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Population Estimates (population + estimate)

Distribution by Scientific Domains

Life Sciences	59%
Medical Sciences	26%
Humanities and Social Sciences	7%
3 Other Domains	8%

Distribution within Life Sciences

Conservation Science	27%
Ecology & Organismal Biology	18%
Ornithology	15%

Selected Abstracts

Seasonal distribution and species composition of daytime biting mosquitoes

ENTOMOLOGICAL RESEARCH, Issue 2 2009
Waseem AKRAM
Abstract Adults and immatures of Aedes mosquito populations were collected at temperatures between 40 and 44°C (summer), while larvae were collected at 0°C (winter). Major mosquito activities were observed from February to mid-December at various collection sites that yielded high populations of Aedes spp. from May to September, and high populations of Culex spp. and Anopheles spp. from March to September. In June to July, mosquito activity was suspended because the relative humidity was high (70%); a result of the monsoon rains. In August, with temperature ranging from 38 to 42°C, the populations of Culex, Anopheles and Aedes began to increase (36.8, 32.1 and 26.3%, respectively). Population estimates (through standard prototype Centers for Disease Control (CDC) and Biogents (BG)-sentinel) and species composition of Aedes in forest habitats indicated a rapid increase in the populations of Ae. albopictus (52.3%), Ae. aegypti (19.1%) and Ae. vittatus (28.5%) following the rainy season in July. Areas positive for Ae. albopictus had identical population levels and distribution ranges of Ae. vittatus, however, there were no Ae. aegypti in Ae. albopictus areas from August to September. The population level, seasonal distribution, habitat and areas of adult activity marked by global positioning system (GPS) coordinates are being used for reference and for species composition data of Anopheles spp. (2), Culex spp. (10) and Aedes spp. (5) in addition to associated temperature, relative humidity and physico-chemical factors of larval habitat. Global meteorological changes have caused an expansion of the active period, leading to the mosquito's possibility of being a vector of disease increasing, resulting in the spread of dengue fever. [source]

Dental Caries Status and Need for Dental Treatment of Pennsylvania Public School Children in Grades 1,3, 9, and 11

JOURNAL OF PUBLIC HEALTH DENTISTRY, Issue 3 2004
Robert J. Weyant DMD
ABSTRACT Objectives: This cross-sectional study was designed to determine the caries status and provide a general evaluation of the level of dental treatment need of Pennsylvania public school children in grades 1, 3, 9, and 11 on a statewide and regional basis. Methods: Between September 1998 and May 2000, caries status and treatment need were assessed using a school-based dental examination, performed on a representative sample (n=6,040) of public school children in grades 1, 3, 9, and 11 (age range=6 to 21 years). Children's caries status in the primary and permanent dentition was assessed. Need for treatment was scored on a three-level categorical scale,no treatment need identified, routine treatment need, and urgent treatment need,and was based on the presence and severity of caries and other oral conditions. Population estimates of the prevalence of untreated dental caries, DMFT and dft scores, and treatment need were calculated by grade and geographically, using the six Pennsylvania health districts and the cities of Pittsburgh and Philadelphia. The inequality of caries distribution in the population was assessed for both permanent and primary caries using Lorenz curves and Gini coefficients. Results: Dental caries has remained highly prevalent among Pennsylvania's public school children. Caries levels varied considerably by health districts and city. Urgent treatment needs were significant and also varied by health district and city. Conclusions: Dental caries remains the most prevalent disease affecting Pennsylvania's schoolchildren. Caries status varies significantly by region of the state, suggesting that environmental, social, and demographic contextual factors may be important determinants of disease prevalence. [source]

Biases associated with population estimation using molecular tagging

ANIMAL CONSERVATION, Issue 3 2000
Juliann L. Waits
Although capture,recapture techniques are often used to estimate population size, these approaches are difficult to implement for a wide variety of species. Highly polymorphic microsatellite markers are useful in individual identification, and these ,molecular tags' can be collected without having to capture or trap the individual. However, several sources of error associated with molecular identification techniques, including failure to identify individuals with the same genotype for these markers as being different, and incorrect assignment of individual genotypes, could bias population estimates. Simulations of populations sampled for the purpose of estimating population size were used to assess the extent of these potential biases. Population estimates tended to be biased downward as the likelihood of individuals sharing the same genotype increased (as measured by the probability of identity (PI) of the multi-locus genotype); this bias increased with population size. Populations of 1000 individuals were underestimated by ,5% when the PI was as small as 1.4 × 10,7. A similar-sized bias did not occur for populations of 50 individuals until the PI had increased to approximately 2.5 × 10,5. Errors in genotype assignment resulted in overestimates of population size; this problem increased with the number of samples and loci that were genotyped. Population estimates were often >200% the size of the simulated populations when the probability of making a genotyping error was 0.05/locus and 7,10 loci were used to identify individuals. This bias was substantially reduced by decreasing genotyping error rate to 0.005. If possible, only highly polymorphic loci that are critical for the identification of the individual should be used in molecular tagging, and considerable efforts should be made to minimize errors in genotype determination. [source]

