Search

Currently, tapping is the only method of obtaining natural rubber, an essential industrial raw material. The stability of the labor force supply for tapping is crucial for the sustainable development of the natural rubber industry. As China's second-largest rubber planting area, Hainan Island had a planting area of 585,800 hectares in 2020, accounting for 45% of the country's total, with over 2 million workers. Labor force shortages and the aging phenomenon in tapping have become increasingly severe and have attracted significant attention. However, the related research lacks detailed spatial information for conversion estimation, which hinders macroeconomic regulation. This study is based on the 2020 Hainan Island natural rubber distribution map, Dynamic World land use classification products, and the WorldPop population distribution dataset. It employs multiple technical operations such as temporal and spatial filtering, removal of small patches, buffer parameter settings, and masking to obtain the 2020 potential tapping labor density map for Hainan's rubber planting areas. Spatial statistical methods are used to analyze the spatial distribution and age structure characteristics of potential tapping labor force in Hainan's rubber planting areas as well as the spatial distribution of labor force shortage degrees after conversion to actual tapping labor force, including the labor force shortage levels and areas for each city and county, revealing the spatial pattern. The results reveal the following: 1) The total number of potential tapping laborers in Hainan's rubber planting areas is 1.567 4 million, with a spatial distribution pattern of high in the north and low in the south. The proportion of the population aged 45~59 years is 34%, indicating a significant aging trend. 2) There are significant spatial differences in the degree of labor shortage. The primary shortage areas are mainly concentrated in the junction areas of the central-western and central-eastern counties, with a belt-like distribution. In contrast, the secondary and tertiary shortage areas are widely distributed in the central-western, central, and some central-eastern county junctions, with shortage in the central area being particularly severe, showing a contiguous distribution. 3) The primary shortage areas in Danzhou City, Baisha County, and Qiongzhong County rank in the top three, with a cumulative area of 50, 500 hectares. Baisha, Qiongzhong, Chengmai, and Ledong Counties are also prominent in the secondary and tertiary shortage areas, covering a total area of 23, 300 hectares. In total, the area of labor shortage regions in Hainan Island is 141, 700 hectares, necessitating a future focus. To address the labor force shortage issue in tapping, it is recommended to strengthen infrastructure construction in the rubber plantations within the shortage areas and actively promote new tapping methods (e. g., low-frequency tapping) or tools (e. g., electric tapping knives) to reduce the labor intensity of tapping and increase the number of trees tapped per capita. This will provide favorable support for the sustainable and healthy development of Hainan's natural rubber industry. By revealing the spatial distribution characteristics and degree of tapping labor shortage, this study aims to provide robust decision-making support for the Hainan provincial government in addressing employment issues of tapping labor, optimizing human resource management strategies, and promoting the sustainable development of the natural rubber industry. [ABSTRACT FROM AUTHOR]

For organisms in temperate environments, seasonal variation in resource availability and weather conditions exert fluctuating selection pressures on survival and fitness, resulting in diverse adaptive responses. By manipulating resource availability on a local spatial scale, we studied seasonal patterns of resource use within natural populations of burying beetles Nicrophorus vespilloides in a Norfolk woodland. Burying beetles are necrophagous insects that breed on vertebrate carcasses. They are active in Europe between April and October, after which they burrow into the soil and overwinter. Using breeding and chemical analyses, we compared the fecundity and physiological state of beetles that differed in their seasonal resource use. We found seasonal variation in carrion use by wild burying beetles and correlated differences in their reproductive success and cuticular hydrocarbon profiles. Our results provide novel insight into the seasonal correlates of behaviour, physiology and life history in burying beetles. [ABSTRACT FROM AUTHOR]

Myctophids are one of the most diverse and abundant fish families in the mesopelagic zone, making them a key component in the marine pelagic community. In the North Atlantic, Benthosema glaciale (glacier lantern fish) is considered the most abundant myctophid north of 35° N, yet some regions within its extensive range lack information on its basic biological parameters. We investigated the growth and described the distribution of B. glaciale in Icelandic waters, including the southern continental shelf, Iceland Basin, and Irminger Sea. Length distribution, growth, relative body condition, age, and otolith‐fish size relationships were analyzed from samples collected opportunistically with pelagic trawls during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS) in July 2020. In total, 1374 individuals were caught, and only a subset of 225 were measured fresh at sea and 89 were frozen and dissected on land. Total lengths of fresh fish ranged from 38 to 85 mm, while dissected individuals ranged from 40 to 74 mm and were 2 to 6 years old. Located over the Reykjanes Ridge in the Iceland Basin region, individuals had a significantly higher mean standard length and mean age, and a lower mean body condition. We reported length–weight relationships for both fresh and frozen samples, indicating evidence that preserving of the specimens through freezing affected relationships. The von Bertalanffy growth curve was calculated along with significant otolith‐fish size relationships where r2 values ranged between 0.87 and 0.92. Our research highlights the importance of cross‐regional studies and provides baseline biology for B. glaciale in Icelandic waters, specifically in the southern continental slope and Reykjanes Ridge. [ABSTRACT FROM AUTHOR]

The survival of relict Taxus wallichiana var. wallichiana (Yunnan yew) is threatened by overexploitation for its quality wood and medicinal properties, particularly for taxol extraction. Understanding the current status of its communities and populations is crucial for protecting existing natural forest resources. We established 53 vegetation plots in Yunnan, southwestern China, where T. wallichiana var. wallichiana is the primary dominant species. These plots were classified into four forest types. The forests were multi-stratified, with T. wallichiana var. wallichiana frequently dominating the subcanopy and shrub layer. Species diversity indices did not significantly differ among the four forest types. The age structure of T. wallichiana var. wallichiana exhibited a multi-modal pattern, with a maximum age of 1165 years. Growth was slow, with an average radial growth rate of 0.78 mm/year. Despite its strong sprouting ability, the species had a poor seedling/sapling bank and suffered from inadequate regeneration. Its seedlings/saplings are shade-intolerant. This study provides a scientific basis for effective conservation strategies, emphasizing the need for in situ regeneration to ensure the survival of T. wallichiana var. wallichiana and its contributions to biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

