Coregonus Lavaretus Research Articles

Discovery and characterization of miRNAs in whitefish (Coregonus lavaretus) challenged with microcystin-LR

Discovery and characterization of miRNAs in whitefish (Coregonus lavaretus) challenged with microcystin-LR

Histopathological and ultrastructural liver changes accompanied by biochemical alterations in the plasma of whitefish (Coregonus lavaretus, L.) after long-term exposure to microcystin-LR

Histopathological and ultrastructural liver changes accompanied by biochemical alterations in the plasma of whitefish (Coregonus lavaretus, L.) after long-term exposure to microcystin-LR

Male Investments in High Quality Sperm Improve Fertilization Success, but May Have Negative Impact on Offspring Fitness in Whitefish.

Many ejaculate traits show remarkable variation in relation to male social status. Males in disfavoured (subordinate) mating positions often invest heavily on sperm motility but may have less available resources on traits (e.g., secondary sexual ornaments) that improve the probability of gaining matings. Although higher investments in sperm motility can increase the relative fertilization success of subordinate males, it is unclear whether status-dependent differences in sperm traits could have any consequences for offspring fitness. We tested this possibility in whitefish (Coregonus lavaretus L.) by experimentally fertilizing the eggs of 24 females with the sperm of either highly-ornamented (large breeding tubercles, dominant) or less-ornamented (small tubercles, subordinate) males (split-clutch breeding design). In comparison to highly-ornamented individuals, less-ornamented males had higher sperm motility, which fertilized the eggs more efficiently, but produced embryos with impaired hatching success. Also offspring size and body condition were lower among less-ornamented males. Furthermore, sperm motility was positively associated with the fertilization success and offspring size, but only in highly-ornamented males. Together our results indicate that male investments on highly motile (fertile) sperm is not necessarily advantageous during later offspring ontogeny and that male status-dependent differences in sperm phenotype may have important effects on offspring fitness in different life-history stages.

MiR-122-5p as a plasma biomarker of liver injury in fish exposed to microcystin-LR.

Recent studies have shown the presence of large amounts of microRNAs (miRNAs; miRs) from damaged cells in the peripheral blood. In this study, we investigated the levels of miRNAs circulating in the blood plasma of whitefish (Coregonus lavaretus) after exposure to microcystin-LR. We used real-time PCR to examine the relative expression of plasma levels of 4 miRNAs (miR-122-5p and let-7c-5p, the liver-enriched microRNAs, miR-148a-3p which promotes the hapatospecific phenotype in mammals, and miR-92a-3p, a cell proliferation and angiogenesis promoter, potentially hepatocarcinogenic) during the first 48h after exposure to MC-LR. We observed a rapid increase of miR-122-5p levels 8h after exposure (P<0.05), which continued to the end of the experiment. Our results demonstrated that the plasma miR-122-5p was indicative of MC-LR-induced liver injury, exhibiting areas under the curve close to 1 in ROC analysis (AUC=0.976, P<0.001). Although plasma levels of miR-148a-3p and miR-92a-3p were significantly elevated by the end of the experiment, their discriminative power was lower than reported for the miR-122-5p. Based on these results and reports on miRNA-based diagnosis of liver injuries in mammals, plasma miR-122-5p could be considered as a robust, new generation diagnostic biomarker in fish, helpful for the non-invasive diagnosis of liver damage.

Thermal habitat segregation among morphotypes of whitefish (Coregonus lavaretus: Salmonidae) and invasive vendace (C. albula): a mechanism for co‐existence?

Summary Aquatic invasive species can have a variety of negative impacts on the ecosystems they invade. Carbon and nitrogen stable isotopes in the muscle tissue of aquatic organisms have proved useful for evaluating post‐invasion dietary shifts among species. However, oxygen and carbon stable isotopes in fish otoliths have the potential to provide additional data on thermal habitat, diet and metabolism, when investigating interactions among sympatric native and invasive fishes. We conducted oxygen and carbon stable isotope analysis on the otoliths of three morphotypes of native whitefish (Coregonus lavaretus) and invasive vendace (Coregonus albula) at two sites within the sub‐Arctic Pasvik watercourse in northern Norway. Mean temperature use among morphotypes and species over the course of the growing season ranged from 7.5 °C to 11.2 °C. Otolith δ13C was significantly positively correlated to fish muscle tissue δ13C (P &lt; 0.05, r2 = 0.53). Significant differences in temperature use and δ13C among morphotypes and between species were found in the downstream site but not the upstream site. Complementary partitioning of thermal and dietary resource use in the downstream site coincides with a higher abundance of whitefish, enabling the coexistence of both species. In contrast, vendace were dominant in the upstream site where no differentiation in resource use among morphotypes and between species was evident. This study demonstrates the usefulness of stable oxygen and carbon otolith isotopes for characterising resource use and highlights the importance of investigating thermal habitat use as a factor influencing the success of invasive fishes.

