Coregonus Lavaretus Research Articles

Do whitefish (Coregonus lavaretus) larvae show adaptive variation in the avoidance of microplastic ingestion?

The presence of microplastics in aquatic ecosystems has recently received increased attention. Small plastic particles may resemble natural food items of larval fish and other aquatic organisms, and create strong selective pressures on the feeding traits in exposed populations. Here, we examined if larval ingestion of 90 μm polystyrene microspheres, in the presence of zooplankton (Artemia nauplii, mean length = 433 μm), shows adaptive variation in the European whitefish (Coregonus lavaretus). A full-factorial experimental breeding design allowed us to estimate the relative contributions of male (sire) and female (dam) parents and full-sib family variance in early feeding traits, and also genetic (co)variation between these traits. We also monitored the magnitude of intake and elimination of microplastics from the alimentary tracts of the larvae. In general, larval whitefish ingested small numbers of microplastics (mean = 1.8, range = 0–26 particles per larva), but ingestion was marginally affected by the dam, and more strongly by the full-sib family variation. Microsphere ingestion showed no statistically significant additive genetic variation, and thus, no heritability. Moreover, microsphere ingestion rate covaried positively with the ingestion of Artemia, further suggesting that larvae cannot adaptively avoid microsphere ingestion. Together with the detected strong genetic correlation between food intake and microplastic intake, the results suggest that larval fish do not readily possess additive genetic variation that would help them to adapt to the increasing pollution by microplastics. The conflict between feeding on natural food and avoiding microplastics deserves further attention.

Offspring phenotype is shaped by the nonsperm fraction of semen.

In a large majority of animal species, the only contribution of males to the next generation has been assumed to be their genes (sperm). However, along with sperm, seminal plasma contains a wide array of extracellular factors that have many important functions in reproduction. Yet, the potential intergenerational effects of these factors are virtually unknown. We investigated these effects in European whitefish (Coregonus lavaretus) by experimentally manipulating the presence and identity of seminal plasma and by fertilizing the eggs of multiple females with the manipulated and unmanipulated semen of several males in a full-factorial breeding design. The presence of both own seminal plasma and foreign seminal plasma inhibited sperm motility, and the removal of own seminal plasma decreased embryo survival. Embryos hatched significantly earlier after both semen manipulations than in control fertilizations; foreign seminal plasma also increased offspring aerobic swimming performance. Given that our experimental design allowed us to control potentially confounding sperm-mediated (sire) effects and maternal effects, our results indicate that seminal plasma may have direct intergenerational consequences for offspring phenotype and performance. This novel source of offspring phenotypic variance may provide new insights into the evolution of polyandry and mechanisms that maintain heritable variation in fitness and associated female mating preferences.

Fish response of metal bioaccumulation to reduced toxic load on long-term contaminated lake Imandra.

The present study analysed the response of whitefish (Coregonus lavaretus L.) to reduced toxicity after the long-term contamination of subarctic Lake Imandra. High concentrations of Ni, Al, and Sr in fish organs and tissues were accompanied by nephrocalcinosis, scoliosis, and myopathy during the period of intense contamination. After reduction of the toxic impact on the lake, the accumulation of Cu, Al, Sr, Cr, Pb, and Hg in the kidney, which is the target organ for toxicity, was two-fold less and that of Cd was 10-fold less in whitefish from the contaminated part of the lake compared with those in whitefish from the non-contaminated parts of the lake. The ecological success of whitefish from the contaminated part of the lake was associated with the limited accumulation of metals in organs and tissues and a more favourable physiological state compared with whitefish from non-contaminated parts of the lake. Redistribution models were constructed for essential and non-essential metals in the fish liver and kidney depending on the physiological state of fish. The results revealed changes in Fe and Zn metabolism: an increase in Fe and a decrease in Zn accumulation in the liver with increasing stage of liver disease and decreasing blood haemoglobin concentration. Furthermore, under the sub-toxic (except for Cu) conditions of Lake Imandra, the strategy of adaptive fish response is to preserve and maintain acid-base regulation system.