Understanding factors that influence population‐level responses to emerging threats in declining species is crucial for informed conservation action. In amphibian species impacted by the chytrid fungus (Batrachochytrium dendrobatidis), a pathogen that has caused amphibian declines globally, a commonly reported pattern is that more severe population declines tend to occur at higher elevations. Previous research has suggested that this pattern could be driven by reduced environmental suitability for chytrid fungus at lower elevations. However, delayed amphibian maturation, which is common in cold, high elevation populations, could also increase vulnerability to population decline. Here, we tackle this key knowledge gap, focusing on the critically endangered corroboree frogs (Pseudophryne corroboree and P. pengilleyi), which have experienced a pattern of extirpation at higher elevations, with remnant populations persisting at lower elevations. First, we quantify the age structure of two extant low elevation P. pengilleyi populations and museum specimens (both species) collected before the emergence of chytrid fungus in Australia. Male age to maturation varied from 1 to 3 years, with the extant population with higher chytrid prevalence displaying severe age structure truncation. Second, we use population simulations to calculate elasticity values under a range of scenarios with varying ages to maturation and chytrid‐associated mortality. When the population growth rate was fixed at 1, adult survival became increasingly important as age to maturation increases, particularly under a scenario of high chytrid‐associated mortality. Our simulation results indicate that delayed maturation could be a previously underappreciated factor associated with an increased risk of amphibian population decline and that earlier maturation could contribute to population persistence. Our study highlights the importance of examining variation in life history traits to better understand population‐level responses to novel threats and guide the development of appropriate conservation actions. [ABSTRACT FROM AUTHOR]

The proportions of individuals in various age classes in a population of wild animals affect population trends, behaviors, learning, and social structures. Knowledge of age structure is needed for effective conservation and management of populations. However, it is not always possible to determine the age or age class of individual animals, and hence the age structure of the population. Penguins, like most birds, cannot be aged once they molt into adult plumage. Spheniscus penguins attain adult plumage at 6 to 24 months of age, and individuals can live more than 30 years. We studied foot darkening in the four species of Spheniscus penguins to determine if age class can be determined from foot color. We compared how foot color changes with age among the four species to investigate potential functions of the darkening. We found that Spheniscus penguins have pale feet at hatching and the feet become darker with age throughout the lives of individuals. We showed that we can accurately predict the age structure of a colony of Magellanic penguins Spheniscus magellanicus, but not the ages of individual penguins, based on a sample of foot colors. The timing of foot darkening within species was consistent with foot color functioning in protection from UV radiation, and not with foot color functioning in thermoregulation. The species that breeds at the lowest latitudes and experiences the highest UV radiation (Galápagos penguins Spheniscus mendiculus) had feet that darkened at the earliest ages, and the species that breed at higher latitudes and experience less intense insolation (African S. demersus and Magellanic penguins) had feet that darkened latest. Humboldt penguins S. humboldti breed mostly at low latitudes and foot darkening was intermediate between Galápagos and Magellanic penguins. We also found that males' feet darken somewhat earlier than females' feet, likely because females spend more time in their nests (burrows or under vegetation) than males and have less sun exposure. We found that feet darkened in an individual over years, but not within a breeding season. The color change is a life-long process, likely an evolutionary adaptation within species, not a seasonal, temporary response to UV radiation. We propose foot darkening as a way to assess age structure in Spheniscus penguins. Foot color in a colony of Magellanic penguins can provide a rapid, noninvasive method to estimate the age structure of the colony. [ABSTRACT FROM AUTHOR]

We use a panel data set of Japanese firms from 2005 to 2019 to examine how a firm's employee age structure affects its productivity and wages. The pooled ordinary-least-squares (OLS) results indicate a negative relationship between the proportion of older employees and labor productivity. However, the effects disappear after applying a fixed effects (FE) model and the generalized method of moments to consider the unobserved heterogeneity among firms. Moreover, the proportion of older employees does not significantly affect firms' wages. We further examine firm heterogeneity as a factor that contributes to the difference between the pooled OLS and FE estimates. The results suggest that differences in corporate stakeholder characteristics and corporate governance, such as the presence of labor unions and proportion of foreign ownership, may be related to the ratio of older workers and corporate performance. [ABSTRACT FROM AUTHOR]

Currently, tapping is the only method of obtaining natural rubber, an essential industrial raw material. The stability of the labor force supply for tapping is crucial for the sustainable development of the natural rubber industry. As China's second-largest rubber planting area, Hainan Island had a planting area of 585,800 hectares in 2020, accounting for 45% of the country's total, with over 2 million workers. Labor force shortages and the aging phenomenon in tapping have become increasingly severe and have attracted significant attention. However, the related research lacks detailed spatial information for conversion estimation, which hinders macroeconomic regulation. This study is based on the 2020 Hainan Island natural rubber distribution map, Dynamic World land use classification products, and the WorldPop population distribution dataset. It employs multiple technical operations such as temporal and spatial filtering, removal of small patches, buffer parameter settings, and masking to obtain the 2020 potential tapping labor density map for Hainan's rubber planting areas. Spatial statistical methods are used to analyze the spatial distribution and age structure characteristics of potential tapping labor force in Hainan's rubber planting areas as well as the spatial distribution of labor force shortage degrees after conversion to actual tapping labor force, including the labor force shortage levels and areas for each city and county, revealing the spatial pattern. The results reveal the following: 1) The total number of potential tapping laborers in Hainan's rubber planting areas is 1.567 4 million, with a spatial distribution pattern of high in the north and low in the south. The proportion of the population aged 45~59 years is 34%, indicating a significant aging trend. 2) There are significant spatial differences in the degree of labor shortage. The primary shortage areas are mainly concentrated in the junction areas of the central-western and central-eastern counties, with a belt-like distribution. In contrast, the secondary and tertiary shortage areas are widely distributed in the central-western, central, and some central-eastern county junctions, with shortage in the central area being particularly severe, showing a contiguous distribution. 3) The primary shortage areas in Danzhou City, Baisha County, and Qiongzhong County rank in the top three, with a cumulative area of 50,500 hectares. Baisha, Qiongzhong, Chengmai, and Ledong Counties are also prominent in the secondary and tertiary shortage areas, covering a total area of 23,300 hectares. In total, the area of labor shortage regions in Hainan Island is 141,700 hectares, necessitating a future focus. To address the labor force shortage issue in tapping, it is recommended to strengthen infrastructure construction in the rubber plantations within the shortage areas and actively promote new tapping methods (e.g., low-frequency tapping) or tools (e.g., electric tapping knives) to reduce the labor intensity of tapping and increase the number of trees tapped per capita. This will provide favorable support for the sustainable and healthy development of Hainan's natural rubber industry. By revealing the spatial distribution characteristics and degree of tapping labor shortage, this study aims to provide robust decision-making support for the Hainan provincial government in addressing employment issues of tapping labor, optimizing human resource management strategies, and promoting the sustainable development of the natural rubber industry.

