			Home About us Contact

Population Trends (population + trend)

Distribution by Scientific Domains

Life Sciences	81%
Medical Sciences	5%
Earth and Environmental Science	3%
3 Other Domains	11%

Distribution within Life Sciences

Conservation Science	19%
Ecology & Organismal Biology	16%
Animal Science Methods	13%
Animal Science & Zoology	8%

Selected Abstracts

DETERMINATION OF MANATEE POPULATION TRENDS ALONG THE ATLANTIC COAST OF FLORIDA USING A BAYESIAN APPROACH WITH TEMPERATURE-ADJUSTED AERIAL SURVEY DATA

MARINE MAMMAL SCIENCE, Issue 3 2004
Bruce A. Craig
Abstract In many animal population survey studies, the construction of a stochastic model provides an effective way to capture underlying biological characteristics that contribute to the overall variation in the data. In this paper we develop a stochastic model to assess the population trend and abundance of the Florida manatee, Trichechus manatus latirostris, along the Atlantic coast of the state, using aerial survey data collected at winter aggregation sites between 1982 and 2001. This model accounts for the method by which the manatees were counted, their movements between surveys, and the behavior of the total population over time. The data suggest an overall increase in the population from 1982 to 1989 of around 5%,7%, a reduction in growth or a leveling off (0%,4% annual growth) from 1990 to 1993, and then an increase again of around 3%,6% since 1994. In winter 2001,2002 (the most recent survey season for which analyses were done), we estimated the adult manatee population along the east coast of Florida to be 1,607 individuals (range = 1,353,1,972; 95% credible interval). Our estimate of manatee abundance corresponds well with maximum counts (approximately 1,600 manatees) produced during synoptic aerial surveys under optimal conditions. Our calculations of trends correspond well with mark and recapture analyses of trends in survival of adult manatees along the east coast through the early 1990s. Our population trend estimates since that time are more optimistic than those generated by mark-recapture models. [source]

Population Trends in BMD Testing, Treatment, and Hip and Wrist Fracture Rates: Are the Hip Fracture Projections Wrong?

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2005
Susan B Jaglal PhD
Abstract A worldwide epidemic of hip fractures has been predicted. Time trends in BMD testing, bone-sparing medications and hip and wrist fractures in the province of Ontario, Canada, were examined. From 1996 to 2001, BMD testing and use of bone-sparing medications increased each year, whereas despite the aging of the population, wrist and hip fracture rates decreased. Introduction: If patients with osteoporosis are being diagnosed and effective treatments used with increasing frequency in the population, rates of hip and wrist fractures will remain stable or possibly decrease. We report here time trends in BMD testing, prescriptions for bone-sparing medications, hip and wrist fracture rates, and population projections of fracture rates to 2005 in the province of Ontario, Canada. Materials and Methods: Ontario residents have universal access to Medicare. To examine time trends in BMD testing, all physician claims for DXA from 1992 to 2001 were selected from the Ontario Health Insurance Plan (OHIP) database. Trends in prescribing were examined from 1996 to 2003 using data from the Ontario Drug Benefit plan, which provides coverage to persons ,65 years of age. Actual numbers of hip and wrist fractures were determined for 1992-2000 and population projections for 2001-2005 using time-series analysis. Wrist fractures were identified in the OHIP database and hip fractures through hospital discharge abstracts. Results: From 1992 to 2001, the number of BMD tests increased 10-fold. There has been a steady increase in the number of persons filling prescriptions for antiresorptives (12,298 in 1996 to 225,580 in 2003) and the majority were for etidronate. For women, the rate of decline for wrist fractures is greater than that for hip fractures. The rate of hip fracture was fairly constant around 41 per 10,000 women ,50 years between 1992 and 1996. In 1997, the hip fracture rate began to decrease, and the population projections suggest that this downward trend will continue to a rate of 33.1 per 10,000 in 2005. Conclusions: Our findings suggest that fracture rates may be on the decline, despite the aging of the population, because of increased patterns of diagnosis and treatment for osteoporosis. [source]

Population trends of Rooks Corvus frugilegus in Spain and the importance of refuse tips

IBIS, Issue 1 2008
PEDRO P. OLEA
Anthropogenic food from refuse tips can affect population dynamics in birds, especially gulls, but the evidence is mostly circumstantial. We combine analyses of long-term population data and natural experiments to show a positive effect of refuse tips on the growth of the Spanish breeding population of Rooks Corvus frugilegus. In this isolated population of around 2000 breeding pairs, monitored since 1976, birds in colonies less than 10 km from tips fed largely on refuse, particularly during periods of lowest natural food availability. Three lines of evidence support the hypothesis that the supply of refuse influenced breeding numbers, suggesting that this population is limited by food: 1) between 1976 and 2003, the two population nuclei that had access to tips increased 2.1 and 3.7 times more than that without a tip nearby; 2) annual colony growth between 1996 and 2003 was strongly correlated with the availability of tips when other potentially important variables were taken into account; 3) the number of breeding pairs in refuse-foraging colonies declined rapidly after the closure of the local tip and recovered only when a supply of refuse was restored. The effect of tips on colony growth was stronger when the availability of natural foraging habitat around the colonies was low, suggesting that anthropogenic food acts as a buffer against shortage of natural food. Artificial food supplementation may be an effective tool to increase the breeding population of target species, especially those facing a reduction of their foraging habitats. The potential effects on bird species of Directive 1999/31/CE, which is enforcing a massive closure of tips in Europe, are discussed. [source]

