Comparative analysis of generative parameters of the roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L., 1758) in the Volga reach of the Rybinsk Reservoir

An analysis of the reproductive potential of roach in the Volga reach of the Rybinsk Reservoir is made on the basis of published data and our own data obtained from 1953 to 2012. Values of fecundity obtained in the 2000s are the most similar to the results of 1976. Parameters of the intensity of the generative exchange of females (absolute and relative fecundity and size and mass of eggs) were high in 2007 and 2012, which indicates a sufficient food supply, especially of medium and large roach.     

Morphological Variability of Roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) from the Volga Reach of Rybinsk Reservoir

A comparative analysis of literature data and our own results on the morphology of roach from the Volga Reach (Rybinsk Reservoir) in different years is conducted. Recently, (from 2007 to 2010), the morphological characteristics of the roach have been similar to those observed between 1976 and 1978. The roach is characterized by an intermediate position between the herbivorous and malacophagous morphs, but it is more similar to the herbivorous morph.     

Use of Oxidative Stress Indices of Freshwater Bivalve <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> (Pallas) as Biomarkers of Anthropogenic Pollution of Rybinsk Reservoir

This article analyzes the indices of oxidative stress activity in freshwater bivalve Dreissena polymorpha (Pallas) from areas of the Rybinsk Reservoir with different levels of anthropogenic load. The following indices are studied: activity of catalase (CAT), glutathione reductase (GST), glutathione S-transferase (GST) and content of reduced glutathione (GSH), malondialdehyde (MDA), and carbonyl groups of oxidized proteins (CG). During the study period (July), the indices of oxidative stress of zebra mussel D. Polymorpha did not differ between sexes. Mussels that were collected in the most polluted part of the reservoir, the Sheksna stretch near the industrial complex of the city of Cherepovets, had a higher activity of catalase, glutathione S-transferase, and glutathione reductase and a higher content of malondialdehyde than zebra mussels taken from the relatively clean Volga stretch.     

American rotifer Kellicottia bostoniensis (Rousselet, 1908) (Rotifera: Brachionidae) in reservoirs of the Upper Volga Basin

Rotifer Kellicottia bostoniensis (Rousselet), typical for North American waterbodies, was found in three reservoirs (Ivankovo, Uglich, and Sheksna) of the Upper Volga Basin in 2005–2012. The size and density of mature rotifers (<4 thousands ind./m³) are comparable to or smaller than in the lakes that are the probable donors of this species.     

Spatial distribution and qualitative composition of polychlorinated biphenyls and organochlorine pesticides in bottom sediments and bream (<Emphasis Type="Italic">Abramis brama</Emphasis> L.) from the Rybinsk Reservoir

Persistent organic pollutants (POPs) were found in bottom sediments and muscles of a freshwater fish, bream (Abramis brama L.), from the Rybinsk Reservoir. The contents of POPs decreased in the following order: PCBs > DDT > HCH > HCB. The POPs contents vary within the ranges of 0.14–50.8, 1.8–6.8, 0.64–2.6, and 0.06–0.41 \gmg/kg wet weight for fish and 24.8–425.6, 2.3–27.1, and 0.34–0.83 fug/kg dry weight for bottom sediments (except for HCH), respectively. The highest and lowest POPs levels were found in the Sheksna and the Mologa reaches of the reservoir, respectively. The differences in the spatial distribution of POPs in the reservoir relate to the ways that contaminants enter and migrate in the waterbody but not to various compositions of bottom sediments. The waste waters of the city of Cherepovets are the main local source of POPs in the Sheksna reach of the reservoir; in the Mologa reach, the contaminants enter with surface runoff and through global transboundary and local atmospheric transports from the Cherepovets industry. The qualitative composition of POPs evidences their continuing income to the reservoir. Considering the revealed levels of POPs accumulation and their legislative safe environment levels, it should be concluded that PCBs represent the highest environmental threat to the reservoir’s ecosystem.     