Relict subtropical coniferous forests in China face severe fragmentation, resulting in declining populations, and some are under significant threat from invasive alien species. Despite the crucial importance of understanding forest dynamics, knowledge gaps persist, particularly regarding the impact of invasive plants on vulnerable natives like Keteleeria evelyniana. In this study, we investigated the impact of invasive plants on the regeneration of forests dominated by K. evelyniana, a subtropical relict species in southwestern China. For this purpose, we characterized forest dynamics of 160 forest plots featuring K. evelyniana as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of K. evelyniana. We identified four distinct forest types in which K. evelyniana was dominant. We found that radial growth of K. evelyniana trees is faster in younger age-classes today than it was for older trees at the same age. The population structure of K. evelyniana in each forest type exhibited a multimodal age-class distribution. However, three forest types lacked established saplings younger than 10 years old, a situation attributed to the dense coverage of the invasive alien Ageratina adenophora. This invasive species resulted in a reduction of understory species diversity. Additionally, our analysis uncovered a significant negative correlation in phylogenetic relatedness (net relatedness index) between native and invasive alien plant species in eastern Yunnan. This suggests closely related invasive species face heightened competition, hindering successful invasion. Taken together, our findings indicate that successful establishment and habitat restoration of K. evelyniana seedling/saplings require effective measures to control invasive plants.

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'. [ABSTRACT FROM AUTHOR]

In this paper, we construct an age-structured epidemic model to analyze the optimal vaccine allocation strategy in an epidemic. We focus on two topics: the first one is the optimal vaccination interval between the first and second doses, and the second one is the optimal vaccine allocation ratio between young and elderly people. On the first topic, we show that the optimal interval tends to become longer as the relative efficacy of the first dose to the second dose (RE) increases. On the second topic, we show that the heterogeneity in the age-dependent susceptibility (HS) affects the optimal allocation ratio between young and elderly people, whereas the heterogeneity in the contact frequency among different age groups (HC) tends to affect the effectiveness of the vaccination campaign. A counterfactual simulation suggests that the epidemic wave in the summer of 2021 in Japan could have been greatly mitigated if the optimal vaccine allocation strategy had been taken.

The study of indigenous pine forests of evolutionary formation as endangered virgin forests is the basic for fundamental research into the processes of formation of sustainable forest communities. The aim of the study presented in the article is a comparative assessment of the structures of tree fractions of phytocenoses according to the parameters of the age series of stands and the successional position, dynamic indicators of woody waste, the influence of the pyrogenic factor, and the presence of rot damage to the stands. Age structures, numerical and linear parameters of pyrogenic factors, their impact on the infestation of trees with rot, volumetric indicators of wood waste and characteristics of natural regeneration, the mass of wood xylolysis products during its decomposition by wood-destroying fungi have been studied in pine biogeocenoses with various dynamic characteristics in the taiga zone of European Russia. Pine biogeocenoses under these conditions have structures of different ages, altered by fires of different types. Using the example of an indigenous pine forest in the Pechora-Ilychskiy Nature Reserve (middle taiga), the influence of pyrogenic effects on the formation of various types of rot and damage to trunks is shown. The volumes of woody waste are distributed according to the stages of decomposition in pine forests with different structural and dynamic characteristics; pine undergrowth – according to height gradations. An example is given of calculating the mass of wood components deposited in the stands and released during the decomposition of woody waste by wood-destroying fungi for the biogeocenosis of the Pechora-Ilychskiy Nature Reserve. The majority of indigenous pine forests in the northern territories have been affected by fires of varying intensity and types, sometimes several times during a development cycle. Pyrogenic effects have a significant on changes in the age structures of pine forests, damage to their trunks, the general infestation of forest stands by wood-destroying fungi of the biotrophic complex, the volumes of woody waste, and the formation of natural regeneration structures.

Amphibians are not only an alternative source of vital protein for humans, but also one of the best bioindicators for ecological studies. In this study, we studied the age structure, body size, and mass of an amphibian species (Pelophylax ridibundus) by sampling from two different frog farms in Türkiye. The age ranged from 4 to 13 (mean: 7.1) years in the Adana site while the age varied from 1 to 12 (mean: 5.2) years in the İstanbul site. Body size ranged between 88.21 and 103.72 mm (mean: 94.99 ± 1.15 mm) in the Adana site and 45.96 and 103.25 mm (mean: 75.90 ± 3.01 mm) in the İstanbul site. The t-test confirmed that the average age, SVL, and weight of the Adana site were higher than those of İstanbul. Body size markedly increased with age and weight (SVL-age: r = 0.659, p < 0.01; SVL-weight: r = 0.877, p < 0.001) in the İstanbul site, while in the Adana site, body size correlated only with weight. In conclusion, our research uses skeletochronology to provide demographic characteristics of marsh frogs from two unexplored frog farms located in the west and south of Türkiye. [ABSTRACT FROM AUTHOR]

Introduction: As a central figure in modern healthcare systems, the family doctor faces a number of challenges, duties and responsibilities. The functioning of a practice for primary medical care is carried out in accordance with constantly emerging and periodically changing regulations and requirements for the economic efficiency of the diagnostic and treatment process on the part of the contractual partner and the institutions to which the doctor is responsible. Objective: To analyze the structure and staffing of the medical staff in primary care in the Plovdiv region during an observed period of time (2017-2022 inclusive). Material and Methods: The object of observation was the Plovdiv Region. A logical unit was the general practitioner (GP, personal physician). Technical units were the established outpatient clinics for primary care. The study was retrospective, for a 6-year period from 2017 to 2022 inclusive. Quantitative and qualitative indicators were used for the analysis. The statistical package SPSS version 27 and Microsoft Excel were used in the computer processing of the collected database. Results: Human resources in primary outpatient medical care are facing the following challenges: an aging population with a negative natural increase, with a deepening imbalance in the territorial distribution and an aging workforce in the health sector, insufficient attractiveness of young generations to some medical specialties. Discussion: A wide range of risk factors related to the conditions, style and lifestyle of people negatively transform the health status and unlock a number of health, social and psychological problems that worsen the quality of life and accelerate the aging process. The results obtained from the analysis of the age structure of the medical staff working in primary care show startling data on the aging of GPs and the lowest percentage of working young doctors. The general practitioner offers their services on the quasi-market of medical services. GPs must have medical, accounting, commercial knowledge and skills as they are practically medical service traders registered under the commercial law. Conclusion: Human resources are not subject to mechanical or mandatory territorial redistribution. A favorable environment, providing opportunities and incentives, activates in the medical specialists themselves (physicians and nurses) a desire to change the workplace and the place of residence. [ABSTRACT FROM AUTHOR]

This paper is concerned with the sustained periodic oscillation phenomenon in a three-species delayed predation system with Holling type II functional response and age structure in top predator. The top predator fertility function is regarded as a piecewise continuous smooth function with regard to their maturation period τ 2 . The complicated dynamic behavior is proved by integrated semigroup theory and Hopf bifurcation theorem for semilinear equations with non-dense domain. Through qualitative analysis and bifurcation study of the system, we yield that this system has a nontrivial periodic solution that bifurcates from the positive equilibrium age distribution when bifurcation parameter τ passes through some critical values. Numerical simulations are also provided to illustrate theoretically analytical results. [ABSTRACT FROM AUTHOR]

