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1

Age, growth, mortality and population structure of Polititapes aureus (Mollusca: Bivalvia) in the Gulf of Gabes, Tunisia

Derbali Abdelkarim

Oceanological and Hydrobiological Studies

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2024

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Vol. 53, No. 2

102--110

EN

The population dynamics of Polititapes aureus from Tunisia were investigated monthly during a one-year period (2018). The possible future commercial benefits of the species as a significant resource of artisanal fisheries require better knowledge of its population dynamics. This study provides the first insight into population parameters by investigating its population structure, growth, mortality, and exploitation rate. Allometric relationships between body size and length were determined. The shell length/total weight ratio indicated a positive allometric growth and was expressed as TW = 0.0002 SL3.103. Length frequency data were analyzed to estimate population parameters using FiSAT ΙΙ software. P. aureus showed lower growth rate (K = 0.46 yr-1) and asymptotic length (L∞ = 38.80) compared to those obtained for other bivalve species (mean values: K = 0.61 and L∞ = 55.02). Longevity (Tmax) and the growth performance index (φ’) were 7.95 yr-1 and 2.84, respectively. Total mortality (Z) was estimated from the length-converted catch curve at 0.85 yr-1 and fishing mortality (F) at 0.03 yr-1. Both values of natural mortality (M = 0.82 yr-1) derived from bivalve literature and based on Pauly’s (1980) empirical equation (M = 0.83 yr-1) developed for fish were comparable. The most intensive growth occurred during the first three years. The data presented herein are crucial for appropriate fisheries management and conservation of clams.

2

Stock mapping, size structure and biological parameters of the clam Polititapes aureus in the shellfish production area of the southern Tunisian waters (Central Mediterranean)

Derbali Abdelkarim, Jarboui Othman

Oceanological and Hydrobiological Studies

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2021

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Vol. 50, No. 2

128--136

EN

The clam Polititapes aureus is one of the most abundant shellfish species in the southern Tunisian waters. Its current exploitation status and management are becoming a major concern for fishing industry in Tunisia. The significant ecological role of the species and possible future commercial benefits require a better knowledge of its stock. This research is the first attempt to investigate its current status in an area with the largest shellfish production. The obtained results showed a scattered distribution. The stock density ranged from 0 to 124 ind. m−2, and biomass values varied from 0 to 300 g m−2. This results in a remarkable biomass of 201.2 (± 64.6) t and high abundance reaching 91.3 ± 32.9 million individuals, estimated an area of 4182 ha. The species distribution was also investigated, with the size ranging from 4.9 to 35.34 mm. The overall sex ratio (F:M) was 1.26:1, which significantly deviated different from parity (1:1). The main environmental factors were identified and several abiotic parameters were found to strongly affect the spread of the clam species. The clam reproduce well and is expected to almost meet the domestic market demand through artisanal fishery.

3

First data of age, condition, growth rate and diet of invasive Neogobius melanostomus (Pallas, 1814) in the Pomeranian Bay, Poland

Rybczyk Agnieszka, Czerniejewski Przemysław, Keszka Sławomir, Janowicz Mariola, Brysiewicz Adam, Wawrzyniak Wawrzyniec

Journal of Water and Land Development

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2020

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no. 47

142--149

EN

Round goby (Neogobius melanostomus (Pallas, 1814)) is an invasive species in the Oder River. In this study, age of 147 fish was determined using scales and otoliths, and the Fraser-Lee back-calculation method was used for population structure and theoretical length growth rates with 3 mathematical models of growth: von Bertalanffy, Ford–Walford and 2nd degree polynomial. Fish condition was determined using Fulton, Le Cren and Clark equations. Average total length and weight of fish was 162.00 mm and 83.00 g, respectively. Males were more abundant than females, representing 70% of the fish caught, and achieved greater total lengths and weights. Age 2+ dominated females and 3+ males age groups. Of the three mathematical models used to estimate fish growth, the 2nd degree polynomial model had the best fit to back-calculated lengths. Males had slightly higher growth rates than females in the first two years of life but comparable in subsequent years. The diet consisted of various benthic organisms that varied with fish age. The most frequently occurring food component was Dreissena polymorpha, which accounted for approximately 70% in the diet of fish with a body length greater than 191 mm.