Lipid Composition of the Tissues of Coregonus lavaretus L. of the Kola Peninsula

The article presents the results of the investigation of the lipid composition of the muscle, liver and eggs of the whitefish Coregonus lavaretus L. of different age groups harvested from lakes Lovozero and Umbozero of the Kola Peninsula. The study of the lipid composition of the tissues to some extent allows evaluating the features of lipid metabolism and the physiological state of an organism. Lipids were extracted from the tissues applying Bligh – Dyer method. Fractional composition of lipids was determined using one-dimensional thin layer chromatography. Individual lipid fractions were determined by densitometry. The content of total lipids in the muscle tissue of mature whitefish from Umbozero Lake was lower than that of the whitefish from Lovozero Lake. With ageing, the content of phospholipids in the muscle tissue of the whitefish from Umbozero unlike the whitefish from Lovozero increases, but the content of triacylglycerols decreases, due to the lack of nutrition and active swimming of the whitefish in cold water of Umbozero Lake. The portion of triacylglycerols in the liver of the whitefish from Lovozero is higher than in the whitefish from Umbozero, which is probably related to the diet of the whitefish from Lovozero. In the whitefish eggs from the two reservoirs structural lipids are dominant and high content of cholesterol was identified. Molar ratio of CHS/PHL and PHCH/PHEA is lower in the whitefish from Umbozero compared to the whitefish from Lovozero, which should lead to an increase in the functional activity of membrane structures, lipid matrix fluidity and metabolism in the fish from Umbozero.

Morphological and Genetic Variability of the Mass Whitefish Forms in Lake Onega

In Lake Onega, the whitefish Coregonus lavaretus has been shown to occur as a variety of forms. Medium- and sparsely-ranked whitefish are most abundant. Analysis of available data indicates that whitefish populations from Karelia’s large lakes display the maximum values of various genetic variability indices. This fact seems to be due to the history of the colonization of the lake by the discrete evolutionary whitefish lineages from various Late Quaternary habitats followed by their hybridization. A great variety of Onega whitefish haplotypes is probably related to the genetic heterogeneity of the whitefish who until recently had occurred as five ecological forms ranking as subspecies. The median network obtained suggests that many of the populations studied have become less abundant. The well-defined “star-like” network structure is characteristic of populations that passed through a narrow “bottleneck” in the near past and then expanded rapidly, as indicated by the abundance of rare haplotype varieties. It seems that the retreat of the Scandinavian glacier was not a momentary event but took a long time during which the populations formed were subjected to demographic transformations.

The relationship between biotic factors and the content of chosen heavy metals (Zn, Fe, Cu and Mn) in six wild freshwater fish species collected from two lakes (Łańskie and Pluszne) located in northeastern Poland

The effect of biotic factors as species, condition factor, body weight and total length of fish on concentrations of iron (Fe), zinc (Zn), copper (Cu) and manganese (Mn) in organs of Rutilus rutilus (L.), Abramis brama (L.), Coregonus lavaretus (L.), Esox lucius (L.), Perca fluviatilis (L.) and Tinca tinca (L.) from reservoirs of Warmia and Mazury region (northeastern Poland) were determined. Differences in the content of metals were observed between species (P ≤ 0.05). Some metals demonstrated specific affinity for particular tissues. The lower content of metals found in muscles and ranged as follows: Zn 3.427-9.950, Fe 1.297-2.550, Cu 0.133-0.279 and Mn 0.050-0.162 (expressed mg/kg wet weight). The highest content of Fe (33.49-123.6) and Cu (3.994-27.14) (except for copper in perch) in liver (P ≤ 0.05) is related to detoxification, whereas high concentration of Mn (1.366-5.113) and Zn (15.91-135.0) (except for Zn in tench) in gills may be associated with excretion processes or uptake (P ≤ 0.05). The two organs (gills and liver) may be used as bioindicators of metal contamination aquatic environments. Studies on the size and condition factor dependency of heavy metal concentrations have showed that, although the relationship is performed, in most cases was not statistically significant for organ. Metal Pollution Index (MPI) in organs of fish examined was 1.503 < MPI < 3.575. Daily consumed a 34 g portion of fish examined (per capita) is 0.317-0.624% of Fe, 1.174-3.408% of Zn, 0.455-0.955% of Cu and 0.085-0.278% of Mn of the RDA reference dose.

A Comparison of Pneumatic and Hand Stripping of Whitefish (Coregonus lavaretus) Eggs for Artificial Reproduction.