The authors propose and analyze a viral infection model with defectively infected cells and age of the latently infected cells. The existence of steady states is determined by the basic reproduction number of virus. With the Lyapunov's direct method, they establish a threshold dynamics of the model with the basic reproduction number of virus as the threshold parameter. To achieve it, a novel procedure is proposed. Its novelties are two-folded. On one hand, the coefficients involved in the specific forms of the used Lyapunov functionals for the two feasible steady states are determined by the same set of inequalities. On the other hand, for the infection steady state, a new approach is proposed to check whether the derivative of the Lyapunov functional candidate along solutions is negative (semi-)definite or not. This procedure not only simplifies the analysis but also exhibits the relationship between the two Lyapunov functionals for the two feasible steady states. Moreover, the procedure is expected to be applicable for other similar models. [ABSTRACT FROM AUTHOR]

This article surveys the growing field of political demography, which explores the political consequences of structural population change. It underscores the importance of integrating demography and political sociology research to better understand the complex and nuanced relationship between demography and political dynamics. The existing research demonstrates profound and multifaceted impacts of demographic shifts on the political landscape, with different demographic factors having distinct political consequences. Notably, population composition and distribution tend to hold greater political significance than sheer population size and growth. Furthermore, while more research is needed, the existing work suggests that the effect of structural demographic factors is neither inevitable nor without limit; rather, the political consequences of demographic change often exhibit nonlinear patterns and interact with prevailing socioeconomic and institutional contexts. As demographic shifts continue to unfold globally, political demography stands as a promising and enlightening area of research that merits further inquiry. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Arctic archipelago of Svalbard is a hotspot of global warming and many fjords experience a continuous increase in seawater temperature and glacial melt while sea‐ice cover declines. In 1996/1998, 2012–2014, and 2021 macroalgal biomass and species diversity were quantified at the study site Hansneset, Kongsfjorden (W‐Spitsbergen) in order to identify potential changes over time. In 2021, we repeated the earlier studies by stratified random sampling (1 × 1 m2, n = 3) along a sublittoral depth transect (0, 2.5, 5, 10, and 15 m) and investigated the lower depth limits of dominant brown algae between 3 and 19 m. The maximum fresh weight (FW) of all seaweeds was 11.5 kg m−2 at 2.5 m and to 99.9% constituted of kelp. Although biomass distribution along the depth transect in 2021 was not significantly different compared to 2012/2013, the digitate kelp community (Laminaria digitata/Hedophyllum nigripes) had transformed into an Alaria esculenta‐dominated kelp forest. Consequently, a pronounced shift in kelp forest structure occurred over time as we demonstrate that biomass allocation to thallus parts is kelp species‐specific. Over the past decade, kelp demography changed and in 2021 a balanced age structure of kelps (juveniles plus many older kelp individuals) was only apparent at 2.5 m. In addition, the abundances and lower depth limits of all dominant brown algae declined noticeably over the last 25 years while the red algal flora abundance remained unchanged at depth. We propose that the major factor driving the observed changes in the macroalgal community are alterations in underwater light climate, as in situ data showed increasing turbidity and decreasing irradiance since 2012 and 2017, respectively. As a consequence, the interplay between kelp forest retreat to lower depth levels caused by coastal darkening and potential macroalgal biomass gain with increasing temperatures will possibly intensify in the future with unforeseen consequences for melting Arctic coasts and fjord ecosystem services. [ABSTRACT FROM AUTHOR]

Shifts in mean body size coinciding with environmental change are well documented across animal species and populations, serving as a widespread and complex indicator of climate-change response. In mammal research, identifying and disentangling the potential drivers of these trends (e.g. thermoregulation, resource availability) is hindered by treating adult size as fixed, ignoring morphological changes that occur throughout life in many species. However, observed population-level size trends may reflect underlying shifts in age structure (i.e. change in the proportion of older, potentially larger individuals in the population). Here, we assessed the role of age structure by explicitly evaluating age as a contributor to temporal variation in skull size (a proxy for body size) in 2 carnivorans, Canadian Lynx (Lynx canadensis) and American Marten (Martes americana). Using a series of linear and nonlinear models, we tested age in years (determined by cementum-layer analysis) as a predictor of skull size alongside other factors previously proposed to be important drivers of body-size trends, including population density for lynx and growing season conditions for martens. In both species, age was a significant predictor of skull size indicating a rapid year-to-year increase in young adult size that diminished in later adulthood. However, temporal shifts in age structure alone did not explain the observed changes in size over time, indicating that age structure acts in concert with other as-yet unidentified factors to drive body-size change. By explicitly evaluating the role of age, we can both refine models of temporal body-size trends and gain insights into size change as a signal of underlying demographic shifts—such as age-specific survivorship—providing a more holistic understanding of how mammals are responding to climate change. [ABSTRACT FROM AUTHOR]

This study examines the changing age structure in Slovakia and ageing process, analyzing district-level data from 2001, 2010, and 2020. The research highlights significant ageing trends across most Slovak districts. These demographic changes have profound implications, including potential labor shortages, increased demand for healthcare and social services, social isolation, pension system strain, and shifting housing needs towards older adults. Understanding these trends and regional variations is vital for effective planning and provision of education, social services, and healthcare for diverse age groups in Slovakia. Our research underscores the complexity of implementing effective measures to mitigate the consequences of demographic ageing, given the regional disparities in ageing intensity. This study offers valuable insights for optimal planning. The challenges identified, such as financing social and healthcare systems and supporting vulnerable groups, are not unique to Slovakia but are shared by many countries undergoing similar demographic transitions. By examining Slovakia's approach, we contribute to the broader discourse on demographic ageing and highlight the need for future research to focus on comparative studies between regions and countries. This will help identify best practices and innovative solutions that can be adapted to various socio-economic contexts, fostering international collaboration and informed policy-making to address the global impact of ageing populations. [ABSTRACT FROM AUTHOR]