4

Body size, condition, growth rate and parasite fauna of the invasive Perccottus glenii (Actinopterygii: Odontobutidae) from small watercourse in the Vistula River basin, Poland

Czerniejewski Przemysław, Linowska Angelika, Brysiewicz Adam, Kasowska Natalia

Journal of Water and Land Development

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2020

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no. 44

33--42

EN

For the last few decades there have been reports not only of the occurrence of new invasive species of European watercourses, but also their increasing expansion. One of such species is the Amur sleeper (Perccottus glenii). The present work contains assessment of age and length distribution, condition as well as growth rate and analysis of the parasite fauna of the Amur sleeper from the waters of the Vistula River tributary in its middle course (the Habdziński Canal). During the catch performed in 2017 and 2019, the total of 177 Amur sleepers were recorded in the studied watercourse and a statistically significant sex structure disproportion was observed. Among the specimens caught in 2017 dominant were fishes with lengths of 50.1–60.1 mm whereas in 2019 the majority of the Amur sleeper specimens measured 30.1–50.0 mm. Six age groups were recorded among the caught fish with a clear prevalence of specimens aged 1+ (70.06%). The most frequently recorded parasite of P. glenii was non-quantifiable Trichodina rostrata ciliate for which the Amur sleeper from the Polish waters appeared to be a new host. Moreover, the presence of an acanthocephalan Acanthocephalus lucii, not recorded in Poland in this host before, was observed in the chyme. Also, accidental presence of larvae of the Opisthioglyphe ranae tremadote, which is a parasite typical of amphibians, was also recorded. Despite unfavourable habitat conditions and increased volumes of biogenic substances in the waters of the Habdziński Canal, the Amur sleeper found convenient conditions to reside in this small watercourse.

5

Evaluation of genetic diversity and population structure of five yellow catfish Pelteobagrus fulvidraco populations by microsatellite markers

Zhong L., Wang M., Pan J., Li D., Tang S., Bian W., Chen X.

Oceanological and Hydrobiological Studies

|

2018

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Vol. 47, No. 2

99--106

EN

Yellow catfish, Pelteobagrus fulvidraco, is an important commercial freshwater species in China. Knowledge about the genetic diversity of the yellow catfish is important to support the management and conservation programs, which would subsequently support the sustainable production of this species. To investigate the genetic diversity and the structure of yellow catfish in the middle and lower reaches of the Yangtze River, 125 individuals from five lakes were genotyped using 13 microsatellite markers. Moderate genetic diversity was determined in all populations, with the observed heterozygosity (HO) ranging from 0.42 to 0.49 and the expected heterozygosity (HE) ranging from 0.51 to 0.61. Low to moderate genetic differentiation among the populations was revealed from pairwise FST values (p < 0.05), as well as from analysis of molecular variance (AMOVA). The UPGMA dendrogram and Bayesian clustering analysis indicated a correlation between genetic differences and geographic distance – four populations from the lower reaches clustered together, whereas the Poyang Lake (PY) population formed a separate cluster. The present study would be helpful in the wild stock management and artificial propagation programs for yellow catfish in the middle and lower reaches of the Yangtze River.

6

Potrzeby osób starszych w zakresie mobilności w mieście

Solecka K.

Autobusy : technika, eksploatacja, systemy transportowe

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2018

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R. 19, nr 6

1252--1259, CD

PL

Problem starzenia się społeczeństwa jest jednym z podstawowych wyzwań współczesnego świata. W artykule przedstawiono podstawowe definicje związane ze starością i starzeniem się społeczeństwa. Szczegółowo przybliżono prognozy ludności na przełomie kilkudziesięciu lat, w różnych regionach świata ze szczególnym zwróceniem uwagi na osoby starsze. Na podstawie dostępnych danych porównano zmiany demograficzne w wybranych krajach UE. Ponadto zaprezentowano dane statystyczne dotyczące ludności w Polsce i wzrost liczby osób starszych w poszczególnych rejonach Polski. Wzrost udziału osób starszych w społeczeństwie ma wpływ na wiele obszarów życia w miastach. Badania statystyczne wykazują, że większość osób starszych pomimo dobrej sprawności intelektualnej posiada pewne ograniczenia, które często uniemożliwiają im właściwe funkcjonowanie w miastach, szczególnie w odniesieniu do aspektu odbywania podróży i osiągania podstawowych celów. W związku z tym należy poznać podstawowe potrzeby osób starszych, aby móc właściwie kształtować rozwój miast pod kątem przyjazności dla osób starszych. W artykule na podstawie przeglądu dostępnej literatury przedstawiono podział zadań przewozowych w krajach UE wśród osób starszych, zidentyfikowano potrzeby osób starszych w zakresie mobilności w mieście oraz zestawiono najważniejsze czynniki mające wpływ na wzrost mobilności osób starszych.