Simple SummaryThis paper describes a technique of pneumatic stripping of whitefish (Coregonus lavaretus) eggs with the use of oxygen, nitrogen, and air. This study demonstrates that pneumatic stripping allows the collection of high-quality whitefish eggs. Moreover, we found that gas flow rates should not exceed 0.5 L∙min−1 to minimize post-spawning mortality in whitefish. The eggs obtained by pneumatic stripping using oxygen, nitrogen, or air had high hatching rates. We assumed that air stripping is a promising approach for improvement of the whitefish stripping procedure.We describe the technique of pneumatic stripping of whitefish (Coregonus lavaretus) eggs with the use of oxygen, nitrogen, and air. Eggs obtained via the traditional method (by pressing the abdominal surfaces) served as a control group. It was established that the gas flow rate during pneumatic stripping should not exceed 0.5 L∙min−1, since higher air flow resulted in increased post-spawning mortality. The pneumatic stripping method of egg collection was no faster than hand stripping; however, the time required per female was more consistent. It was found that the pH of the ovarian fluid obtained during hand and pneumatic stripping was not related to the success rate of fertilization. Pneumatic stripping resulted in a higher quality of collected eggs and a higher and more consistent hatching rate as compared with the hand-stripped samples, regardless of the gas used. The results presented here lead us to recommend the pneumatic method for obtaining eggs from whitefish, since it is a simple, reproducible method and improves the reproductive performance and developmental success of the fish eggs.

Complete mitochondrial genomes of Baikal endemic coregonids: omul and lacustrine whitefish (Salmonidae: Coregonus sp.)

Coregonid fishes are among the most successful groups in the subarctic, boreal, and subalpine fresh waters of the northern hemisphere. Limnetic–benthic sympatric species-pairs from two different evolutionary lineages, the North American lake whitefish (Coregonus clupeaformis species complex), and the European whitefish (Coregonus lavaretus species complex), are becoming the subject of close attention to explore the role of natural selection during the ecological speciation. Baikal endemic coregonids, limnetic omul (Coregonus migratorius), and benthic lacustrine whitefish (Coregonus baicalensis) are the only representatives of another unique lineage that has not left the lake since the divergence from the two above. Due to Pleistocene oscillations sympatric limnetic–benthic divergence has been replicated here many times within the same water body over a long geological period in contrast to both Europe and America where sympatric species-pairs are the results of post-glacial secondary-contacts between glacial isolates during the Late Pleistocene on the territory of each continent. Mitochondrial genomes encode genes that are essential for respiration and metabolism. Data on complete mitogenomes of Baikal endemic coregonids provided here will complement ongoing investigations on energy metabolism as the main biological function involved in the divergence between limnetic and benthic whitefish.

Fatty acid composition of the tissues of Coregonus lavaretus L. of the Kola Peninsula

The study reveals the results of the analysis of fatty acid composition of muscle, liver and gonad tissues of the whitefish Coregonus lavaretus L. of different ages from lakes Lovozero and Umbozero of the Kola Peninsula. The analysis of fatty acid composition in organs and tissues allows to evaluate the physiological characteristics of the organism. It was found that the content of monoenoic fatty acids in the muscles of the whitefish from lake Lovozero is higher than that of the whitefish from Umbozero. It is probably due to the features of the food base of the objects studied. In the muscles of immature whitefish of lake Umbozero the content of polyenic fatty acids is higher compared to the fish from Lovozero. The content of PUFA significantly increases in the mature whitefish from Umbozero lake perhaps due to the temperature regime in water bodies and different rates of motor activity of fish. Lower levels of PUFA in the liver of the whitefish from Lovozero lake may indicate reduced metabolism in hepatocytes. In the gonads of female whitefish from the studied water bodies, the content of saturated fatty acids is low compared to the polyene fatty acids which is characteristic for the viscosity reduction in the membranes of oocytes.

The effect of diet on the structure of gut bacterial community of sympatric pair of whitefishes (Coregonus lavaretus): one story more.