Population trends of widespread woodland birds in Europe

IBIS, Issue 2007
RICHARD D. GREGORY
We explore population trends of widespread and common woodland birds using data from an extensive European network of ornithologists for the period 1980,2003. We show considerable differences exist in the European trends of species according to the broad habitat they occupy and the degree to which they specialize in habitat use. On average, common forest birds are in shallow decline at a European scale; common forest birds declined by 13%, and common forest specialists by 18%, from 1980 to 2003. In comparison, populations of common specialists of farmland have declined moderately, falling on average by 28% from 1980 to 2003. These patterns contrast with that shown by generalist species whose populations have been roughly stable over the same period, their overall index increasing by 3%. There was some evidence of regional variation in the population trends of these common forest species. The most obvious pattern was the greater stability of population trends in Eastern Europe compared with other regions considered. Among common forest birds, long-distance migrants and residents have on average declined most strongly, whereas short-distance migrants have been largely stable, or have increased. There was some evidence to suggest that ground- or low-nesting species have declined more strongly on average, as have forest birds with invertebrate diets. Formal analysis of the species trends confirmed the influence of habitat use, habitat specialization and nest-site; the effects of region and migration strategy were less clear-cut. There was also evidence to show that year-to-year variation in individual species trends at a European scale was influenced by cold winter weather in a small number of species. We recommend that the species trend information provided by the new pan-European scheme should be used alongside existing mechanisms to review the conservation status of European birds. The analysis also allows us to reappraise the role of common forest bird populations as a potential barometer of wider forest health. The new indicator appears to be a useful indicator of the state of widespread European forest birds and might prove to be a useful surrogate for trends in forest biodiversity and forest health, but more work is likely to be needed to understand the interaction between bird populations and their drivers in forest. [source]

Population trends of large non-migratory wild herbivores and livestock in the Masai Mara ecosystem, Kenya, between 1977 and 1997

AFRICAN JOURNAL OF ECOLOGY, Issue 3 2000
Wilber K. Ottichilo
The total of all non-migratory wildlife species in the Masai Mara ecosystem has declined by 58% in the last 20 years. This decline ranges from 49% in small brown antelopes to 72% in medium brown antelopes. In individual wildlife species, the decline ranges from 52% in Grant's gazelle to 88% in the warthog. Declines of over 70% have been recorded in buffalo, giraffe, eland and waterbuck. Only elephant, impala and ostrich have not shown any significant decline or increase. Overall, there has not been any significant difference in decline of all wildlife population sizes inside and outside the reserve, except for Thomson's gazelle and warthog. Livestock have not significantly declined over the entire analysis period. However, livestock and cattle populations significantly declined during the 1983,88 period. Donkey declined by 67%, while shoats (goats and sheep) remained stable. In the case of wildlife, land use and vegetation changes, drought effects and poaching are considered to be among the potential factors that may have been responsible for the decline; the decline in livestock during the 1983,84 period was probably due to drought effects. Résumé Le total de toutes les espèces animales non migratrices a baissé de 58% dans l'écosystème du Masai Mara au cours des vingt dernières années. Ce déclin va de 49% chez les petites antilopes brunes à 72% chez les antilopes de taille moyenne. Pour les espèces prises individuellement, la baisse va de 52% pour la Gazelle de Grant à 88% pour le phacochère. On a rapporté des baisses de plus de 70% chez les buffles, les girafes, les élands et les waterbucks. Seuls les éléphants et les autruches ne présentent ni hausse ni baisse significatives. Dans l'ensemble, il n'y a aucune différence significative dans le déclin des tailles de toutes les populations de faune sauvage dans et en dehors de la réserve, sauf pour la Gazelle de Thomson et le phacochère. Le cheptel n'a pas baissé significativement pendant la durée de l'étude. Cependant, les populations du cheptel et du bétail ont baissé significativement entre 1983 et 1988. Les ânes ont diminué de 67%, tandis que chèvres et moutons restaient stables. Dans le cas de la faune sauvage, les changements d'utilisation des terres et de la végétation, les effets de la sécheresse et du braconnage sont à compter parmi les facteurs qui peuvent avoir été responsables du déclin; le déclin du cheptel en 1983,1984 était probablement dûà la sécheresse. [source]

Population trends and habitat use of Harlequin Ducks in Rhode Island

JOURNAL OF FIELD ORNITHOLOGY, Issue 3 2007
Christine M. Caron
ABSTRACT To assess population trends of Harlequin Ducks (Histrionicus histrionicus) in Rhode Island (U.S.A.), we analyzed Christmas Bird Counts and other historical surveys and also conducted surveys during the winter of 2005,2006. We estimated sex and age ratios, evaluated the effects of tidal regime and time of day on survey precision, and quantified habitat use. The population in Rhode Island experienced logistic growth from 1976 to 2004, with approximately 150 birds now wintering at three primary sites in the state. We estimated that the current ratio of males to females in the region was 1.6:1 (62% males) and that 13% of males were first-winter birds. Most Harlequin Ducks were observed in rocky habitats within 50 m of the shore or offshore islands. We detected the greatest numbers of birds, with the least amount of variation, during morning surveys at low tide, suggesting that this may be the most appropriate time for population monitoring. Increases in the Rhode Island population and male-biased sex ratios may indicate a local population recovery resulting from a hunting ban initiated in 1990. Although most Harlequin Ducks in eastern North America winter in Maine, the population in Rhode Island represents one of the largest in the southern part of their range. SINOPSIS Para determinar las tendencias poblacionales de arlequines (Histrionicus histrionicus), en Rhode Island, analizamos los conteos navideños, otros censos históricos y además llevamos a cabos censos durante el invierno de 2005,2006. Cuantificamos el uso de habitat, estimamos la tasa de edad y sexos y evaluamos el efecto del régimen de mareas y la hora del dia en la presición de los censos. La población de patos arlequines experimentó un crecimiento logístico de 1976,2004, con unos 150 patos pasando el invierno en tres localidades primarias, del estado. Estimamos una tasa de 1.6:1 de machos a hembras (62% de machos), siendo un 13% de los machos individuos de primer invierno. La mayoría de las aves fueron observadas en hábitats rocosos a unos 50 m de la playa o en islas cerca de la playa. Detectamos el mayor número de aves, con la menor variación, en los censos que se llevaron a cabo durante la marea baja, lo que sugiere que este es el momento más apropiado para monitorear sus poblaciones. El aumento de estas aves en Rhode Island, el sesgo en su sexo, hacia mayor cantidad de machos, pudiera indicar, de un recobro poblacional como resultado la prohibición de su cacería a partir de 1990. Aunque la mayoría de los arlequines de la parte este de los EUA pasan el invierno en Maine, la población de Rhode Island representa una de las mayores en la parte sur de su distribución. [source]

