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At least 1,153 records · Page 64Linked to original sources
USGS1989

Growth and fatbody cycles in feral populations of the African clawed frog, Xenopus laevis (Pipidae), in California with comments on reproduction

Feral populations of the African clawed frog (Xenopus laevis) exist in several areas of southern California. By following the first cohort of progeny produced by African clawed frogs at a recently colonized site, data on the growth rates and age at first maturity were obtained in field conditions. Females reached maturity at an earlier age than males, grew faster than males, and attained body lengths up to 25% larger than males. Larger females were capable of producing larger numbers of eggs than small females and, therefore, had greater reproductive potential. The relatively stable ambient temperatures of southern California contributed to the possibility of reproduction of clawed frogs during all but the coolest periods of the year. Cycles detected in the mass of fatbodies suggested that nutrients were mobilized from fat prior to and during ovulation. The amount of fat in females varied widely, but fat in males tended to accumulate as the males grew during the study period.

Southwestern Naturalist↗
USGS1999

Predicting chick survival and productivity of Roseate Terns from data on early growth

Early growth of Roseate Tern (Sterna dougallii) chicks is a strong predictor of chick survival and hence of productivity. We developed discriminant functions to predict chick survival from body-masses measured during the first 3 days of life. Productivity is estimated by assuming that almost all A-chicks (first-hatched in each brood) survive to fledging, and using the discriminant functions to predict survival of B-chicks (second-hatched in each brood). A relation between survival rates and classification rates is derived, allowing discriminant function results to be used in predicting survival rates. In the absence of predation, the resulting estimates of chick survival and productivity are almost as good as those obtained by more intensive methods, but require much less effort and much less disturbance. This approach might be useful for other seabird species in which chick survival is determined primarily by parental performance.

Waterbirds↗
USGS2008

Long-term trends in breeding birds in an old-growth Adirondack forest and the surrounding region

Breeding bird populations were sampled between 1954 and 1963, and 1990 and 2000 in an old-growth forest, the Natural Area of Huntington Wildlife Forest (HWF), in the Adirondack Mountains of New York. Trends were compared with data from regional North American Breeding Bird Surveys (BBS) and from a forest plot at Hubbard Brook Experimental Forest, New Hampshire. Trends for 22 species in the HWF Natural Area were negative, eight were positive, and one was zero; 20 were significant. Fifteen of 17 long-distance migrants declined, whereas 7 of 14 short-distance migrants and permanent residents declined. Most (74%) HWF Natural Area species, despite differences in sampling periods and local habitat features, matched in sign of trend when compared to Adirondack BBS routes, 61% matched northeastern BBS routes, and 71% matched eastern United States BBS routes, while 66% matched Hubbard Brook species. The agreement in population trends suggests that forest interior birds, especially long-distance migrants, are affected more by regional than local factors. The analysis indicated that bird trends generated from BBS routes may not be as biased toward roads as previously suggested.

Wilson Journal of Ornithology↗
USGS2003

Comment on "Evaluation of X-ray diffraction methods for determining the crystal growth mechanisms of clay minerals in mudstones, shales and slates," by L. N. Warr and D. R. Peacor

A recent paper by Warr and Peacor (2002) suggested that our use of the Bertaut-Warren-Averbach technique (MudMaster computer program) for studying changes in crystallite thickness distributions (CTDs) of clay minerals during diagenesis and very low-grade metamorphism is not reliable because it is dependent on many variables which can not be fully controlled. Furthermore, the authors implied that the measured shapes of CTDs cannot be used with confidence to deduce crystal growth mechanisms and histories for clays, based on our CTD simulation approach (using the Galoper computer program). We disagree with both points, and show that the techniques are powerful, reliable and useful for studying clay mineral alteration in rocks. ?? 2003 Schweiz. Mineral. Petrogr. Ges.

Schweizerische Mineralogische und Petrographische ↗
USGS2005

Reserve growth of the world's giant oil fields

Analysis of estimated total recoverable oil volume (field size) of 186 well-known giant oil fields of the world (>0.5 billion bbl of oil, discovered prior to 1981), exclusive of the United States and Canada, demonstrates general increases in field sizes through time. Field sizes were analyzed as a group and within subgroups of the Organization of Petroleum Exporting Countries (OPEC) and non-OPEC countries. From 1981 through 1996, the estimated volume of oil in the 186 fields for which adequate data were available increased from 617 billion to 777 billion bbl of oil (26%). Processes other than new field discoveries added an estimated 160 billion bbl of oil to known reserves in this subset of the world's oil fields. Although methods for estimating field sizes vary among countries, estimated sizes of the giant oil fields of the world increased, probably for many of the same reasons that estimated sizes of oil fields in the United States increased over the same time period. Estimated volumes in OPEC fields increased from a total of 550 billion to 668 billion bbl of oil and volumes in non-OPEC fields increased from 67 billion to 109 billion bbl of oil. In terms of percent change, non-OPEC field sizes increased more than OPEC field sizes (63% versus 22%). The changes in estimated total recoverable oil volumes that occurred within three 5-year increments between 1981 and 1996 were all positive. Between 1981 and 1986, the increase in estimated total recoverable oil volume within the 186 giant oil fields was 11 billion bbl of oil; between 1986 and 1991, the increase was 120 billion bbl of oil; and between 1991 and 1996, the increase was 29 billion bbl of oil. Fields in both OPEC and non-OPEC countries followed trends of substantial reserve growth.