EN

Nowadays population ageing is one of the most important challenge in the world. In this paper basic definitions related to old age and population ageing were presented. Predictions of population growth in several dozen of years in different world regions were described in detail. Predictions taking the elderly people into account were emphasized. Based on available data, demographic changes in chosen EU countries were compared. In addition statistic data related to population in Poland and increase in the number of elderly people in several Polish regions were presented. The growth of elderly people in population influences many aspects of urban life. Statistic research shows that most of elderly people, despite of good mental fitness, meet some restrictions, that make their life in cities more difficult, especially including travelling and achieving basic travel purposes. Thus it is necessary to get knowledge on basic elderly people's needs, as it allows to design cities which are friendly to seniors. The modal split in the elderly peoples' journeys in EU countries was presented on the basis of the literature review. Also elderly people's mobility needs as well as the most important factors influencing seniors’ mobility were identified.

7

Significance of Stump-Sprouting for the Population Size Structure and Spatial Distribution Patterns of Endangered Species, Magnolia cylindrical

Li J., Wu Y., Wu T., Cao L., Chen J., Qiu Z., Zhang Y., Xu G., Zhang J., Liu P.

Polish Journal of Ecology

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2017

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Vol. 65, nr 2

247--257

EN

Magnolia cylindrica Wils. is one of the third most-protected wild plants in China. To describe the size structure and dynamics of its population, field data were obtained from eight newly established sites, using a contiguous grid quadrate method in Jiulong Mountain of East China. The population size structure and spatial distribution pattern were discussed based on a theoretical distribution model and assembling intensity index. The population size structure showed a declining trend because of the lack of seedlings. The number of stump-sprouting, size class III (sapling trees) individuals was large enough to make up for the shortage of small seedlings and the complete regeneration of populations through sprouting. The distributions of M. cylindrica, both seedling populations (Group A) and overall populations (Group B), were mostly clumped. The spatial pattern intensities of the populations at different stages (mainly small trees, middle trees, and big trees) were higher for Group A than those for Group B. The two groups have the same tendency in that the pattern intensity declined from small trees to the larger ones. Group A and Group B differed in spatial pattern: small and middle trees were randomly distributed in seedling populations, but aggregated in overall populations. The populations of M. cylindrica (both group A and B) were characterized by the pattern scale between 16 to 32 m2, measured by Greig-Smith and Kershaw methods. These results suggest that sprouting should be seriously considered in population rehabilitation and forest tending management and the area of forest tending management should be close to the maximum intensity.

8

Growth Rate, Age and Size Structure of the Alien Pumpkinseed, Lepomis gibbosus (L., 1758) Population from a Heated-water Discharge Canal of a Power Plant in the Lower Stretch of the Oder River, Poland

Domagała J., Czerniejewski P., Pilecka-Rapacz M.

Rocznik Ochrona Środowiska

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2016

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Tom 18, cz. 1

273--290

EN

In 2010-2013, 1077 pumpkinseed individuals were caught using an electric pulse device and subjected to population studies aimed to determine their sex, length and age structure, as well as biological studies assessing fish growth rate and condition. Moreover, an annual cycle of seasonal changes in these parameters was demonstrated. In the sex structure of the population, males prevailed over females, constituting 57.38% and 33.43%, respectively, while individuals of unspecified sex were 9.19% (including 3.9% of juvenile individuals). The mean total length (TL) of the caught fish was 162.62 mm, with the mean weight per individual of 83.21 g. Among the caught fish, males represented 70.07% and females represented 29.93%. As regards the age structure, most individuals belonged to the groups aged 3+ and 4+, which together constituted 58.31% of the fish. The mean weight per individual of the caught pumpkinseed was 41.65 g (SD = 24.81), with a total length of 11.98 cm (SD = 2.97). The largest annual increments in the length of the investigated fish were observed in the first year of life (5.87 cm), with increments nearly 3 times lower in the following years. The growth rate of the pumpkinseed was significantly higher in comparison to the populations inhabiting other European waters and was similar to the fast-growing populations occurring in the natural range of occurrence. The probable factor allowing the higher growth rate of the pumpkinseed in the Warm Canal is water temperature much higher than that in natural waters.