Patterns of commonness and rarity in central European birds: reliability of the core-satellite hypothesis within a large scale

ECOGRAPHY, Issue 4 2002
David Storch
The frequency distribution of species' area of occupancy is often bimodal, most species being either very rare or very common in terms of number of occupied sites. This pattern has been attributed to the nonlinearity associated with metapopulation dynamics of the species, but there are also other explanations comprising sampling artifact and frequency distribution of suitable habitats. We tested whether the bimodal frequency distribution of occupied squares in central European birds could be derived solely from the frequency distribution of species population sizes (i.e. the sampling artifact hypothesis) or from the spatial distribution of their preferred habitats. Both models predict high proportion of very common species, i.e. the right side of frequency distribution. Bimodality itself is well predicted by models based on random placement of individuals according to their abundances but neither model predicts the observed prevalence of rare species. Even the combined models that assume random placement of individuals within the squares with suitable habitat do not predict such a high proportion of rare species. The observed distribution is more aggregated, rare species occupying a smaller portion of suitable habitat than predicted on the basis of their abundance. The pattern is consistent with metapopulation processes involving local population extinctions. The involvement of these processes is supported by two further observations. First, species rarity is associated with significant population trend and/or location on the edge of their ranges within central Europe, both situations presumably associated with metapopulation processes. Second, suitable habitats seem to be either saturated or almost unoccupied, which is consistent with the predictions of the metapopulation model based on nonlinear dynamics of extinction and colonization. Although the habitat suitability is an important determinant of species distribution, the rarity of many species of birds within this scale of observation seems to be affected by other factors, including local population extinctions associated with fragmentation of species' habitats. [source]

Age-dependent reproductive performance in Northern Goshawks Accipiter gentilis

IBIS, Issue 1 2003
Jan Tøttrup Nielsen
The age-specific reproductive performance of Northern Goshawks Accipiter gentilis was studied over 22 years in Denmark. The age of the breeding female in relation to the number of young raised was known in 929 breeding attempts, while the age of both the male and the female was known in 496 breeding attempts. The number of fledglings raised per breeding attempt increased with both male and female age, but only for females was it possible to conduct a detailed analysis of this age-dependent relationship. The annual production of fledglings increased with female age from 1 to 7 years of age, whereupon it started to decline. A longitudinal analysis showed that this mean population trend could be attributed to similar age-related trends in individual females. Previous breeding experience did not influence the number of fledglings produced by individual females, and poorly performing females apparently survived with the same probability as well performing ones. The most likely explanation for the age-dependent reproductive performance in the observed Goshawk population appeared to be age-related improvements in competence, such as foraging efficiency. [source]

DETERMINATION OF MANATEE POPULATION TRENDS ALONG THE ATLANTIC COAST OF FLORIDA USING A BAYESIAN APPROACH WITH TEMPERATURE-ADJUSTED AERIAL SURVEY DATA

When are genetic methods useful for estimating contemporary abundance and detecting population trends?

MOLECULAR ECOLOGY RESOURCES, Issue 4 2010
DAVID A. TALLMON
Abstract The utility of microsatellite markers for inferring population size and trend has not been rigorously examined, even though these markers are commonly used to monitor the demography of natural populations. We assessed the ability of a linkage disequilibrium estimator of effective population size (Ne) and a simple capture-recapture estimator of abundance (N) to quantify the size and trend of stable or declining populations (true N = 100,10,000), using simulated Wright,Fisher populations. Neither method accurately or precisely estimated abundance at sample sizes of S = 30 individuals, regardless of true N. However, if larger samples of S = 60 or 120 individuals were collected, these methods provided useful insights into abundance and trends for populations of N = 100,500. At small population sizes (N = 100 or 250), precision of the Ne estimates was improved slightly more by a doubling of loci sampled than by a doubling of individuals sampled. In general, monitoring Ne proved a more robust means of identifying stable and declining populations than monitoring N over most of the parameter space we explored, and performance of the Ne estimator is further enhanced if the Ne/N ratio is low. However, at the largest population size (N = 10,000), N estimation outperformed Ne. Both methods generally required , 5 generations to pass between sampling events to correctly identify population trend. [source]

Physical activity, food intake, and body weight regulation: insights from doubly labeled water studies