In the Coregonus lavaretus complex may be found lacustrine sympatric pairs, which serves as an intriguing model for studying different aspects of fish evolutionary biology. One such sympatric whitefish pair inhabits Teletskoye Lake (West Siberia, Russia) and includes a “large” form (Coregonus lavaretus pidschian (Gmelin, 1789)) and a “small” form (C. l. pravdinellus (Dulkeit, 1949)). C. l. pravdinellus has a narrow trophic specialization and feeds on zooplankton, whereas the diet of C. l. pidschian is based on benthic prey. In the present study we aimed to address the question of how the gut microbial community reflects the divergence in diet of a sympatric pair of whitefish. Studied samples included the mucosa and content were collected for cardiac and pyloric stomach, anterior, middle, and posterior intestine, but only mucosa was collected for the pyloric caeca. In addition, water, sediment, macrophyte (environmental microbiota) and invertebrate (microbiota of prey) samples were collected in the same location. The V3–V4 region of the 16S rRNA genes was chosen for microbiome analysis and the software PICRUSt used to estimate the difference functional roles of the microbiota. The number of OTUs and Chao1 index in mucosa and content of cardiac and pyloric stomach were significantly different between whitefish. Significant differences were observed between whitefish for content from different parts of the intestine in terms of OTU number and Chao1 indices, whereas for mucosa from the same parts of intestine these differences were absent. No significant differences were found for diversity estimates of mucosa and content of different parts of the gut (there were a few exceptions) between whitefish. The form of whitefish and the segment of the digestive system were factors with a significant determinative effect on the structure of the microbiota from gut mucosa and content. The most dominant phyla in mucosa and content of cardiac and pyloric stomach was Proteobacteria (57.0–84.0%) for both whitefish. Throughout the intestine of C. l. pidschian the dominant phyla in mucosa were Proteobacteria (38.8%) and Firmicutes (15.6%), whereas for C. l. pravdinellus–Tenericutes (49.6%) and Proteobacteria (28.1%). For both forms, the phylum Spirochaetes was found in a significant amount (20.0–25.0%) in the mucosa of the posterior intestine. While for the content obtained from anterior, middle and posterior intestines, the dominant bacterial phyla were the same as those described for mucosa from the same parts of the intestine for both whitefish. The bacterial community of the prey and environment was significantly different from bacterial communities found for all parts of the gut mucosa for both whitefish, with the exception of the mucosa of the cardiac stomach. According to PICRUSt the highest level of differences between whitefish at the L3 level were found for the intestinal mucosa (75.3%), whereas the lowest one was registered for stomach content (38.8%).

Investigating fish migration, mortality, and physiology to improve conservation planning of anadromous salmonids: a case study on the endangered North Sea houting (Coregonus oxyrinchus)

Understanding migratory behavior, mortality, and physiology is essential for conservation of many species, particularly anadromous fish. In this study, freshwater and marine migrations of the endangered salmonid North Sea houting (Coregonus oxyrinchus (Linnaeus, 1758)) were investigated using telemetry. Furthermore, physiological samples were collected from North Sea houting and from resident and anadromous populations of the closely related European whitefish (Coregonus lavaretus (Linnaeus, 1758)) to compare hypo-osmotic tolerances. On average, North Sea houting spent 193 days at sea where the mortality was 36%. Most fish returned from sea in the autumn, and river entry correlated inversely with river temperature and positively with discharge. Fish spent an average of 49 days in the estuarine area. Artificial lakes negatively affected migration speeds. Migration speeds did not differ consistently between individuals (i.e., not a repeatable trait) but correlated positively with water temperature. Fish arrived at spawning areas in November. In the post-spawning state, Na+/K+-ATPase activities were elevated in North Sea houting and anadromous whitefish compared with resident whitefish, while osmolality was elevated only in North Sea houting. Our study provides important information for conservation planning related to the Habitat Directive of the European Union that lists the North Sea houting as critically endangered.

Polygenic selection drives the evolution of convergent transcriptomic landscapes across continents within a Nearctic sister species complex.