PL

Bass słoneczny jest gatunkiem obcym w wodach Europy, a występowanie populacji jest punktowe i ograniczone tylko do wód o korzystnych warunkach środowiskowych dla tego gatunku. W Polsce rozsiedlony jest w wodach kanału ciepłego elektrowni Dolna Odra, o termice wody znacznie wyższej niż w wodach naturalnych. W latach 2010-2013, przy pomocy elektrycznego urządzenia impulsowego, do badań złowiono 1077 bassów słonecznych, które poddano badaniom populacyjnym określając struktury płci, długości i wieku oraz biologicznych, oceniając tempo wzrostu długości i kondycję ryb. Ponadto wskazano sezonowe zmiany tych parametrów w cyklu rocznym. W strukturze płci dominowały samce, stanowiące 57,38%, samice stanowiły 33,43%, natomiast osobniki z nieoznaczoną płcią 9,19%, w tym osobniki juwenilne 3,9 %. Średnia długość całkowita (TL) złowionych ryb wyniosła 162,62 mm, przy średniej masie jednostkowej 83,21 g. Wśród złowionych ryb dominowały samce stanowiące 70,07% ryb, samice stanowiły 29,93%, W strukturze wieku ryb najwięcej osobników stwierdzono w grupach wieku 3+ i 4+, które stanowiły łącznie 58,31% ryb. Średnia masa jednostkowa złowionych bassów wyniosła 41,65 g (SD = 24,81), przy długości całkowitej 11,98 cm (SD = 2,97). Największe roczne przyrosty długości u badanych ryb zanotowano w pierwszym roku życia (5,87cm), podczas gdy w kolejnych przyrosty były blisko 3 krotnie niższe. Tempo wzrostu długości bassów słonecznych było zdecydowanie wyższe w porównaniu do populacji zamieszkujących inne wody Europy i zbliżone do szybkorosnących populacji występujących w naturalnym zasięgu występowania. Prawdopodobnie czynnikiem warunkującym szybki wzrost bassów z wód kanału ciepłego jest woda o podwyższonej termice w stosunku do wód naturalnych.

9

Struktura populacji cisa pospolitego Taxus baccata L. w Wysokiej Lelowskiej

Majchrzak B., Tomala R.

Chemistry, Environment, Biotechnology

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2015

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Vol. 18

19--30

PL

Badania populacji cisa przeprowadzono w latach 2010‒2011 w Wysokiej Lelowskiej niedaleko wsi Żarki Letnisko i Przybynów. Wyznaczono 4 poletka badawcze o wymiarach 10 × 20 m. Dla każdego poletka oznaczono wszystkie gatunki roślin, sporządzono listę florystyczną oraz wykonano zdjęcie fitosocjologiczne w aspekcie wiosennym i letnim. Na tej podstawie określono zbiorowisko roślinne jako zdegradowaną postać Fraxino-Alnetum. Populacja cisa składa się z 71 osobników, u których wykonano pomiar wysokości i pierśnicy. Pierśnica cisów zawiera się w przedziale 1‒29 cm. Średnia grubość wynosi 7.27 cm, a średnia wysokość wszystkich osobników to 6.98 m. Najwyższy cis mierzy 13.3 m. Większość cisów jest rozgałęziona (59%) i posiada najczęściej 5, 3 lub 2 pnie. 38% populacji jest jednopniowa. 2 osobniki (3%) mają formę krzewiastą. Średnie zagęszczenie cisów na wszystkich powierzchniach badawczych wynosi 8.8/100 m2. Struktura płciowa została określona dla 97% populacji: 62% to osobniki żeńskie, a 33% męskie. Pomimo przewagi liczby osobników żeńskich w Wysokiej Lelowskiej, populacja nie odnawia się. Odnaleziono tylko 6 siewek o wysokości do 10 cm. Powodem braku odnawiania się cisów może być nadmiernie rozwinięte runo. Z uwagi na dużą liczbę osobników cisa oraz ich dobrą kondycję, badana populacja powinna zostać objęta ochroną rezerwatową.