Aboriginal deaths in Western Australia: 1985,89 and 1990,94

AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 2 2000
Michael Gracey
Objective: To examine death data for Aboriginal and non-Aboriginal persons in Western Australia (WA) in 1985,89 and 1990,94. Methods: Population estimates were provided by the Health Information Centre of the WA Health Department based on data from the Australian Bureau of Statistics (ABS). Death data came from the WA Registrar-General's Office. Standard methods were used to obtain rates and levels of significance. Results: Main causes of deaths among Aboriginal males in 1990,94 were circulatory conditions, respiratory, injury and poisoning, neoplasms and endocrine diseases; in Aboriginal females they were circulatory, neoplasms, endocrine diseases, respiratory diseases, and injury and poisoning. From 1985,89 to 1990,94, the Aboriginal male all-cause age-standardised death rates fell 3% (ns) while the non-Aboriginal male rate fell 11% (p<0.05). The Aboriginal female all-cause death rate rose 11% (ns) while the non-Aboriginal rate fell 5% (p<0.05). The allcause death rate ratio (Aboriginahnon-Aboriginal) changed from 2.4 to 2.6 (males) and 2.5 to 2.9 (females). There was a major increase in deaths from endocrine diseases among Aborigines and non-Aborigines. This increase was proportionally much greater among Aborigines. In non-Aborigines there was a significant decrease in deaths from circulatory diseases (mainly ischaemic heart disease); this did not occur among Aborigines. Conclusions: Over the study period, Aboriginal health standards, as reflected by death rates, apparently worsened relative to non-Aboriginal standards. Implications: Better health promotion, disease prevention and disease care are required to help achieve acceptable health standards among Aboriginal peoples. [source]

Medical visits among adults with symptoms commonly associated with an overactive bladder

BJU INTERNATIONAL, Issue 3 2006
SUNNY H. KIM
OBJECTIVES To examine nationally representative data and thus obtain estimates of the use of healthcare providers associated with the overactive bladder (OAB) symptoms, a condition characterized by frequency, urgency and nocturia, with or with no urge incontinence, as although it is ranked among the 10 most common chronic medical conditions in the USA, the level of OAB-associated medical treatment remains largely unknown. METHODS To estimate the number of annual OAB-associated medical visits among patients aged ,18 years, three national databases in the USA (year 2000) were examined: the National Ambulatory Medical Care Survey, the National Hospital Ambulatory Medical Care Survey, and the National Hospital Discharge Survey. Population estimates were constructed using design-based statistical analyses to account for the complex survey designs of data. RESULTS During 2000, adult Americans made 1.4 million (95% confidence interval 1.1,1.8 million) ambulatory visits to non-Federal office-based physicians with International Classification of Disease (ICD-9) coding indicative of OAB symptoms. Accounting for emergency and outpatient department visits, as well as non-Federal short-stay hospital discharges, the estimated number of medical visits with OAB-associated ICD-9 coding was <1.5 million. CONCLUSION The prevalence of OAB was estimated to be 34 million adult Americans. When 1.4 million ambulatory visits were compared with this prevalence, as few as 4% of adult Americans with OAB sought medical treatment during the year 2000. The present results therefore suggest a large unmet medical need among the population of adult Americans with OAB. [source]

Factors Affecting Population Assessments of Desert Tortoises

CONSERVATION BIOLOGY, Issue 5 2000
Jerome E. Freilich
With a wide geographic range and more living individuals than any other listed land animal, biologists have needed to detect population trends against a "noisy" background of strong annual changes. We obtained annual population estimates of desert tortoises over 6 consecutive years at a 2.59-km2 plot in Joshua Tree National Park, California. Our estimates, based on weekly spring surveys, varied substantially, particularly between wet and dry years. Concurrently, we followed 10 radiotagged animals for 3 years to corroborate the surveys. Population density was determined separately for each year and for all years combined. Our best population estimate was an average of 67 adult tortoises, three times more than the density reported in a 1978 survey of the same site. Annual mortality was low ( <10%), and the animals showed extreme site fidelity. Apparent changes in population size were most strongly related to the animals' varying susceptibility to capture. In dry years, home ranges decreased, captures decreased, and effort required to find each tortoise nearly doubled. Our data confirm that tortoises are likely to be undercounted during dry years and call into question earlier studies conducted during droughts. Resumen: Las tortugas del desierto han sido tema de controversia desde que fueron enlistadas como amenazadas en 1990. Con un amplio rango de distribución geográfica y más individuos vivos que cualquier otro animal terrestre enlistado, los biólogos han necesitado detectar tendencias poblacionales contra un trasfondo "ruidoso" de cambios anuales fuertes. Obtuvimos estimaciones de la población anual de tortugas del desierto por seis años consecutivos en un cuadrante de 2.59 Km2 en el Parque Nacional Joshua Tree de California. Nuestras estimaciones, basadas en sondeos semanales de primavera, variaron sustancialmente, particularmente al comparar años lluviosos con años secos. Al mismo tiempo, monitoreamos por tres años a 10 animales marcados con radiotransmisores para corroborar los sondeos. La densidad poblacional estuvo determinada por separado para cada año y para todos los años combinados. Nuestras mejores estimaciones de densidad poblacional fueron en promedio de 67 adultos, tres veces más que la densidad reportada en un sondeo de 1978 en el mismo sitio. La mortalidad anual fue baja ( <10%) y los animales mostraron una fidelidad extrema por el sitio. Los cambios aparentes en el tamaño poblacional estuvieron más fuertemente relacionados con la variación en la susceptibilidad de captura de los animales. En años secos, el rango de hogar disminuyó, las capturas disminuyeron, y el esfuerzo requerido para encontrar cada tortuga fue de casi el doble. Nuestros datos confirman que las tortugas son probablemente mal contadas ( menos) durante los años de seca y ponen en duda estudios previos realizados durante secas. [source]