Conference Paper↗
USGS2007

Bedrock aquifers and population growth in the Denver Basin, Colorado, USA

The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills aquifers. The number of bedrock wells has increased from 12,000 in 1985 to over 33,700 in 2001 and the withdrawal of groundwater has caused water level declines in excess of 75 meters. Water level declines now range from 3 to 12 meters per year in the critical Arapahoe Aquifer. The groundwater supplies were once thought to be sufficient for 100 years but there is concern that they may be depleted in 10 to 15 years in areas on the west side of the basin. Groundwater is being mined from the aquifer system because the withdrawal through wells exceeds the rate of recharge. Increased groundwater withdrawal will cause further water level declines, increased costs to pump groundwater, and reduced yield from existing wells. In the Denver Basin, hydrologists have some capability to monitor declines in water levels for the Arapaho Aquifer, but generally have a limited ability to monitor water use. More complete and accurate water use data are needed to predict groundwater longevity for the Arapahoe Aquifer. The life of the Arapahoe Aquifer can be extended with artificial recharge using imported surface water, water reuse, restrictions on lawn watering, well permit restrictions and other conservation measures. Availability of groundwater may limit growth in the Denver Basin over the next 20 years unless residents are willing to pay for additional new sources of supply.

Episodes↗
USGS2012

Genetic differences in growth, migration, and survival between hatchery and wild steelhead and Chinook salmon: Introduction and executive summary

This report presents results of studies testing for genetically based differences in performance (growth, migration, and survival) between hatchery and wild populations of steelhead and Chinook salmon (Project Number 90-052). The report is organized into 10 chapters with a general study introduction preceding the first chapter. A growing body of data shows that domestication and a resulting loss of fitness for natural rearing occur in hatchery populations of anadromous salmonids; however, the magnitude of domestication will vary among species and hatchery programs. Better information on domestication is needed to accurately predict the consequences when hatchery and wild fish interbreed. The intent of hatchery supplementation is to increase natural production through introduction of hatchery fish into natural production areas. The goal of this study was to provide managers with information on the genetic risks of hatchery supplementation to wild populations of Columbia River Basin summer steelhead and spring Chinook salmon.

Book chapter↗
USGS2014

Population dynamics of bowfin in a south Georgia reservoir: latitudinal comparisons of population structure, growth, and mortality

The objectives of this study were to evaluate the population dynamics of bowfin (Amia calva) in Lake Lindsay Grace, Georgia, and to compare those dynamics to other bowfin populations. Relative abundance of bowfin sampled in 2010 in Lake Lindsay Grace was low and variable (mean±SD; 2.7±4.7 fish per hour of electrofishing). Total length (TL) of bowfin collected in Lake Lindsay Grace varied from 233–683 mm. Age of bowfin in Lake Lindsay Grace varied from 0–5 yr. Total annual mortality (A) was estimated at 68%. Both sexes appeared to be fully mature by age 2 with gonadosomatic index values above 8 for females and close to 1 for males. The majority of females were older, longer, and heavier than males. Bowfin in Lake Lindsay Grace had fast growth up to age 4 and higher total annual mortality than the other populations examined in this study. A chi-square test indicated that size structure of bowfin from Lake Lindsay Grace was different than those of a Louisiana population and two bowfin populations from the upper Mississippi River. To further assess bowfin size structure, we proposed standard length (i.e., TL) categories: stock (200 mm, 8 inches), quality (350 mm, 14 inches), preferred (460 mm, 18 inches), memorable (560 mm, 22, inches), and trophy (710 mm, 28 inches). Because our knowledge of bowfin ecology is limited, additional understanding of bowfin population dynamics provides important insight that can be used in management of bowfin across their distribution.