The virus infections pose a significant threat to human health, necessitating a profound comprehension of these diseases to effectively manage epidemics and avert fatalities. This study delves into a comprehensive analysis of a mathematical model that incorporates the age of infection and distributed time delays in the context of pathogenic epidemics. The framework of this model accommodates the nonlocal diffusion of the pathogen within cells. Our investigation showcases the well‐posed nature of the model and establishes the compactness of the solutions. We derive the basic reproduction number, denoted as R0$$ {R}_0 $$, and substantiate that when R0$$ {R}_0 $$ is less than 1, the disease‐free equilibrium (E0$$ {E}&amp;#x0005E;0 $$) achieves global asymptotic stability. Furthermore, we construct a global attractor within a bounded set and affirm the existence of the complete trajectory (ψ$$ \psi $$). This research also delves into scenarios where R0$$ {R}_0 $$ surpasses 1, illustrating the presence of the endemic steady state (E∗$$ {E}&amp;#x0005E;{\ast } $$) through the utilization of super‐subsolutions. We establish the globally asymptotic stability of E∗$$ {E}&amp;#x0005E;{\ast } $$ for cases where R0$$ {R}_0 $$ is greater than 1 by employing a well‐suited Lyapunov function. To validate the robustness of our mathematical computations, we conclude by presenting a set of numerical results. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Generally, golden eagles have a favourable conservation status but they are threatened in some parts of their range. A nationwide breeding survey of the golden eagles in Bulgaria found that the species is in a decline. Contrary to the last estimation for 212 pairs, only 93 territories were found occupied while 81 were vacant. Only half of the pairs were in adult plumage and the other half had at least one of the members in non-adult plumage. The adult sex ratio was biased towards males (1.31 males per female), with the male older in 26 out of 33 territories, where the birds differed in their age classes. The obtained results could be explained by a very high unnatural mortality of territorial birds. [ABSTRACT FROM AUTHOR]

The generator of the semigroup associated with linear age-structured population models including spatial diffusion is shown to have compact resolvent. [ABSTRACT FROM AUTHOR]

A diffusive age-structured predator-prey model with Ivlev-type functional response is considered. Taking advantage of the Hopf bifurcation theorem for non-densely defined cauchy problem and the persistence of nondegenerate Hopf bifurcation for singularly perturbed second order equation, we prove the existence of periodic wave train solutions of our model. Finally, numerical simulations are carried out as supporting evidences of our analytical results. [ABSTRACT FROM AUTHOR]

ABSTRACT Myctophids are one of the most diverse and abundant fish families in the mesopelagic zone, making them a key component in the marine pelagic community. In the North Atlantic, Benthosema glaciale (glacier lantern fish) is considered the most abundant myctophid north of 35° N, yet some regions within its extensive range lack information on its basic biological parameters. We investigated the growth and described the distribution of B. glaciale in Icelandic waters, including the southern continental shelf, Iceland Basin, and Irminger Sea. Length distribution, growth, relative body condition, age, and otolith‐fish size relationships were analyzed from samples collected opportunistically with pelagic trawls during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS) in July 2020. In total, 1374 individuals were caught, and only a subset of 225 were measured fresh at sea and 89 were frozen and dissected on land. Total lengths of fresh fish ranged from 38 to 85 mm, while dissected individuals ranged from 40 to 74 mm and were 2 to 6 years old. Located over the Reykjanes Ridge in the Iceland Basin region, individuals had a significantly higher mean standard length and mean age, and a lower mean body condition. We reported length–weight relationships for both fresh and frozen samples, indicating evidence that preserving of the specimens through freezing affected relationships. The von Bertalanffy growth curve was calculated along with significant otolith‐fish size relationships where r2 values ranged between 0.87 and 0.92. Our research highlights the importance of cross‐regional studies and provides baseline biology for B. glaciale in Icelandic waters, specifically in the southern continental slope and Reykjanes Ridge.

ABSTRACT For organisms in temperate environments, seasonal variation in resource availability and weather conditions exert fluctuating selection pressures on survival and fitness, resulting in diverse adaptive responses. By manipulating resource availability on a local spatial scale, we studied seasonal patterns of resource use within natural populations of burying beetles Nicrophorus vespilloides in a Norfolk woodland. Burying beetles are necrophagous insects that breed on vertebrate carcasses. They are active in Europe between April and October, after which they burrow into the soil and overwinter. Using breeding and chemical analyses, we compared the fecundity and physiological state of beetles that differed in their seasonal resource use. We found seasonal variation in carrion use by wild burying beetles and correlated differences in their reproductive success and cuticular hydrocarbon profiles. Our results provide novel insight into the seasonal correlates of behaviour, physiology and life history in burying beetles.

The proportions of individuals in various age classes in a population of wild animals affect population trends, behaviors, learning, and social structures. Knowledge of age structure is needed for effective conservation and management of populations. However, it is not always possible to determine the age or age class of individual animals, and hence the age structure of the population. Penguins, like most birds, cannot be aged once they molt into adult plumage. Spheniscus penguins attain adult plumage at 6 to 24 months of age, and individuals can live more than 30 years. We studied foot darkening in the four species of Spheniscus penguins to determine if age class can be determined from foot color. We compared how foot color changes with age among the four species to investigate potential functions of the darkening. We found that Spheniscus penguins have pale feet at hatching and the feet become darker with age throughout the lives of individuals. We showed that we can accurately predict the age structure of a colony of Magellanic penguins Spheniscus magellanicus, but not the ages of individual penguins, based on a sample of foot colors. The timing of foot darkening within species was consistent with foot color functioning in protection from UV radiation, and not with foot color functioning in thermoregulation. The species that breeds at the lowest latitudes and experiences the highest UV radiation (Galápagos penguins Spheniscus mendiculus) had feet that darkened at the earliest ages, and the species that breed at higher latitudes and experience less intense insolation (African S. demersus and Magellanic penguins) had feet that darkened latest. Humboldt penguins S. humboldti breed mostly at low latitudes and foot darkening was intermediate between Galápagos and Magellanic penguins. We also found that males’ feet darken somewhat earlier than females’ feet, likely because females spend more time in their nests (burrows or under vegetation) than males and have less sun exposure. We found that feet darkened in an individual over years, but not within a breeding season. The color change is a life-long process, likely an evolutionary adaptation within species, not a seasonal, temporary response to UV radiation. We propose foot darkening as a way to assess age structure in Spheniscus penguins. Foot color in a colony of Magellanic penguins can provide a rapid, noninvasive method to estimate the age structure of the colony.

The portfolio effect plays a critical role in population productivity and stability. Age structure of spawning salmon represents an example of portfolio effects such that the risks of experiencing unfavorable conditions are spread across time. However, the distribution ofmaturation ages for Pacific salmon (Oncorhynchus spp.) is increasingly concentrated into fewer and younger ages, whichmay impact population resilience to climate change.We explored the population dynamics of Sacramento River fall-run Chinook salmon (O. tshawytscha) under different age structure scenarios using a life-cycle model and compared twomechanisms that can underlie these changes--mortality and maturation. In addition, we tested whether age structure promotes resilience to drought.We found that high age structure diversity increased the stability of population size and harvest compared with low diversity. However, mean population size responded differently depending on the underlying mechanism. Reduced mortality of adult fish ages 4-5 increased escapement, whereas delayed maturation decreased escapement. Overall, high age structure diversity was able to buffer against the adverse effects of droughts by reducing the variability of population size and harvest compared with low diversity. Our results suggest that age structure promotes stability of salmon in an increasingly variable climate.