In contrast to the plethora of studies focusing on the genomic basis of adaptive phenotypic divergence, the role of gene expression during speciation has been much less investigated and consequently less understood. Yet, the convergence of differential gene expression patterns between closely related species-pairs might reflect the role of natural selection during the process of ecological speciation. Here, we test for intercontinental convergence in differential transcriptional signatures between limnetic and benthic sympatric species-pairs of Lake Whitefish (Coregonus clupeaformis) and its sister lineage, the European Whitefish (Coregonus lavaretus), using six replicated sympatric species-pairs (two in North America, two in Norway and two in Switzerland). We characterized both sequence variation in transcribed regions and differential gene expression between sympatric limnetic and benthic species across regions and continents. Our first finding was that differentially expressed genes (DEG) between limnetic and benthic whitefish tend to be enriched in shared polymorphism among sister lineages. We then used both genotypes and covariation in expression in order to infer polygenic selection at the gene level. We identified parallel outliers and DEG involving genes primarily overexpressed in limnetic species relative to the benthic species. Our analysis finally revealed the existence of shared genomic bases underlying parallel differential expression across replicated species-pairs from both continents, such as a cis-eQTL affecting the pyruvate kinase expression level involved in glycolysis. Our results are consistent with a long-standing role of natural selection in maintaining trans-continental diversity at phenotypic traits involved in ecological speciation between limnetic and benthic whitefishes.

Shapes of otoliths in some Baltic fish and their proportions

Abstract Otoliths are bony structures inside the fish labyrinth. They are used to determine the age of fish and to identify species based on their remains. The objective of this study was to describe the shape of otoliths in adult European perch (Perca fluviatilis), Atlantic herring (Clupea harengus), European sprat (Sprattus sprattus), lesser sand eel (Ammodytes tobianus), great sand eel (Hyperoplus lanceolatus), round goby (Neogobius melanostomus), European whitefish (Coregonus lavaretus), Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), European eel (Anguilla anguilla), viviparous eelpout (Zoarces viviparus), turbot (Scophthalmus maximus), European flounder (Platichthys flesus), European plaice (Pleuronectes platessa) and European smelt (Osmerus eperlanus). Fish were caught in the Gulf of Gdańsk. The relationships between the size of otoliths and the length of fish were established for adult European perch, European flounder, Atlantic herring and round goby. Otoliths of taxonomically related species were similar. It was not possible to differentiate otoliths of Ammodytidae, Pleuronectidae, Scophthalamidae, Anguilidae by comparing the presented results with the literature data. Otoliths of Zoarcidae, Osmeridae, Clupeidae, Gadidae, Gobiidae, Percidae and Salmonidae were quite similar but distinguishable. In most of the investigated species, otoliths grow proportionally to the fish size. Their shape does not change during the fish life. The shape of otoliths in the round goby changes significantly. Otoliths of small fish are rounded and significantly lengthen during the growth of fish.

Seasonal changes in European whitefish muscle and invertebrate prey fatty acid composition in a subarctic lake

Abstract Ambient light and temperature show extreme seasonal variation in subarctic lakes due to the midnight sun period in summer and cold polar night period in winter. These changes have clear impacts on fish feeding and reproduction cycles, potentially affecting the fatty acid (FA) composition of muscle. Despite extensive research into fish FA over recent decades, we know little about intra‐annual changes of fish FA profile and content. We studied intra‐annual changes in the FA profile (mol%) and content (mg g‐1 dry weight) of sexually mature European whitefish (Coregonus lavaretus) muscle in a large and deep subarctic lake located in northern Fennoscandia. We collected fish, zooplankton, and benthic macroinvertebrate samples during 3 ice‐covered months, including December (during whitefish spawning), and 3 open‐water months. Fish size, age, sex, stomach content and fullness, and gonadosomatic index were also assessed as co‐variates. Whitefish changed diet from benthic macroinvertebrates in winter to zooplankton in summer. Generally, whitefish somatic growth was slow and most energy was used for gonad growth. Zooplankton had higher total content and different profile of FA compared to benthic macroinvertebrates. Increased zooplanktivory in summer was detected with higher α‐linolenic acid (ALA, 18:3n‐3) and stearidonic acid (SDA, 18:4n‐3) percentage and content as well as increased the ratio of polyunsaturated FAs (PUFAs) of n‐3 and n‐6 family (n‐3/n‐6 ratio) in fish muscle. Whitefish gonadal growth and development occur during the summer growing season and continue until the initiation of spawning in early winter. We found that the content of physiologically crucial PUFA, eicosapentaenoic acid (EPA, 20:5n‐3), docosahexaenoic acid (DHA, 22:6n‐3), and arachidonic acid (ARA, 20:4n‐6) decreased by c. 60% between late summer and the spawning period in early winter. After spawning, total FA content of whitefish muscle increased rapidly, reaching the maximum recorded level in mid‐summer. Intra‐annual changes in whitefish muscle FA profiles and contents were modified both by available diet and reproductive phase; however, reproductive physiology was clearly a stronger driver of the changes in muscle FA composition. Results suggest marked changes in intra‐annual FA composition of fish muscle, an important factor that should be considered in future studies and especially in long term monitoring programs. Future studies are needed to determine whether these inter‐annual FA patterns revealed in this study can be extended to different regions and to e.g. adipose or spring spawning species.