Georgia↗
USGS1993

Growth and survival of Mountain Plovers

Growth and survival rates of Mountain Plovers ( Charadrius montanus ) were monitored using radiotelemetry from hatching until birds left the breeding grounds on the Pawnee National Grassland, Weld County, Colorado. Chick weights increased logarithmically ( r ) = 0.961) and tarsus length linearly ( r = 0.948) with age. Using the average fledgling weight of 69.8 g and an age/weight regression we predicted that the average age at fledging was 36 d. Fourteen Mountain Plover nests each had three effs; an average of 2.6 eggs hatched in seven nests, whereas remaining nests were lost to predation, storms, or trampling by a cow. Twenty-four adult Mountain Plovers were monitored for 275 telemetry days with no mortalities. Twenty flightless chicks had a calculated daily survival rate of 0.979 for 233 telemetry-days. Mortalities of flightless chicks were due to predation or unknown causes. The daily survival rate predicted that 1.2 of the 2.6 chicks hatched per nest lived to fly. Eight fledged chicks were monitored for 74 telemetry-days, with a daily survival rate of 0.974. Mortalities of fledglings were all attributed to predation. The combined survival rates predicted that 0.7 or the 2.6 hatched chicks lived to leave the nesting area. Survival rates of flightless chicks were similar to those reported 20 yr ago, implying that recent declines in Mountain Plover numbers on the continent are not attributable to either longer-term declines in nesting productivity or phenomena occurring at non-breeding locales.

Journal of Field Ornithology↗
USGS2009

Age, growth, mortality, and reproduction of Roughtongue bass, Pronotogrammus martinicensis 9Serranidae), in the northeastern Gulf of Mexico

The inaccessibility of outer continental shelf reefs has made it difficult to investigate the biology of Pronotogrammus martinicensis, a small sea bass known to be numerous and widely distributed in such habitat. This study takes advantage of a series of cruises in the northeastern Gulf of Mexico that collected 1,485 individuals. Fish were collected over or in the vicinity of reef habitats with hook and line, otter trawl, and rotenone. We present a preliminary validation of an otolith ageing method and report that P. martinicensis reached a maximum size of 143 mm standard length (SL), grew to about 50% of this size within their first year, and lived to a maximum age of 15 yr. Size at age data (n = 490) fitted to the von Bertalanffy growth model yielded the predictive equation: SLt = 106.3(1 2 e [20.641{t20.646}]), where t = age in years. Gonad histology (n = 333) was examined to confirm that P. martinicensis is a protogynous, monandric hermaphrodite. We found no evidence of simultaneous hermaphroditism, which had been tentatively proposed in a previous study. Most P. martinicensis matured as females in their second year (age 1), primary oocytes developed asynchronously into secondary oocytes, and females were batch spawners. Males were postmaturational. Seminiferous tissue formed as early as age 1, but, although the rate of sex change is unknown, most fish did not function as a male until age 3 or age 4. These data provide age-based benchmarks of a common reef fish species living on the outer continental shelf of the tropical western North Atlantic Ocean.

Gulf of Mexico↗
USGS2007

Economic Growth and Landscape Change

Prato and Fagre offer the first systematic, multi-disciplinary assessment of the challenges involved in managing the Crown of the Continent Ecosystem (CCE), an area of the Rocky Mountains that includes northwestern Montana, southwestern Alberta, and southeastern British Columbia. The spectacular landscapes, extensive recreational options, and broad employment opportunities of the CCE have made it one of the fastest growing regions in the United States and Canada, and have lead to a shift in its economic base from extractive resource industries to service-oriented recreation and tourism industries. In the process, however, the amenities and attributes that draw people to this “New West” are under threat. Pastoral scenes are disappearing as agricultural lands and other open spaces are converted to residential uses, biodiversity is endangered by the fragmentation of fish and wildlife habitats, and many areas are experiencing a decline in air and water quality. Sustaining Rocky Mountain Landscapes provides a scientific basis for communities to develop policies for managing the growth and economic transformation of the CCE without sacrificing the quality of life and environment for which the land is renowned. This forthcoming edited volume focuses on five aspects of sustaining mountain landscapes in the CCE and similar regions in the Rocky Mountains. The five aspects are: 1) how social, economic, demographic and environmental forces are transforming ecosystem structure and function, 2) trends in use and conditions for human and environmental resources, 3) activating science, policy and education to enhance sustainable landscape management, 4) challenges to sustainable management of public and private lands, and 5) future prospects for achieving sustainable landscapes.

