Estimates Of Population Numbers Research Articles

Fine-grained population mapping from coarse census counts and open geodata

Fine-grained population maps are needed in several domains, like urban planning, environmental monitoring, public health, and humanitarian operations. Unfortunately, in many countries only aggregate census counts over large spatial units are collected, moreover, these are not always up-to-date. We present Pomelo, a deep learning model that employs coarse census counts and open geodata to estimate fine-grained population maps with 100,m ground sampling distance. Moreover, the model can also estimate population numbers when no census counts at all are available, by generalizing across countries. In a series of experiments for several countries in sub-Saharan Africa, the maps produced with Pomelo are in good agreement with the most detailed available reference counts: disaggregation of coarse census counts reaches R^2 values of 85–89%; unconstrained prediction in the absence of any counts reaches 48–69%.

Comparison of three methods of estimating the population size of an arboreal mammal in a fragmented rural landscape

Abstract Context Precise and accurate estimates of animal numbers are often essential for population and epidemiological models, as well as for guidance for population management and conservation. This is particularly true for threatened species in landscapes facing multiple threats. Estimates can be derived by different methods, but the question remains as to whether these estimates are comparable. Aims We compared three methods to estimate population numbers, namely, distance sampling, mark–recapture analysis, and home-range overlap analysis, for a population of the iconic threatened species, the koala (Phascolarctos cinereus). This population occupies a heavily fragmented forest and woodland habitat on the Liverpool Plains, north-western New South Wales, Australia, on a mosaic of agricultural and mining lands. Key resultsAll three methods produced similar estimates, with overlapping confidence intervals. Distance sampling required less expertise and time and had less impact on animals, but also had less precision; however, future estimates using the method could be improved by increasing both the number and expertise of the observers. ConclusionsWhen less intrusive methods are preferred, or fewer specialised practitioners are available, we recommend distance sampling to obtain reliable estimates of koala numbers. Although its precision is lower with a low number of sightings, it does produce estimates of numbers similar to those from the other methods. However, combining multiple methods can be useful when other material (genetic, health and demographic) is also needed, or when decisions based on estimates are for high-profile threatened species requiring greater confidence. We recommend that all estimates of population numbers, and their precision or variation, be recorded and reported so that future studies can use them as prior information, increasing the precision of future surveys through Bayesian analyses.

How to estimate population size in crocodylians? Population ecology of American crocodiles in Coiba Island as study case

AbstractReliable estimates of crocodylian population size are desirable for both understanding the ecology and natural history of species and developing sound conservation and management plans. However, choosing appropriate methods to estimate population numbers can be difficult due to the paucity of comprehensive analyses regarding their effectiveness, robustness, and applicability. We estimated the American crocodile population size in the southern tip of Coiba Island, Panama, using both spotlight surveys (Messel's and King's visible fraction estimations) and mark–recapture (POPAN formulation–superpopulation) methods. We assessed and compared the outcomes of these methods with the overall capture record for the study area from 2009 to 2013, evaluating their applicability, accuracy, strengths, and limitations. Using historical and current capture data, we defined a minimum population size of ~112 non‐hatchling animals in our study area, which was larger than both Messel's (19.00 ± 7.50 individuals) and King's (25.71 ± 7.25 individuals) population size estimates, revealing that these latter approaches clearly underestimate population numbers. We estimated a total population size that range between 147 and 257 individuals based on POPAN formulation grouping the data by sex and age groups as the most plausible population size of the American crocodile population in this area at the time. We analyzed and discussed sources of bias in population size estimations for all methods used in the present study, providing recommendations to minimize errors and improve estimations. Finally, we analyzed and compared population ecology attributes obtained in our study with what have been reported in other insular and coastal areas across the American crocodile range, increasing knowledge about the ecology of the species.