NUTRITION REVIEWS, Issue 3 2010
Klaas R Westerterp
Body weight and energy balance can be maintained by adapting energy intake to changes in energy expenditure and vice versa, whereas short-term changes in energy expenditure are mainly caused by physical activity. This review investigates whether physical activity is affected by over- and undereating, whether intake is affected by an increase or a decrease in physical activity, and whether being overweight affects physical activity. The available evidence is based largely on studies that quantified physical activity with doubly labeled water. Overeating does not affect physical activity, while undereating decreases habitual or voluntary physical activity. Thus, it is easier to gain weight than to lose weight. An exercise-induced increase in energy requirement is typically compensated by increased energy intake, while a change to a more sedentary routine does not induce an equivalent reduction of intake and generally results in weight gain. Overweight and obese subjects tend to have similar activity energy expenditures to lean people despite being more sedentary. There are two ways in which the general population trend towards increasing body weight can be reversed: reduce intake or increase physical activity. The results of the present literature review indicate that eating less is the most effective method for preventing weight gain, despite the potential for a negative effect on physical activity when a negative energy balance is reached. [source]

One Hundred Fifty Years of Change in Forest Bird Breeding Habitat: Estimates of Species Distributions

CONSERVATION BIOLOGY, Issue 6 2005
LISA A. SCHULTE
aptitud del hábitat; ecología aviar; ecología de paisaje; planificación de conservación Abstract:,Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant change. We propose pre-Euro-American settlement as an alternative baseline for assessing changes in bird populations. We evaluated the amount, quality, and distribution of breeding bird habitat during the mid-1800s and early 1990s for three forest birds: the Pine Warbler (Dendroica pinus), Blackburnian Warbler (D. fusca), and Black-throated Green Warbler (D. virens). We constructed models of bird and habitat relationships based on literature review and regional data sets of bird abundance and applied these models to widely available vegetation data. Original public-land survey records represented historical habitat conditions, and a combination of forest inventory and national land-cover data represented current conditions. We assessed model robustness by comparing current habitat distribution to actual breeding bird locations from the Wisconsin Breeding Bird Atlas. The model showed little change in the overall amount of Pine Warbler habitat, whereas both the Blackburnian Warber and the Black-throated Green Warbler have experienced substantial habitat losses. For the species we examined, habitat quality has degraded since presettlement and the spatial distribution of habitat shifted among ecoregions, with range expansion accompanying forest incursion into previously open habitats or the replacement of native forests with pine plantations. Sources of habitat loss and degradation include loss of conifers and loss of large trees. Using widely available data sources in a habitat suitability model framework, our method provides a long-term analysis of change in bird habitat and a presettlement baseline for assessing current conservation priority. Resumen:,La evaluación de tendencias de las poblaciones de aves requiere de datos de referencia. En Norte América, los primeros datos disponibles de poblaciones son del final de la década de 1960. Sin embargo, las condiciones de los bosques en los estados de los Grandes Lagos (E.U.A.) han experimentado sucesión desde que la región fue talada en los inicios del siglo veinte, y se espera que las poblaciones de aves hayan experimentado cambios concomitantes. Proponemos que se considere al período previo a la colonización euro americana como referencia alternativa para evaluar los cambios en las poblaciones de aves. Evaluamos la cantidad, calidad y distribución del hábitat para reproducción de tres especies de aves de bosque (Dendroica pinus, D. fusca y D. virens) a mediados del siglo XIX e inicios del XX. Construimos modelos de las relaciones entre las aves y el hábitat con base en la literatura y conjuntos de datos de abundancia de aves y los aplicamos a los datos de vegetación ampliamente disponibles. Los registros topográficos de tierras públicas originales representaron las condiciones históricas del hábitat, y una combinación de datos del inventario forestal y de cobertura de suelo representaron las condiciones actuales. Evaluamos la robustez del modelo mediante la comparación de la distribución de hábitat actual con sitios de reproducción de aves registrados en el Wisconsin Breeding Bird Atlas. El modelo mostró poco cambio en la cantidad total de hábitat de Dendroica pinus, mientras que tanto D. fusca como D. virens han experimentado pérdidas sustanciales de hábitat. Para las especies examinadas, la calidad del hábitat se ha degradado desde antes de la colonización y la distribución espacial del hábitat cambió entre ecoregiones, con la expansión del rango acompañando la incursión de bosques en hábitats anteriormente abiertos o el reemplazo de bosques nativos con plantaciones de pinos. Las fuentes de pérdida y degradación de hábitats incluyen la pérdida de coníferas y de árboles grandes. Mediante la utilización de fuentes de datos ampliamente disponibles en un modelo de aptitud de hábitat, nuestro método proporciona un análisis a largo plazo de los cambios en el hábitat de aves y una referencia precolonización para evaluar prioridades de conservación actuales. [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]

Trends in morphine prescriptions, illicit morphine use and associated harms among regular injecting drug users in Australia

DRUG AND ALCOHOL REVIEW, Issue 5 2006
LOUISA DEGENHARDT
Abstract This paper examines population trends in morphine prescriptions in Australia, and contrasts them with findings from annual surveys with regular injecting drug users (IDU). Data on morphine prescriptions from 1995 to 2003 were obtained from the Drug Monitoring System (DRUMS) run by the Australian Government Department of Health and Ageing. Data collected from regular IDU as part of the Australian Illicit Drug Reporting System (IDRS) were analysed (2001,2004). The rate of morphine prescription per person aged 15,54 years increased by 89% across Australia between 1995 and 2003 (from 46.3 to 85.9 mg per person). Almost half (46%) of IDU surveyed in 2004 reported illicit morphine use, with the highest rates in jurisdictions where heroin was less available. Recent morphine injectors were significantly more likely to be male, unemployed, out of treatment and homeless in comparison to IDU who had not injected morphine. They were also more likely to have injected other pharmaceutical drugs and to report injection related problems. Among those who had injected morphine recently, the most commonly reported injecting harms were morphine dependence (38%), difficulty finding veins into which to inject (36%) and scarring or bruising (27%). Morphine use and injection is a common practice among regular IDU in Australia. In some cases, morphine may be a substitute for illicit heroin; in others, it may be being used to treat heroin dependence where other pharmacotherapies, such as methadone and buprenorphine, are perceived as being unavailable or undesirable by IDU. Morphine injection appears to be associated with polydrug use, and with it, a range of problems related to drug injection. Further research is required to monitor and reduce morphine diversion and related harms by such polydrug injectors. [source]

