It was revealed that Gibel carp, Carassius gibelio (Bloch, 1782) spawning phenology is determined by regular patterns of variability in temperature and precipitation over the period of time after spawning in the previous year. The sensitivity to temperature of water as a stimulus to spawning was shown as being dependent on the characteristics of the environment and fish development trajectories over the previous year. Information about fish spawning was collected in the Dnipro-Orylskiy Nature Reserve in the following locations: Nikolayev system of water bodies, River Protoch system and the Obukhov floodplain, the channel of the River Dnipro, water bodies of the Taromske ledge. The materials that formed the basis of this research were collected from the waters of the reserve in the years 1997–2018. There are dependencies between the air and water temperatures that have their own characteristics depending on the type of water body. These dependencies are described by a logistic equation. The temperature regime in water bodies of the Taromske ledge is very similar to the temperature regime of Nikolayev system of water bodies. The difference is that the spring period of the temperature increase in water bodies of the Taromske ledge comes earlier – in late February – early March. The air temperature dynamics over the year is described by the fourth degree polynomial. The residuals of the polynomial regression for each year were subjected to principal component analysis. The principal component analysis allowed us to identify 8 principal components of the temperature regimes, which together describe 59.2% of the variation of the residual of the polynomial trend. Deviations from the linear trend of the precipitation are systematic throughout the year, reflecting the uneven nature of rainfall during the year. The residuals of linear trend regression models of cumulative precipitation can be used as indicators of the dynamics characteristic of precipitation during the year. The residuals were used for principal component analysis, which revealed that the dynamics of the precipitation can be divided into five orthogonal principal components. The first five principal components explain 82.6% of the feature space variation. The timing of the onset of C. gibelio spawning in 95% of cases occurs on the 113–139th days of the year (on average, it takes place on the 125th day). Regression analysis revealed that the climate principal components and types of the lake systems can explain 79% of the variation in the timing of the onset of C. gibelio spawning. The water temperature at the time of C. gibelio spawning was exposed to natural dynamics in year aspect. The local minimum of the onset of spawning temperatures occured in the mid 2000s. Total of 69% of the water temperature variation at which spawning begins can be described by climatic predictors and water biotope types. The variation explained by some temperature principal components may be increased considerably after including as covariates such variables as the precipitation principal component and the biotope type. This principal component which represents the high frequency variation of the air temperature regime with a characteristic period 20 and 45 days has the highest explanation ability of all the components and is a constant explanatory predictor for all considered spawning characteristics.

Надано оцінку впливу чисельності та різноманіття угруповань земноводних на стан лісових екосистем у різних парцелах. Серед досліджених видів земноводних за допомогою факторів ентропії, коефіцієнтів різноманіття встановлено домінантний вид. Урахування впливу предикторів дає можливість виявити чисельність і таксономічне різноманіття амфібій в умовах заплавної липово-ясеневої діброви. У результаті обліку виявлено Pelobates fuscus (Laurenti, 1768), Rana arvalis Nilsson, 1842, Bufo bufo (Linnaeus, 1758), Bombina bombina (Linnaeus, 1758). За чисельностю амфібій відбувалися зміни протягом років спостереження. Характерна особливість динаміки амфібій-інваріантне співвідношення компонентів угруповання, порядок домінування популяцій завжди залишається постійним. Різноманіття метаугруповання (гамма-різноманіття) становить 3,76, різноманіття на рівні сайтів (альфа-різноманіття)-3,52, бета-різноманіття-1,07. Серед досліджених факторів найбільше значення у формуванні різноманіття має фактор сезонності. Загальний чинник, який впливає на чисельність тварин,-стабільність структури метаугруповання амфібій, що відображено за допомогою індексів різноманіття. Фактор року майже не впливає на стан популяцій амфібій і проявляється у стабільному розподілі популяцій за парцелами біогеоценозу та інваріантному стосовно років співвідношенню чисельностей популяцій, які складають угруповання. Стабільний рівень видового багатства угруповання амфібій у досліджуваному біогеоценозі робить головною причиною варіабельності різноманіття зміну чисельності видів. Варіабельність різноманіття між угрупованнями зумовлена саме динамікою видів.