ESTIMATION OF POPULATION NUMBER VIA LIGHT ACTIVITIES ON NIGHT-TIME SATELLITE IMAGES

Abstract. Estimation and accurate assessment regarding population gets harder and harder day by day due to growth of world population in a fast manner. Estimating tendencies to settlements in cities and countries, socio-cultural development and population numbers is quite difficult. In addition to them, selection and analysis of parameters such as time, work-force and cost seems like another difficult issue. In this study, population number is guessed by evaluating light activities in İstanbul via night-time images of Turkey. By evaluating light activities between 2000 and 2010, average population per pixel is obtained. Hence, it is used to estimate population numbers in 2011, 2012 and 2013. Mean errors are concluded as 4.14 % for 2011, 3.74 % for 2012 and 3.04 % for 2013 separately. As a result of developed thresholding method, mean error is concluded as 3.64 % to estimate population number in İstanbul for next three years.

Using simulations of past and present elephant (Loxodonta africana) population numbers in the Okavango Delta Panhandle, Botswana to improve future population estimates

An ability to reliably estimate population numbers, trends and densities of wildlife has a prominent role in conservation and management of wetlands. We use aerial surveys and simulation techniques to explore the results of past and present elephant population surveys in the Okavango Delta Panhandle, Botswana, and use these to propose a technique of simulation to improve counts in the future. Population numbers and density estimates from past survey results show large fluctuations, which are unlikely to come from reproduction. Reasons for such variations could be attributed to imprecision in survey techniques or may be because only part of the elephant range is being surveyed. Simulated surveys of hypothetical elephant populations were used to explore the effect of different survey techniques, spatial distributions of animals and spatial scale on the precision of aerial survey population estimates and trends. Our study reveals the usefulness of using simulations to test the reliability of survey data and plan more efficient surveys. We also find that while there may be some uncertainty in individual population estimates, there is more certainty in the recorded trends. These findings reinforce the need to address elephant management in the Okavango and surrounding wetland systems and call for the urgent consideration of management strategies such as fence realignments to affect the objectives of the Kavango Zambezi Transfrontier Conservation Area (KAZA TFCA) initiative, which will help relieve elephant population pressure.

The 2013 National Nursing Workforce Survey of Registered Nurses

The 2013 National Nursing Workforce Survey of Registered Nurses

Comprehensive Assessment of Bacterial Communities and Analysis of PCB Congeners in PCB-Contaminated Sediment with Depth

The potential effectiveness and time scales for monitored natural attenuation of polychlorinated biphenyl (PCB)-contaminated sediments are difficult to predict. Little is known about the depth- and time-dependent dechlorination of PCBs and the microbial communities that give rise to dechlorination processes. The present work describes evaluation of a single sediment core from the Grasse River (Massena, New York) using a combination of molecular techniques to provide detailed insight of dechlorination potential. Primers specific for 16S rRNA genes from the bacterial domains, putative dechlorinating organisms in the phylum Chloroflexi, the Dehalococcoides genus, and two PCB degrading organism strains, o-17 and DF-1, were used to construct phylogenetic microbial community profiles using denaturing gradient gel electrophoresis (DGGE). Further, quantitative polymerase chain reaction (Q-PCR) was used to estimate population numbers of putative PCB-related organisms in the sediments along the depth of the core. PCB congener analysis was used in conjunction with Molar Dechlorination Product Ratio (MDPR, the sum of five PCB end products over total PCBs), chlorine content, chlorine per biphenyl (CPB), and PCB composition changes with depth in the core to evaluate the extent of dechlorination. All core samples contained populations of Chloroflexi, Dehalococcoides, and o-17/DF-1 related organisms, representing the first report of putative dechlorinating organisms with depth in PCB-contaminated sediment. A clear pattern of dechlorination was observed, with deeper (older) sediments showing more extensive dechlorination and middle sediments showing less dechlorination. The evaluation of putative dechlorinating bacterial populations in conjunction with congener shifts resulting from dechlorination enables a critical association that may lead to better prediction of successful natural attenuation of PCB-contaminated sediment.