Resource polymorphism in European whitefish: Analysis of fatty acid profiles provides more detailed evidence than traditional methods alone.

Resource polymorphism—whereby ancestral generalist populations give rise to several specialised morphs along a resource gradient—is common where species colonise newly formed ecosystems. This phenomenon is particularly well documented in freshwater fish populations inhabiting postglacial lakes formed at the end of the last ice age. However, knowledge on how such differential exploitation of resources across contrasting habitats might be reflected in the biochemical compositions of diverging populations is still limited, though such patterns might be expected. Here, we aimed to assess how fatty acids (FA)—an important biochemical component of animal tissues—diverged across a polymorphic complex of European whitefish (Coregonus lavaretus) and their closely related monomorphic specialist congener vendace (Coregonus albula) inhabiting a series of six subarctic lakes in northern Fennoscandia. We also explored patterns of FA composition in whitefish’s predators and invertebrate prey to assess how divergence in trophic ecology between whitefish morphs would relate to biochemical profiles of their key food web associates. Lastly, we assessed how information on trophic divergence provided by differential FA composition compared to evidence of resource polymorphism retrieved from more classical stomach content and stable isotopic (δ13C, δ15N) information. Examination of stomach contents provided high-resolution information on recently consumed prey, whereas stable isotopes indicated broad-scale patterns of benthic-pelagic resource use differentiation at different trophic levels. Linear discriminant analysis based on FA composition was substantially more successful in identifying whitefish morphs and their congener vendace as distinct groupings when compared to the other two methods. Three major FA (myristic acid, stearic acid, and eicosadienoic acid) proved particularly informative, both in delineating coregonid groups, and identifying patterns of pelagic-benthic feeding throughout the wider food web. Myristic acid (14:0) content and δ13C ratios in muscle tissue were positively correlated across fish taxa, and together provided the clearest segregation of fishes exploiting contrasting pelagic and benthic niches. In general, our findings highlight the potential of FA analysis for identifying resource polymorphism in animal populations where this phenomenon occurs, and suggest that this technique may provide greater resolution than more traditional methods typically used for this purpose.

Depuration of geosmin- and 2-methylisoborneol-induced off-flavors in recirculating aquaculture system (RAS) farmed European whitefish Coregonus lavaretus

European whitefish Coregonus lavaretus has increasingly become an important species for aquatic food production, especially in the Nordic countries. Whitefish is produced in traditional cage and pond operations, and in recirculating aquaculture system (RAS) in which, unfortunately, off-flavors and odors, mostly caused by geosmin (GSM) and 2-methylisoborneol (MIB), can accumulate in fish flesh from the circulating water. GSM and MIB have very low human sensory detection limits and, therefore, often disliked by consumers even at low concentrations. In this study, concentrations of GSM and MIB in RAS farmed European whitefish were studied by an analytical method based on headspace solid phase microextraction and gas chromatography–mass spectrometry. Concentrations were determined in different parts of fish: fillet, neck, belly, and tail during a depuration period and in depuration water. The highest initial concentrations were on average 32 ng g−1 (GSM) and 24 ng g−1 (MIB) in European whitefish fillet and 128 ng L−1 (GSM) and 94 ng L−1 (MIB) in water, respectively. After a depuration period of 16 days, concentrations decreased to below the detection limits, indicating the importance of the depuration period.

