Age Structure Of Population Research Articles

Population characteristics, seasonal distribution, and suppression potential of introduced Northern Pike in a Great Plains stream

AbstractObjectiveThe objectives of this study were to describe the population dynamics, reproductive characteristics, and movement of Northern Pike Esox lucius in the Niobrara River drainage of Wyoming. This information was used to estimate the necessary level of suppression to meaningfully reduce their abundance and thereby facilitate persistence of native nongame fishes.MethodsIn 2019 and 2020, Northern Pike were sampled to describe population size structure, age structure, growth, and mortality. An additional 42 gravid female Northern Pike were collected across 2020–2023 to determine a length–fecundity relationship. Vulnerability to recruitment overfishing was modeled with a static spawning potential ratio model. Finally, 15 mature fish were implanted with radio transmitters in 2021 and 2022 and tracked for 1 year to determine seasonal dispersal and spawning locations.ResultSampled Niobrara River drainage Northern Pike (n = 213) varied from 127 to 749 mm total length. Estimated ages of fish were between 0 and 8 years, and total annual mortality was estimated at 42% (95% confidence interval = 36–48%) in the presumed absence of fishing mortality. Recruitment was extremely stable, and growth was relatively fast through age 2. Some females matured at age 1, and all females were mature by age 2 and spawned annually. Estimated total fecundity for females between 297 and 914 mm total length varied from 3573 to 154,877 eggs. Most telemetered fish moved little throughout the year, but movements as large as 5.9 river kilometers were observed. Modeling suggests that exploitation of age‐1 and older Northern Pike should exceed 42% and exploitation of age‐2 and older fish should exceed 85% to meaningfully reduce the population's reproductive potential.ConclusionNorthern Pike growth and reproductive potential at older ages may be more limited in small prairie streams than within their native range. Observed annual home range was small, and spawning occurred annually in consistent locations. The necessary intensity of mechanical removal to achieve meaningful suppression in this system will likely require an intensive and ongoing interstate effort.

A Hierarchical Bayesian Model for Estimating Age-Specific COVID-19 Infection Fatality Rates in Developing Countries.

The COVID-19 infection fatality rate (IFR) is the proportion of individuals infected with SARS-CoV-2 who subsequently die. As COVID-19 disproportionately affects older individuals, age-specific IFR estimates are imperative to facilitate comparisons of the impact of COVID-19 between locations and prioritize distribution of scarce resources. However, there lacks a coherent method to synthesize available data to create estimates of IFR and seroprevalence that vary continuously with age and adequately reflect uncertainties inherent in the underlying data. In this article, we introduce a novel Bayesian hierarchical model to estimate IFR as a continuous function of age that acknowledges heterogeneity in population age structure across locations and accounts for uncertainty in the estimates due to seroprevalence sampling variability and the imperfect serology test assays. Our approach simultaneously models test assay characteristics, serology, and death data, where the serology and death data are often available only for binned age groups. Information is shared across locations through hierarchical modeling to improve estimation of the parameters with limited data. Modeling data from 26 developing country locations during the first year of the COVID-19 pandemic, we found seroprevalence did not change dramatically with age, and the IFR at age 60 was above the high-income country estimate for most locations.

The Potential of Internal Migration to Shape Rural and Urban Populations Across Africa, Asia, and Latin America

AbstractSubnational divergence in the age and sex structures of populations can have far‐stretching consequences for development: from marriage markets to the potential for violence to economic growth. With urbanization and the demographic transition still underway, rural and urban populations continue to differ across low‐ and middle‐income countries. We examine the extent by which internal migration contributes to these differences, from 1970 to 2014 using estimates of migration between rural and urban sectors based on census data from 45 countries. We found that despite heavily delineated migration profiles by age and sex, internal migration does not alter sex and age structures of rural and urban populations. All the same, internal migration does increase urban growth in Asia and Latin America and the Caribbean. In contrast, in Africa, internal migration has little leverage with the urban transition. Across the continents, there is a potential for de‐urbanization, driven by a rural/urban gap in fertility. As such, the rural population may continue to constitute a significant proportion of national populations, necessitating critical investments to ensure they are not left behind.