Reproductive output and ultrasonography of an endangered population of East Pacific green turtles

AbstractReproductive output is one of the most relevant aspects of life history. We analyzed the reproductive output of the endangered East Pacific green turtle (Chelonia mydas) nesting in Nombre de Jesús, Costa Rica. We supplemented beach patrols with ultrasonography to estimate clutch frequency. With ultrasound scans, we classified the stage of turtle ovaries as: early stage (2 or more clutches), late stage (1 clutch), and depleted ovaries (no clutches). We calculated mean (±SD) estimated clutch frequency (ECF) to be 3.7 ± 1.8 (n = 24) and an adjusted frequency considering individual stage (ECFU; ECF + number of clutches remaining as observed in the last ultrasound) as 5.1 ± 1.3. This is greater than previously described for East Pacific green turtles. Greater individual output could be representative of a healthier population; but could also indicate a decrease in the estimate population numbers previously reported. © 2011 The Wildlife Society.

Population Policy and the Demographic Transition: Performance, Prospects, and Options

In countries that comprise the majority of the world’s population, the demographic transition has now reached its putative endpoint: a state marked by low fertility and low mortality. It is expected that the rest of the world’s countries are headed in the same direction, prompted by modernizing social change and nudged also by looming physical constraints. What were the roles of deliberate policies, and in particular of policies aimed at affecting fertility, in prompting this momentous transformation? What lessons might that experience hold for shaping population policies in the contemporary world, and shaping them in the future, after transitions have been completed? The discussion below seeks to give at least some partial answers to these questions. Before the transition: Population change without policy as a driver In traditional societies, fertility and mortality are high. In modern societies, fertility and mortality are low. In between, there is demographic transition. Few demographers would be satisfied with this lapidary definition of the transition, yet it states the key determining parameters of that process. But it does not explain its driving forces and of course does not inform about the particular demographic characteristics of the post-transition state. The pre-transition era’s essential demographic characteristics are reasonably well known. Although estimates of population numbers before about 1700 lack accuracy, it is certain that for large population aggregates over long periods of time—such as the preceding one or two millennia—the average rate of growth was extremely low; positive yet barely distinguishable from zero. It is then difficult not to attribute an underlying collective rationality to the behavioral patterns that yielded fertility levels that generated such long-run near-stationary equilibrium. Lower fertility would have led to population decline. To the extent that higher fertility would have been possible, the control mechanism keeping growth rates in check described by Malthus—an upward adjustment of mortality—would have been triggered. This mechanism is self-regulated: to talk about population policy in the sense as the notion is understood today— conscious government efforts to influence the determinants of population change—would be plainly anachronistic.

Quantitative estimation of population numbers of shrews (mammalia, insectivora) after wintering

Autumn-winter mortality in shrews (Sorex araneus, S. caecutiens, S. minutus) was estimated on the basis of long-term (12 years) live-trapping on the permanent transect lines in Tver oblast. Relative as well as absolute population numbers were estimated. Lesser shrew (S. minutus) has permanently low population numbers. Fall in this species made 40.1%, and it was scattered through this term. Common shrew (Sorex araneus) lose 89.3% of population and in masked shrew (S. caecutiens) those lost was 73.6%. The most lost was found in autumn and winter fall was as least as 38,2% and 30.4% in the latter two species. The mortality is positively dependent on population density in preceding summer and with severity of winter.

Estimating Populations of Adult <I>Ixodes scapularis</I> in Mississippi Using a Sequential Bayesian Algorithm

A sequential Bayesian algorithm and accompanying computer program were developed and validated to estimate population numbers of adult blacklegged tick, Ixodes scapularis Say, using mark-release-recapture methodology in field plots in central Mississippi. In fieldwork, data taken in February 2005 in a 1-ha plot yielded an estimate of 317 adult I. scapularis per ha Data from another field plot in 2006, 3 km away, yielded an estimate of 280 adult I. scapularis per ha The number of ticks collected per hour in both plots averaged 4.5. In eight of 14 (57%) of sampling events, the number of ticks collected per hour hovered closely around 5.0 (4.8-5.3). The computer program developed in this study readily produced statistical measures such as mean number of ticks per plot, mode, variance, and standard deviation, as well as easy-to-read graphs of estimated tick populations for each sampling period.

