Dynamics of structural indices of populations of zander Stizostedion lucioperca (Percidae) of the Rybinsk Reservoir for 1954–2010

Data on the age and size dynamics, linear and weight growth, and feeding of zander Stizostedion lucioperca collected in the Rybinsk Reservoir in 1954–2010 were generalized. The main factors determining the numbers of zander population and causing changes in its structural indices are the intensity of fishery and feeding conditions. Beginning from the mid-1990s, commercial load considerably exceeds the adaptation possibilities of the zander population; under the impact of this factor, its numbers declined, and the age structure changed towards the domination of individuals of junior ages. Introduction of the Black-Sea sprat Clupeonella cultriventris along with of climate warming led to negative changes in the populations of prey fish, as a result of which the proportion of their own juveniles increased in the feeding of adult zander. During recent years, zander fingerlings throughout summer cannot pass to predatory feeding, which leads to a decrease in the rate of linear and weight growth of mature individuals.     

Dynamics and the state of fishery resources in the Rybinsk Reservoir from 1950–2010

Data on dynamics of the main commercial fish populations in the Rybinsk Reservoir over the period of 1950–2010 have been generalized. Fishing intensity is the main factor that determines the state of fish resources. It affects not only the abundance of commercial fish but also determines changes in population characteristics, i.e., changes in age and size structure and increase in the portion of young individuals. The effect of fishing on populations of some species depends on their commercial value. Commercial fishing affects notably such species as bream Abramis brama, zander Sander lucioperca, and pike Esox lucius. Commercial fishing affects, to a lesser extent, populational characteristics of such mass fish species as roach Rutilus rutilus and blue bream Abramis ballerus whose commercial value is lower.     

The state of reproductive glands of the pike Esox lucius from water bodies of the Chernobyl trail in 1999–2004

The state of the reproductive system of the pike Esox lucius, descendants of individuals exposed to X-ray irradiation due to the catastrophe at the Chernobyl Nuclear Power Plant in 1986, was studied. The material was collected in water bodies of Ukraine contaminated with radionuclides—Kiev Reservoir, the Teterev River, and Lake Glubokoe in the postcatastrophe period 1999–2004. It was shown that the total number and the extent of disturbances in the pike gonads are positively correlated with the levels of contamination of the water bodies: in the cleanest water body, the Teterev River, the proportion of fish with gonads without considerable deviations was 70%; in the Kiev Reservoir, it was 45%; no individuals with normal gonads were recorded in Lake Glubokoe. The great number of anomalies in sexual cells and gonads has led to a decrease in the reproductive capacity of the pike populations studied. A unique case was revealed of synchronous hermaphroditism in a pike from the Kiev Reservoir that belonged to the fourth generation (F₄) of fish that underwent emergency loads. Among postemergency pike generations, the maximum number of disturbances in sexual cells and gonads was recorded in F_2–4, which is possibly accounted for by the phenomenon of “prolonged mutagenesis.”     

Behavior of juveniles of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (cyprinidae), produced by breeders from a tributary of the Rybinsk Reservoir and from a nonfreezing area of the Moskva River at variable temperatures

The study has revealed differences in search behavior among juvenile individuals of the roach Rutilus rutilus produced by breeders from a tributary of the Rybinsk Reservoir and from nonfreezing areas of the Moskva River. It has been shown that differences in behavioral responses of juveniles are minimal at a stable temperature (approximately 20°C). Gradually rising or falling temperatures lead to an increase in the variation of behavioral parameters. Response to rising temperature is more pronounced in juvenile roach individuals produced by breeders from the Rybinsk Reservoir tributary, while response to decreasing temperature is, on the contrary, more pronounced in individuals produced by breeders from the nonfreezing Moskva River area. Year-round occurrence in zones with heated water in the nonfreezing Moskva River area has probably contributed to a change in the roach population’s adaptation to cold, consolidated by selection at the genetic level over several generations.     

Dynamics of structural parameters of populations of the bream <Emphasis Type="Italic">Abramis brama</Emphasis> (Cyprinidae) in Rybinsk Reservoir in 1954–2007

The data on age, size, and sex structure of the population, on the linear and weight growth of bream Abramis brama are generalized for the period of 1954–2007 in Rybinsk Reservoir. Analysis of dynamics of these parameters demonstrated that recently a high fishing intensity is both reflected on the size of the stock but also determines the changes in structural parameters of the bream population. At present, in the exploited stock of bream, the specimens of junior ages dominate. The part of specimens older than ten years, which previously made the bulk of catches, now compose not more than 10–15%. This resulted in a rather noticeable decrease of mean age and size in catches. The previously observed sex ratio, near 1: 1, shifted towards a significant prevalence of males. The age of the first spawning and of the fish spawning for the first time decreased. These changes indicate that the fishing load surpasses adaptational potential of bream.     

