose Minnesota farms to wolf predation on cattle

Wolf (Canis lupus) depredations on livestock cause considerable conflict and expense in Minnesota. Furthermore, claims are made that such depredations are fostered by the type of animal husbandry practiced. Thus, we tried to detect factors that might predispose farms in Minnesota to wolf depredations. We compared results of interviews with 41 cattle farmers experiencing chronic cattle losses to wolves (chronic farms) with results from 41 nearby matched farms with no wolf losses to determine farm characteristics or husbandry practices that differed and that therefore might have affected wolf depredations. We also used a Geographic Information System (GIS) to detect any habitat differences between the 2 types of farms. We found no differences between chronic and matched farms in the 11 farm characteristics and management practices that we surveyed, except that farms with chronic losses were larger, had more cattle, and had herds farther from human dwellings. Habitat types were the same around farms with and without losses. The role of proper carcass disposal as a possible factor predisposing farms to wolf depredations remains unclear

Wildlife Society Bulletin↗
USGS2016

A cellular automata downscaling based 1 km global land use datasets (2010–2100)

Global climate and environmental change studies require detailed land-use and land-cover(LULC) information about the past, present, and future. In this paper, we discuss a methodology for downscaling coarse-resolution (i.e., half-degree) future land use scenarios to finer (i.e., 1 km) resolutions at the global scale using a grid-based spatially explicit cellular automata (CA) model. We account for spatial heterogeneity from topography, climate, soils, and socioeconomic variables. The model uses a global 30 m land cover map (2010) as the base input, a variety of biogeographic and socioeconomic variables, and an empirical analysis to downscale coarse-resolution land use information (specifically urban, crop and pasture). The output of this model offers the most current and finest-scale future LULC dynamics from 2010 to 2100 (with four representative concentration pathway (RCP) scenarios—RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5) at a 1 km resolution within a globally consistent framework. The data are freely available for download, and will enable researchers to study the impacts of LULC change at the local scale.

Science Bulletin↗
USGS1957

Military geology in the United States sector of the European theater of operations during World War II

Geology, which was of far-reaching importance on the Western Front of World War I, played a less spectacular role during World War II in so far as the United States armies in Europe were concerned. The U. S. Army in the European Theater of Operations (ETO) used geologists in two capacities: (1) to make staff studies at the level of Theater Headquarters, and (2) as officer personnel in a water-supply unit. In the first category, only one group of seven geologists was employed, forming part of the Information Section, Intelligence Division, Office of the Chief Engineer, ETO. The products of this group consisted largely of regional and localized terrain (trafficability) studies that ranged geographically from the Normandy invasion beaches to Czechoslovakia. Problems of water supply, sources of road material, and many other questions of a geologic nature also arose. French geologists collaborated closely with the work of the section. As the campaign progressed, the Military Geology Unit of the U. S. Geological Survey made important contributions to the geologic intelligence of Germany.

Geological Society of America Bulletin↗
USGS2008

Testing small-aperture array analysis on well-located earthquakes, and application to the location of deep tremor

We have here analyzed local and regional earthquakes using array techniques with the double aim of quantifying the errors associated with the estimation of propagation parameters of seismic signals and testing the suitability of a probabilistic location method for the analysis of nonimpulsive signals. We have applied the zero-lag cross-correlation method to earthquakes recorded by three dense arrays in Puget Sound and Vancouver Island to estimate the slowness and back azimuth of direct P waves and S waves. The results are compared with the slowness and back azimuth computed from the source location obtained by the analysis of data recorded by the Pacific Northwest seismic network (PNSN). This comparison has allowed a quantification of the errors associated with the estimation of slowness and back azimuth obtained through the analysis of array data. The statistical analysis gives ??BP = 10?? and ??BS = 8?? as standard deviations for the back azimuth and ??SP = 0.021 sec/km and ??SS = 0.033 sec /km for the slowness results of the P and S phases, respectively. These values are consistent with the theoretical relationship between slowness and back azimuth and their uncertainties. We have tested a probabilistic source location method on the local earthquakes based on the use of the slowness estimated for two or three arrays without taking into account travel-time information. Then we applied the probabilistic method to the deep, nonvolcanic tremor recorded by the arrays during July 2004. The results of the tremor location using the probabilistic method are in good agreement with those obtained by other techniques. The wide depth range, of between 10 and 70 km, and the source migration with time are evident in our results. The method is useful for locating the source of signals characterized by the absence of pickable seismic phases.

Bulletin of the Seismological Society of America↗
USGS2007

Integrating a geographic information system, a scientific visualization system, and a precipitation model

Investigating natural, potential, and human-induced impacts on hydrologic systems commonly requires complex modeling with overlapping data requirements, plus massive amounts of one- to four-dimensional data at multiple scales and formats. Given the complexity of most hydrologic studies, the requisite software infrastructure must incorporate many components including simulation modeling and spatial analysis with a flexible, intuitive display. Integrating geographic information systems (GIS) and scientific visualization systems (SVS) provides such an infrastructure. This paper describes an integrated system consisting of an orographic precipitation model, a GIS, and an SVS. The results of this study provide a basis for improving the understanding of hydro-climatic processes in mountainous regions. An additional benefit of the integrated system, the value of which is often underestimated, is the improved ability to communicate model results, leading to a broader understanding of the model assumptions, sensitivities, and conclusions at a management level.Investigating natural, potential, and human-induced impacts on hydrologic systems commonly requires complex modeling with overlapping data requirements, plus massive amounts of one- to four-dimensional data at multiple scales and formats. Given the complexity of most hydrologic studies, the requisite software infrastructure must incorporate many components including simulation modeling and spatial analysis with a flexible, intuitive display. Integrating geographic information systems (GIS) and scientific visualization systems (SVS) provides such an infrastructure. This paper describes an integrated system consisting of an orographic precipitation model, a GIS, and an SVS. The results of this study provide a basis for improving the understanding of hydro-climatic processes in mountainous regions. An additional benefit of the integrated system, the value of which is often underestimated, is the improved ability to communicate model results, leading to a broader understanding of the model assumptions, sensitivities, and conclusions at a management level.

Water Resources Bulletin↗
USGS2003

Effect of analytical conditions in wavelength dispersive electron microprobe analysis on the measurement of strontium-to-calcium (Sr/Ca) ratios in otoliths of anadromous salmonids

The use of strontium-to-calcium (Sr/Ca) ratios in otoliths is becoming a standard method to describe life history type and the chronology of migrations between freshwater and seawater habitats in teleosts (e.g. Kalish, 1990; Radtke et al., 1990; Secor, 1992; Rieman et al., 1994; Radtke, 1995; Limburg, 1995; Tzeng et al. 1997; Volk et al., 2000; Zimmerman, 2000; Zimmerman and Reeves, 2000, 2002). This method provides critical information concerning the relationship and ecology of species exhibiting phenotypic variation in migratory behavior (Kalish, 1990; Secor, 1999). Methods and procedures, however, vary among laboratories because a standard method or protocol for measurement of Sr in otoliths does not exist. In this note, we examine the variations in analytical conditions in an effort to increase precision of Sr/Ca measurements. From these findings we argue that precision can be maximized with higher beam current (although there is specimen damage) than previously recommended by Gunn et al. (1992).

Fishery Bulletin↗