Heroin users in Australia: population trends

DRUG AND ALCOHOL REVIEW, Issue 1 2004
C. YALÇIN KAYA Senior Lecturer
Abstract The aim of this paper is to identify certain important population trends among heroin users in Australia for the period 1971 , 97, such as: population growth, initiation, i.e. the number who were initiated to heroin in a given year, and quitting, i.e. the number that quit using heroin. For this purpose, we summarize and extract relevant characteristics from data from National Drug Strategy Household Survey (NDSHS 1998) conducted in Australia in 1998. We devise a systematic procedure to estimate historical trends from questions concerning past events. It is observed from our findings that the size of the heroin user population in Australia is in a sharp increase, especially from the early 1980s onwards. The general trend obtained for the period 1971 , 97 is strikingly similar to that obtained by Hall et al. (2000) for the dependent heroin user population in Australia, even though their study was based on different datasets and a different methodology. In our reconstruction of the time history we also detect a levelling-off prior to 1990. Initiation is also observed to be on a sharp increase. The latter trend is accompanied by a similar trend of quitting, perhaps indicating a relatively short heroin use career. A sharp decrease in both initiation and quitting is observed after 1990. In conclusion, in the case of the trend in the population of heroin users a high rate of growth has been identified that is consistent with the existing literature. In the process, we demonstrated that even a static survey such as NDSHS 1998 can, sometimes, be used to extract historical (dynamic) trends of certain important variables. [source]

Using fishers' anecdotes, naturalists' observations and grey literature to reassess marine species at risk: the case of the Gulf grouper in the Gulf of California, Mexico

FISH AND FISHERIES, Issue 2 2005
Andrea Sáenz, Arroyo
Abstract Designing fishing policies without knowledge of past levels of target species abundance is a dangerous omission for fisheries management. However, as fisheries monitoring started long after exploitation of many species began, this is a difficult issue to address. Here we show how the ,shifting baseline' syndrome can affect the stock assessment of a vulnerable species by masking real population trends and thereby put marine animals at serious risk. Current fishery data suggest that landings of the large Gulf grouper (Mycteroperca jordani, Serranidae) are increasing in the Gulf of California. However, reviews of historical evidence, naturalists' observations and a systematic documentation of fishers' perceptions of trends in the abundance of this species indicate that it has dramatically declined. The heyday for the Gulf grouper fishery occurred prior to the 1970s, after which abundance dropped rapidly, probably falling to a few percent of former numbers. This decline happened long before fishery statistics were formally developed. We use the case of the Gulf grouper to illustrate how other vulnerable tropical and semi-tropical fish and shellfish species around the world may be facing the same fate as the Gulf grouper. In accordance with other recent studies, we recommend using historical tools as part of a broad data-gathering approach to assess the conservation status of marine species that are vulnerable to over-exploitation. [source]

Night sampling improves indices used for management of yellow perch in Lake Erie

FISHERIES MANAGEMENT & ECOLOGY, Issue 1 2010
P. M. KOCOVSKY
Abstract, Catch rate (catch per hour) was examined for age-0 and age-1 yellow perch, Perca flavescens (Mitchill), captured in bottom trawls from 1991 to 2005 in western Lake Erie: (1) to examine variation of catch rate among years, seasons, diel periods and their interactions; and (2) to determine whether sampling during particular diel periods improved the management value of CPH data used in models to project abundance of age-2 yellow perch. Catch rate varied with year, season and the diel period during which sampling was conducted as well as by the interaction between year and season. Indices of abundance of age-0 and age-1 yellow perch estimated from night samples typically produced better fitting models and lower estimates of age-2 abundance than those using morning or afternoon samples, whereas indices using afternoon samples typically produced less precise and higher estimates of abundance. The diel period during which sampling is conducted will not affect observed population trends but may affect estimates of abundance of age-0 and age-1 yellow perch, which in turn affect recommended allowable harvest. A field experiment throughout western Lake Erie is recommended to examine potential benefits of night sampling to management of yellow perch. [source]

Financial Exclusion in Rural and Remote New South Wales, Australia: a Geography of Bank Branch Rationalisation, 1981,98

GEOGRAPHICAL RESEARCH, Issue 2 2000
N.M. Argent
The provision of financial services in rural Australia is a significant public policy issue, reflected in the high level of media and political interest in the recent spate of branch closures. There are, however, many aspects of the current debate regarding the delivery of financial services to rural communities that are, at best, less than ideal and, at worst, erroneous. Using telephone directories for New South Wales, non-metropolitan bank branch listings for the period 1981 to 1998 were collated. A recategorisation of these data according to the Rural, Remote and Metropolitan Areas classification reveals, amidst a spatial realignment of financial service provision, that rural and remote New South Wales have been disproportionately affected by a relatively recent and concerted withdrawal of services. The research demonstrates that corporate-level responses to increased competition within the financial system are significantly more important in deciding rural access to banking services than local and regional population trends. Indeed, two-thirds of rural localities that have lost branches had experienced healthy population growth during the study period. In the wake of the post-deregulation reconfiguration of the bank branch network, the socio-economic marginalisation of rural communities is being compounded, a process of ,financial exclusion' recognised in other parts of the developed world. [source]