Experimental evidence of gradual size‐dependent shifts in body size and growth of fish in response to warming

A challenge facing ecologists trying to predict responses to climate change is the few recent analogous conditions to use for comparison. For example, negative relationships between ectotherm body size and temperature are common both across natural thermal gradients and in small‐scale experiments. However, it is unknown if short‐term body size responses are representative of long‐term responses. Moreover, to understand population responses to warming, we must recognize that individual responses to temperature may vary over ontogeny. To enable predictions of how climate warming may affect natural populations, we therefore ask how body size and growth may shift in response to increased temperature over life history, and whether short‐ and long‐term growth responses differ. We addressed these questions using a unique setup with multidecadal artificial heating of an enclosed coastal bay in the Baltic Sea and an adjacent reference area (both with unexploited populations), using before‐after control‐impact paired time‐series analyses. We assembled individual growth trajectories of ~13,000 unique individuals of Eurasian perch and found that body growth increased substantially after warming, but the extent depended on body size: Only among small‐bodied perch did growth increase with temperature. Moreover, the strength of this response gradually increased over the 24 year warming period. Our study offers a unique example of how warming can affect fish populations over multiple generations, resulting in gradual changes in body growth, varying as organisms develop. Although increased juvenile growth rates are in line with predictions of the temperature–size rule, the fact that a larger body size at age was maintained over life history contrasts to that same rule. Because the artificially heated area is a contemporary system mimicking a warmer sea, our findings can aid predictions of fish responses to further warming, taking into account that growth responses may vary both over an individual's life history and over time.     

Warmer and browner waters decrease fish biomass production

Climate change studies have long focused on effects of increasing temperatures, often without considering other simultaneously occurring environmental changes, such as browning of waters. Resolving how the combination of warming and browning of aquatic ecosystems affects fish biomass production is essential for future ecosystem functioning, fisheries, and food security. In this study, we analyzed individual‐ and population‐level fish data from 52 temperate and boreal lakes in Northern Europe, covering large gradients in water temperature and color (absorbance, 420 nm). We show that fish (Eurasian perch, Perca fluviatilis) biomass production decreased with both high water temperatures and brown water color, being lowest in warm and brown lakes. However, while both high temperature and brown water decreased fish biomass production, the mechanisms behind the decrease differed: temperature affected the fish biomass production mainly through a decrease in population standing stock biomass, and through shifts in size‐ and age‐distributions toward a higher proportion of young and small individuals in warm lakes; brown water color, on the other hand, mainly influenced fish biomass production through negative effects on individual body growth and length‐at‐age. In addition to these findings, we observed that the effects of temperature and brown water color on individual‐level processes varied over ontogeny. Body growth only responded positively to higher temperatures among young perch, and brown water color had a stronger negative effect on body growth of old than on young individuals. Thus, to better understand and predict future fish biomass production, it is necessary to integrate both individual‐ and population‐level responses and to acknowledge within‐species variation. Our results suggest that global climate change, leading to browner and warmer waters, may negatively affect fish biomass production, and this effect may be stronger than caused by increased temperature or water color alone.     

Climate change and large‐scale human population collapses in the pre‐industrial era