Estimating Populations of Adult Ixodes scapularis in Mississippi Using a Sequential Bayesian Algorithm

A sequential Bayesian algorithm and accompanying computer program were developed and validated to estimate population numbers of adult blacklegged tick, Ixodes scapularis Say, using mark-release-recapture methodology in field plots in central Mississippi. In fieldwork, data taken in February 2005 in a 1-ha plot yielded an estimate of 317 adult I. scapularis per ha. Data from another field plot in 2006, 3 km away, yielded an estimate of 280 adult I. scapularis per ha. The number of ticks collected per hour in both plots averaged 4.5. In eight of 14 (57%) of sampling events, the number of ticks collected per hour hovered closely around 5.0 (4.8–5.3). The computer program developed in this study readily produced statistical measures such as mean number of ticks per plot, mode, variance, and standard deviation, as well as easy-to-read graphs of estimated tick populations for each sampling period.

Muslims in Ottoman Europe: Population from 1800 to 1912

Investigating the Muslim population of Ottoman Europe is the stuff of a demographer's nightmare. There is no lack of material to study; thousands of estimates of Balkan population were made throughout the nineteenth and early twentieth century. Unfortunately, almost all of them were nonsense, the prejudiced guesses of nationalistic advocates or estimates made by travellers who felt a journey through a land provided enough information for accurate estimates of population numbers.

Depletion as a Technique to Estimate Commercial Pond Inventories of Channel Catfish

Abstract A depletion population estimation method was tested in three trials in experimental ponds and in 19 commercial ponds that held channel catfish Ictalurus punctatus. Estimates of population numbers in experimental ponds differed from measured population numbers by +6.5%, −3.8%, and −18.4%, respectively. Estimates of population weights differed from measured population weights by −0.1%, 0%, and −7.7%, respectively. Estimated population numbers in two commercial ponds in 1995 differed from measured population numbers by −0.3% to −2.4%, and estimated population weights differed from measured population weights by −3.5% to −6.1%. In 1996, depletion estimates of population weight from 17 commercial channel catfish ponds differed from measured weights by −1.4 ± 13.7%. A fourth sampling point (tested in five commercial ponds) did not significantly (P ≥ 0.05) improve the accuracy of population estimates. The depletion method appears to have potential as an alternative management tool that could be used per...

2nd World Congress of Herpetology

Abstract Temporary removal sampling was used to investigate the population dynamics of the salamander Desmognathus monticola in the southern Appalachian Mountains, USA. Sampling was conducted over 5 years, mainly in July, on one or two plots each year, with seven removal samples being taken in each set of samples. By using size‐frequency distributions, it was possible to separately estimate population numbers for three juvenile age‐classes and a mixed age‐class of older individuals that included adults. Repetition of the procedure in successive years provided data for both time‐specific (vertical) and cohort life tables. Fecundity values obtained by dissection and age data derived by skeletochronology provided a means for refining the life table. The results confirmed and extended earlier findings of life‐history traits of D. monticola, and showed that annual survival rates of 0.5–0.6 are required for population equilibrium. Removal sampling is considered to be a promising technique for evaluating demographics in multispecies communities of desmognathine salamanders, but requires intensive sampling of relatively large plots over several years.

Periodic Counts for Estimating the Size of the Spawning Population of Alewives, Alosa pseudoharengus (Wilson)

The number of migrating alewives in the Parker River, Massachusetts, can be counted visually by standing at the upper end of each of the 6 fish ladders in the system. Estimating the entire run of up to a month’s duration by this procedure is not economically feasible, but we suggest a subsampling procedure that can provide sufficient accuracy and be economical. The reliability of periodic sample counts when used to estimate population numbers of anadromous alewives (Alosa pseudoharengus) was indicated by the low variance of paired counts, small random errors of individual counts, and by the low variability between counts on days of large runs in the Parker River. Analyses of computer-simulated runs using actual data suggested that short counts taken frequently are superior to longer counts taken less often. Both field and computer-simulated data suggested that ten-minute counts taken hourly will estimate the true population of alewife runs within 10% error at the .05 level of probability.