Interspecific differences in population trends of Spanish birds are related to habitat and climatic preferences

GLOBAL ECOLOGY, Issue 1 2008
Javier Seoane
ABSTRACT Aim, Animal monitoring programmes have allowed analyses of population trends, most of which now comment on the possible effect of global climate change. However, the relationship between the interspecific variation in population trends and species traits, such as habitat preferences, niche breadth or distribution patterns, has received little attention, in spite of its usefulness in the construction of ecological generalizations. The objectives of this study were: (1) to determine whether there are characteristics shared among species with upwards or downwards trends, and (2) to assess whether population changes agree with what could be expected under global warming (a decrease in species typical of cooler environments). Location, The Spanish part of the Iberian Peninsula (c. 500,000 km2) in the south-western part of the Mediterranean Basin. Methods, We modelled recent breeding population changes (1996,2004), in areas without apparent land use changes, for 57 common passerine birds with species-specific ecological and distributional patterns as explanatory variables. Results, One-half of these species have shown a generalized pattern towards the increase of their populations, while only one-tenth showed a significant decrease. One half (54%) of the interspecific variability in yearly population trends is explained considering species-specific traits. Species showing more marked increases preferred wooded habitats, were habitat generalists and occupied warmer and wetter areas, while moderate decreases were found for open country habitats in drier areas. Main conclusions, The coherent pattern in population trends we found disagrees with the proposed detrimental effect of global warming on bird populations of western Europe, which is expected to be more intense in bird species inhabiting cooler areas and habitats. Such a pattern suggests that factors other than the increase in temperature may be brought to discussions on global change as relevant components to explain recent changes in biodiversity. [source]

Determining the effects of habitat management and climate on the population trends of a declining steppe bird

IBIS, Issue 3 2009
MARÍA PAULA DELGADO
The Little Bustard Tetrax tetrax is one of the most threatened steppe bird species in Europe, due mainly to agricultural intensification. Despite the relative importance of the Iberian population (approximately 50% of the global population) little is known about its dynamics and trends, especially in core distribution areas. This study evaluates the influences of meteorological factors and land management on the oscillations and medium-term trends of two Little Bustard populations in Central Spain. During 2001,2007, surveys of breeding male and female Little Bustards were carried out in two central Spanish locations: Valdetorres, in Special Protection Area (SPA) no. 139 (1600 ha), and Campo Real, in Important Bird Area (IBA) no. 075 (1150 ha). Densities were 3.3,4.0 and 1.1,2.1 males/km2 in Campo Real, and 1.8,2.2 and 0.6,1.3 females/km2 in Valdetorres. The sex ratio was biased towards males in both cases. Both populations declined during 2001,2007, especially in Valdetorres (60%). Variation in habitat composition did not explain variation in the numbers of males. Both populations were influenced by total precipitation in the preceding October,May period. Results suggest that the Little Bustard may be sensitive to future climate trends in Europe. Finally, different simulated demographic scenarios suggest that low female survival and productivity may be the immediate cause of the decline in Little Bustard populations, which is consistent with their sensitivity to climatic conditions. [source]

Population trends of widespread woodland birds in Europe

Impacts of a volcanic eruption on the forest bird community of Montserrat, Lesser Antilles

IBIS, Issue 2 2007
B. DALSGAARD
Volcanic eruptions are an important and natural source of catastrophic disturbance to ecological communities. However, opportunities to study them are relatively rare. Here we report on the effects of the eruption of the Soufrière Hills volcano on the forest bird community of the Lesser Antillean island of Montserrat. The island's species-poor avifauna includes 11 restricted-range species, including the Critically Endangered endemic Montserrat Oriole Icterus oberi. Analysis of monitoring data from 1997 to 2005 indicates that counts of most species were substantially lower following major ashfalls. However, this effect was short-lived, with rapid population recovery in subsequent years. Furthermore, levels of seasonal rainfall appear to have been at least as important in determining population trends as ashfall. Overall, most species were at least as abundant at the end of the study as at the start, and no forest bird species have been extirpated from Montserrat. We discuss potential ecological drivers of ashfall impacts on populations: there is some evidence that terrestrial foragers were most severely affected. [source]

Analysis and discussion of Maned wolf Chrysocyon brachyurus population trends in Brazilian institutions: lessons from the Brazilian studbook, 1969,2006

INTERNATIONAL ZOO YEARBOOK, Issue 1 2010
R. E. T. VANSTREELS
The Maned wolf Chrysocyon brachyurus is the largest canid of South America and is considered Near Threatened by IUCN. Annual studbook questionnaires were sent to 62 institutions in Brazil, and data were obtained for 932 animals (422.406.104) from 1969 to 2006. The historical trend has shown that the Brazilian captive population has progressed towards a maximum size plateau of 140 individuals; several demographic parameters indicated a poor overall breeding success in the population (only 14% of all the potential founders have effectively bred, mean breeding population each year was 18%), low gene flow (only 22% of the animals were transferred between institutions), high infant mortality (79% of all captive-born cubs die within their first year) and poor management of over-represented individuals (20% of the breeding animals had ten or more cubs). A high influx of wild-caught animals was noted (median 12 captures year,1), with most being captured in the economically developed south-eastern region. It is concluded that the captive population is demographically unstable and highly dependent on the influx of wild-caught animals. Broader collaborations with field conservationists and paired research programmes are advised to maximize future ex situ contribution to the conservation of Maned wolf in Brazil. [source]