Comparative immunochemical analysis of intraspecies distinctions of serum proteins of starred sturgeon <Emphasis Type="Italic">Acipenser stellatus</Emphasis> (Acipenseriformes,Acipenseridae) from the Caspian basin

By methods of immunochemical analysis, antigenic characteristics of serum proteins of starred sturgeon Acipenser stellatus migrating to the Volga, the Ural, and the Kura are studied. Antigens of serum proteins of starred sturgeon with normal homo- and heteroantisera are differentiated immunoelectochemically into 22–25 components. Cross absorption of antisera revealed the presence of specific antigens. Volga starred sturgeon differs from the Ural starred sturgeon in one antigen which belongs to α₂-globulins and differs from the Kura starred sturgeon in two antigens which manifest themselves in the zone of β₁-globulins. Kura starred sturgeon differs from the Ural starred sturgeon in two antigens which are in the zone of α₂-globilins. It is concluded that presence of specific antigens in the Volga and the Kura population of starred sturgeon and in their absence in the Ural starred sturgeon indicate the reproductive independence of these intraspecies groups.     

Distribution and special traits of naturalization of new and rare zooplankton species in waterbodies of the Upper Volga basin

More than ten new zooplankton species were registered in reservoirs of the Upper Volga during 2002–2005. Since 2003, the cladoceran Diaphanosoma orghidani Negrea, had intensively settled in different biotopes of Ivankovo, Uglich, Rybinsk, and Sheksna reservoirs and is the most abundant (16 000 ind./m³) in the latter one. The rotifer Asplanchna henrietta Langh. was found for the first time in Rybinsk Reservoir in 1985, and by 2004, this species had also occurred in Ivankovo, Uglich reservoirs, Lake Nero, and some small waterbodies of the basin. In Lake Nero its density reaches especially high values (>1 million ind./m³). Causes, mechanisms, and ecological consequences of the expansion of new zooplankton species are discussed.     

Comparison of nutrition range in <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> and <Emphasis Type="Italic">Dreissena bugensis</Emphasis> mussels by biochemical markers

Based on biochemical markers, we studied the nutrition ranges of populations of Dreissena polymorpha and Dreissena bugensis mussels that inhabit the Volga reach of the Rybinsk reservoir and differ in the long-term population dynamics. Features of the nutrition ranges of mussels are regarded as the probable cause of changes in the number of mollusca.     

Growth,size-age structure of catches and reproduction of the Volga zander <Emphasis Type="Italic">Sander volgensis</Emphasis> (Percidae) in the upper part of the Volga stretch of the Kuibyshev Reservoir

Conditions of reproduction, size-age structure of catches, and the growth of the Volga zander Sunder volgensis in the upper part of the Volga stretch of the Kuibyshev Reservoir from 2002 to 2007, as well as its fishery in this water body, are considered. A decrease in catches of the proportion of large elder age groups of the Volga zander in the period of destabilization of the reservoir ecosystem, as compared to the phase of its relative stabilization from the 1970s to the 1980s, and a decrease in the commercial catch were established. Besides, retardation of its growth in connection with the deterioration of the ecological situation is observed, but the average level of reproduction is retained, which at the organization of rational fishery can lead to the restoration of the Volga zander stock.     

Comparison of behavioral and physiological–biochemical indices in fingerlings of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) from the Ild River and Ild Bay in the Rybinsk Reservoir

It is found that the size–mass, physiological–biochemical, and behavioral parameters in roach fingerlings from the upper and lower (mouth) reaches of the Ild River differed during the autumn season. Compared with the roach from the upper reach of the river, the fingerlings of the same age from the mouth part have larger lengths and weights and a higher concentration of cations in the body. In experiments, the fish from the mouth part selected a lower (~4°C) temperature and showed a lower resistance to the water flow. The reason for differences in behavioral responses in two groups of juveniles of roach is probably, on the one hand, their physiological and biochemical characteristics and, on the other hand, the motivational component of fish behavior in different environments—hydrological, thermal, and hydrochemical conditions and different food items in geographically remote parts of the same river. It is assumed that in autumn roach fingerlings migrate from the littoral of the mouth part of the river into deeper parts under a decrease in water temperature before the downstream migration of the fingerlings in the rivers. This is probably due to the earlier achievement of the migration status of fingerlings from the mouth part than that in fish from the upper reach of the river and due to the peculiarities of their physiological state. Negative rheoreaction, manifested in the experiment in ~80% of the fish from the bay of the reservoir and ~55% of the fish from river, confirms the fish readiness to migrate and is likely due to the behavioral mechanism of fish migration from the littoral and downstream the river.     