Population age structure and conservation status of Ferula sinkiangensis (Apiaceae) in Xinjiang, China

Abstract Ferula sinkiangensis K.M. Shen is a threatened medicinal plant endemic to Xinjiang, China, with a small population size and a narrow distribution range. We assessed the status of this species with respect to its population age structure, the level of threat and extinction risk. Only one population remains, in Yining County, Xinjiang. We conducted field surveys of the population in 2022 and 2023, counting 2,033 and 1,515 individuals, respectively, in 144 sample quadrats. We assessed the age structure of the population by counting the number of basal leaves of each individual. The frequency distribution had an inverted J-shape, indicative of a relatively stable age structure. However, the number of mature individuals was small, raising concerns about the risk of genetic drift and inbreeding. This species is also threatened by habitat destruction and inappropriate collection practices. We recommend that F. sinkiangensis is categorized as Critically Endangered on the IUCN Red List on the basis of criteria B2ab(iii), C2a(i) and D.

Insights into trypanosomiasis transmission: Age, infection rates, and bloodmeal analysis of Glossina fuscipes fuscipes in N.W. Uganda.

Tsetse flies (Glossina) transmit species of Trypanosoma which cause human African trypanosomiasis (HAT) and animal African trypanosomiasis (AAT). Understanding the epidemiology of this disease and controlling the vector rationally requires analysis of the abundance, age structure, infection rates and feeding patterns of tsetse populations. We analysed a population of G. fuscipes fuscipes in the Koboko district of Uganda. Seasonal variation in the abundance of tsetse was assessed from the numbers of tsetse caught in pyramidal traps. The age structure of the population was assessed by dissecting female tsetse to estimate their ovarian categories. Classical and PCR-based methods were utilised to determine the presence of the three major pathogenic species of salivarian trypanosomes: T. vivax, T. congolense and T. brucei in a subset (n = 2369) of flies. Further, bloodmeal analysis was carried out using PCR to amplify and sequence a portion of the vertebrate cytb gene. The abundance and age structure of tsetse populations were relatively stable and a slight seasonal four-fold variation in abundance appeared to be correlated with rainfall. Analyses of age structure suggests a low natural daily mortality of 1.75% (1.62-1.88). Infection rates estimated were significantly greater (1.9-9.3 times) using the PCR-based method compared to the classical dissection-based method. Positive rates for T. brucei sl, T. congolense and T. vivax were 1.6% (1.32-2.24), 2.4% (1.83-3.11and 2.0% (1.46-2.63), respectively by PCR. The majority of bloodmeals were identified as cattle (39%, 30.5-47.8) and human (37%, 28.4-45.6). The seasonally stable abundance, low mortality rate and high proportion of bloodmeals from humans may explain, in part, why this district has historically been a focus of sleeping sickness. Additionally, the high rates of cattle feeding indicate insecticide treated cattle may prove to be a useful vector control strategy in the area.

Shifting Sands: Examining and Mapping the Population Structure of Greece Through the Last Three Censuses

This paper aims to facilitate a more nuanced understanding of regional disparities in the population age structure at a local scale by applying a recent method for visualizing these disparities. Utilizing data from the three most recent population censuses in Greece, this method applies advanced data visualization techniques to map age distributions, highlighting significant variations in aging patterns across municipalities, towns, and districts. Traditional demographic analysis often overlooks local heterogeneities, leading to broad policies that often fail to address the unique needs of specific regions. Detailed maps are created by integrating geographic data with census data (using R and GIS), enabling policymakers to pinpoint areas with specific demographic challenges and opportunities. This localized approach reveals critical insights, such as regions experiencing rapid population aging, areas with younger population profiles, and zones undergoing demographic transitions. The visualization tool significantly improves the formulation of targeted strategies, enhancing the effectiveness of policies related to healthcare, workforce planning, and social services distribution. Through case studies and comparative analysis, we demonstrate the practical applications and advantages of this method in shaping public policy and strategic planning. This paper contributes to the field of geodemography by introducing and demonstrating a visualization method that enhances the accuracy of demographic analysis, providing policy makers with useful information to better address local demographic challenges and tailor strategies to specific regional needs.

The ecology of ageing in wild societies: linking age structure and social behaviour.

