Impact of the Introduction of Kokanee (Oncorhynchus nerka) and Opossum Shrimp (Mysis relicta) on a Subalpine Lake

Introductions of opossum shrimp (Mysis relicta) and kokanee salmon (Oncorhynchus nerka) are common management tools for improvement of local sport fisheries. This paper summarizes published information from varied sources and presents supplemental data on the impact of these introductions on the Lake Tahoe zooplankton and fish communities. Concomitant with peak spawning runs of kokanee and the establishment and high densities of Mysis was the disappearance of the three pelagic cladoceran species in the lake. Population dynamics analysis of the cladoceran populations indicate that their elimination was due to increasing death rates (related to Mysis and kokanee predation) and decreasing birth rates (possibly related to cultural eutrophication). Changes have also been observed in the fish populations. Lake trout have altered their food habits to include large quantities of Mysis, but this has been done to the exclusion of other prey types. Thus, improvement in lake trout condition has been indicated only in years when Mysis is abundant. Recent evidence of a sustained decline in the mysid population suggests that unless lake trout shift back to more traditional food sources, their condition could deteriorate to below pre-mysid levels. Finally, mean weight and abundance of kokanee spawners have declined since the cladoceran disappearance, suggesting a negative impact on the whole population which fed heavily on cladocerans. Key words: opossum shrimp, kokanee salmon, population dynamics, cladoceran decline, introductions, subalpine lake

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Long-term population dynamics of the red deer and European roe deer at the protected and not-protected areas in Mountain Crimea

Ukrainian Journal of Ecology ◽

10.15421/2017_88 ◽

2017 ◽

Vol 7 (4) ◽

pp. 65-72

Author(s):

V. N. Shmagol' ◽

V. L. Yarysh ◽

S. P. Ivanov ◽

V. I. Maltsev

Keyword(s):

Population Dynamics ◽

Protected Areas ◽

Red Deer ◽

Nature Reserve ◽

Roe Deer ◽

Precipitation Amount ◽

Annual Precipitation ◽

Population Number ◽

The Impact

The long-term population dynamics of the red deer (Cervus elaphus L.) and European roe deer (Capreolus capreolus L.) at the mountain and forest zone of Crimea during 1980-2017 is presented. Fluctuations in numbers of both species are cyclical and partly synchronous. Period of oscillations in the population of red deer is about 25 years, the average duration of the oscillation period of number of roe deer is 12.3 years. During the fluctuations in the number the increasing and fall in population number of the red deer had been as 26-47 %, and roe deer – as 22-34 %. Basing on the dada obtained we have assumed that together with large-scale cycles of fluctuations in population number of both red deer and roe deer the short cycles of fluctuations in the number of these species with period from 3.5 to 7.5 years take place. Significant differences of the parameters of cyclical fluctuations in the number of roe deer at some sites of the Mountainous Crimea: breaches of synchronicity, as well as significant differences in the duration of cycles are revealed. The greatest deviations from the average values of parameters of long-term dynamics of the number of roe deer in Crimea are noted for groups of this species at two protected areas. At the Crimean Nature Reserve the cycle time of fluctuations of the numbers of roe deer was 18 years. At the Karadag Nature Reserve since 1976 we can see an exponential growth in number of roe deer that is continued up to the present time. By 2016 the number of roe deer reached 750 individuals at a density of 437 animals per 1 thousand ha. Peculiarity of dynamics of number of roe deer at some sites proves the existence in the mountain forest of Crimea several relatively isolated groups of deer. We assumed that "island" location of the Crimean populations of red deer and European roe deer, their relatively little number and influence of permanent extreme factors of both natural and anthropogenic origination have contributed to a mechanism of survival of these populations. The elements of such a mechanism include the following features of long-term dynamics of the population: the reduction in the period of cyclic population fluctuations, while maintaining their amplitude and the appearance of additional small cycles, providing more flexible response of the population to the impact of both negative and positive environmental factors. From the totality of the weather conditions for the Crimean population of roe deer the recurring periods of increases and downs in the annual precipitation amount may have relevance. There was a trend of increase in the roe deer population during periods of increasing annual precipitation.

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Population dynamics driven by truncated stable processes with Markovian switching

Journal of Applied Probability ◽

10.1017/jpr.2020.102 ◽

2021 ◽

Vol 58 (2) ◽

pp. 505-522

Author(s):

Zhenzhong Zhang ◽

Jinying Tong ◽

Qingting Meng ◽

You Liang

Keyword(s):

Population Dynamics ◽

Sufficient Conditions ◽

Necessary And Sufficient Conditions ◽

Markovian Switching ◽

Stable Processes ◽

Necessary And Sufficient ◽

The Impact

AbstractWe focus on the population dynamics driven by two classes of truncated $\alpha$-stable processes with Markovian switching. Almost necessary and sufficient conditions for the ergodicity of the proposed models are provided. Also, these results illustrate the impact on ergodicity and extinct conditions as the parameter $\alpha$ tends to 2.