Book chapter↗
USGS1998

Noninvasive monitoring of fetal growth and development in the Siberian polecat (Mustela eversmanni)

The Siberian polecat (Mustela eversmanni) is the preferred species to assess procedures and establish normative values for application in the related and endangered black-footed ferret (Mustela nigripes). This study was undertaken to physically, ultrasonographically, and radiographically evaluate fetal development in a spontaneously breeding captive Siberian polecat population. Ultrasonographically, fetal sac enlargement allowed presumptive preg nancy detection as early as 12 days of gestation, the fetal pole was the first definitive sign of pregnancy at about 18 days of gestation, when the fetal heart beat also appeared, and definitive pregnancy detection by ultrasound was essentially 100% accurate after 18 days. The estimation of fetal number by ultrasound was less reliable than by radiography, as it is in other litter-bearing species. Crown-rump growth, organ differentiation, and calcification patterns resembled those of domestic carnivores except that comparable developmental stages in polecats occurred at dispro portionately later times, suggesting that young Siberian polecats are delivered in a less developed state. Careful palpation permitted detection of pregnancy after day 17 but with less certainty than with ultrasound. Radiographic evaluation was insensitive and of limited value for pregnancy detection until near term. Litter number and fetal detail were difficult to assess until ossification could be observed, 3-6 days before parturition.

Journal of Zoo and Wildlife Medicine↗
USGS1982

Growth faulting and salt diapirism; their relationship and control in the Carolina Trough, eastern North America

The Carolina Trough is a long, linear, continental margin basin off eastern North America. Salt domes along the trough's seaward side show evidence of active diapirism and a normal growth fault along its landward side has been continually active at least since the end of the Jurassic. This steep fault extends to a strong reflection event at about 11 km depth that may represent the top of a salt layer. We infer that faulting is caused by seaward flow of salt from the deep part of the trough into domes, thereby removing support for the overlying block of sedimentary rock. Diapirs off eastern North America seem to be concentrated in the Carolina Trough and Scotian Basin, where basement seems to be thinner than in other basins off eastern North America, south of Newfo ndland. Thinner basement, probably due to greater stretching during rifing, may have resulted in earlier subsidence below sea level, a longer life for the salt evaporating pans in these basins, and thus a thicker salt layer, which would be more conducive to diapirism.

Book chapter↗
USGS1987

Roosevelt elk density in old-growth forests of Olympic National Park

We explored the feasibility of censusing Roosevelt elk from a helicopter in the dense old growth forests of Olympic National Park. WA. Mean observed densities ranged from 8.0-11.6 elk/km 2 , with coefficients of variation averaging 19.9 percent. A provisional sightability factor of 74 percent suggested that actual mean densities ranged from 10.8-16.0 elk/km 2 . We conclude that estimates of elk density probably could be refined, but not without a cost and level of disturbance in the park that seem unwarranted at present. The effort required to conduct the 18 counts made during 1985-86 was substantial. For almost every successful count an unsuccessful attempt was made. These included aborting five flights when counting conditions turned sour. Actual counting time for the successful flights was 15.7 and 16.2 hours in 1985 and 1986, respectively. Additional flight time for traveling to and from the census zones, refueling, and aborted attempts added 12.2 and 10.8 hours for the respective years

Washington↗
USGS2003

Survival and growth of Atlantic white cedar plantings in Louisiana and Missisippi

Atlantic white cedar (cedar) is a native forest dominant in isolated areas throughout the Atlantic Coastal Plain and in a portion of the Gulf of Mexico Coastal Plain. Although the range of this species extends west to southern Mississippi, stands are uncommon in this area. In addition, most of the existing Mississippi stands are privately owned and afforded little long-term protection. To examine the feasibility of planting cedar at the western edge of its range and to determine if the species is a viable replacement for pine in wet areas, one-year-old seedlings were planted at three pine plantation sites in Louisiana and wildings at two bay-head locations in Mississippi. Overall, survival was high (87%), especially in the Louisiana sites, and after 10 growing seasons the trees averaged 5.3 m in height and 6.1 cm in diameter. This growth rate compared favorably with cypress and slash pine of other studies. The results of this study have shown that cedar can be a viable choice for restoration efforts or forest product plantings.

Louisiana, Mississippi↗
USGS2019

Age and growth of cottonwood trees along the Missouri River, North Dakota

The relict plains cottonwood ( Populus deltoides subsp. monilifera ) forest along the Missouri River between Lakes Sakakawea and Oahe includes trees as large as two meters in diameter. We cored 24 of these trees to determine their age and suitability for flow reconstruction. Because most of the trees were rotten in the center, we developed a method to estimate the date of the center ring that accounts for the increase in ring width toward the center. Estimated center ring dates were as early as 1806. Cottonwood growth at a dry site was correlated with April–August flow prior to construction of Lake Sakakawea (1929–1953; r = 0.50, P = 0.011) and to Palmer Drought Severity Index following construction (1954–2014; r = 0.38, P = 0.003). We conclude that cottonwood rings can be used to improve reconstructions of Missouri River flows before the beginning of stream-gage records.

North Dakota↗