Identification of Cryptosporidium Species in Fish from Lake Geneva (Lac Léman) in France.

Cryptosporidium, a protozoan parasite that can cause severe diarrhea in a wide range of vertebrates including humans, is increasingly recognized as a parasite of a diverse range of wildlife species. However, little data are available regarding the identification of Cryptosporidium species and genotypes in wild aquatic environments, and more particularly in edible freshwater fish. To evaluate the prevalence of Cryptosporidiumspp. in fish from Lake Geneva (Lac Léman) in France, 41 entire fish and 100 fillets (cuts of fish flesh) were collected from fishery suppliers around the lake. Nested PCR using degenerate primers followed by sequence analysis was used. Five fish species were identified as potential hosts of Cryptosporidium: Salvelinus alpinus, Esox lucius, Coregonus lavaretus, Perca fluviatilis, and Rutilus rutilus. The presence of Cryptosporidium spp. was found in 15 out of 41 fish (37%), distributed as follows: 13 (87%) C. parvum, 1 (7%) C. molnari, and 1 (7%) mixed infection (C. parvum and C. molnari). C. molnari was identified in the stomach, while C. parvum was found in the stomach and intestine. C. molnari was also detected in 1 out of 100 analyzed fillets. In order to identify Cryptosporidium subtypes, sequencing of the highly polymorphic 60-kDa glycoprotein (gp60) was performed. Among the C. parvum positive samples, three gp60 subtypes were identified: IIaA15G2R1, IIaA16G2R1, and IIaA17G2R1. Histological examination confirmed the presence of potential developmental stages of C. parvum within digestive epithelial cells. These observations suggest that C. parvum is infecting fish, rather than being passively carried. Since C. parvum is a zoonotic species, fish potentially contaminated by the same subtypes found in terrestrial mammals would be an additional source of infection for humans and animals, and may also contribute to the contamination of the environment with this parasite. Moreover, the risk of human transmission is strengthened by the observation of edible fillet contamination.

Gill raker counting for approximating the ratio of river- and sea-spawning whitefish, Coregonus lavaretus (Actinopterygii: Salmoniformes: Salmonidae) in the Gulf of Bothnia, Baltic Sea

Background. The ability to distinguish between stocks in mixed fisheries is a prerequisite for a sustainable fisheries management. In the Gulf of Bothnia the relative contribution of endangered river-spawning and sea-spawning whitefish, Coregonus lavaretus (Linnaeus, 1758), to fisheries catches are currently not well known. This also applies to the southern &#197;land Islands, a major feeding ground for river-spawning whitefish from northern rivers. River- and sea-spawning whitefish are mixed while away from the breeding grounds and off the spawning season, and cannot be distinguished based on external features. Materials and methods. Analysis on gill raker numbers of river-spawning (n = 480) and sea-spawning (n = 456) whitefish from twelve locations at the Finnish west coast and the &#197;land Islands was performed. In whitefish sampled from feeding grounds at the &#197;land Islands the strontium concentration was analysed in otoliths from fish (n = 20) with low (27) and high (30) number of gill rakers. Results. A marked difference in the mean gill raker number of the river- and sea-spawning whitefish stocks was observed. The weighted mean of gill rakers of whitefish caught at spawning locations showed that the number of gill rakers of fish from rivers and the sea were 29.9 &#177; 2.14&#160; (n = 480) and 26.7 &#177; 2.21&#160; (n = 456), respectively. The difference between the two groups was highly significant (t = 22.50, df = 934, P &#60; 0.0001). The means differed by 3.20 (2.92&#8211;3.48, 95% CL) indicating the groups are well separated.&#160; In whitefish sampled at feeding grounds at the &#197;land Islands, otolith strontium concentration was higher (t = 2.09, df = 18, P = 0.04) in fish having 27 gill rakers (3.86 &#177; 0.30 mg &#183; g&#8211;1, n = 10), compared to those having 30 gill rakers (3.54 &#177; 0.35 mg &#183; g&#8211;1, n = 10).&#160; Otolith strontium analysis thereby supported the utility of gill raker counting data for estimating the proportion of river- and sea-spawning whitefish in mixed populations. As expected, the gill raker counting method successfully indicated temporal alterations in the proportions of river- and sea-spawning whitefish on feeding grounds. Conclusion. Gill raker counting is an easy, fast, and inexpensive method that can be used to estimate the spatiotemporal occurrence and migratory patterns of river- and sea-spawning whitefish at the southern feeding grounds in the Gulf of Bothnia, and thereby aid in a sustainable management of whitefish stocks.