The age of individuals has consequences not only for their fitness and behaviour but also for the functioning of the groups they form. Because social behaviour often changes with age, population age structure is expected to shape the social organization, the social environments individuals experience and the operation of social processes within populations. Although research has explored changes in individual social behaviour with age, particularly in controlled settings, there is limited understanding of how age structure governs sociality in wild populations. Here, we synthesize previous research into age-related effects on social processes in natural populations, and discuss the links between age structure, sociality and ecology, specifically focusing on how population age structure might influence social structure and functioning. We highlight the potential for using empirical data from natural populations in combination with social network approaches to uncover pathways linking individual social ageing, population age structure and societal functioning. We discuss the broader implications of these insights for understanding the social impacts of anthropogenic effects on animal population demography and for building a deeper understanding of societal ageing in general.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Population age structure shapes selection on social behaviour in a long-lived insect.

Social traits are expected to experience highly context-dependent selection, but we know little about the contextual factors that shape selection on social behaviours. We hypothesized that the fitness consequences of social interactions will depend on the age of social partners, and therefore that population age structure will shape evolutionary pressures on sociality. Here, we investigate the consequences of age variation at multiple levels of social organization for both individual fitness and sexual selection on social network traits. We experimentally manipulated the age composition of populations of the forked fungus beetle Bolitotherus cornutus, creating 12 replicate populations with either young or old age structures. We found that fitness is associated with variance in age at three different levels of organization: the individual, interacting social partners, and the population. Older individuals have higher reproductive success, males pay a fitness cost when they interact with old males and females achieve lower fitness in older populations. In addition to influencing fitness, population age structure also altered the selection acting on social network position in females. Female sociality is under positive selection only in old populations. Our results highlight age structure as an understudied demographic variable shaping the landscape of selection on social behaviour.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Health, an ageing labour force, and the economy: Does health moderate the relationship between population age-structure and economic growth?

Abstract Research often suggests that population ageing will be detrimental for the economy due to increased labour market exits and lost productivity, however the role of population health and disability at older ages is not well established. Identifying whether the health of older people affects economic outcomes is challenging due to methodological issues. Using country-level panel data, we estimate the relationship between the size of the older working age population (aged 55-69) and economic growth across 180 countries from 1990 to 2017. We run models using annual data and 5-year moving averages of real per capita GDP growth as dependent variables. This enables us to quantify the gains in real per capita GDP growth associated with a healthy older working-age population on a country-by-country basis. The initial models confirm an inverse-U or hump-shaped relationship between population age groups and economic growth. In the 5 year average GDP growth model, the coefficient for the inverse of YLDs among 55-69 year olds is positive and significant at p < 0.01. The interaction term is significant at p < 0.001 in the same model. Across all countries, a 5% improvement in YLDs is associated with at minimum 0.3% predicted additional annual real per capita GDP growth. While a larger share of the older working-age population at ages 55-69 has historically been associated with slower real per capita GDP growth, low levels of disability in this age group can reduce or even eliminate these adverse economic effects. We consistently find a significant positive interaction between disability and the share of the population at ages 55-69, suggesting that adverse economic effects are amenable to policy intervention.

The concept of critical age group for density dependence: bridging the gap between demographers, evolutionary biologists and behavioural ecologists.

Density dependence plays an important role in population regulation in the wild. It involves a decrease in population growth rate when the population size increases. Fifty years ago, Charlesworth introduced the concept of 'critical age group', denoting the age classes in which variation in the number of individuals most strongly contributes to density regulation. Since this pioneering work, this concept has rarely been used. In light of Charlesworth's concept, we discuss the need to develop work between behavioural ecology, demography and evolutionary biology to better understand the mechanisms acting in density-regulated age-structured populations. We highlight demographic studies that explored age-specific contributions to density dependence and discuss the underlying evolutionary processes. Understanding competitive interactions among individuals is pivotal to identify the ages contributing most strongly to density regulation, highlighting the need to move towards behavioural ecology to decipher mechanisms acting in density-regulated age-structured populations. Because individual characteristics other than age can be linked to competitive abilities, expanding the concept of critical age to other structures (e.g. sex, dominance rank) offers interesting perspectives. Linking research fields based on the concept of the critical age group is key to move from a pattern-oriented view of density regulation to a process-oriented approach.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Age structure of carp and catfish catch as a tool to assess ecological health of fished stocks from the Ganga River system with special reference to Mahseer Tor tor (Hamilton, 1822)