Comparative changes in adult vs. juvenile survival affecting population trends of African ungulates

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2005
NORMAN OWEN-SMITH
Summary 1Among large mammalian herbivores, juvenile survival tends to vary widely and may thus have a greater influence on population dynamics than the relatively constant survival rates typical of adults. However, previous studies yielding stage-specific survival rates have been mostly on temperate zone ungulates and in environments lacking large predators. 2Annual censuses coupled with assessments of population structure enabled annual survival rates to be estimated for the juvenile, yearling and adult segments of nine ungulate species in South Africa's Kruger National Park. Four of these populations persisted at high abundance after initial increases (zebra, wildebeest, impala and giraffe), while five showed progressive declines during the latter part of the study period (kudu, waterbuck, warthog, sable antelope and tsessebe). 3The magnitude of the reduction in adult survival between periods showing contrasting population trends was similar to or greater than the corresponding change in juvenile survival for five of the nine species. Accordingly alterations in population phase, from increasing to stable or stable to declining, were brought about mostly through reduced survival within the adult segment. Elevated predation risk may have been responsible. 4Estimates were derived of the relative survival rates of juveniles, yearlings and adult segments associated with zero population growth, and the survival differential between adult males and females, for all nine species. Stage-specific survival rates appeared dependent on body mass, but with some anomalies. The sex difference in adult survival showed no obvious relation with sexual size dimorphism. 5For large mammalian herbivores, assessments of relative elasticities of stage-specific survival rates on population growth are problematic for several reasons. Sensitivity to corresponding increments in either survival or mortality rates provides a better basis for ecological or adaptive interpretation. Survival rates of adults seem to vary more over multiyear periods compared with mainly annual fluctuations in juvenile survival. More studies are needed on tropical species and in environments retaining large predators to support generalizations about factors influencing ungulate life-history patterns. [source]

Time to extinction in relation to mating system and type of density regulation in populations with two sexes

JOURNAL OF ANIMAL ECOLOGY, Issue 5 2004
BERNT-ERIK SÆTHER
Summary 1Population viability models usually consider only the female segment of the population. However, random variation in sex ratio as well as the mating system may also affect variation in fitness among females. Here we develop population models incorporating demographic stochasticity in both sexes. Furthermore, we consider the effects on the estimated time to extinction and whether density regulation acts only on females or on total population size. 2We applied these models to two populations of polygynous great reed warblers Acrocephalus arundinaceus L. with differences in population trends to investigate the importance of considering sex in population viability models. 3Demographic stochasticity was larger in a polygynous than in a monogamous mating system. 4The estimated time to extinction was considerably shorter for a monogamous than for a polygynous mating system, particularly if density regulation acted only on females than rather on the total population. 5This study demonstrates that structure of mating system must be included when making population viability analysis based on counts of total population sizes. It is especially important to model the specific effects of density regulation on the two sexes. [source]

Linking resources with demography to understand resource limitation for bears

JOURNAL OF APPLIED ECOLOGY, Issue 6 2007
MELISSA J. REYNOLDS-HOGLAND
Summary 1,Identifying the resources that limit growth of animal populations is essential for effective conservation; however, resource limitation is difficult to quantify. Recent advances in geographical information systems (GIS) and resource modelling can be combined with demographic modelling to yield insights into resource limitation. 2,Using long-term data on a population of black bears Ursus americanus, we evaluated competing hypotheses about whether availability of hard mast (acorns and nuts) or soft mast (fleshy fruits) limited bears in the southern Appalachians, USA, during 1981,2002. The effects of clearcutting on habitat quality were also evaluated. Annual survival, recruitment and population growth rate were estimated using capture,recapture data from 101 females. The availability of hard mast, soft mast and clearcuts was estimated with a GIS, as each changed through time as a result of harvest and succession, and then availabilities were incorporated as covariates for each demographic parameter. 3,The model with the additive availability of hard mast and soft mast across the landscape predicted survival and population growth rate. Availability of young clearcuts predicted recruitment, but not population growth or survival. 4,Availability of hard mast stands across the landscape and availability of soft mast across the landscape were more important than hard mast production and availability of soft mast in young clearcuts, respectively. 5,Synthesis and applications. Our results indicate that older stands, which support high levels of hard mast and moderate levels of soft mast, should be maintained to sustain population growth of bears in the southern Appalachians. Simultaneously, the acreage of intermediate aged stands (10,25 years), which support very low levels of both hard mast and soft mast, should be minimized. The approach used in this study has broad application for wildlife management and conservation. State and federal wildlife agencies often possess long-term data on both resource availability and capture,recapture for wild populations. Combined, these two data types can be used to estimate survival, recruitment, population growth, elasticities of vital rates and the effects of resource availability on demographic parameters. Hence data that are traditionally used to understand population trends can be used to evaluate how and why demography changes over time. [source]

An astronomical pattern-matching algorithm for computer-aided identification of whale sharks Rhincodon typus