Gill raker counting for approximating the ratio of river- and sea-spawning whitefish, Coregonus lavaretus (Actinopterygii: Salmoniformes: Salmonidae) in the Gulf of Bothnia, Baltic Sea

Gill raker counting for approximating the ratio of river- and sea-spawning whitefish, Coregonus lavaretus (Actinopterygii: Salmoniformes: Salmonidae) in the Gulf of Bothnia, Baltic Sea

Disinfection of non-hardenedCoregonus lavaretuseggs with iodophor solution: effect on embryo and larvae viability and on egg hardening

Aquaculture ResearchVolume 47, Issue 11 p. 3694-3696 Short Communication Disinfection of non-hardened Coregonus lavaretus eggs with iodophor solution: effect on embryo and larvae viability and on egg hardening Franz Lahnsteiner, Corresponding Author Franz Lahnsteiner franz.lahnsteiner@baw.at Federal Agency for Water Management, Institute for Water Ecology, Fisheries and Lake Research, Mondsee, Austria Fishfarm Kreuzstein, Unterach, AustriaCorrespondence: F Lahnsteiner, Federal Agency for Water Management, Institute for Water Ecology, Fisheries and Lake Research, Scharfling 18, A-5310 Mondsee, Austria. E-mail: franz.lahnsteiner@baw.atSearch for more papers by this authorManfred Kletzl, Manfred Kletzl Federal Agency for Water Management, Institute for Water Ecology, Fisheries and Lake Research, Mondsee, Austria Fishfarm Kreuzstein, Unterach, AustriaSearch for more papers by this author Franz Lahnsteiner, Corresponding Author Franz Lahnsteiner franz.lahnsteiner@baw.at Federal Agency for Water Management, Institute for Water Ecology, Fisheries and Lake Research, Mondsee, Austria Fishfarm Kreuzstein, Unterach, AustriaCorrespondence: F Lahnsteiner, Federal Agency for Water Management, Institute for Water Ecology, Fisheries and Lake Research, Scharfling 18, A-5310 Mondsee, Austria. E-mail: franz.lahnsteiner@baw.atSearch for more papers by this authorManfred Kletzl, Manfred Kletzl Federal Agency for Water Management, Institute for Water Ecology, Fisheries and Lake Research, Mondsee, Austria Fishfarm Kreuzstein, Unterach, AustriaSearch for more papers by this author First published: 23 May 2015 https://doi.org/10.1111/are.12798Citations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume47, Issue11November 2016Pages 3694-3696 RelatedInformation

C-myc in whitefish (Coregonus lavaretus): structure, expression, and insights into possible posttranscriptional regulatory mechanism.

