The growth and reproductive biology of the invasive goldfi sh Carassius auratus auratus were studied in Lake Trasimeno, central Italy. The results of the research revealed that the population is made up of eight age-classes. The sex ratio proved to be extremely unbalanced (1 : 19 in favour of females). Growth can be deemed rapid, the von Bertalanffy growth in length function being TL = 43.019{1- e(-0.272(t+0.162) )} for the total sample and Ф’ = 2.702. No sexual dimorphism in growth was observed. Back-calculation analysis suggested the existence of an inverse Lee phenomenon among 1 year-old specimens. The reproductive period covers a broad time-span, from March to June. In females, sexual maturity is reached after the second winter of life (2+ age-class); however, a small percentage (7.55%) of females is able to reproduce at the age of 1 year. Most of the males attained sexual maturity in the fi rst year (60.61%). The reproductive investment of the females is high; the relationship between SL and the number of eggs was Ne = 0.0041 SL4.368. Fecundity varied from 286 to 219104 eggs, with an average relative fecundity of 103 ± 5 eggs g-1; the mean diameter of the eggs was 1.27 ± 0.01 mm. The reproductive investment of the females was not homogeneous across the ageclasses; in addition to absolute fecundity, relative fecundity and egg diameter were seen to increase with the size of the specimens.
Stáří a stárnutí jedinců jsou bezpochyby fenomény, které zaujímaly významné místo ve společnosti již v dobách dávno minulých. Během 20. století však nabrala otázka stárnutí nového rozměru, neboť začala nově přesahovat z úrovně individuální na úroveň celospolečenskou. V důsledku zlepšování některých společenských podmínek (např. lékařské péče, životního stylu, hygieny, životní úrovně atd.), jež bylo nastartováno již zhruba na počátku 19. století, dochází k odsouvání úmrtí do vyšších věků, a lidé tak žijí déle. V moderních společnostech je tento jev obvykle doprovázen poklesem porodnosti a plodnosti. Kombinace těchto dvou faktorů pak ve svém konečném důsledku způsobuje proces, který nazýváme demografickým stárnutím. Obecně je tedy třeba rozlišovat dva pohledy na problematiku stárnutí. První pohled se zaměřuje na tzv. stárnutí individuální, druhý přístup se zabývá demografickým stárnutím lidských populací, ovšem je zřejmé, že obě dvě hlediska jsou mezi sebou navzájem provázaná. Podobně tomu bude i v následujícímpříspěvku, jenž se bude zabývat nejen přehledem problematiky demografického stárnutí, ale dotkne se také otázek o dlouhověkosti a kvalitě života, které se dostávají do popředí v souvislosti s tematikou stárnutí jednotlivců., Old age and aging of individuals are phenomenons that took important place in society as early as former times. During twentieth century the question of aging got new meaning, because it newly started to overreach from individual level to all-society. As a result of improvement of some social conditions (f.e. medical care, lifestyle, hygiene, living standard etc.), that was already initiated approximately at the beginning of the nineteenth century, dying started to be moved to higher age and people live longer. In modern societies this event usually goes with decline of natality and fertility. In final effect combination of these two factors causes the process that is known as demographic aging. In general we have to distinction between two views of problems of aging. The first view is focused on individual aging, the second one on demographic aging of human population. But it is clear that both of these views relate to each other. Similarly this article offers the roundup of problems of demographic aging, but also gives a touch of questions about longevity and quality of life, that gain ground in connection with theme of individual aging., Michaela Dimitrová., and Seznam literatury
A study on the effects of prescribed burning on rodent community ecology was conducted in Serengeti National Park, Tanzania. The study aimed at generating ecological knowledge about the changes in rodent communities when areas of the park are intentionally burned to regulate grasslands or reduce undergrowth that can lead to uncontrolled forest fires. A completely randomized design (CRD) factorial layout with two treatments (burned and unburned) and two replications was applied. A total of 148 animals comprising six species of rodent and one insectivore were captured over 2,940 trap nights. Among the trapped individuals, 41.9% were adults, 16.1% juveniles and 41.9% sub-adults. Males and females were at parity between treatments. Species abundance was estimated using the minimum number alive (MNA) method for different rodent species and was found to vary with treatment where Mastomys natalensis declined in burned plots whilst Arvicanthis niloticus increased. However, species diversity did not differ across treatments (F1, 10 = 0.15, p = 0.70). Differences in the reproductive condition of female M. natalensis (z = 4.408, df = 15, p < 0.001) and A. niloticus (z = 2.381, df = 15, p = 0.017) were observed between treatments showing that higher numbers of reproductively active females were observed in burned plots in March, whilst in unburned plots more were observed from November to February. Conservation strategies involving periodic habitat burning should, therefore, consider small mammal reproductive periods to ensure that species potentially at risk are not adversely affected and able to rapidly recover from the effects of burning in temporarily lowering food resources and longer term impacts of increased predation caused by reduced cover.
According to hunting statistics in the last two decades, both the population numbers and harvesting of roe deer in Poland have been on the increase from 597000 to 876000 animals and from 158000 to 172000 harvested individuals, respectively. The number of roe deer reported by hunters are mainly based on guesswork, therefore the objective of the study was to verify the inventory of roe deer conducted by hunting clubs in the Myślibórz Forest District (north-western Poland) and to determine the sex ratio and age structure this species. The study area is including 86 small size forest complexes and covers 12990 ha. Roe deer number were determined over four years from 2002 to 2006. In sampling plots (February 2002) data from snow tracking and driving census showed significant correlation (r = 0.663, p = 0.003) between the relative population density (N/km) – independent variable and population density (N/1000 ha) – dependent variable. Roe deer snow tracks were counted during five days each year on 16 line transects (length 66.4 km) and the relative population densities (animal per km*day–1) for the whole study area were calculated. These indices were inserted into the regression formula that was obtained from sampling plots. It allowed to calculate the population density (N/1000 ha) and then roe deer numbers inhabiting the study area. Population density ranged from 300.1-319.0 individuals/1000 hectares of forest, and the differences between the four years of study were statistically insignificant. In summer, the sex ratio of the population was 1:1.4 in favour of females, and the autumn increment of young animals amounted to 70.2 fawns/100 does. The average population number of roe deer assessed for these four years was 3568 individuals and was more than two times higher than the average population size (n = 1670) given by hunters.