In the 20th centuary, the economically important carp species Labeo rohita, Tor tor, & Labeo calbasu and the catfishes Rita rita & Bagarius bagarius contributed substantially to the total fish catch from the Ganga River system in India. Samples were recorded between December 2003 and June 2004 from fish landing centers in the Ken, Paisuni, and Tons rivers for L. rohita, T. tor and L. calbasu. Rita rita and B. bagarius were sampled between September 2001 and September 2003 in the Ganga River system. The data were used to evaluate the growth and age structures of fish populations. Age classes varied 0+–5+ for L. rohita in the Ken & Paisuni rivers and 0+–8+ in the Tons River. For T. tor, the age classes varied 1+–6+ in the Ken & Paisuni rivers and 1+–8+ in the Tons. Age classes of L. calbasu varied 1+–6+ in the Ken River, 1+–5+ in the Paisuni River, and 1+–7+ in the Tons. In the Ganga River, age classes of R. rita & B. bagarius varied 0+–7+ and 0+–6+, respectively. The L. rohita, age pyramid showed a tendency for bell shape in Ken River, base tends to be broader through bell shape in Paisuni River, and bell-shaped age pyramid was slightly distorted in Tons River. In case of T. tor, tendency for bell shape in Ken River and bell-shaped age pyramid in Paisun River & Tons River were obtained. In case of L. calbasu, heavy bottom shaped age pyramid was recorded in Ken and Paisuni rivers, while base tends to be broader in the Tons River. Bell shaped age pyramid was recorded for B. bagarius in the Ganga River while heavy bottom shape for R. rita in the Ganga River. Overall, T. tor is facing heavy fishing pressure and also targeted fish species by fishermen from the Ganga River system.

Reconstruction of China’s population age and education structure from 2000 to 2020—based on the data from the 5th to 7th national population censuses in China

Reconstruction of China’s population age and education structure from 2000 to 2020—based on the data from the 5th to 7th national population censuses in China

Age, Growth, Sex Composition, and Diet of the Burbot, Lota lota, the Only Freshwater Species of the Family Lotidae in the Amur (Heilongjiang) River, Northeast China

Information about the population structure, including the age and sex composition, growth characteristics, and diet of fish, is essential for the conservation and sustainable exploitation of fish stock. The burbot, Lota lota, is the only freshwater species of the family Lotidae in the Amur (Heilongjiang) River catchment located in northeastern China. Information on the biological characteristics and data on the population structure of this fish from the Amur River are scarce. To study these factors in burbot, Lota lota, in the Amur River of China, 749 specimens from four sampling areas were taken and analyzed in October 2022, January 2023, and May 2023. The ages of the sampled fish ranged from 1+ to 7+ years. The female/male ratio was 1.04:1, and body length and mass varied from 175 to 595 mm and 73.5 to 1958.7 g, respectively. The length–weight regression parameter b value was estimated as 2.80. The parameters of the von Bertalanffy growth model were L∞ = 596, K = 0.221, and t0 = −0.771 for all sampled fish; L∞ = 625, K = 0.208, and t0 = −0.756 for females; and L∞ = 584, K = 0.219, and t0 = −0.980 for males. The analysis of the stomach contents showed fish to be the major source of nutrition across all areas and sampling periods. In January, the secondary prey of burbots in the Huma reach of the upper Amur River was aquatic insect larvae, while, in the Tongjiang and Fuyuan reaches of the middle Amur River, the secondary prey was shrimp. The mean stomach fullness index and rate of empty stomachs differed with the sampling area, with the greatest proportion of empty stomachs observed in the Luobei reach of the middle Amur River, and the lowest in the Tongjiang and Fuyuan reaches. The mean stomach fullness index showed the opposite trend. In the Huma reach, the contributions of fish to the diet and the mean stomach fullness index were significantly higher in May than in October and January. The study provides the first detailed information on the population age and sex structure, growth patterns, and feeding ecology of burbots from the Amur River, China. The results will aid in formulating management strategies and regulations for local populations of burbots in the Amur River, China.