EN

The research of yew population was carried out in the years 2010‒2011 in Wysoka Lelowska near villages Żarki Letnisko and Przybynów. 4 research plots were established, 10 × 20 meters in dimension. For each research plot, all species was marked and the floristic list was made. The phytosociologial analysis was made in terms of spring and summer. On this basis was stated that the plant community is a degenerated form of Fraxino-Alnetum. The yew population consist of 71 specimens were measured in terms of height and breast height. Breast height of yews ranged between 1 and 29 cm. The average diameter is 7.27 cm and the average height of all specimens is 6.98 m. The tallest yew has reached 13.3 m in height. Most of the yews are branched (59%) and had 5, 3, 2 trunks. 38% population have a monopodium. Two specimens (3%) had a shrubby form. The average density of yews on all plots is 8.8/100 m2. Sex identity was determined in 97% of yews population: 62% were male and 33% female specimens. Despite, that the presence of the female specimens population in Wysoka Lelowska is not regeneration. The seedlings were found in the amount 6 of up to 10 cm. Maybe for reason the yews are not regeneration is over-developed undergrowth. Due to the large number of yews and good condition this population should be protected in nature reserve.

10

Age structure and reproduction rates of the ring-necked pheasant (Phasianus colchicus L.) population in agriculture landscape (Czech Republic)

Zíka T., Šálek M., Holá M., Hanzal V., Hart V., Kušta T., Ježek M.

Polish Journal of Ecology

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2014

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Vol. 62, nr 4

751--759

EN

Detailed knowledge of demographic parameters (such as age structure and reproduction rates) is crucial for guiding conservation and management decisions regarding wildlife populations. Such parameters of wild ring-necked pheasant populations in the current agricultural landscape remain very poorly described. We researched age structure and reproduction rates of predominantly wild populations of the ring-necked pheasant (Phasianus colchicus L.) across the intensively managed agricultural landscape of the Czech Republic. The study area is influenced only marginally by hand-reared pheasants (i.e. as shown by comparison of the average number of released individuals in the study area: 0.3 ♂/yr/1km2 and 0.9 ♀/yr/1km2 and average number of released individuals and harvested in the study area: 8.6 ♂/yr/1km2) and there is a long-term huntable pheasant population. To determine the age of individuals, we used proximal primary feather shaft diameters of 1487 feather samples from males hunted between 2009 and 2011. Moreover, we evaluated the age structure of females as well as both sexes together based on the sex ratio and annual game census. We found a relatively high proportion of adults in the population in comparison with other studies. However, the number of adults decreased throughout the years: 2009 (♂ 44.7%; ♀ 69.5%; ♂♀ 60.7%), 2010 (♂ 35.2%; ♀ 61.3%; ♂♀ 51.5%), 2011 (♂ 29.8%; ♀ 57.4%; ♂♀ 47.0%). The decrease of adults went hand in hand with increase of juveniles and reproduction rates of the study population: 2009 (♂ 124%; ♀ 44%; ♂♀ 65%), 2010 (♂ 184%; ♀ 63%; ♂♀ 94%), 2011 (♂ 236%; ♀ 74%; ♂♀ 113%). Only males were hunted in the study area so we determined higher proportions of females in population for all years. This is the main reason why the reproduction rate of females was lower in percentage expression. Generally, our results showed lower productivity of pheasants in the Czech agricultural landscape in comparison with earlier published studies conducted in the US and UK. However, these studies were published many years ago and thus do not reflect the actual environmental conditions and changes which took place recently (i.e. agricultural intensification).

11

Population structure of a clonal endangered plant species Iris sibirica L. in different habitat conditions

Kostrakiewicz K.