Wader recruitment indices suggest nesting success is temperature-dependent in Dunlin Calidris alpina

IBIS, Issue 3 2006
COLIN M. BEALE
Measures of annual breeding success are an important component of species monitoring programmes. It has been suggested that effective monitoring of breeding productivity for arctic breeding waders may be achieved from an analysis of annual variation in the proportion of juveniles in winter flocks. Here, we attempt to generate a recruitment index for Dunlin Calidris alpina caught during the winter in north Wales. This index revealed significant annual variation and we show that this is strongly correlated with summer temperature (but not rainfall) on the breeding grounds. Years with high recruitment were also correlated with increases in the national winter population estimate. In years of intermediate summer temperature, the recruitment index was highest and we discuss the possible implications this has for Dunlin under scenarios of future climate change. We were unable to generate a significant index for Common Redshank Tringa totanus and discuss possible reasons for this. [source]

Breeding biology and conservation of the Black-vented Shearwater Puffinus opisthomelas

IBIS, Issue 4 2003
Bradford S. Keitt
The Black-vented Shearwater Puffinus opisthomelas is endemic to the Pacific coast of Baja California, Mexico. We studied the breeding biology of this species at Natividad Island in 1997 and 1998. The colony at Natividad Island covers approximately 2.5 km2 and we estimated there to be 114 455 (± 27 520 95% CI) burrows in the colony. In 1997 burrow occupancy was 66.9%, providing a population estimate of 76 570 (± 18 411 95% CI) breeding pairs, representing about 95% of the world's population of this species. In 1997 the peak in egg laying occurred in early March and hatching began on 7 May. The incubation period averaged 51 days (± 6 sd) and chick rearing averaged 69 days (± 3 sd). In 1998 burrow occupancy was lower (19.6%) and nest initiation was later (peak egg laying in mid-April), perhaps a result of El Niño conditions that prevailed in the Eastern Pacific at that time. We calculated that the development of the town and roads on Natividad Island have destroyed over 15% (26 532 burrows) of the breeding habitat on the island. [source]

Census error and the detection of density dependence

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2006
ROBERT P. FRECKLETON
Summary 1Studies aiming to identify the prevalence and nature of density dependence in ecological populations have often used statistical analysis of ecological time-series of population counts. Such time-series are also being used increasingly to parameterize models that may be used in population management. 2If time-series contain measurement errors, tests that rely on detecting a negative relationship between log population change and population size are biased and prone to spuriously detecting density dependence (Type I error). This is because the measurement error in density for a given year appears in the corresponding change in population density, with equal magnitude but opposite sign. 3This effect introduces bias that may invalidate comparisons of ecological data with density-independent time-series. Unless census error can be accounted for, time-series may appear to show strongly density-dependent dynamics, even though the density-dependent signal may in reality be weak or absent. 4We distinguish two forms of census error, both of which have serious consequences for detecting density dependence. 5First, estimates of population density are based rarely on exact counts, but on samples. Hence there exists sampling error, with the level of error depending on the method employed and the number of replicates on which the population estimate is based. 6Secondly, the group of organisms measured is often not a truly self-contained population, but part of a wider ecological population, defined in terms of location or behaviour. Consequently, the subpopulation studied may effectively be a sample of the population and spurious density dependence may be detected in the dynamics of a single subpopulation. In this case, density dependence is detected erroneously, even if numbers within the subpopulation are censused without sampling error. 7In order to illustrate how process variation and measurement error may be distinguished we review data sets (counts of numbers of birds by single observers) for which both census error and long-term variance in population density can be estimated. 8Tests for density dependence need to obviate the problem that measured population sizes are typically estimates rather than exact counts. It is possible that in some cases it may be possible to test for density dependence in the presence of unknown levels of census error, for example by uncovering nonlinearities in the density response. However, it seems likely that these may lack power compared with analyses that are able to explicitly include census error and we review some recently developed methods. [source]

A test of methods for estimating population size of the invasive land snail Achatina fulica in dense vegetation

JOURNAL OF APPLIED ECOLOGY, Issue 4 2002
Paul G. Craze
Summary 1Physical inaccessibility often complicates censuses of poorly mobile organisms. We therefore assessed the effectiveness of using a sample of quadrat counts to generate a population estimate corrected for inaccessible areas. The result is directly applicable to management of the introduced snail Achatina fulica on Ile aux Aigrettes, a small island off Mauritius, but also has implications for counting this and similar species elsewhere. Accurate counting of A. fulica is important given that this species is such a widespread and serious pest. 2Counts were made in 17 quadrats taken from a grid covering the island. These were used to produce one population estimate by interpolating for the rest of the grid using GIS software (method 1). A second estimate assumed equal density of snails in accessible and inaccessible parts of the 17 quadrats, again with the population estimate interpolated (method 2). 3Four further quadrats were cleared of vegetation and, by comparison of counts before and after clearance, the relationship between initial count and true snail number was estimated. This resulted in two further population estimates, with the relationship used to adjust counts in the 17 experimental quadrats before interpolation (methods 3 and 4). 4All four estimates were tested using 35 additional quadrats of two types. Type 1 quadrats were physically cleared of vegetation; type 2 quadrats were fully accessible without clearance. Predicted counts in these quadrats were assessed for accuracy by comparison with actual counts. 5The method 1 estimate was clearly inadequate; method 4 gave a consistent overestimate; method 2 gave the smallest error in both quadrat types. In type 1 quadrats, method 2 and 3 estimates were not significantly different and method 2 had a slight tendency to underestimate. Overall, for studies of A. fulica, method 2 is recommended. However, it should be noted that the study took place towards the end of the wet season. In the dry season, damp refuges under inaccessible vegetation may be more important and methods 3 and 4 may then give a better estimate. 6The population of A. fulica with shell length > 10 mm on Ile aux Aigrettes near the end of the wet season in 2000 was between 37 300 and 45 100, with 39 700 being the best estimate. 7The results underline the importance of considering inaccessible areas when accurate counts of species are needed, and a method is suggested by which a simple census technique can be adjusted. In the case of A. fulica, more accurate estimates of population size and distribution are invaluable in the management, monitoring and eradication of this invasive species. [source]