Надано оцінку стійкості популяцій земноводних на основі даних динаміки чисельності. Зроблено спробу оцінити напрям динамічних змін популяцій земноводних. Визначено швидкість відхилення системи від стаціонарного стану внаслідок впливу можливих чинників навколишнього середовища за допомогою такого поняття як реактивність, ступінь реактивності та еластичності системи із застосуванням їх індексів. Установлено, що стаціонарний стан угруповань земноводних заплави р. Самара стійкий. Характерною ознакою є еластичність системи. Підтверджено еластичність системи особин Bufo bufo (Linnaeus, 1758). Визначено Pelobates fuscus (Laurenti, 1768) як фактор стійкості екосистеми у кількісному відношенні. Встановлено залежність динамічних показників популяцій від їх чисельності за допомогою рівняння регресії. Динаміка угруповання залежить від дії можливих предикторів, у відповідь на яких популяція B. bufo не змінюється. Стаціонарний стан угруповання нестабільний відносно динамічної матриці, яка описує поведінку угруповання в околиці першого стаціонарного стану. Другий стаціонарний стан стабільний, але система повертається у нього протягом хвилеподібної динаміки. На основі проведених досліджень встановлено, що чисельність угруповань земноводних залишається стійкою, системи поводяться по-різному, динаміка їх повернення до стаціонарного стану еластична або реактивна.

The paper identifies regularities of temporary dynamics of the communities of juvenile fish communities in different types of reservoirs of the Dnipro-Orylskiy” Nature Reserve during 1997–2015 and assesses the role of the Reserve as a factor of fish population reproduction within the water area, which is exposed to a significant anthropogenic impact. During the research period, we have identified representatives of 38 fish species. The main trends in the dynamics of synecological characteristics of the juvenile fish communities are explained by the influence of three sources of variation: controlled discharge of the Dnieper River as a result of the creation of a dam cascade, eutrophication, and the reserve regime. The first two sources of influence are negative, while the creation of a protective regime in the Reserve is a positive factor. Eutrophication in the direction of its influence coincides with the negative effects of regulated discharge and significantly enhances them. The creation of a reservoir and regulation of the Dnieper River flow manifests itself differently in different types of reservoirs in the Reserve depending on their typological characteristics. The influence of the eutrophication factor may also manifest itself differently in different types of lake systems. The results we have obtained indicate that for the studied system of reservoirs in general, there is no tendency to change the number of fish communities and this indicator is stationary over time. For the channel part of the Dnieper River and its immediate vicinity, the Orel River mouth has established a trend of increasing the number of fish fry communities, while in other types of reservoirs there is no stable trend, except for reservoirs of Obukhovskie floodplain, where the number of juvenile fish communities has been constantly decreasing. In terms of biomass, there is also an upward trend in these water bodies as well as in the water bodies of the Taromsk ledge. An increase in the number and biomass of communities is accompanied by an increase in the number of species and diversity in Shannon. We explain the decrease in the number of fry communities in the Obukhov floodplain by intensive eutrophication processes, which are most active in these very reservoirs. We attribute the greatest activation of eutrophication processes to the construction of the Orel Canal in the Obukhov floodplain reservoir system. This artificial reservoir drains the lakes of the Obukhovskaya system, eventually contributing to the accumulation of organic matter and the development of oxygen deficiency phenomena in them. In the event of flooding, which is generally less likely due to the regulated flow of the Dnieper River, a fixed level in the Obukhov floodplain is maintained due to the close proximity of the Orel Canal. Water exchange and the associated evacuation of excess organics from the lakes are significantly limited. Stagnation and constant accumulation of organic remains create unfavorable conditions for life and development of young fish. As prospects for further studies, we plan to carry out geobotanical descriptions of aquatic macrophyte communities for phytoindication of ecological regimes of living conditions of fish population in water bodies.

The article reveals the patterns of the temporal dynamics of juvenile fish communities under conditions of eutrophication of water bodies. The study was conducted in the reservoirs of the nature reserve “Dniprovsko-Orilsky”. Ichthyological sampling was carried out according to standard methods used in the study of the quantitative and qualitative composition of fish communities. During the study period, representatives of 38 species of juvenile fish were established in the surveys. Numbers of fish communities showed temporal patterns and differed significantly between habitat types. At presence of the general temporary trends of abundance, each of types of biotopes is characterized by the features of temporary dynamics. The highest level of abundance was characteristic of the channel part of the Dnieper River. Lake ecosystems of the Dnieper River floodplain were characterized by a much lower level of fish abundance. Among lake ecosystems, the highest number of juvenile fish communities was established for the reservoirs of the Taromsky ledge. The highest biomass was established for the channel part of the Dnieper River. The biomass of juvenile fish communities was significantly lower in the lacustrine water bodies. Species diversity of juvenile fish communities statistically reliably depends on habitat type and year as a categorical variable. The number of species increases with the growth of community abundance up to a certain level, after which there is an exit to a plateau: the growth of abundance is not accompanied by a significant increase in the number of species in the community. Biotopes can be divided into three groups according to the level of diversity. It has been substantiated that the establishment of protected areas and the maintenance of a fish conservation regime within them is an important factor in stabilizing the temporal dynamics of abundance, diversity and sustainability of fish populations over a much larger area than the territory of the reserve itself. Young fish communities are a sensitive indicator of the temporal dynamics of the ecological state of water bodies and respond both to the negative impact of anthropogenic activities and to positive measures of protection of biological diversity in protected areas.