Polish Journal of Ecology

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2008

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Vol. 56, nr 4

581-592

EN

The investigations of structure of the genets and populations of Iris sibirica L. were carried out in the period 1999-2002. The studies were conducted in Molinietum caeruleae patches localized in Southern Poland. The patch labelled MW ("more wet") measured 5,600 m[^2] and was chracterised by presence of large depressions filled with stagnant water, concentrated chiefly in the central part of the site. In this locality species with a high competitive potential (like Phagmites australis Trin., Chamanerion angustifolium (L.) Scop., Epilobium hirsutum L., Filipendula ulmaria (L.) Maxim. and others) prevailed. The patch called LW ("less wet") measured 1,800 m[^2] and was characterised by small number of depressions scattered throughout the site. In this locality dominated the plants of minor competitive abilities (like Lathyrus pratensis L., Lotus corniculatus L. and others). The spatial pattern of populations was described on the basis of the locations of all ramet clusters in 100 m[^2] square plots. Each ramet cluster was attributed to a developmental stage. The differences in height of ramets between stages was estimated on the basis of lenght of the tallest leaf and generative shoot measured in all genets and ramet clusters in both populations (30 leaves and all generative shoots in 5 clusters of ramet at generative and senile stages and 4 - at fragmentation phase in both populations). In study year 2000 Iris sibirica population in LW locality was consisted of 26 ramet clusters and showed an aggregation structure, while population growing in MW site was consisted of 502 ramet clusters and presented the group-aggregation spatial structure constituted by groups of dozen or so ramet clusters, forming large aggregations. Both populations showed signs of senility in effect of absence of genets in prereproductive stages. In 2001 and 2002 the seedlings and juvenile genets appeared only in artificially made gaps. The genets in initial stage are much lower (about 40 %) than older ones and the ramet in MW locality reached greather height (6 to 23%) than in LW site. The evaluation of structure of populations taken as indicator of their vitality, show that the population from less wet locality was in better condition despite of low abundance. Domination of ramet cluster at generative stage and vicinity of plants with low competitive potential enables longer existence of Iris sibirica in occupied site. In more wet locality the I. sibirica population is worse equiped to survive. Advanced senility and the vicinity of plants with high competitive potential might inhibit the proliferation of I. sibirica ramet clusters, accelerate their fragmentation or even eliminate from occupied site.

12

Morphological and genetical variability of Rubus hirtus (Waldst. & Kitt.) plants under partly open forest canopy

Gazda Anna, Szwagrzyk Jerzy, Nybom Hilde, Werlemark Gun

Polish Journal of Ecology

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2007

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Vol. 55, nr 1

49-55

EN

Blackberries growing in forests regenerate mainly in a vegetative way; however, detailed studies have shown substantial variability in performance of Rubus individuals. The main problem is if the differences among plants are genetically based, or are due to site heterogeneity? This study was aimed at determining 1) how large are the differences in performance of individual plants and how persistent they are during consecutive years, 2) how much of that variability can be explained by the local environmental conditions, especially the intensity of competition among plants, and whether the performance of individual plants is related to their genetic characteristics. In a partially cut mature beech forest in Western Carpathians 35 randomly chosen individuals of Rubus hirtus (Waldst. & Kitt.) were tagged and measured each year for 9 years. Ten largest and ten smallest individuals were selected for genetic analysis. Mean size of individual plants differed between consecutive growing seasons, but the overall size ranking was quite consistent throughout the entire period of study. Analysis of environmental variables: relative light intensity and local abundance of potential competitors explained about 24% of the differences in individual plant performance. In the genetic analysis the five primers were applied to analyse all 20 samples. The five primers produced 10 polymorphic bands, showing a high variability. Only a few samples displayed identical band patterns, indicating either vegetative propagation or apomictic origin. Distribution of the results of Spearman's rank correlation of plant size among genetically related individuals did not differ significantly from the distribution of rank correlation coefficients in the entire sample. In the analysed population genetical affinity did not seem to correlate withwith the performance of Rubus hirtus.

13

Distribution, population structure and ecosystem effects of the invader Cercopagis pengoi (Polyphemoidea, Cladocera) in the Gulf of Finland and the open Baltic Sea

Litvinchuk L.F., Telesh I.V.