A meta‐analysis of latitudinal variations in life‐history traits of roach,Rutilus rutilus,over its geographical range: linear or non‐linear relationships?

1. We collated information from the literature on life history traits of the roach (a generalist freshwater fish), and analysed variation in absolute fecundity, von Bertalanffy parameters, and reproductive lifespan in relation to latitude, using both linear and non-linear regression models. We hypothesized that because most life history traits are dependent on growth rate, and growth rate is non-linearly related with temperature, it was likely that when analysed over the whole distribution range of roach, variation in key life history traits would show non-linear patterns with latitude.
2. As fecundity depends strongly on length, and the length structure of females varied among populations, latitudinal patterns in fecundity were examined based on residuals from the length–fecundity relationship. The reproductive lifespan of roach was estimated as the difference between age at maturity and maximum age of females in each population.
3. The three life history traits of roach analysed all varied among populations and were non-linearly related to latitude. Only the relationship between reproductive lifespan and latitude was a better fit to a linear that to a quadratic model, although Loess smoothing curves revealed that this relationship was actually closer to biphasic than linear in form. A latitude of 50°N formed a break point in all three life history traits.
4. The negative relationships we have described between (i) fecundity and reproductive lifespan and (ii) fecundity and egg mass suggest that lower fecundity is compensated for by longer lifespan, while lower fecundity is compensated for by an increased egg mass, when analysed independently of location.     

Structure and functioning of the microbial loop in a boreal reservoir

The abundance and biomass of the main components of the microbial plankton food web (“microbial loop”)—heterotrophic bacteria, phototrophic picoplankton and nanoplankton, heterotrophic nanoflagellates, ciliates and viruses, production of phytoplankton and bacterioplankton, bacterivory of nanoflagellates, bacterial lysis by viruses, and the species composition of protists—have been determined in summer time in the Sheksna Reservoir (the Upper Volga basin). A total of 34 species of heterotrophic nanoflagellates from 15 taxa and 15 species of ciliates from 4 classes are identified. In different parts of the reservoir, the biomass of the microbial community varies from 26.2 to 64.3% (on average 45.5%) of the total plankton biomass. Heterotrophic bacteria are the main component of the microbial community, averaging 63.9% of the total microbial biomass. They are the second (after the phytoplankton) component of the plankton and contribute on average 28.6% to the plankton biomass. The high ratio of the production of heterotrophic bacteria to the production of phytoplankton indicates the important role of bacteria, which transfer carbon of allochthonous dissolved organic substances to a food web of the reservoir.     

Expression of gonadotropin subunits in roach (Rutilus rutilus, Cyprinidae) infected with plerocercoids of the tapeworm Ligula intestinalis (Cestoda)

Plerocercoids of the tapeworm Ligula intestinalis (Cestoda: Bothriocephalidea) have been reported to inhibit gametogenesis of their intermediate fish hosts. However, mechanistic studies are rare and the proximate cues leading to impaired reproduction still remain unknown. In the present study we investigated the effects of infection by L. intestinalis on reproductive parameters of roach (Rutilus rutilus, Cyprinidae), a common fish host of this parasite. Field studies on roach demonstrated that in both genders infection prevented gonad development. As revealed by quantitative PCR, infection was accompanied by essentially lower pituitary expression of follicle-stimulating hormone β-subunit (FSHβ) and luteinizing hormone β-subunit (LHβ) mRNA compared with uninfected roach, providing clear evidence for gonadotropin-insufficiency as the cause of arrested gametogenesis. Under controlled laboratory conditions infected roach showed lower mRNA levels of FSHβ but not of LHβ, despite histology revealing similar gonad stages as in uninfected conspecifics. These findings indicate the involvement of FSH rather than LH in mediating effects of infection early during gonad development in roach. Moreover, the impact of L. intestinalis on reproductive parameters of roach appeared to be independent of the parasite burden. Together, these data provide valuable information on the role of FSH and LH as mediators of parasite-induced sterilization in a vertebrate and implicate the selective inhibition of host reproduction by L. intestinalis as a natural source of endocrine disruption in fish.     