A Laboratory Study of Interactive Segregation between two New Zealand Stream-Dwelling Fish

The common river galaxias (Galaxias vulgaris Stokell) and the upland bully (Gobiomorphus breviceps (Stokell)), are common freshwater fish in the South Island of New Zealand. The habitat requirements of Galaxias vulgaris appear to be more stringent than those of Gobiomorphus breviceps which occurs in all types of water, both lotic and lentic (Cranfield 1962; Woods 1967; Lane & Skrzynski 1972). Stokell (1955) noted that G. breviceps showed 'remarkable adaptability to different types of habitat'. He transferred specimens from a rapid alpine stream to a small landlocked lake which previously contained no native fish and found that they immediately adapted themselves to the new conditions and 'multiplied so rapidly that the lake was fully stocked in three years'. On the other hand, Galaxias vulgaris is found only in rivers and streams, and does not occur in lakes (Stokell 1949,1955; Hopkins & McDowall 1970; McDowall 1970; Lane & Skrzynski 1972). Stokell (1955) transferred 'some hundreds of specimens' of G. vulgaris into a small lake fed by seepage from a number of small streams which did not normally flow directly into the lake. He found that the fish existed in the lake for about one year, but 'escaped' into the largest tributary during a period of connected water. Both G. vulgaris and Gobiomorphus breviceps occur together in a number of rivers and streams, e.g. the Glentui River in the Province of Canterbury. In the Glentui, adult Galaxias vulgaris occupy the more turbulent parts of riffles, whereas adult Gobiomorphus breviceps occur in quiet stretches including the quieter parts of riffles. During an investigation into the ecology of Galaxias vulgaris in the Glentui (Cadwallader 1975c, d, e), monthly collections were made over a period of one year. Although no estimates of population numbers were made, it appeared that adult Gobiomorphus breviceps increased in numbers in areas from which Galaxias vulgaris was removed. This suggested that interactive segregation (Nilsson 1967) was occurring within the river. The present study was undertaken to investigate interactive segregation between adults of the two species in a laboratory stream tank.

Population Counts and Estimates in a Bantu Rural Area

Abstract In the light of criticism levelled in the past at censuses of the Department of Statistics and of the Department of Bantu Administration and Development, a brief resume is given of the use of sample surveys and airphotos in South Africa as aids in the estimation of population numbers of particular areas. The need for reliable estimates is outlined. Based on the identification of hut groups on airphotos and a sample survey, the de facto population of the Modjadji Location is estimated. The value of airphotos in conjunction with sample surveys is stressed in arriving at feasible present and past population figures, especlal1y in Bantu Areas.

Normal (Gaussian) response of juvenile marron, Cherax tenuimanus (Smith) (Decapoda: Parastacidae), to capture by baited sampling units

The possibility that a population of freshwater crayfish contains members with permanent zero "vulnerability" to capture by baited nets has been investigated. After five capture-mark-release opportunities a pond year-class cohort of juvenile marron, Cherax tenuimanus (Smith), was completely examined, as suggested by Cormack (1968). The observed frequencies of marron in the six capture classes, i.e. including the uncaptured marron, were shown to approximate to a truncated normal (Gaussian) distribution using a statistical procedure given by Thompson (1951). Thus, the uncaptured marron only differed quantitatively in their capture response in comparison to the other marron, and therefore, did not contain members with permanent zero "vulnerability". Of the variability in probability of capture, or "catchability", 26.5% was accounted for by a positive correlation with individual size. Sex was also influential amongst the larger members of the year-class. Since equations used to estimate population numbers are based upon a basic assumption of equal "catchability" of individuals, the results presented have considerable practical importance with respect to the validity of these estimates for marron and, at least, related species.