Oceanologia

|

2006

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No. 48 (S)

243-257

EN

Spatial distribution, density, biomass, population structure, predation effects, and the influence of abiotic environmental characteristics (salinity, water temperature, transparency, and depth) on a population of the Ponto-Caspian invasive cladoceran Cercopagis pengoi (Ostroumov, 1891) were studied in the Gulf of Finland and the open Baltic Sea (August 1999 and 2004). In our study in 1999, this species was first recorded in plankton of open south-eastern Baltic waters. The age and sexual structure of the C. pengoi population were interrelated with population density. The strongest impact of C. pengoi predation on the pelagic community in the Gulf of Finland was registered at the stations where the percentage of C. pengoi in the total zooplankton biomass was the highest. The calculated impact values of C. pengoi exceeded those registered a decade ago, during the first years after Cercopagis had invaded the eastern Gulf of Finland.

14

Population structure and regeneration of Phragmites australis (Cav.) Trin. ex Steud. in flood control ditches in the depression wetland (Żuławy Wiślane, Northern Poland)

Boszke P., Bociąg K., Szmeja J.

Polish Journal of Ecology

|

2005

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Vol. 53, nr 1

3-12

EN

The population structure of Phragmites australis (Cav.) Trin. ex Steud. was examined in seven categories of overgrowing flood control ditches, differing on time which had elapsed from the last clean-up. Density, biomass, frequency of development stages, as well as the size and habit of the shoots, were determined in the populations. Site conditions in the ditches and the proportion of the common reed in the total biomass of plants were also examined. The rate at which populations in cleaned ditches regenerate is very quick. Three years after the maintenance works in ditches the reed population is already fully regenerated. Well developed reed rushes, which biomass is about 650 g d.w.m-2, are dominant. Its density amounts to 76 ± 25 shoots m-2. Flowering and fruiting shoots are the most numerous. The first signs of population regression were observed in the ditches left without cleaning for more than 5 years. Population density is gradually lower, the proportion of generative shoots is reduced, and the reed is lighter and has smaller assimilation area. In the 11-year-old and older ditches the reed is replaced by other plant species, mainly grasses and shrubs.

15

Changes of population structure of Taxus baccata L. during 25 years in protected area (Carpathians, Western Ukraine)

Iszkuło G., Boratyński A., Didukh Y., Romashenko K., Pryazhko N.

Polish Journal of Ecology

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2005

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Vol. 53, nr 1

13-23

EN

The aim of the study was to assess the present state of the Taxus baccata L. population in the Knyazhdvir Nature Reserve (West Ukraine) and to analyse the population structure changes that had occured during 25 years. We found the tendency towards population ageing but with relatively numerous young individuals and seedlings. Surprisingly, specimens with bi- or trifurcate trunks (polycormic) were significantly thicker than those with single trunks (monocormic). This attest to some kind of dominance of polycormic specimens over monocormic ones.

16

A novel polymorphic mtDNA marker for population studies of the pink shrimp, Farfantepenaeus duorarum (Crustacea, Penaeidae)

Grabowski M., Grater W. D., Stuck K. C.

Oceanologia

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2004

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No. 46 (1)

147-151

EN

The pink shrimp, Farfantepenaeus duorarum, is one of the most important shrimp species commercially harvested along the Gulf and Atlantic coasts of the US. In this study we developed a mitochondrial marker suitable for population studies of the species. A 611-617 bp hypervariable portion of the AT-rich region of the mt genome was amplified and sequenced. The 617 bp long consensus sequence contained 15 polymorphic insertion/deletion sites and 165 polymorphic substitution sites. Kimura 2-parameter distances ranged from 0.00 to 0.06 with a mean of 0.02. Among the 104 sequences, 100 haplotypes were counted if all mutations were included. If transitions were omitted, 34 haplotypes were observed. The results indicate that the hypervariable portion of the AT-rich region may be an effective marker for revealing the genetic structure of the pink shrimp off the southeast US.

17

Population structure in the Penna model

Sitarz M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2003

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Vol. 7, No 2

263-269

EN

Numerical simulations of growing population, based on the Penna model, are presented. We consider biological ageing as a result of the accumulation of mutations in the genotype. We present an example of simulated population structure and compare it with that of a real population. We also discuss the role of bad mutations threshold parameter T in the Penna model, to reproduce a smooth transition from the oversimplified logistic model (T --> ?) to the Penna model.