Recent developments within the IUCN and the Convention on Biological Diversity have affirmed the increasingly key role that effective population size (Ne) and the effective size: census size ratio (Ne/N) play in applied conservation and management of global biodiversity. This paper reviews and synthesizes information regarding the definition of Ne and demographic and genetic methods for estimating effective size, census size, and their ratio. Emphasis is on single‐generation estimates of contemporary Ne/N, which are the most informative for practical applications. It is crucial to clearly define which individuals are included in the census size (N). Defining N as the number of adults alive at a given time facilitates comparisons across species. For a wide range of applications and experimental designs, inbreeding Ne is simpler to calculate and interpret than variance Ne. Effects of skewed sex ratio are generally modest, so most reductions to Ne/N arise from overdispersed (greater‐than‐Poisson) variance in offspring number (σk2$$ {\sigma}_k^2 $$). Even when fecundity changes with age, overdispersed within‐age variance generally contributes most to overall σk2$$ {\sigma}_k^2 $$, and both random and deterministic (mediated by selection) factors can be important. Most species are age‐structured, so it is important to distinguish between effective size per generation (Ne) and the effective number of breeders in one season or year (Nb). Both Ne and Nb are important for applied conservation and management. For iteroparous species, a key metric is variance in lifetime reproductive success (σk•2$$ {\sigma}_{k\bullet}^2 $$), which can be affected by a variety of additional factors, including variation in longevity, skip or intermittent breeding, and persistent individual differences in reproductive success. Additional factors that can be important for some species are also discussed, including mating systems, population structure, sex reversal, reproductive compensation, captive propagation, and delayed maturity. [ABSTRACT FROM AUTHOR]

The age, growth, and longevity parameters of crocodile shark, Pseudocarcharias kamoharai, from Santa Rosa, Ecuador were estimated. A number of 328 organisms were analyzed, 158 females (69 to 117 cm total length, TL) and 170 males (72.5 to 110 cm TL). The relationship between the vertebra's radius and TL was moderate (r2 = 0.63), indicating a relation between structure growth and the organism's size. Females were four to 14 years old and males were four to 12 years. The multimodal approach determined that the suitable equations were: The Von Bertalanffy growth function model with a fixed L0 (45.5 cm TL), VBGM2P (L∞ = 118.4 cm cm TL, k = 0.15) for combined sexes with a weight of evidence (Wi) to its favour of 43.9%; logistic growth model (L∞ = 109.5 cm TL, k = 0.41, L0 = 33.1 cm TL) for females with Wi = 28.4% and VBGM2P (L∞ = 110.4 cm TL, k = 0.16) for males with a Wi = 39.4%. No model obtained a sufficient evidence to be declared the best adjusted. The calculated longevities were 18 years for combined sexes, 16 for females, and 14 for males. [ABSTRACT FROM AUTHOR]

This paper studies an epidemic model that incorporates the population diffusion and infection age. The threshold conditions for the existence of traveling wave solutions are established, which answer two open problems in Ducrot and Magal (Nonlinearity, 24 (2011), 2891-2911). More specifically, the restriction for the diffusion coefficients of susceptible population and infectious population is removed and the existence of traveling wave solution with critical wave speed is obtained. [ABSTRACT FROM AUTHOR]

This paper focuses on a SIRS infectious model of nonlocal dispersal adopted with age structure. We primarily investigate the existence and nonexistence of traveling wave solutions connecting the disease-free equilibrium state and the endemic equilibrium state. To be more precise, we obtain the existence of traveling wave solutions by constructing suitable upper and lower solutions and then applying Schauder's fixed point theorem when R0 > 1 and c > c*. In addition, we prove the nonexistence of traveling wave solutions by applying the Laplace transform for R0 > 1 and 0 < c < c*. [ABSTRACT FROM AUTHOR]

The size and distribution of the population are crucial factors determining the demand for water resources. Considering the significant decline in total population growth, the evolution of China's economic and social water demand is directly related to macro-level decision-making in water resource management. By analyzing the demographic composition of China's population in terms of urban- rural distribution and age distribution, this paper clarifies the impacts of these factors on economic and social water demand. It further establishes a water demand change curve based on these demographic characteristics, which is used to predict the evolution of economic and social water demand trends and peak projections. The research findings indicate that the peak projection of China's economic and social water demand may occur in 2042, reaching an estimated scale of 730 billion cubic meters; before 2050, the total water demand in urban areas will continue to rise, whereas the peak projection in rural areas will likely occur around 2030. The scale of economic and social water demand is a boundary condition determining the characteristics of regional water usage. As China's economic and social water demand is yet to reach an inflection point, and as the international trade environment is becoming more volatile, future efforts to ensure water supply security in China should maintain a certain degree of flexibility and resilience. [ABSTRACT FROM AUTHOR]

Background and Objectives The co-occurring trends of population aging and climate change mean that rising numbers of U.S. older adults are at risk of intensifying heat exposure. We estimate county-level variations in older populations' heat exposure in the early (1995–2014) and mid (2050) 21st century. We identify the extent to which rising exposures are attributable to climate change versus population aging. Research Design and Methods We estimate older adults' heat exposure in 3,109 counties in the 48 contiguous U.S. states. Analyses use NASA NEX Global Daily Downscaled Product (NEX-GDDP-CMIP6) climate data and county-level projections for the size and distribution of the U.S. age 69+ population. Results Population aging and rising temperatures are documented throughout the United States, with particular "hotspots" in the Deep South, Florida, and parts of the rural Midwest. Increases in heat exposure by 2050 will be especially steep in historically colder regions with large older populations in New England, the upper Midwest, and rural Mountain regions. Rising temperatures are driving exposure in historically colder regions, whereas population aging is driving exposure in historically warm southern regions. Discussion and Implications Interventions to address the impacts of temperature extremes on older adult well-being should consider the geographic distribution and drivers of this exposure. In historically cooler areas where climate change is driving exposures, investments in warning systems may be productive, whereas investments in health care and social services infrastructures are essential in historically hot regions where exposures are driven by population aging. [ABSTRACT FROM AUTHOR]