c-myc has a crucial function in growth control, differentiation, and apoptosis of vertebrate cells. Despite the important role of c-myc in mediating the biological effects, studies of c-myc gene expression and factors that control it in organisms other than mammals, such as fish, have been rare. In the current study, we asked whether c-myc mRNA of whitefish, a feasible organism for pollution monitoring in aquatic systems and a model in toxicological research, contains activity sites for regulatory motifs in its 5'- and 3'-UTRs, similar to those found in mammals. We were particularly interested in whether miRNA-34, a known negative regulator of c-myc's in mammals, is able to regulate c-myc in fish. To answer these questions, we determined the mRNA sequence of whitefish c-myc and inferred the structure of the protein that it codes for. We found that the active sites of mRNA and structures of the inferred c-myc protein are similar to those found in mammals and other fish. Remarkably, levels of c-myc mRNA expression were very high in ovaries compared to other tissues of whitefish, thus corroborating previous data in fish. Using bioinformatic searches on c-myc 3'-UTR, we confirmed the presence of two miRNA-34a(miR-34a)response elements. Luciferase reporter assay showed that activity of reporters containing either the miR response elements or entire c-myc 3'-UTR was significantly reduced (p<0.001) by ectopic expression of miR-34a. Therefore, we further investigated possible involvement of miR-34a in c-myc gene silencing by profiling the expression of both genes in livers of whitefish treated for 8, 24, 48h with MC-LR, a potent c-myc inducer in mammals. Although the difference was only significant at p=0.08, the expression of c-myc mRNA in challenged whitefish after 24h of the treatment was notably higher than that in livers of control fish. Concurrently, we noticed slight but significant up-regulation of miR-34a after 24 and 48h of the challenge (p<0.05); however, we found no significant correlation of the c-myc mRNA levels and miR-34a expression. Together, these results suggest that miR-34a might regulate c-myc gene expression in whitefish liver; however, their involvement in MC-LR hepatotoxicity should be clarified in future studies.

Spermatozoa motility traits influenced by activation media in the European whitefish (Coregonus lavaretusL. 1758)

The use of a properly selected activating solution during artificial fertilization permits improvement in spermatozoa motility characteristics and enhancement of the fertilization success. This is particularly important for species characterised by low motility parameters. The aim of the study was to determine the types of environments favourable for whitefish (Coregonus lavaretus L.) spermatozoa activation on the basis of analysis of the spermatozoa motility parameters. Motility parameters were evaluated for four activation media: 30 mm NaCl, Billard's solution, 120 mm NaHCO3 and hatchery water, using computer assisted sperm analysis (CASA). The study was divided into two experiments: (i) in the first, the effects of three solutions were tested: 30 mm NaCl, Billard's solution and 120 mm NaHCO3; (ii) in the second, the effects of hatchery water and 30 mm NaCl were compared. The durations of the active motility phase in the three tested solutions were similar (approximately 150 s), while that measured in hatchery water was significantly shorter (115 s). Upon activation, motility (MOT) was similar in all activating media but the highest values of curvilinear velocity (VCL), straight line velocity (VSL) and amplitude of lateral head displacement (ALH) were observed in 30 mm NaCl. NaCl solution was a suitable environment for the whitefish spermatozoa activation. The velocity parameters obtained in this medium exceed those noted in other tested environments, particularly upon activation.

Generation of a neutral FST baseline for testing local adaptation on gill raker number within and between European whitefish ecotypes in the Baltic Sea basin.

Divergent selection at ecologically important traits is thought to be a major factor driving phenotypic differentiation between populations. To elucidate the role of different evolutionary processes shaping the variation in gill raker number of European whitefish (Coregonus lavaretus sensu lato) in the Baltic Sea basin, we assessed the relationships between genetic and phenotypic variation among and within three whitefish ecotypes (sea spawners, river spawners and lake spawners). To generate expected neutral distribution of FST and to evaluate whether highly variable microsatellite loci resulted in deflated FST estimates compared to less variable markers, we performed population genetic simulations under finite island and hierarchical island models. The genetic divergence observed among (FCT = 0.010) and within (FST = 0.014-0.041) ecotypes was rather low. The divergence in gill raker number, however, was substantially higher between sea and river spawners compared to observed microsatellite data and simulated neutral baseline (PCT > FCT ). This suggests that the differences in gill raker number between sea and river spawners are likely driven by divergent natural selection. We also found strong support for divergent selection on gill raker number among different populations of sea spawners (PST > FST ), most likely caused by highly variable habitat use and diverse diet. The putative role of divergent selection within lake spawners initially inferred from empirical microsatellite data was not supported by simulated FST distributions. This work provides a first formal test of divergent selection on gill raker number in Baltic whitefish, and demonstrates the usefulness of population genetic simulations to generate informative neutral baselines for PST -FST analyses helping to disentangle the effects of stochastic evolutionary processes from natural selection.