An assessment of the puku (Kobus vardonii Livingstone 1857) population at Lake Rukwa, Tanzania

AFRICAN JOURNAL OF ECOLOGY, Issue 4 2009
Matthias Waltert
Abstract The population of puku, Kobus vardonii, at Lake Rukwa, one of only two in Tanzania, is poorly known. A multi-species dry season game count carried out in Rukwa Game Reserve (RGR) in 2004 estimated a population size of 1729, but was associated with a high margin of error [coefficient of variation (CV) 0.88]. To increase the precision for the local puku population estimate, we conducted a zig-zag line transect survey restricted only to areas occupied by puku in the dry season of 2006. This survey technique produced an estimate of 776 individuals and the CV was considerably reduced to 0.29. Puku herd size was comparable with the studies carried out in the Kilombero valley, Tanzania and in Kasanka National Park, Zambia, thus broadly confirming the herding ecology of this species. We found that pukus were restricted to the central parts of the floodplains, suggesting an avoidance of habitats used by pastoralists at the edge of RGR. Compared with the estimates of the puku population made in the 1980s, the puku population has declined. We recommend regular monitoring and enforcement of the current management plan to conserve the local puku population. Résumé Le statut de la population du puku Kobus vardonii au lac Rukwa, une des deux seules populations de Tanzanie, est mal connu. Un dénombrement de nombreuses espèces animales réalisé en saison sèche dans la Réserve de Faune de Rukwa (RGR) en 2004 a estimé la taille de la population à 1 729, mais ce chiffre était associéà une grande marge d'erreur (CV 0,88). Pour améliorer la précision de l'estimation de la population de pukus, nous avons mené une étude par transect en zigzag limitée aux zones occupées par les pukus, pendant la saison sèche de 2006. Cette technique d'étude a donné une estimation de 776 individus, et la CV était considérablement réduite, à 0,29. La taille des hardes de pukus était comparable à celle relevée dans la vallée de Kilombero, en Tanzanie, et dans le Parc National de Kasanka, en Zambie, confirmant ainsi l'écologie en harde de cette espèce. Nous avons découvert que les pukus se limitaient aux parties centrales des plaines inondables, ce qui suggère qu'ils évitent les habitats fréquentés par les pasteurs à la limite de la Réserve de Faune de Rukwa. Comparée aux estimations de cette population de pukus réalisées dans les années 1980, cette population a décliné. Nous avons recommandé d'assurer un suivi régulier et d'appliquer le plan de gestion actuel pour conserver la population locale de pukus. [source]

Shifts in purchasing patterns of non-alcoholic, water-based beverages in Australia, 1997,2006

NUTRITION & DIETETICS, Issue 4 2007
Gina LEVY
Abstract Aim:, To describe trends in purchasing patterns of non-alcoholic, water-based beverages (WBBs) in Australia, 1997,2006. Methods:, Trends in volume sales of WBBs were determined from data supplied by the Australian beverage industry, not including fruit juice or milk-based drinks. Change was calculated as per cent difference between 1997 and 2006, volume share by proportion of total sales in the category and per capita consumption by dividing total volume sales by population estimate for that year. Sugar supply from WBBs was calculated by multiplying sales by sugar content. Demographic trends from AC Nielsen surveys were shown as per cent households purchasing beverages and as volume share by age and sex. Results:, Total volume sales of WBBs increased by 13% from 1997 to 2006, largely accounted for by increases in sales of plain still water and non-sugar carbonated soft drink (CSD). Sales in the CSD category saw a shift away from sugar-sweetened to non-sugar. There was a concomitant increase in sales of sugar-sweetened sports and energy drinks, and iced tea. Younger people and high-income households were the major purchasers of CSDs, and for sports and energy drinks, it was young males. Conclusion:, The increased sales of beverages by 2006 appear to reflect a greater trend towards purchasing fluids, particularly increases in bottled water and non-sugar CSDs. Sugar supply from beverages has declined, mostly because of decreasing sales of sugar-sweetened CSDs since 2002. Industry-generated data proved useful in forming a picture of apparent non-alcoholic, WBB consumption patterns in Australia. [source]

Evaluating capture,recapture population and density estimation of tigers in a population with known parameters