Interannual Changes in the Quantitative Parameters and Structure of Invertebrates in the Littoral and Pelagic Zones of Lake Sevan (Armenia) with Fluctuations in Meteorological Conditions and Fish Biomass. I. Summer Zooplankton

Annual changes in the quantitative characteristics and structure of zooplankton in the pelagic and littoral zones of Lake Sevan in October have been determined by a number of factors, among which the biomass of the main planktophage, whitefish (Coregonus lavaretus L., 1758), have the greatest effect. The richest communities form due to Cladocera upon a decreased biomass of whitefish, minimum increase in the water level, and high average monthly temperatures for the period of April–October. In the littoral zone, the zooplankton is affected by a number of unaccounted factors, and the influence of planktophagous fish, mainly inhabiting deepwater areas, is less pronounced. A significant increase in biomass of planktophagous fish in 2016–2017 leads to a reduction in the quantitative characteristics of zooplankton, resulting in decreased water clarity.

Differential selection pressures result in a rapid divergence of donor and refuge populations of a high conservation value freshwater fish Coregonus lavaretus (L.)

As a conservation measure to protect European whitefish in Scotland, a translocated population was established in Loch Sloy from Loch Lomond stock between 1988 and 1990. Previous study has assumed that current morphological differences between adults from the donor and refuge lakes have arisen through phenotypic plasticity. The present study compared the morphologies of whitefish at three life stages: alevins and fry raised in a common garden, and wild-caught adults. Alevins were clearly distinguishable by their lake of origin. Loch Sloy alevins were distinguishable also by family, although this was not the case for Loch Lomond. Differential allometric trajectories facilitated the persistence of morphological differences associated with lake of origin through the fry stage into adulthood. Overall, the whitefish from Loch Lomond displayed morphologies associated with pelagic feeders, while the more robust heads and ventrally positioned snouts of the Loch Sloy whitefish conformed to expectations for more benthic feeding habits. That differences between populations were present not only in wild adults, but also in alevins and fry from a common garden setup, strongly suggests that the divergence between populations is due to inheritance mechanisms, rather than differential plastic responses, and questions the effectiveness of translocation as a conservation measure.

Effect of visible implant elastomers (VIE) and coded wire tags (CWT) on the growth, survival, and tag retention of juvenile European whitefish (Coregonus lavaretus)

Abstract This study examined the effect of visual implant elastomers (VIE) and coded wire tags (CWT) on the growth, survival, and tag retention of juvenile European whitefish, Coregonus lavaretus (L.), (mean body weight 18.7 ± 0.4 g, mean body length 9.7 ± 0.4 cm). The VIE tags were implanted subcutaneously in the anterior head, and the CWTs were implanted intramuscularly under the left gill operculum. The experiment consisted of two stages. The first stage (70 days) examined the effects of tagging on growth and survival, while the second stage (days 71-140) focused on assessing tag retention. Daily and specific growth rates, feed conversion factor, condition factor, coefficient of body weight variation, and survival did not differ significantly between the control fish and those tagged with the VIE tags and CWTs. Tag retention was high in the fish tagged with both VIE tags (100%) and CWTs (93%).

PATTERNS OF HEAVY METALS ACCUMULATION IN FISH IN LAKES OF THE FENNOSCANDIAN GREEN BELT (IN THE MURMANSK REGION)

The patterns of heavy metals (HM) accumulation in fish from lakes of the Murmansk Region within the Green Belt of Fennoscandia (GBF) exposed to long-term air-borne pol-lution associated with the operation of a non-ferrous metal processing enterprise have been studied. The detrimental effects of air-borne water pollution from the Kola GMK mine and smelter do not depend on the dominant wind directions. The reduction in emis-sions from the Nickel site of the Kola GMK in the past decades has not led to a significant decrease in the level of anthropogenic load. On the contrary, a long-term upward trend is observed in the content of Cu in the organs of whitefish, char, pike and perch in all the lakes studied. The accumulation of Cu and Ni in fish target organs tended to decrease along the distance gradient from the source of pollution. The revealed pattern is con-sistent with the intensity of pathologies development in whitefish organs. The common whitefish (Coregonuslavaretus(L., 1758)) is the most reliable test object that reflects the degree of pressure from long-term exposure to HM. The size of the catchment area is supposed to predetermine the intensity and rate of HM accumulation in fish organisms. The cumulative effect of persistent anthropogenic HM load on waterbodies in the study area, climate change processes, and man-induced eutrophication of waters can show in a decline in the biological diversity of the fish fauna in GBF, reduction in the number of valuable fish species. The identified patterns can be used in assessing the state both of existing and planned protected areas inside GBF.