Genetic characteristics of Polish whitefish (Coregonus lavaretus maraena) broodstocks - recommendations for the conservation management

European whitefi sh Coregonus lavaretus maraena is an important fi sh species in Poland. Unfor - tunately, most of the whitefi sh populations are currently threatened with extinction, generally due to water pollution and over fi shing. Because the whitefi sh populations have decreased drastically in Poland, a protec - tion plan has been developed, which includes the creation of whitefi sh broodstocks in aquaculture condi - tions. During its implementation, genetic analysis of these valuable fi sh populations should be performed. This manuscript describes a study, in which microsatellite DNA analysis was applied to investigations into the genetic structure of two whitefi sh broodstocks maintained in Poland (Pomorska Bay and Galadus) and two natural populations from Lebsko Lake and Mamry Lake, northern Poland. Genetic differentiation was detected between the analyzed populations through the pairwise genetic differentiation index ( F ST ). The D A measure of genetic distance between pairs of populations indicated that the shortest distance was between the Pomorska Bay broodstock and the Lebsko Lake population (0.062), while the longest one was between the Lebsko Lake and the Galadus populations (0.172). The present results reveal genetic characterization of important popula - tions of whitefi sh in Poland and provide the first information about the genetic condition of these fi sh stocks.

Rearing Larvae of Different Strains of Coregonus lavaretus under Cold Water Conditions: Comparison of a Special Cold-Water Line with a Standard Agglomerated Microdiet

We studied the performance of a commercial, agglomerated larval microdiet in terms of survival, growth and feed acceptance and compared a dedicated “cold water line” of the product to the standard product involving a Baltic and an Alpine strain of whitefish. Experiments were conducted under cold water conditions < 8 °C (average 5.1 °C) for 60 days after hatching. Replicate tanks of 400 and 200 liter volume received filtered lake water disinfected with ozone and UV light and were stocked with 15 larvae per liter. Daily rations of 4% body weight were manually delivered in six portions every two hours and group samples were taken weekly to determine length, weight and feed acceptance. Dead larvae were removed and counted daily. Before our experiment was influenced by an outbreak of an unknown disease during the last two weeks, we observed similar growth, survival and feed acceptance for each of the feed types with low variability within each of the two strains. Strains showed characteristic differences in growth and survival related to lower feed acceptance during the first four weeks of the Alpine strain. We concluded that the specific cold water line of the commercial microdiet did not provide any advantage compared to the standard product under low temperature conditions. However, differential performance might exist under different temperature regimes.

Seasonal depletion of resources intensifies trophic interactions in subarctic freshwater fish communities

Summary Climate change in recent decades has resulted in an increase in both the density and diversity of consumers in subarctic freshwater ecosystems. Despite this, harsh winter conditions in the region limit productivity and may serve as a bottleneck driving trophic interactions within the fish community, potentially determining the outcome of climate change for resident biota. However, due to the difficulties in sampling during winter months, few studies have assessed seasonal variation in the ecological interactions between native and range‐expanding species in subarctic regions. We examined seasonal variation in activity, diet (stomach content) and resource use (δ13C and δ15N stable isotope ratios) of two fishes: the resident cold‐water‐adapted European whitefish (Coregonus lavaretus L.) and the range‐expanding cool‐water‐adapted ruffe (Gymnocephalus cernua L.) in lakes with low and high consumer density. Results were contrasted with seasonal availability of benthic and pelagic resources and indirect measures of individual fitness, that is condition, growth and estimated lipid content (muscle elemental C : N ratio) of both species. The effects of fish density were apparent in both the diet and resource use of whitefish, which altered their diet and displayed reduced stomach fullness during winter in high‐density lakes. This was associated with an overall reduction in whitefish growth, condition and estimated lipid content in high‐density lakes, which was especially pronounced during winter. Ruffe utilised a greater proportion of profundal resources than whitefish in both summer and winter, potentially exploiting a vacant niche. Ruffe maintained condition and lipid reserves throughout the winter, highlighting the potential for further northward range expansion of the species. Winter acts as a seasonal bottleneck in subarctic lakes, but assumptions that this bottleneck primarily selects against warmer‐water‐adapted invasive species such as ruffe may be too restrictive. The effects of seasonal resource depletion on fish condition and invertebrate density were most severe in lakes with a high density of fish, and in these conditions, the cold‐water‐adapted resident whitefish was most adversely affected.