ANIMAL CONSERVATION, Issue 1 2010
R. K. Sharma
Abstract Conservation strategies for endangered species require accurate and precise estimates of abundance. Unfortunately, obtaining unbiased estimates can be difficult due to inappropriate estimator models and study design. We evaluate population,density estimators for tigers Panthera tigris in Kanha Tiger Reserve, India, using camera traps in conjunction with telemetry (n=6) in a known minimum population of 14 tigers. An effort of 462 trap nights over 42 days yielded 44 photographs of 12 adult tigers. Using closed population estimators, the best-fit model (program capture) accounted for individual heterogeneity (Mh). The least biased and precise population estimate ( (SE) []) was obtained by the Mh Jackknife 1 (JK1) [14 (1.89)] in program care -2. Tiger density ( (SE) []) per 100 km2 was estimated at 13 (2.08) when the effective trapping area was estimated using the half mean maximum distance moved (1/2 MMDM), 8.1 (2.08), using the home-range radius, 7.8 (1.59), with the full MMDM and 8.0 (3.0) with the spatial likelihood method in program density 4.1. The actual density of collared tigers (3.27 per 100 km2) was closely estimated by home-range radius at 3.9 (0.76), full MMDM at 3.48 (0.81) and spatial likelihood at 3.78 (1.54), but overestimated by 1/2 MMDM at 6 (0.81) tigers per 100 km2. Sampling costs (Rs. 450 per camera day) increased linearly with camera density, while the precision of population estimates leveled off at 25 cameras per 100 km2. At simulated low tiger densities, a camera density of 50 per 100 km2 with an effort of 8 trap nights km,2 provided 95% confidence coverage, but estimates lacked precision. [source]

Rangeland degradation is poised to cause Africa's first recorded avian extinction

ANIMAL CONSERVATION, Issue 3 2009
C. N. Spottiswoode
Abstract Rangeland degradation by livestock threatens several restricted-range species, but is largely overlooked by conservation biologists. The Sidamo lark Heteromirafra sidamoensis, confined to the Liben Plain grassland in southern Ethiopia, is critically endangered by bush encroachment, permanent settlement and agricultural conversion. Its global range was previously estimated at 760 km2, but in 2007,2008 available habitat covered<35 km2. Density estimates from multi-model inference analysis of distance transect data provided a global population estimate of 90,256 adults (possibly with a serious sex-ratio bias towards males). Logistic regression models of habitat selection showed that males preferentially occurred in areas of grassland with greater cover of medium-length grass (5,15 cm), less cover of bare ground and fewer bushes. Habitat transects extending outward from its core range revealed massive and rapid bush encroachment, corroborating information from semi-structured interviews. The survival of both local Borana pastoralism and this species , mainland Africa's likeliest first avian extinction , depends on restoring seasonal patterns of grazing, resisting agricultural conversion of grasslands, reversing fire suppression policies and clearing bush. [source]

Dolphins in a bottle: abundance, residency patterns and conservation of bottlenose dolphins Tursiops truncatus in the semi-closed eutrophic Amvrakikos Gulf, Greece

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2008
Giovanni Bearzi
Abstract 1.Boat surveys were conducted between 2002 and 2005 to study bottlenose dolphins living in the 400 km2 Amvrakikos Gulf, western Greece. During 116 survey days, 4705 km of total effort resulted in the individual photo-identification of 106 animals, through long-term natural markings on their dorsal fins. 2.Mark,recapture analyses based on the Mth model provided estimates of 82 marked individuals in 2003 (95% CI=80,91), 92 in 2004 (95% CI=86,108) and 98 in 2005 (95% CI=94,110). To include the unmarked portion of the population, the proportion of unmarked individuals was computed based on the number of photographs of marked and unmarked dorsal fins. The mean proportion of unmarked animals in the population was 0.338 (95% CI=0.288,0.389). By adding this to the estimate for marked animals in 2005, considered as the most robust, a total population estimate of 148 individuals (95% CI=132,180) was obtained. 3.Dolphin encounter rates in 2003,2005 did not show significant variations, and averaged 7.2 groups per 100 km or 72.5 individuals per 100 km. Encounter rates within the Gulf were about one order of magnitude greater than those found for bottlenose dolphins in nearby eastern Ionian Sea coastal waters. 4.Mean dolphin density in the Gulf was 0.37 animals km,2. This relatively high density, together with high levels of site fidelity shown by most individuals, was thought to be related primarily to prey availability, particularly of epipelagic schooling fish. 5.The importance of the semi-closed Amvrakikos Gulf for bottlenose dolphins and other threatened species encourages the adoption of measures aimed to conserve its valuable ecosystems and raise the naturalistic profile of the area, while promoting environment-conscious development. Meaningful action includes restoring natural hydrology (e.g. freshwater input from rivers), curtailing pollution from various sources, responsible fisheries and aquaculture management, and control of illegal fishing. Interactions between dolphins and fisheries also deserve careful quantitative investigation. Copyright © 2007 John Wiley & Sons, Ltd. [source]

How has the remnant population of the threatened frog Leiopelma pakeka (Anura: Leiopelmatidae) fared on Maud Island, New Zealand, over the past 25 years?