Abstract The Arctic archipelago of Svalbard is a hotspot of global warming and many fjords experience a continuous increase in seawater temperature and glacial melt while sea‐ice cover declines. In 1996/1998, 2012–2014, and 2021 macroalgal biomass and species diversity were quantified at the study site Hansneset, Kongsfjorden (W‐Spitsbergen) in order to identify potential changes over time. In 2021, we repeated the earlier studies by stratified random sampling (1 × 1 m2, n = 3) along a sublittoral depth transect (0, 2.5, 5, 10, and 15 m) and investigated the lower depth limits of dominant brown algae between 3 and 19 m. The maximum fresh weight (FW) of all seaweeds was 11.5 kg m−2 at 2.5 m and to 99.9% constituted of kelp. Although biomass distribution along the depth transect in 2021 was not significantly different compared to 2012/2013, the digitate kelp community (Laminaria digitata/Hedophyllum nigripes) had transformed into an Alaria esculenta‐dominated kelp forest. Consequently, a pronounced shift in kelp forest structure occurred over time as we demonstrate that biomass allocation to thallus parts is kelp species‐specific. Over the past decade, kelp demography changed and in 2021 a balanced age structure of kelps (juveniles plus many older kelp individuals) was only apparent at 2.5 m. In addition, the abundances and lower depth limits of all dominant brown algae declined noticeably over the last 25 years while the red algal flora abundance remained unchanged at depth. We propose that the major factor driving the observed changes in the macroalgal community are alterations in underwater light climate, as in situ data showed increasing turbidity and decreasing irradiance since 2012 and 2017, respectively. As a consequence, the interplay between kelp forest retreat to lower depth levels caused by coastal darkening and potential macroalgal biomass gain with increasing temperatures will possibly intensify in the future with unforeseen consequences for melting Arctic coasts and fjord ecosystem services.

The aim of this study was to investigate the age structure and reproductive strategy of the lesser white-toothed shrew (Crocidura suaveolens Pallas 1811) population in the Askania-Nova Biosphere Reserve, Ukraine. The age structure of the population of this shrew species was studied in the protected steppe based on specimens collected in 1980–1986. The lesser white-toothed shrew is one of the most abundant species of small mammals in the reserve and a key species of the family Soricidae, which is the main consumer of the local mesofauna. In some periods, its population reaches an abundance of 200–300 individuals per hectare. To determine the age of individuals, we used the degree of tooth wear. The first multicusped tooth of the upper jaw (Pm4) was chosen for age estimation. The ratio of the height of the paracone to its width was used to level out individual variability. An attempt was made to find a correspondence between the relative value of the dental index and the absolute age of the individuals. This was based on the assumption that individuals with the weakest tooth wear (mean index 0.92) correspond to the age of early independent life, i.e. one month. Based on the analysis of the available data, it was found that the rate of decrease in the dental index was 0.026 per 10 days. Pregnant animals were found at the age of 45 days or less, which corresponds to the data of other authors. Based on the data obtained, individuals older than nine months were not captured (dental index mostly 0.26). In the Askania-Nova steppe, the breeding season of the lesser white-toothed shrew mostly begins in April and ends by the first half of October. However, single cases of breeding were recorded beyond this period. In early January, a one-month-old individual was caught. In May, catches of lesser white-toothed shrews aged about five months were recorded. In early July, two individuals aged 6.5 and 7 months were caught. In May, young animals accounted for about half of the captures. By mid-summer, overwintered animals were no longer found. The last cases of catching old animals were noted in the second half of June and early July. The study shows a distinct age structure dynamics of the population of the lesser white-toothed shrew during the year, which is determined by seasonal changes in the reproduction of the population under the conditions of the Askania-Nova protected steppe.

AbstractThe stone moroko (Pseudorasbora parva) is an invasive species which spreads rapidly in European water bodies and occupies free ecological niches. In the years 2019–2020, monthly analyses of its population structure were carried out in the Wardynka River (western Poland), determining the age, size (TL and SL), body weight, growth, Fulton’s condition factor, and the parameters of the length–weight relationship. In addition, quantitative descriptions of the parasite communities were made. End-point PCR was used to verify the presence of Sphaerothecum destruens in the fish. The age structure of the population was dominated by fish at the age of 1+ to 3+, and the maximum age was 5 + . The TL of the fish ranged from 2.50 to 10.60 cm (average 6.24 cm), SL from 2.10 to 9.50 cm (average 5.20 cm), and body weight from 0.15 to 11.43 g (average 2.74 g). The average body weight and length of males were higher than in females. The average Fulton’s condition factor for the whole sample was 1.44 ± 0.24 and was similar for both sexes. The slope of the regression line (b > 3) indicates an allometric relationship between the length and weight of fish of both sexes. Back-calculated estimates of standard length fitted the von Bertalanffy growth function, although Taylor’s criterion showed that the asymptotic length (Linf) was overestimated. Comparison of the von Bertalanffy growth function parameters revealed differences between sexes. The presence of parasites not previously recorded in stone moroko in Poland was confirmed: Dactylogyrus squameus, Phyllodistomum elongatum, P. folium, Posthodiplostomum cuticola (metacercaria), and Bivalvia gen. sp. (glochidia). Electrophoresis of the end-point PCR product did not reveal any signs of amplification for either of the primer sets used. S. destruens was not detected in any of the analysed samples of stone moroko.

The survival of relict Taxus wallichiana var. wallichiana (Yunnan yew) is threatened by overexploitation for its quality wood and medicinal properties, particularly for taxol extraction. Understanding the current status of its communities and populations is crucial for protecting existing natural forest resources. We established 53 vegetation plots in Yunnan, southwestern China, where T. wallichiana var. wallichiana is the primary dominant species. These plots were classified into four forest types. The forests were multi-stratified, with T. wallichiana var. wallichiana frequently dominating the subcanopy and shrub layer. Species diversity indices did not significantly differ among the four forest types. The age structure of T. wallichiana var. wallichiana exhibited a multi-modal pattern, with a maximum age of 1165 years. Growth was slow, with an average radial growth rate of 0.78 mm/year. Despite its strong sprouting ability, the species had a poor seedling/sapling bank and suffered from inadequate regeneration. Its seedlings/saplings are shade-intolerant. This study provides a scientific basis for effective conservation strategies, emphasizing the need for in situ regeneration to ensure the survival of T. wallichiana var. wallichiana and its contributions to biodiversity and ecosystem services.