Predation by signal crayfish Pacifastacus leniusculus on fish eggs and its consequences for coregonid recruitment.

The character and magnitude of predation by the invasive, ectothermic Pacifastacus leniusculus, a crayfish widely introduced to Europe and Japan from North America, on the eggs of coregonid fishes, vendace Coregonus albula and whitefish Coregonus lavaretus were examined by experimentation, modelling and field data. The present results showed that P. leniusculus has the potential to be very efficient predator of fish eggs under winter conditions, but the predation by P. leniusculus did not significantly decrease production of coregonid larvae during the years with a high P. leniusculus population in the study lake. Hence, the mortality caused by the novel invertebrate predator appeared to compensate for other yet unexplored mortality factors instead of having an additive effect on the present salmonids.

Selection of optimal spawner pairs based on the polymorphism of microsatellite loci in a partially tetraploid fish species (Coregonus lavaretus)

Selection of optimal spawner pairs based on the polymorphism of microsatellite loci in a partially tetraploid fish species (Coregonus lavaretus)

Revisiting Echinorhynchid Acanthocephalans in Lake Baikal with the Use of Scanning Electron Microscopy, with some Taxonomic Reconsiderations

Ten species of acanthocephalans are known from 30 species of fish in Lake Baikal. Three species in the family Echinorhynchidae were studied and reported: (1) Echinorhynchus salmonis Müller, 1784 ( = Metechinorhynchus salmonis (Müller 1784) Petrochenko, 1956), previously designated as Echinorhynchus salmonis baicalensis Bogolepova, 1957 (actually Dogiel and Bogolepova, 1957) that we consider invalid. Echinorhynchus s. baicalensis was studied from whitefish Coregonus lavaretus (Linnaeus, 1758) (Family Salmonidae) in Chivyrkui Bay and from Kessler's (sand) sculpin Leocottus kesslerii (Dybowski, 1874) (Family Cottocomephoridae) at Goryachinsk on the eastern shore of Lake Baikal in Pribaikalsk District, Republic of Buryatia. Our scanning electron microscopy observations demonstrate miniapical proboscis hooks, hooks with dorsal indentation, 2 anteroventral trunk bumps, and variable position of male and female gonopores, for the first time. (2) Echinorhynchus cinctulus (Porta, 1905) Amin, 2013 ( = Pseudoechinorhynchus borealis (von Linstow, 1901) Petrochenko, 1956) was studied from burbot, Lota lota (Linnaeus, 1758) (Family Lotidae) in Chivyrkui Bay and Khankh. The thorny hooks, inconsistencies in proboscis armature, hook size, dermal micropores, and position of male and female gonopores are reported. (3) Echinorhynchus truttae Schrank, 1788 ( = Metechinorhynchus truttae (Schrank, 1788) Petrochenko, 1956) was studied from L. kesslerii in Goryachinsk. Features of the proboscis, hooks, female gonopore, dermal micropores, and eggs are presented.

Effect of 11β-hydroxyandrostenedione (OHA) on the gonadal differentiation in whitefish Coregonus lavaretus L.

Effect of 11β-hydroxyandrostenedione (OHA) on the gonadal differentiation in whitefish Coregonus lavaretus L.

Feeding of whitefish Coregonus lavaretus pidschian (Coregonidae) in the lower reaches of the Northern Dvina River

Analysis was performed of the feeding of whitefish in the basin of the Northern Dvina River, including the tributary of the first order—Emtsa River and the middle course of the river, its delta part, and sites of the near-mouth offshore. It was established that, according to the pattern of feeding, whitefish is a euryphage with sufficiently wide food spectrum, including over 40 groups of food organisms at the level of classes, orders, families, and genera. The bulk of its feeding is formed by aquatic larvae of insects (mainly chironomid larvae), secondary food consists of mollusks, crustaceans, worms, and sponges. Changes in the feeding of whitefish depending on habitats, food biotopes, and difference with respect to years and seasons of the year, as well as on the age of fish, were revealed. Sufficiently high feeding intensity, as well as small changes in the feeding of whitefish in different years and at different sections of the channel indicate stable feeding conditions in the middle part of the Dvina basin. Food possibilities of the delta and the near-mouth offshore also satisfy trophic demands of the feeding school of whitefish.