AUSTRAL ECOLOGY, Issue 3 2010
BEN D. BELL
Abstract Despite widespread global reports of declining amphibian populations, supporting long-term census data are few, limiting opportunities to study changes in numbers and survival over time. However, in New Zealand, for the past 25 years (1983,2008), we studied Leiopelma pakeka, a threatened, terrestrial frog that inhabits rocky boulder banks under forest on Maud Island. Using night sampling at least annually on two 12 × 12 m plots, we had 5390 captures of 1000+ individuals, 327 on one plot (grid 1), 751 on the other (grid 2). The mean (±SE) number of frogs found per night was 11.3 (±0.6) on grid 1 and 25.6 (±1.4) on grid 2. We used capture-recapture models to estimate population size, proportion of animals remaining beneath the surface and survival rate. The mean (±SE) population estimate was 131 (±14.7) frogs on grid 1 and 367 (±38.7) on grid 2. Over 25 years the estimated population increased on grid 1 and fluctuated on grid 2. Some frogs were captured on most sampling visits, others less often, evidently failing to emerge from cover each visit. Using a combination of open and closed population models, we estimated the mean (±SE) proportion remaining underground was 0.63 (±0.12) on grid 1 and 0.53 (±0.07) on grid 2. Our research represents one of the longest-run population studies of any frog, and we recorded significant longevity, two males reaching 35+ and 37+ years, a female 34+ years. No significant differences occurred between mean annual survival rates of apparent females and males, or between the two sites. The number of toes clipped for individual identification had little influence on the return rate, once the effect of time of first capture was removed. [source]

Desloratadine dose selection in children aged 6 months to 2 years: comparison of population pharmacokinetics between children and adults

BRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2 2007
Samir K. Gupta
What is already known about this subject ,,According to recent literature, the pathophysiologies of allergic rhinitis and chronic idiopathic urticaria are thought to be similar in adults and children. In addition, the response to antihistamine treatment is similar in adults and children, suggesting a similar concentration-response relationship. ,,However, an appropriate dose selection and the pharmacokinetics of desloratadine in children of ,6 months,,2 years old have never been addressed in the literature. What this study adds ,,This study demonstrated that desloratadine syrup offers a safe treatment option for allergic conditions in young children. ,,A suitable dose for children aged ,6 months,<1 year is 1.0 mg, while the corresponding predicted dose for children aged ,1 year,,2 years is 1.25 mg. These paediatric doses yielded similar systemic desloratadine exposures (AUC) to those seen with a typical adult dose of 5.0 mg. Aims The aim of this study was to identify the dose of desloratadine in children aged ,6 months,,2 years that would yield a single-dose target exposure (AUC) comparable with that in adults taking 5 mg desloratadine as syrup. Methods In a phase 1, single-dose, open-label, pharmacokinetic study in 58 children aged ,6 months,<1 year and ,1 year,,2 years were randomly assigned to desloratadine syrup 0.625 mg (1.25 ml) and 1.25 mg (2.5 ml), respectively. Because the volume of blood that could be collected from individual subjects was limited, a population pharmacokinetic approach was used to estimate the pharmacokinetics of desloratadine. Safety was assessed based on results of screening and postdose physical examinations, laboratory safety tests, vital signs, and adverse events. Results The apparent clearance (CL/F) of desloratadine, population estimate (%CV), in children aged ,6 months,<1 year was 27.8 l h,1 (35) and corresponding values in children ,1 year,,2 years was 35.5 l h,1 (51), compared with 137 l h,1 (58) for adults. The CL/F ratios (children to adults) indicated that doses of 1 mg for ,6 months,<1 year and 1.25 mg for ,1 year,,2 years would result in similar systemic exposure to that observed in adults receiving the recommended 5 mg dose. Desloratadine was well tolerated with no safety issues. Conclusions Doses of 1.0 and 1.25 mg in children aged ,6 months,,2 years should result in an exposure to desloratadine similar to that of adults receiving doses of 5 mg. [source]

Factors Affecting Population Assessments of Desert Tortoises

Disease burden of chronic lymphocytic leukaemia within the European Union

EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2008
Louise Watson
Abstract Objective:, Whilst Chronic lymphocytic leukaemia (CLL) is considered a rare disease, to our knowledge, the current prevalence of CLL within the European Union (EU) member states is not published. Understanding the number of individuals with CLL is vital to assess disease burden within the wider population. Methods:, Using 2002 data from the International Agency for Research on Cancer, we estimated the number of individuals with CLL (ICD-10 C91.1) from those reported for all leukaemias (C91,95) and extrapolated the figures by the population increase within the EU between 2002 and 2006, the last year with fully updated community population estimates. One- and 5-yr partial prevalence estimates are reported (i.e. the number of individuals still living 1,5 yr post-diagnosis). We then applied proportional estimates from the literature to assess those requiring immediate treatment, those under observation and their likely progression rates. Results:, We found that within the 27 EU states plus Iceland, Norway and Lichtenstein, 1- and 5-yr CLL partial prevalence estimates totalled approximately 13 952 and 46 633 individuals respectively in 2006. By applying Binet staging to the 1-yr estimate, 40% of patients will be stage B/C and require immediate treatment. Thus, 5581 individuals may be treated within the first year of diagnosis. Of the 60% (8371) under observation, by 5 yr up to 33% (2763) may have more advanced disease with increased risk of mortality. Conclusion:, Whilst CLL is a rare disease, the number of individuals burdened by the disease within the EU is considerable and thousands of patients require treatment and physician care, which has cost implications for member states. [source]

The use of fyke nets as a quantitative capture technique for freshwater eels (Anguilla spp.) in rivers