Bioresources of lake Mostovoye and ways of their rational use

The ichthyofauna of most water bodies in the Altai Krai is represented by low-value and slow-growing fish. Fish productivity is largely determined by the degree of exploitation of the reservoir and the form of organization of the fishery. Rational fishery in natural reservoirs should ensure the exploitation of the ecosystem of the reservoir as a single whole. Mostovoe Lake is located in the Zavyalovsky and Baevsky districts of the Altai Krai, is one of the largest freshwater lakes in the Altai Territory, belonging to the floodplain of the Kulunda River. The water in the reservoir is of the sulfate-chloride class of the first type, fully meets all fish farming requirements. The collection of ichthyological material was carried out by the method of control catches. The species composition and spatial distribution of fish were studied by setting a set of fixed gill nets in the reservoirs. Information on the size and age structure of populations, catches of the main commercial fish and crayfish in Mostovoe Lake is provided. The magnitude of the fishing effort and the assessment of the state of aquatic bioresources (ichthyofauna) in the reservoir were carried out using one of the expert assessment options — the point systems method. The ichthyofauna of Mostovoe Lake includes six species that are subject to commercial fishing: common pike, roach, silver carp, river perch, common carp (carp), and common pike perch. Of the commercial invertebrates, crayfish is caught. The indicators of the commercial stock and the recommended catch of bioresources in the reservoir were calculated. Recommendations for regulating fisheries based on ichthyological monitoring are proposed. A certain effect for stabilizing the structure of the ichthyocenosis of the reservoir can be made by fishery melioration: the introduction of herbivorous fish — white amur (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) for a more complete use of the food base of the lake — phytoplankton and macrophytes. It is necessary to continue monitoring studies of the lake’s winter oxygen regime.

A Survey on Computational Methods in Drug Discovery for Neurodegenerative Diseases.

Currently, the age structure of the world population is changing due to declining birth rates and increasing life expectancy. As a result, physicians worldwide have to treat an increasing number of age-related diseases, of which neurological disorders represent a significant part. In this context, there is an urgent need to discover new therapeutic approaches to counteract the effects of neurodegeneration on human health, and computational science can be of pivotal importance for more effective neurodrug discovery. The knowledge of the molecular structure of the receptors and other biomolecules involved in neurological pathogenesis facilitates the design of new molecules as potential drugs to be used in the fight against diseases of high social relevance such as dementia, Alzheimer's disease (AD) and Parkinson's disease (PD), to cite only a few. However, the absence of comprehensive guidelines regarding the strengths and weaknesses of alternative approaches creates a fragmented and disconnected field, resulting in missed opportunities to enhance performance and achieve successful applications. This review aims to summarize some of the most innovative strategies based on computational methods used for neurodrug development. In particular, recent applications and the state-of-the-art of molecular docking and artificial intelligence for ligand- and target-based approaches in novel drug design were reviewed, highlighting the crucial role of in silico methods in the context of neurodrug discovery for neurodegenerative diseases.

A convergence analysis for the approximation to the solution of an age-structured population model with infinite lifespan

Considering the numerical approximation of the density distribution for an age-structured population model with unbounded lifespan on a compact interval [0,T], we prove second order of convergence for a discretization that adaptively selects its truncated age-interval according to the exponential rate of decay with age of the solution of the model. It appears that the adaptive capacity of the length in the truncated age-interval of the discretization to the infinity lifespan is a very convenient approach for a long-time integration of the model to establish the asymptotic behavior of its dynamics numerically. The analysis of convergence uses an appropriate weighted maximum norm with exponential weights to cope with the unbounded age lifespan. We report experiments to exhibit numerically the theoretical results and the asymptotic behavior of the dynamics for an age-structured squirrel population model introduced by Sulsky.

Analysis Of the Impact of China's Population Age Structure on Residential Commercial Housing Prices

With the intensification of global aging, the impact of changes in population age structure on the real estate market is becoming increasingly significant. This article aims to explore the impact of changes in China's population age structure on the prices of residential commercial housing, to provide a scientific basis for regulating the real estate market. By analyzing data from 30 provinces and cities in China from 2013 to 2022, this article finds that as aging population intensifies and the number of children decreases, both the old-age dependency ratio and the child-age dependency ratio have a negative impact on housing prices. This means that the aging society and the economic pressure of childcare may weaken the demand for home purchases. Household Saving Rate and increase in total population positively drive house prices, while the relationship between per capita income and house prices is not significant. From a regional perspective, the aging population in the eastern region has a significant effect on suppressing housing prices, while the impact is gradually evident in the central region. The western region has a smaller impact and population growth suppresses housing price increases. The study emphasizes the impact of changes in the age structure of the Chinese population on the prices of residential properties and proposes policy recommendations such as improving old-age security and optimizing the housing supply structure to promote the steady development of the real estate market.