Fish parasites as bioindicators of the pollution of bodies of water]

The paper presents the results of studies on the effect of wastes of the Cherepovets iron-and-steel works containing phenol, naphthaline and oil products on fish parasites of the Sheksna part of the Rybinsk water reservoir (the Volga river system). It has been shown that the number of highly sensitive ectoparasites of Abramis brama (Protozoa, Dactylogyrus monogeneans, Ergasilus sieboldi crustaceans and Caspiobdella fadejewi leeches) considerably decreases in the zone of pollution. It has been first suggested to use Diplozoon paradoxum and Caryophyllaeus laticeps, parasites of bream highly resistant to toxic effect, the number of which considerably increases in the zone of pollution, as indicators of anthropogenic pollution and ecological state of a water body. Among diplozoons there have been first discovered individuals having structural anomalies (reduction of the attachment organs, violation in the symmetry of arrangement and number of valves) that serves as evidence of mutagenic effect of toxic substances of polluted waters on morphogenesis of the parasite.     

Fish recruitment in a large,temperate floodplain: the importance of annual flooding,temperature and habitat complexity

1. Large river floodplains are considered key nursery habitats for many species of riverine fish. The lower Volga River floodplains (Russian Federation) are still relatively undisturbed, serving as a suitable model for studying the influence of flooding and temperature on fish recruitment in floodplain rivers. 2. We examined the interannual variability in recruitment success of young‐of‐the‐year (YOY) fish in the lower Volga floodplain in relation to flood pulse characteristics and rising water temperatures in the spring. We sampled four areas with different flooding regimes, in three consecutive years (2006–2008). 3. Extensive areas with a long duration of flooding accommodated high densities of young fish. This suggests that extended inundation improves the recruitment success of river fish. In areas with extensive flooding, the biomass of YOY of most fish species was about three times higher in 2006 and 2007 than in 2008. We hypothesise that low spring temperatures in 2008 may have caused this reduced recruitment and that a flood synchronised with rising temperature enhances recruitment success. 4. Extensive flooding was particularly favourable for species characterised by large body size, delayed maturation, high fecundity and low parental investment, such as pike Esox lucius, roach Rutilus rutilus and ide Leuciscus idus. Gibel carp Carassius gibelio, a species tolerant of high temperature and hypoxia, did particularly well in small waterbodies in the driest parts of the floodplain. 5. Structural characteristics of floodplain waterbodies explained much of YOY fish density. These species–environment associations varied from year to year, but some species such as common bream Abramis brama, roach and gibel carp showed consistent relationships with structural habitat characteristics in all years, despite large interannual fluctuations in flood pulse and spring temperature.     

Mobility of individual roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) in three weir-fragmented Belgian rivers

Adult roach Rutilus rutilus (L.) (N = 24; 19.9–36.1 cm FL) from three highly fragmented Belgian rivers were tagged with surgically implanted radio transmitters. Their seasonal movements were observed from March to August 2004 (circum reproduction period) in river stretches delimited by two physical barriers. In the three rivers, roach displayed similar patterns of movements which were mainly influenced by the date of observation (movements increased in late April–May) and water temperature (travel distances were more important when water temperature ranged between 10°C and 14°C). Roach sometimes cleared physical obstacles. The mean distances travelled in each river were relatively short (max. 2.5 km) and mainly influenced by the length of the study reach, which was delimited by physical barriers.     