Aim It has long been assumed that deteriorating climate (cooling and warming above the norm) could shrink the carrying capacity of agrarian lands, depriving the human population of sufficient food. Population collapses (i.e. negative population growth) follow. However, this human–ecological relationship has rarely been verified scientifically, and evidence of warming‐caused disaster has never been found. This research sought to explore quantitatively the temporal pattern, spatial pattern and triggers of population collapses in relation to climate change at the global scale over 1100 years. Location Various countries/regions in the Northern Hemisphere (NH) during the pre‐industrial era. Methods We performed time‐series analysis to examine the association between temperature change and country‐wide/region‐wide population collapses in different climatic zones. All of the known population collapse incidents in the NH in the period ce 800–1900 were included in our data analysis. Results Nearly 90% of population collapses in various NH countries/regions occurred during periods of climate deterioration characterized by shrinking carrying capacity of the land. In addition, we found that cooling dampened the human ecosystem and brought about 80% of the collapses in warmer humid, cooler humid and dry zones, while warming adversely affected the ecosystems in dry and tropical humid zones. All of the population collapses and growth declines in periods of warm climate occurred in dry and tropical humid zones. Malthusian checks (famines, wars and epidemics) were the dominant triggers of population collapses, which peaked dramatically when climate deteriorated. Main conclusions Global demographic catastrophes and most population collapse incidents occurred in periods with great climate change, owing to overpopulation caused by diminished carrying capacity of the land and the resultant outbreak of Malthusian checks. Impacts of cooling or warming on land carrying capacity varied geographically, as a result of the diversified ecosystems in different parts of the Earth. The observed climate–population synchrony challenges Malthusian theory and demonstrates that it is not population growth alone but climate‐induced subsistence shortage and population growth working synergistically, that cause large‐scale human population collapses on the long‐term scale.     

Phytoplankton in the Littoral and Pelagial Zones of the Rybinsk Reservoir in Years with Different Temperature and Water-Level Regimes

The features of the floristic composition and dynamics of the biomass of phytoplankton in shallow and deep areas of the Volga reach in the Rybinsk Reservoir have been studied during years with different thermal and water-level regimes (2009–2011). The floristic diversity and biomass of phytoplankton increase with a decrease in depth. The increase in water temperature at low water level stimulates phytoplankton vegetation in the pelagial zone and a decrease in biomass in the littoral zone, while a high diversity of algocenoses is recorded irrespective of habitat. The contribution of filamentous algae and cyanoprokaryotes to the biomass increases in the shallow littoral part; in the open part of the reservoir, the biomass of mixotrophic flagellates decreases. Their abundance, as well as the abundance of zignematales, increases with decreasing depth.     

Harvest-induced disruptive selection increases variance in fitness-related traits

The form of Darwinian selection has important ecological and management implications. Negative effects of harvesting are often ascribed to size truncation (i.e. strictly directional selection against large individuals) and resultant decrease in trait variability, which depresses capacity to buffer environmental change, hinders evolutionary rebound and ultimately impairs population recovery. However, the exact form of harvest-induced selection is generally unknown and the effects of harvest on trait variability remain unexplored. Here we use unique data from the Windermere (UK) long-term ecological experiment to show in a top predator (pike, Esox lucius) that the fishery does not induce size truncation but disruptive (diversifying) selection, and does not decrease but rather increases variability in pike somatic growth rate and size at age. This result is supported by complementary modelling approaches removing the effects of catch selectivity, selection prior to the catch and environmental variation. Therefore, fishing most likely increased genetic variability for somatic growth in pike and presumably favoured an observed rapid evolutionary rebound after fishery relaxation. Inference about the mechanisms through which harvesting negatively affects population numbers and recovery should systematically be based on a measure of the exact form of selection. From a management perspective, disruptive harvesting necessitates combining a preservation of large individuals with moderate exploitation rates, and thus provides a comprehensive tool for sustainable exploitation of natural resources.     

Growth in length and in body depth in young‐of‐the‐year perch with different predation risk

Body shape of young‐of‐the‐year (YOY) perch Perca fluviatilis , and number and size of potential predators (perch and pike Esox lucius ) were compared across five lakes in northern Sweden. Body depth and dorsal fin ray length of YOY perch differed between lakes, with high relative body depth and long dorsal fin rays found in the lakes where the number of large piscivores was the highest. The most slender fish were found in the lake where the perch population had the smallest individuals and pike occurred in very low numbers. The average body mass in YOY perch from the two lakes with highest and lowest body depth, respectively, were the same, which indicates a difference between lakes in the relation between growth in length and in depth. Both body depth and fin ray length were correlated with predation risk by pike. Fin ray length was also correlated with number of piscivorous perch. Selection for different body shapes can be caused by different biotic and abiotic factors, singly or in combination, and the results from this study indicates that predation risk is one of these factors affecting body depth and fin ray length in perch.     