Stand structure and disturbance history of old-growth blue pine (Pinus wallichiana) forests in the Bhutan Himalaya

Blue pine (Pinus wallichiana) forests are of significant ecological, economic, and cultural importance in the Himalayas. We used dendrochronological methods to investigate the role of natural and human disturbance in shaping the development of these forests. Analyses of the age structure and growth patterns of blue pine populations over the period 1760–2020 at two different sites in central Bhutan revealed that blue pine tends to establish as single-cohort stands following relatively intense disturbances and as multi-cohort stands after low-to-moderate severity disturbances. Shifting cultivation, which was common across the region, likely led to the establishment of single-cohort stands, particularly near human settlements, whereas natural disturbances are likely responsible for the development of multi-cohort stands. Tree-ring records revealed an acute change in recruitment patterns in the early 1970s associated with the 1969 Forest Act of Bhutan, which limited traditional practices, such as firewood collection and grazing, within the forests. This led to a sudden and sustained increase in the recruitment of broadleaf tree species and effectively curtailed blue pine regeneration over the past half century due to thick understory and midstory vegetation reducing the amount of light reaching the forest floor. These results highlight the role of disturbances, both human and natural, in driving forest stand dynamics in Himalayan forests and how forest policy and traditional practices can alter those dynamics.

Resource stock, age structure, and seed prediction of ferula sinkiangensis K.M. Shen

Ferula sinkiangensis K.M. Shen (FS) is an endemic species in Xinjiang, China. It has extremely high economic and medicinal value but is on the brink of extinction. A comprehensive survey of the distribution area of FS was conducted to study its resource stock, age structure and yielding capacity of seeds. Results show that there is one existing distribution area of FS with an area of 322.84 hm2 and a total plant quantity of 907,100. The age structure of FS population is reasonable showing a growing type of population. After low-temperature treatment and indoor germination of the seeds of FS, the utilization efficiency of seeds was increased by 15.45 times and 1165.81 times respectively. The establishment of the original habitat protection zone has played a huge role in promoting the recovery of the population of FS and the indoor germination of seeds would greatly alleviate the problem of seeds shortage of FS. Bangladesh J. Bot. 53(3): 765-772, 2024 (September) Special

Marine reserves can buffer against environmental fluctuations for overexploited but not sustainably harvested fisheries.

Globally, decision-makers are seeking management levers that can mitigate the negative effects of climate change on ecosystems that have already been transformed from their natural state by the effects of fishing. An important question is whether marine reserves can provide buffering (i.e., population-level resilience) against climate disturbances to fished populations. Here, we examine one aspect of this question, by asking whether marine reserves can reduce the variability in either overall biomass or in fishery yield, in the face of environmental variability. This could happen because greater reproduction of longer-lived, larger fish inside reserves could supplement recruitment to the fished portion of the population. We addressed this question using age-structured population models, assuming a system where some proportion of the coastline is protected in marine reserves (0%-30%), and the remainder is fished (at a range of possible harvest rates). We modeled populations with sedentary adults and dispersal via a larval pool. Since recent extreme climate events (e.g., marine heatwaves) have reduced juvenile survival for some fish species, we assumed that environmental variability affected the survival of the first age class in our model. We viewed population variability as a question of buffering, measured as the proportion of time a simulated population spent below a target reference point, with the idea that marine reserves could prevent the population from reaching low levels in the face of fishing and environmental variability. We found that fisheries with more area in marine reserves always had less variability in biomass. However, adding marine reserves only reduced variability in fisheries yield when the fished part of the population was being harvested at a rate exceeding the maximum sustainable yield. This new result on reducing variability is in line with previous findings that the "spillover" effects of marine reserve benefits to fishery yields only accrue when the fishery outside reserve boundaries is being overharvested.