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Parasitism of Aedes albopictus by Ascogregarina taiwanensis lowers its competitive ability against Aedes triseriatus

Parasites & Vectors ◽

10.1186/s13071-021-04581-0 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Emma Stump ◽

Lauren M. Childs ◽

Melody Walker

Keyword(s):

Population Dynamics ◽

Competitive Advantage ◽

Aedes Albopictus ◽

Abiotic Factors ◽

Mosquito Species ◽

Disease Spread ◽

Aedes Triseriatus ◽

La Crosse Virus ◽

The Impact ◽

Ascogregarina Taiwanensis

Abstract Background Mosquitoes are vectors for diseases such as dengue, malaria and La Crosse virus that significantly impact the human population. When multiple mosquito species are present, the competition between species may alter population dynamics as well as disease spread. Two mosquito species, Aedes albopictus and Aedes triseriatus, both inhabit areas where La Crosse virus is found. Infection of Aedes albopictus by the parasite Ascogregarina taiwanensis and Aedes triseriatus by the parasite Ascogregarina barretti can decrease a mosquito’s fitness, respectively. In particular, the decrease in fitness of Aedes albopictus occurs through the impact of Ascogregarina taiwanensis on female fecundity, larval development rate, and larval mortality and may impact its initial competitive advantage over Aedes triseriatus during invasion. Methods We examine the effects of parasitism of gregarine parasites on Aedes albopictus and triseriatus population dynamics and competition with a focus on when Aedes albopictus is new to an area. We build a compartmental model including competition between Aedes albopictus and triseriatus while under parasitism of the gregarine parasites. Using parameters based on the literature, we simulate the dynamics and analyze the equilibrium population proportion of the two species. We consider the presence of both parasites and potential dilution effects. Results We show that increased levels of parasitism in Aedes albopictus will decrease the initial competitive advantage of the species over Aedes triseriatus and increase the survivorship of Aedes triseriatus. We find Aedes albopictus is better able to invade when there is more extreme parasitism of Aedes triseriatus. Furthermore, although the transient dynamics differ, dilution of the parasite density through uptake by both species does not alter the equilibrium population sizes of either species. Conclusions Mosquito population dynamics are affected by many factors, such as abiotic factors (e.g. temperature and humidity) and competition between mosquito species. This is especially true when multiple mosquito species are vying to live in the same area. Knowledge of how population dynamics are affected by gregarine parasites among competing species can inform future mosquito control efforts and help prevent the spread of vector-borne disease.

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The influence of density in population dynamics with strong and weak Allee effect

Journal of the Egyptian Mathematical Society ◽

10.1186/s42787-021-00114-x ◽

2021 ◽

Vol 29 (1) ◽

Author(s):

Kamrun Nahar Keya ◽

Md. Kamrujjaman ◽

Md. Shafiqul Islam

Keyword(s):

Population Dynamics ◽

Allee Effect ◽

Global Bifurcation ◽

Reaction Diffusion ◽

Logistic Growth ◽

Allee Effects ◽

Reaction Diffusion Model ◽

Positive Steady States ◽

The Stability ◽

The Impact

AbstractIn this paper, we consider a reaction–diffusion model in population dynamics and study the impact of different types of Allee effects with logistic growth in the heterogeneous closed region. For strong Allee effects, usually, species unconditionally die out and an extinction-survival situation occurs when the effect is weak according to the resource and sparse functions. In particular, we study the impact of the multiplicative Allee effect in classical diffusion when the sparsity is either positive or negative. Negative sparsity implies a weak Allee effect, and the population survives in some domain and diverges otherwise. Positive sparsity gives a strong Allee effect, and the population extinct without any condition. The influence of Allee effects on the existence and persistence of positive steady states as well as global bifurcation diagrams is presented. The method of sub-super solutions is used for analyzing equations. The stability conditions and the region of positive solutions (multiple solutions may exist) are presented. When the diffusion is absent, we consider the model with and without harvesting, which are initial value problems (IVPs) and study the local stability analysis and present bifurcation analysis. We present a number of numerical examples to verify analytical results.

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Long-term data indicates that supplementary food enhances the number of breeding pairs in a Cape Vulture Gyps coprotheres colony

Bird Conservation International ◽

10.1017/s0959270915000350 ◽

2016 ◽

Vol 27 (1) ◽

pp. 140-152 ◽

Cited By ~ 4

Author(s):

DANA G. SCHABO ◽

SONJA HEUNER ◽

MICHAEL V. NEETHLING ◽

SASCHA RÖSNER ◽

ROGER UYS ◽

...

Keyword(s):

Population Dynamics ◽

Breeding Success ◽

Food Sources ◽

Breeding Colony ◽

Supplementary Food ◽

Adequate Food ◽

Vulture Conservation ◽

Positive Effect ◽

Term Data

SummaryThe number of vultures is declining in many parts of the world due to numerous threats, such as poisoning and collisions with power-lines as well as the lack of adequate food sources. Vulture restaurants, i.e. supplementary feeding stations, have become a widespread conservation tool aimed at supporting vulture colonies. However, it is poorly understood how vulture restaurants influence population dynamics and whether they affect breeding success of vulture populations. We used a 12-year dataset from a breeding colony of the Cape Vulture Gyps coprotheres and a nearby vulture restaurant in South Africa to investigate the effect of supplementary food on population dynamics and breeding success. We found a significantly positive effect of supplementary food during the nest-building stage on the number of breeding pairs. However, breeding success, i.e. the proportion of successful nests, did not depend on supplementary food during the incubation and rearing stage. Especially during the critical rearing stage, the amount of food supplied might not have been sufficient to meet food demands of the colony. Still, our results indicate that carefully managed vulture restaurants might stabilise vulture colonies and can therefore aid vulture conservation.

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