Effects of temperature and growth hormone on individual growth trajectories of wild‐type and transgenic coho salmon Oncorhynchus kisutch

In this study, individual growth patterns of wild‐type and growth‐enhanced coho salmon Oncorhynchus kisutch at 8, 12 and 16° C water temperature were followed. Despite large differences among individuals in growth rates, there was generally little variation in the shape of the growth curves among O. kisutch individuals of both genotypes and at all temperatures. Typically, individuals that were relatively large initially were also relatively large at the end of the growth period. The limitation in variation was more pronounced in the growth‐enhanced O. kisutch than in the wild type, where the relative size of some individuals reared at 12 and 8° C changed by the end of the trial. As a warmer temperature seems to decrease the plasticity of growth trajectories in wild‐type fish, it is possible that global warming will influence the ability of wild fish to adapt their growth to changing conditions.     

Plasticity in the timing of a major life‐history transition and resulting changes in the age structure of populations of the salamander Hynobius retardatus

Variation in age and size at life‐history transitions is a reflection of the diversifying influence of biotic or abiotic environmental change. Examples abound, but it is not well understood how such environmental changes influence the age structure of a population. I experimentally investigated the effects of water temperature and food type on age and body size at metamorphosis in larvae of the salamander Hynobius retardatus. In individuals grown at a cold temperature (15 °C) or given Chironomidae as prey, the time to metamorphosis was significantly prolonged, and body size at metamorphosis was significantly enlarged, compared with individuals grown at a warmer temperature (20 °C) or fed larvae. I also examined whether larval density (a possible indicator of cannibalism in natural habitats) generated variation in the age structure of natural populations in Hokkaido, Japan, where the climate is subarctic. Natural ponds in Hokkaido may contain larvae that have overwintered for 1 or 2 years, as well as larvae of the current year, and I found that the number of age classes was related to larval density. Although cool water temperatures prolong the larval period and induce later metamorphosis, in natural ponds diet‐based enhancement of development translated into a shorter larval duration and earlier metamorphosis. Geographic variation in the frequency of cannibalism resulted in population differences in metamorphic timing in H. retardatus larvae. It is important to understand how environmental effects are ultimately transduced through individual organisms into population‐level phenomena, with the population response arising as the summation of individual responses. Without a thorough comprehension of the mechanisms through which population and individual responses to environmental conditions are mediated, we cannot interpret the relationship between population‐level and individual‐level phenomena. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 100–114.     

Size-age characteristics and population structure of Clupeonella cultriventris at its naturalization in the Rybinsk Reservoir

Based on materials of 2000–2003, the characteristics of the distribution, size-age composition, and growth rate of Clupeonella cultrivensis from the Rybinsk Reservoir is given. Comparative data on reservoirs of the Middle Volga are provided. It is shown that, during these three years, C. cultriventris was distributed unevenly over stretches of water and increased its numbers tenfold. A decrease in the linear sizes and the body weight occurred against the background of the increased abundance.     

Climate change modifies the size structure of assemblages of emerging aquatic insects

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Both life‐history plasticity and local adaptation will shape range‐wide responses to climate warming in the tundra plant Silene acaulis

Many predictions of how climate change will impact biodiversity have focused on range shifts using species‐wide climate tolerances, an approach that ignores the demographic mechanisms that enable species to attain broad geographic distributions. But these mechanisms matter, as responses to climate change could fundamentally differ depending on the contributions of life‐history plasticity vs. local adaptation to species‐wide climate tolerances. In particular, if local adaptation to climate is strong, populations across a species’ range—not only those at the trailing range edge—could decline sharply with global climate change. Indeed, faster rates of climate change in many high latitude regions could combine with local adaptation to generate sharper declines well away from trailing edges. Combining 15 years of demographic data from field populations across North America with growth chamber warming experiments, we show that growth and survival in a widespread tundra plant show compensatory responses to warming throughout the species’ latitudinal range, buffering overall performance across a range of temperatures. However, populations also differ in their temperature responses, consistent with adaptation to local climate, especially growing season temperature. In particular, warming begins to negatively impact plant growth at cooler temperatures for plants from colder, northern populations than for those from warmer, southern populations, both in the field and in growth chambers. Furthermore, the individuals and maternal families with the fastest growth also have the lowest water use efficiency at all temperatures, suggesting that a trade‐off between growth and water use efficiency could further constrain responses to forecasted warming and drying. Taken together, these results suggest that populations throughout species’ ranges could be at risk of decline with continued climate change, and that the focus on trailing edge populations risks overlooking the largest potential impacts of climate change on species’ abundance and distribution.     