FISHERIES MANAGEMENT & ECOLOGY, Issue 4 2005
D. J. JELLYMAN
Abstract, Fyke netting is a convenient and effective technique for capturing freshwater eels, and catch-per-unit-effort is usually assumed to be an index of eel abundance. The present study investigated the potential of depletion fishing using baited fyke nets to obtain population estimates of longfin eels Anguilla dieffenbachii Gray, in a river in the South Island of New Zealand. The probability of capture (capture efficiency) of a single night's fishing increased with increasing size of eel, and ranged from 0.2 to 0.9 for eels <400 mm, to 0.7,0.9 for eels ,500 mm. The capture efficiency of baited vs unbaited nets was assessed in a small stream that was electric fished after netting trials were completed. Baited nets proved to be an effective method of assessing abundance of longfin eels (>400 mm) but not shortfins (A. australis Richardson); capture efficiency of the population of longfins (the sum of fyke caught and electric fished eels) was 0.4 for a single night's fyke netting, increasing to 0.8 over four nights. Comparable efficiencies for shortfins were <0.1 and 0.3 respectively. Unbaited nets were markedly less efficient for both species. [source]

Population size, weight distribution and food in a persistent population of the rare medicinal leech, Hirudo medicinalis

FRESHWATER BIOLOGY, Issue 8 2008
J. M. ELLIOTT
Summary 1. It is important for species recovery and conservation management projects to know the minimum viable population size for rare and endangered species, such as the medicinal leech, Hirudo medicinalis. Therefore, using a catch-removal method, this study estimated every two years (1986, 1988, 1990, 1992) the total number of medicinal leeches in a tarn in the English Lake District, and the number of mature adults in the population. 2. Four samples were taken each year in June and July, when water temperatures exceeded 20 °C. Population size was estimated both by maximum likelihood and regression methods. All leeches were weighed alive and size groups were separated by polymodal frequency analysis. A small sample of the blood meal in each leech gut was taken before the leeches were returned to the tarn, and was used to estimate the proportion of mammalian and non-mammalian blood in the meals. 3. Both methods of estimation produced similar values, increasing confidence in the population estimates. Values for the total population in June and July varied among years from 248 to 288, the maximum value being only 16% higher than the minimum. Values for the number of mature leeches varied from 48 to 58 (19,20% of the total population), and this was an estimate of the effective population size. 4. There were four size groups. The largest mature leeches (live weight >5 g) in group IV formed only 1% of the population, and the smallest (0.02,0.5 g) in group I 14,17%. Most leeches were in two overlapping groups of immature (64,67% of population) and mature (18%) leeches with size ranges of 0.4,3.4 g and 2.5,5 g respectively. The percentage of leeches in each size group was very consistent among years. Blood meals were found in 38,44% of the leeches in group I, 45,50% in group II, 70,75% in group III, and 100% in group IV, but mammalian blood was present only in larger mature leeches (>3.5 g). 5. Medicinal leeches were first detected in the tarn in 1980 and are still present in 2007, so the population has persisted for at least 27 years. Compared with minimum viable population sizes for other species, including many endangered species, values for this medicinal leech population are extremely low, but may be typical of some rare freshwater invertebrates in isolated habitats. [source]

Population Estimation Using Landsat Enhanced Thematic Mapper Imagery

GEOGRAPHICAL ANALYSIS, Issue 1 2007
Changshan Wu
An assessment of two groups of approaches for estimating urban population with remote-sensing information is presented in this article. These approaches, zonal and pixel-based models, are applied to Landsat Enhanced Thematic Mapper images of a portion of Columbus, Ohio, to generate population estimates. The zonal approach uses impervious surface fraction, spectral radiance, and land-use/land-cover classification to derive population estimates. The pixel-based approach uses impervious surface fraction and spectral radiance to estimate the population of residential areas. To assess robustness, these models were applied to Dayton, Ohio. A comparative study indicates that the models generated promising results in estimating regional population counts. However, zonal regression with spectral radiance produced large errors (76%) for census block groups, whereas other models gave significantly better estimation accuracy. Comparing the performance of the indicators, impervious surface fraction is competitive, and slightly but consistently better than land-use classification. In comparison with traditional zonal approaches, pixel-based models give somewhat better estimation accuracy. [source]

The first record of Brown Skua Catharacta antarctica in Europe

IBIS, Issue 1 2004
Stephen C. Votier
Evidence from mtDNA suggests that two skuas, one discovered in the Scilly Islands Cornwall in October 2001, the other in Glamorgan in February 2002, belong to the Brown Skua group Catharacta antarctica, a species not previously recorded in the North Atlantic. These molecular data do not exclude the possibility of either bird being a hybrid between Brown Skua and South Polar Skua C. maccormicki, but population estimates suggest that this is unlikely. More importantly, biometrics show that the Glamorgan bird is much smaller than hybrids but matches Falkland Skua C. a. antarctica. The distributions of C. antarctica subspecies at sea are not well known, but the discovery of two of these birds in the UK suggests that they may wander more extensively than previously thought. [source]

Population stability in salmon species: effects of population size and female reproductive allocation