Larger and older fish contribute disproportionately to spawning and play an important role in the replenishment of exploited stocks. Fishing often removes specific size‐ and age‐classes, with direct impacts on stock productivity and population resilience. Despite this, fisheries advice is commonly based on estimates of spawning stock biomass (SSB) and fishing mortality (F) and makes little reference to the importance of size and/or age structure. Consequently, there is a need for indicators of size and/or age structure to better inform fisheries management and help assess global sustainability goals. Here, we introduce a new age‐based indicator ABIMSY that monitors age structure relative to the equilibrium age structure at FMSY. We apply this new indicator to 72 commercially important stocks in the Northeast Atlantic, covering 26 species, which collectively contributed 86% of all commercial catches in the region in 2019. We estimate that 62% (45 stocks) currently have proportionally fewer older fish relative to FMSY conditions, whereas 38% (27 stocks) have proportionally more older fish; we also note patterns with respect to geographic area and taxonomic family. Simulation testing demonstrated that ABIMSY is responsive to overfishing and generally tracks (with high sensitivity and specificity) a common measure of stock depletion, SSB relative to BMSY. Throughout, we show that ABIMSY provides information on the age structure of exploited stocks that is complementary to conventional reference points for SSB and F. Further, the framework used to estimate ABIMSY make it well placed for integration into current advisory frameworks on fisheries management. [ABSTRACT FROM AUTHOR]

In order to understand population size composition, age structure and growth characteristics of Corbicula fluminea in Tai Lake, 638 individuals of C. fluminea collected from six sampling sites in Tai Lake were analyzed. The shell length, shell width, shell heigth and wet weight of C. fluminea were measured and the ages of all individuals were determined. Furthermore, the growth equations of shell length and wet weight of C. fluminea were established. The research results are as follows. (1) The shell length, shell width, shell height and wet weight of C. fluminea ranged from 5.45 to 40.34 mm, from 6.68 to 24.89 mm, from 7.15 to 37.41 mm and from 0.15 to 19.27 g, respectively, the corresponding average values were (20.17±0.60) mm, (13.57±0.33) mm, (19.13±0.53) mm and (4.09±0.32) g, respectively. (2) The C. fluminea population consisted of five age groups (0+ - 4+ ), in which the number of individuals aging from 0+ to 2+ yr accounted for 91.85%, and the number of individuals aging from 3+ to 4+ yr accounted for 8.15%. (3) The relationship between shell length and wet weight was expressed as W = 2.0×10–3L2.477 (R² =0.954) which indicated that C. fluminea grew at an allometric rate. (4) The relationships between shell length and age were described by Von Bertalanffy equations: Lt = 41.99×[1–e–0.27(t+1.47)], and the relationships between wet weight and age were described by Von Bertalanffy equations: Wt = 19.28×[1–e–0.27(t+1.47)] 2.477. The growth inflection point of C. fluminea occurred at age 2.22 yr, with the corresponding shell length of 26.48 mm and wet weight of 6.16 g. The present results suggested that small size and low age individuals dominated the C. fluminea population and the intensity of resource utilization was too high. Therefore, it is urgent to take measures to protect the natural resources of C. fluminea in Tai Lake. [ABSTRACT FROM AUTHOR]

In 2001, many planktonic larvae of the lancelet Branchiostoma japonicum were found in the western Seto Inland Sea. To know their subsequent state, the benthic population at a small sandbank, named Ohzu, located there was surveyed with a grab sampler in total 26 times from November 2001 to November 2005. The mean population abundance at six stations was around 100 ind. m-2 until July 2002, and abruptly increased to 1041 ind. m-2 until November 2002 by a mass recruitment. Thereafter, the abundance decreased with fluctuations to around 200 ind. m-2 in November 2005. The 2002-year class continued to be the strongest year class until at least 2005. Planktonic larvae collected in July 2005 at 4-km intervals along an 80-km line showed strongly patchy aggregations with scales ranging 4 to 12 km. Their patchy aggregation probably resulted from a spawning habit known for lancelets, which spawn within a short time at night and synchronously a few times in summer. The mass recruitment in 2002 and the large interannual fluctuation of the benthic population were most likely caused by the accidental settlement of patchy larval aggregation. Populations at Ohzu and a site (Kaihara) about 6.5 km apart in June 2006 showed a similar age structure having the strongest age class is still regarded as the 2002-year class, suggesting that the two sites were settled by the same larval patch or different patches with different fertilization dates. [ABSTRACT FROM AUTHOR]

The current status of the stocks, the dynamics of commercial fisheries, and the distribution of the saffron cod Eleginus gracilis in the fishery areas of the Far East are analyzed. In the Far Eastern basin, saffron cod makes the greatest contribution to the total catch of aquatic biological resources in the Karaginsky subzone (8.1%) and off western Kamchatka (3.6%). The total saffron cod catch from the Far Eastern seas in 2003–2022 ranged within 16 700–50 600 tons, with an average of 33 900 t. According to the data of bottom trawl surveys conducted in 2016–2023, the largest saffron cod aggregations are traditionally observed in the shelf waters off western Kamchatka, in the southwestern and northwestern Bering Sea, where the catch per unit effort reaches 4500 kg per trawling hour. Off western Kamchatka, the biomass of this species was estimated at 197 400 t; in the Karaginsky subzone, 100 400 t; in the West Bering Sea zone, 32 800 t; in the East Sakhalin and Petropavlovsk-Commander subzones, the values were similar, 17 100 and 17 200 t, respectively; and in the North Okhotsk Sea area, 8700 t. Almost all the exploited stocks in recent years have been above their average long-term annual level or fluctuated within its range. In general, the status of the saffron cod stocks in the fishery subzones at the present time can be considered satisfactory. [ABSTRACT FROM AUTHOR]

Rodents are notable for their unique life history traits that render a fast-breeding capacity. Their short generation times allow local adaptations to appear, and several studies have tried to understand if—and how—geographical variables influence local adaptation in life history traits. We compared demographic and life history traits of the Neotropical cricetid Necromys lasiurus based on 7,400 museum specimens collected daily and simultaneously over 5 years at several sites in the Caatinga biogeographic domain subject to heterogeneous geographic and climatological variables. This sample, assembled by the National Plague Service between 1951 and 1955, includes skulls, skins, and individual specimen data currently deposited in the Museu Nacional (Rio de Janeiro, Brazil). Based on this material, we analyzed population fluctuation, breeding season, sexual size dimorphism, sexual maturity, and litter size. We also hypothesized that geographic variables (elevation, rainfall, temperature, longitude, and latitude) influence key life history traits, such as size at birth and litter size. Overall, N. lasiurus showed plastic reproductive patterns, with few traits shared among populations. Notably, there is strong seasonal variation in population fluctuation patterns, breeding events clumped in early dry season and old individuals distributed throughout all the year, as has been seen for populations in other biomes. Geography had no influence on size at birth but litter size was explained by the interaction between maternal weight and geographical variables. Plastic life history traits so intimately responsive to climatological variables likely contribute to N. lasiurus having one of the largest geographic ranges among Neotropical cricetids, as well as to its status as the most important plague reservoir in the Caatinga domain. [ABSTRACT FROM AUTHOR]