Assessment of Possible Causes of Changes in Аbundance and Sexual Structure in Populations of Prussian Carp (<Emphasis Type="Italic">Carassius auratus gibelio</Emphasis> Bloch., 1783)

The prevalence of processes of the increase in abundance and changes in the sexual structure of Prussian carp populations in waterbodies differing dramatically in ecological properties and distant from each other (Lake Sevan and Rybinsk Reservoir) indicates the presence of global factors affecting climatic zones. The increase in environmental temperature due to global warming may be such a factor. Experimentally proven high thermophilicity and the thermal stability of Prussian carp, as well as its low sensitivity to hypoxia, provide some advantages for this species over many other fish inhabiting the same waterbodies.     

Climate warming and the evolution of morphotypes in a reptile

Climate warming is known to have effects on population dynamics through variations in survival, fecundity and density. However, the impacts of climate change on population composition are still poorly documented. Morphotypes are powerful markers to track changes in population composition. In the common lizard, Lacerta vivipara , individuals display two types of dorsal patterns: reticulated (R individuals) and linear (L individuals). We examined how local warming affected intrapopulation frequencies of these morphotypes across 11 years. We observed changes in morph frequency of dorsal patterns across years, paralleling the rise of spring temperatures. The proportion of R individuals increased with June temperatures in juveniles, yearlings, and adult males and females. Three mechanisms could explain these changes: phenotypic plasticity, microevolution and/or dispersal between populations. We investigated the ontogenetic determinism, fitness and recruitment rates associated with dorsal morphotypes. Dorsal pattern ontogeny showed temperature dependence but this relationship was not associated with the warming trend during this study. We found variation by morphotype in survival and clutch size, but these factors did not explain R frequency increases. Among all the parameters considered in this study, only a decrease of immigration, which was more pronounced in the L morphotype, could explain the change in population composition. To our knowledge, this provides the first evidence of the impact of climate warming on population composition due to its effects on immigration.     

On the physiological-biochemical state of kilka Clupeonella cultriventris (Clupeidae, Clupeiformes) in Rybinsk Reservoir (Russia)

The results of studies into lipid total content and fractional composition in the tissue and wholebody levels in kilka (Clupeonella cultriventris) are given. The fish studied belonged to various size-age groups and were sampled in Rybinsk Reservoir during active feeding periods in 2002 and 2005. A trend was revealed of deterioration of the physiological-biochemical state in adult specimens of this invasive species. This was especially true of the modal (in terms of their proportion in population) two-year-old fish. This was evidenced by a decrease in contents of total and reserve (triacylglycerol) lipids in fish muscles during the whole study period. It is shown that, in young kilka caught in all reservoir stretches in autumn, the values of these parameters depend on the time and rate of the reservoir water level decrease during the active feeding period. Probable reasons for changes in the physiological-biochemical state in adult and young specimens in the kilka population are discussed. The discussion is in view of the recent state of the Rybinsk Reservoir ecosystem which undergoes successional modification of the pelagic zooplankton community both at the level of large taxa and of some dominant species.     

Diatoms can be an important exception to temperature–size rules at species and community levels of organization

Climate warming has been linked to an apparent general decrease in body sizes of ectotherms, both across and within taxa, especially in aquatic systems. Smaller body size in warmer geographical regions has also been widely observed. Since body size is a fundamental determinant of many biological attributes, climate‐warming‐related changes in size could ripple across multiple levels of ecological organization. Some recent studies have questioned the ubiquity of temperature–size rules, however, and certain widespread and abundant taxa, such as diatoms, may be important exceptions. We tested the hypothesis that diatoms are smaller at warmer temperatures using a system of geothermally heated streams. There was no consistent relationship between size and temperature at either the population or community level. These field data provide important counterexamples to both James’ and Bergmann's temperature–size rules, respectively, undermining the widely held assumption that warming favours the small. This study provides compelling new evidence that diatoms are an important exception to temperature–size rules for three reasons: (i) we use many more species than prior work; (ii) we examine both community and species levels of organization simultaneously; (iii) we work in a natural system with a wide temperature gradient but minimal variation in other factors, to achieve robust tests of hypotheses without relying on laboratory setups, which have limited realism. In addition, we show that interspecific effects were a bigger contributor to whole‐community size differences, and are probably more ecologically important than more commonly studied intraspecific effects. These findings highlight the need for multispecies approaches in future studies of climate warming and body size.