JOURNAL OF APPLIED ECOLOGY, Issue 6 2005
Z. ARZOUMANIAN
Summary 1The formulation of conservation policy relies heavily on demographic, biological and ecological knowledge that is often elusive for threatened species. Essential estimates of abundance, survival and life-history parameters are accessible through mark and recapture studies given a sufficiently large sample. Photographic identification of individuals is an established mark and recapture technique, but its full potential has rarely been exploited because of the unmanageable task of making visual identifications in large data sets. 2We describe a novel technique for identifying individual whale sharks Rhincodon typus through numerical pattern matching of their natural surface ,spot' colourations. Together with scarring and other markers, spot patterns captured in photographs of whale shark flanks have been used, in the past, to make identifications by eye. We have automated this process by adapting a computer algorithm originally developed in astronomy for the comparison of star patterns in images of the night sky. 3In tests using a set of previously identified shark images, our method correctly matched pairs exhibiting the same pattern in more than 90% of cases. From a larger library of previously unidentified images, it has to date produced more than 100 new matches. Our technique is robust in that the incidence of false positives is low, while failure to match images of the same shark is predominantly attributable to foreshortening in photographs obtained at oblique angles of more than 30°. 4We describe our implementation of the pattern-matching algorithm, estimates of its efficacy, its incorporation into the new ECOCEAN Whale Shark Photo-identification Library, and prospects for its further refinement. We also comment on the biological and conservation implications of the capability of identifying individual sharks across wide geographical and temporal spans. 5Synthesis and applications. An automated photo-identification technique has been developed that allows for efficient ,virtual tagging' of spotted animals. The pattern-matching software has been implemented within a Web-based library created for the management of generic encounter photographs and derived data. The combined capabilities have demonstrated the reliability of whale shark spot patterns for long-term identifications, and promise new ecological insights. Extension of the technique to other species is anticipated, with attendant benefits to management and conservation through improved understanding of life histories, population trends and migration routes, as well as ecological factors such as exploitation impact and the effectiveness of wildlife reserves. [source]

The accuracy of matrix population model projections for coniferous trees in the Sierra Nevada, California

JOURNAL OF ECOLOGY, Issue 4 2005
PHILLIP J. VAN MANTGEM
Summary 1We assess the use of simple, size-based matrix population models for projecting population trends for six coniferous tree species in the Sierra Nevada, California. We used demographic data from 16 673 trees in 15 permanent plots to create 17 separate time-invariant, density-independent population projection models, and determined differences between trends projected from initial surveys with a 5-year interval and observed data during two subsequent 5-year time steps. 2We detected departures from the assumptions of the matrix modelling approach in terms of strong growth autocorrelations. We also found evidence of observation errors for measurements of tree growth and, to a more limited degree, recruitment. Loglinear analysis provided evidence of significant temporal variation in demographic rates for only two of the 17 populations. 3Total population sizes were strongly predicted by model projections, although population dynamics were dominated by carryover from the previous 5-year time step (i.e. there were few cases of recruitment or death). Fractional changes to overall population sizes were less well predicted. Compared with a null model and a simple demographic model lacking size structure, matrix model projections were better able to predict total population sizes, although the differences were not statistically significant. Matrix model projections were also able to predict short-term rates of survival, growth and recruitment. Mortality frequencies were not well predicted. 4Our results suggest that simple size-structured models can accurately project future short-term changes for some tree populations. However, not all populations were well predicted and these simple models would probably become more inaccurate over longer projection intervals. The predictive ability of these models would also be limited by disturbance or other events that destabilize demographic rates. [source]

Predicted population trends for Cozumel Curassows (Crax rubra griscomi): empirical evidence and predictive models in the face of climate change

JOURNAL OF FIELD ORNITHOLOGY, Issue 4 2009
Miguel A. Martínez-Morales
ABSTRACT We assessed the current conservation status and population trends of Cozumel Curassows (Crax rubra griscomi), a critically endangered and endemic cracid of Cozumel Island, Mexico. Distance sampling was used to estimate the population size in 2005 and compare it with a previous estimate in 1995. Population viability analysis (PVA) was used to model population trends, considering ecological and environmental conditions prevailing in 1995 and 2005. Additional PVA models were constructed using different hypothetical scenarios to assess the effects of particular factors and management strategies on population trends. We estimated a population size of 372 ± 155 curassows in the island's tropical semideciduous forest, before two hurricanes hit Cozumel Island in 2005. PVA modeling predicted a steep decline in population size in the ensuing decades as a result of an increased frequency and intensity of hurricanes related to global climate change, and an observed female bias in the sex ratio likely caused by a higher mortality rate for adult males. We recommend urgent management actions for the long-term conservation of Cozumel Curassows, including a ban on hunting, eradication of the feral fauna, particularly dogs, and implementation of a captive-breeding program to supplement the wild population. RESUMEN Evaluamos el estado de conservación actual y las tendencias poblacionales del hocofaisán de Cozumel (Crax rubra griscomi), un crácido críticamente amenazado y endémico a la Isla de Cozumel, México. Se empleó el muestreo de distancias para estimar su tamaño poblacional en 2005 y compararlo con la estimación previa de 1995. Se emplearon análisis de viabilidad poblacional (AVP) para modelar tendencias poblacionales considerando las condiciones ecológicas y ambientales prevalecientes en 1995 y 2005. Adicionalmente, se construyeron modelos de AVP bajo diferentes escenarios hipotéticos para evaluar los efectos de factores específicos y estrategias de manejo sobre su tendencia poblacional. Estimamos un tamaño poblacional de 372 ± 155 hocofaisanes en la selva mediana subcaducifolia de la isla, antes del impacto de dos huracanes sobre Cozumel en 2005. El AVP predijo una severa declinación en el tamaño poblacional en las siguientes décadas como resultado de un incremento en la frecuencia e intensidad de huracanes relacionado con el cambio climático global, y de un sesgo en la proporción sexual hacia las hembras, probablemente asociado a una mayor mortalidad de machos adultos. Recomendamos acciones de manejo urgentes para la conservación a largo plazo del hocofaisán de Cozumel, incluyendo una efectiva prohibición de la cacería, la erradicación completa de fauna feral, particularmente perros, y la implementación de un programa de reproducción en cautiverio para suplementar la población silvestre. [source]