Size-dependent attack rate and handling capacity: inter-cohort competition in a zooplanktivorous fish

Two size‐dependent processes, metabolic requirements and foraging capacity, heavily influence the competitive ability of organisms. We studied the size‐dependent competitive ability of roach (Rutilus rutilus) in a laboratory experiment to determine the attack rate of roach as a function of roach and zooplankton sizes. The estimated size‐dependent attack rates, size‐dependent metabolic demands and handling capacities were subsequently used to interpret the outcome of a competition experiment between two size classes of roach. Furthermore, size‐dependent attack rates were implemented in an optimal foraging model to predict consumption rates and zooplankton selection to reveal the mechanisms behind competition.
The attack rate first increased with roach size to a maximum around 160 mm to thereafter decrease. Based on this result, we predicted that, small (150 mm) roach had a double advantage in competition for zooplankton in the pond experiment due to their higher attack rate and their lower metabolism compared to large (230 mm) roach. As expected, small roach depressed total zooplankton biomass to a higher extent than large roach, included more zooplankton in their diet and consumed smaller zooplankton. Predicted smallest size class of zooplankton in the diet was close to the observed. Also as expected, large roach fed more on the benthic resource and depressed the benthic resource to a larger extent than small roach. Large roach affected large zooplankton to a higher extent during the first part of the experiment, which could be related to their overall higher handling capacity. The higher impact of large roach on large zooplankton during the first part of the experiment, in turn, resulted in a lower estimated mass intake of zooplankton by small roach in the mixed treatment compared to small roach only treatments. Both small and large roach had a lower growth rate in the mixed treatment compared to single size class treatments. We relate the lower growth rate of small roach in the mixed treatment to large roach's higher efficiency on benthic resources and on large zooplankton during the first part of the experiment. In correspondence with diet data, large roach preferred the shore area of the pond with more benthic invertebrates and were also found more often close to the bottom. Although our results are explainable by exploitative interactions, the fact that the presence of large roach affected the feeding position of small roach points to that social interactions were also involved. Overall, our study implies that a mechanistic understanding is crucial for the interpretation of competition experiments, especially in systems with size‐structured interactions.     

Trophic dynamics in a whole lake experiment: size-structured interactions and recruitment variation

Horizontal and vertical heterogeneity as a result of size‐structured processes are important factors influencing indirect effects in food webs. In a whole‐lake experiment covering 5 years, we added the intermediate consumer roach (Rutilus rutilus) to two out of four lakes previously inhabited by the omnivorous top predator perch (Perca fluviatilis). We focused our study on the direct consumption effect of roach presence on zooplankton (and indirectly phytoplankton) versus the indirect effect of roach on zooplankton (and phytoplankton) mediated via effects on perch reproductive performance. The patterns in zooplankton and phytoplankton abundances were examined in relation to population density of roach and perch including young‐of‐the‐year (YOY) perch in the light of non‐equilibrium dynamics. The presence of roach resulted in changed seasonal dynamics of zooplankton with generally lower biomasses in May–June and higher biomasses in July–August in roach lakes compared to control lakes. Roach presence affected perch recruitment negatively and densities of YOY perch were on average higher in control lakes than in treatment lakes. In years when perch recruitment did not differ between lakes as a result of experimental addition of perch eggs, total zooplankton biomass was lower in treatment lakes than in control lakes. Phytoplankton biomass showed a tendency to increase in roach lakes compared to control lakes. Within treatment variation in response variables was related to differences in lake morphometry in treatment lakes. Analyses of the trophic dynamics of each lake separately showed strong cascading effects of both roach and YOY perch abundance on zooplankton and phytoplankton dynamics. Consideration of the long transients in the dynamics of top predators (fish) in aquatic systems that are related to their long life span involving ontogenetic niche shifts is essential for making relevant interpretations of experimental perturbations. This conclusion is further reinforced by the circumstance that the intrinsic dynamics of fish populations may in many cases involve high amplitude dynamics with long time lags.     

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.     

Structural and functional characteristics of the bacterioplankton of rivers flowing through a large city (Cherepovets,Upper Volga Region)

The structural and functional properties of the bacterioplankton in two small rivers and the Sheksna River that run through the large industrial city of Cherepovets were studied from April to October 2009–2011. The three-year average numbers and biomass of planktonic bacteria in small rivers were 18.7–18.8 million cells/mL and 3.5–4.9 g/m³, respectively; these values in the Sheksna River’s littoral zone were 15.8 million cells/mL and 2.2 g/m³. The bacterioplankton production in the small water courses exceeded that in the Sheksna River by a factor of 1.8–2.2. The contribution of bacterial filaments to the total biomass and the total bacterioplankton production increases in small polluted rivers.