JOURNAL OF ANIMAL ECOLOGY, Issue 5 2003
Sigurd Einum
Summary 1Population stability (i.e. level of temporal variation in population abundance) is linked commonly to levels of environmental disturbances. However, populations may also differ in their propensity to dampen or amplify the effects of exogenous forces. Here time-series of population estimates were used to test for such differences among 104 populations of six salmon species. 2At the species level, Atlantic (Salmo salar L.), chinook (Oncorhynchus tshawytscha Walbaum) and coho salmon (O. kisutch W) were less variable than sockeye (O. nerka W) and pink salmon (O. gorbuscha W). Chum salmon (O. keta W) was more similar to sockeye and pink salmon. These differences may be related in part to differences in body size, and hence susceptibility to adverse environmental conditions, at the time when they migrate to the sea or lakes. 3At the population level no effect of fecundity on variability was found, in contrast to findings for marine fishes, nor of egg size. Whereas substantial differences in the temporal stability of environmental factors among geographically close populations may over-ride any effects of fecundity or egg size in fresh water, this is less likely in the marine environment where spatial autocorrelations of environmental variability are more pronounced. 4Variation in population sizes was related positively to the duration of time-series when using standard deviations of ln-transformed population estimates, and also when using linearly detrended population variation, suggesting non-linear long-term abundance trends in salmon populations that extend beyond the 7-year period of the shortest time-series. 5When controlling for differences among species, stability increased with increasing population size, and it is hypothesized that this is due to large populations having a more complex spatial and genetic structure than small populations due to wider spatial distribution. The effects of population size on stability, as well as differences in stability among species, suggest that population- and organism-specific characteristics may interact with exogenous forces to shape salmon population dynamics. [source]

Management implications of the Macquarie Island trophic cascade revisited: a reply to Dowding et al. (2009)

JOURNAL OF APPLIED ECOLOGY, Issue 5 2009
Dana M. Bergstrom
Summary 1. The management of non-indigenous species is not without its complications. In Bergstrom et al.'s (2009) study, we demonstrated that feral cats Felis catus on sub-Antarctic Macquarie Island were exerting top-down control on the feral rabbit Oryctolagus cuniculus population, and that the eradication of the cats led to a substantial increase in rabbit numbers and an associated trophic cascade. 2. Dowding et al. (2009) claim our modelling was flawed for various reasons, but primarily that a reduction in the application of the rabbit control agent, Myxoma virus, coinciding with cat removal, was a major driver of rabbit population release. 3. We explore this proposition (as well as others) by examining rates of Myxoma viral release between 1991 and 2006 (with an attenuation factor for the years, 2003,2006) in association with presence/absence of cats against two estimates of rabbit population size. Myxoma viral release was a significant factor in the lower estimates of rabbit population, but the effect was small, and was not significant for higher rabbit population estimates. By contrast, the presence or absence of cats remained highly significant for both estimates. 4.Synthesis and applications. We re-affirm our position that top-down control of rabbit numbers by cats, prior to their eradication, was occurring on Macquarie Island. Nonetheless, we agree with Dowding et al. (2009) that systems with multiple invasive species represent complex situations that require careful scrutiny. Such scrutiny should occur in advance of, during, and following management interventions. [source]

A test of methods for estimating population size of the invasive land snail Achatina fulica in dense vegetation

Sensitivity of comparative analyses to population variation in trait values: clutch size and cavity excavation tendencies

JOURNAL OF AVIAN BIOLOGY, Issue 4 2000
Mikko Mönkkönen
Importance of within-species (population) variation in trait values to correlations of traits among species has received very little attention in comparative analyses. We use randomization and bootstrapping techniques to provide a sensitivity analysis of the influence of population variation on correlations between clutch size and propensity to excavate. These traits are predicted to be negatively correlated under the limited breeding opportunities hypothesis, but opposing results have been found by two studies using different population estimates for western Palearctic Paridae. Our analyses support the limited breeding opportunities hypothesis and suggest low sensitivity to within-species variation in trait values. Yet, a small proportion of population data provide non-significant results. Checking for the effects of this variation on the postulated association between traits is necessary in comparative studies if one wishes to avoid type I and type II errors. [source]

Dung decay and its implication for population estimates of duikers (Cephalophus and Philantoba spp.) and red river hogs (Potamochaerus porcus) in the Nouabalé-Ndoki National Park, Republic of Congo

AFRICAN JOURNAL OF ECOLOGY, Issue 2 2010
Thomas Breuer
First page of article [source]

Dung survey bias and elephant population estimates in southern Mozambique

AFRICAN JOURNAL OF ECOLOGY, Issue 2 2009
Pieter I. Olivier
First page of article [source]

Genetic testing for HFE hemochromatosis in Australia: The value of testing relatives of simple heterozygotes

JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 7 2002
JULEEN A CAVANAUGH
AbstractBackground : It is unclear whether screening of relatives of C282Y and H63D heterozygotes (other than compound heterozygotes) for hemochromatosis will detect sufficient numbers of cases to justify introduction of this screening strategy. Methods : Conditional probabilities were determined using published Australian allele frequencies and penetrance data to determine the detection rate of hemochromatosis by testing the siblings and offspring of heterozygotes (subjects with only one HFE mutation). Results : The number of individuals who are at risk of developing increased body iron stores because of HFE mutations is substantially higher (1 in 80) than previously estimated. In addition, 33% of the Australian population are heterozygous for either C282Y or H63D. Based on population estimates, the relative risk to the offspring of C282Y and H63D heterozygotes of developing increased iron stores is 4.1 and 1.5, respectively, while the relative risk to each sibling is 2.3 and 1, respectively. The risk of developing clinical features of hemochromatosis or hepatic fibrosis is likely to be substantially lower. Conclusions : Although the detection rate from testing the families of unaffected heterozygotes is low, this can be justified as a clinically useful screening strategy. At the present time this strategy should be restricted to first-degree relatives of heterozygotes. Further studies are recommended to determine if cascade genetic screening is a cost-effective alternative to general population screening. © 2002 Blackwell Publishing Asia Pty Ltd [source]