No 6 (2024)

Lepidocephalichthys guntea, commonly known as loach, is a popular freshwater fish found in various water bodies. This study collected 210 specimens (148 females, 62 males) from fish markets in Noakhali, Bangladesh, to measure various length, weight, gonado-somatic index (GSI), fecundity and condition factor. To establish correlations, the relationships between length-length, length-weight, and GSI with both length and weight were analyzed. Body weight ranged from 1.99 to 8.89 g (mean 4.21 ± 1.49 g), and total length from 6.5 to 10.3 cm (mean 7.91 ± 0.77 cm). GSI peaked in June (8.63±1.16%), followed by May (6.58±0.89%), with the lowest values in September (0.01%). Mean fecundity was 7415.3±1168.54 in May and June (spawning season). The condition factor (K_F) was highest (1.04) in fish between 9.5–10.4 cm and lowest (0.87) in the 7.5–8.4 cm group. The coefficient of correlation (r²) values showed a strong positive relationship between body weight (BW) and both total length (TL) and standard length (SL). Moderate positive correlations were found between BW and head length (HL), and BW and body circumferences (BD) in pooled and female samples. However, in male, the correlations for BW vs. HL, BW vs. BD, as well as TL vs. HL and TL vs. BD, were asymmetrical. The relationships between GSI and both BW and gonad weight (GW) showed moderate positive correlations. Conversely, the coefficient of correlation between GSI and TL in the pooled sample, and GSI with both TL and BW in males, were indicating weak correlations. This study will provide valuable insights for conservation policymakers and hatchery owners, aiding in efforts to prevent the extinction of this species in the wild.

The purpose of the study is to identify the possibilities of mathematical modeling in solving problems of quantitative assessment and prediction of hydrothermodynamic characteristics of lakes of different origins in the permafrost zone based on available information about their morphometry. The object of the study is 420 of morphometrically studied lakes in Yakutia of different genetic origin. The choice of an adequate hydrothermodynamic model of processes in the “atmosphere – lake – bottom sediments” system, as well as sources of information on the atmospheric impact on lakes (reanalysis and climate prediction) for the studied region was substantiated. Simulation calculations were carried out to assess the retrospective interannual and intraannual dynamics of abiotic processes in water and bottom sediments of lakes located in the permafrost zone of different climatic regions of Yakutia. To assess the interannual dynamics of the studied processes in water and bottom sediments of thermokarst lakes located in permafrost zones and being the most widespread in the region, forecast calculations were carried out. In this case, two RCP scenarios for the evolution of anthropogenic greenhouse gas emissions into the atmosphere in the future were used – “best” and “worst” in terms of environmental impact. The prospects for further use of modeling methods in the creation of a system of remote monitoring of unstudied and poorly studied lakes in the Arctic regions of the Russian Federation was assessed.

Due to the lack of a unified sampling methodology for studying microplastics, there are difficulties in comparing the results obtained when sampling using different methods. A comparison was made of a pump filtration system and a Manta trawl to assess their effectiveness and applicability in collecting water samples for studying microplastics content using the example of Lake Ladoga, the Svir River and small lakes in the Leningrad region (Sukhodolskoye, Michurinskoye, Krasnoye). The results supported that despite higher average microplastics concentrations when sampling with the pump system (8.5±11.5 particles/m³) compared to the Manta trawl (0.7±0.6 particles/m³), the data were comparable. The methods have opposite advantages and disadvantages and are complementary. The Manta trawl is more suitable for collecting large volumes of water from the surface layer relatively quickly and in conditions with high contents of suspended matter present. Meanwhile, the pump filtration system is suitable for collecting samples at different water layers and in the surface layer of water when there is a small content of suspended matter and provides more accurate estimating of the sample volume. It is necessary to ensure the sampling of a large volume of water, which in the case of a pump filtration system is only possible during the period when the plankton content and water turbidity are minimal.

Araphid diatoms of the genus Ulnaria are the dominant species in many freshwater ecosystems of Eurasia. Diatom populations are genetically heterogeneous and represent a combination of different genotypes. Genetic diversity is a necessary factor for adaptation to different environmental conditions and successful dispersal of species. We were analyzed the genetic diversity of the species Ulnaria danica and Ulnaria ulna using the example of monoclonal strains isolated from geographically distant water bodies of the continental part of Eurasia: Lake Ritsa, Lake Goluboe and Lake Baikal. Phylogenetic analysis of cox1 gene fragments of the studied strains demonstrated for the first time the heterogeneity of populations and the absence of geographic isolation for individual genotypes of the studied species. By analyzing the 18S rRNA marker genes, rbcL and cox1, the possibility of horizontal gene transfer between closely related species Fragilaria radians, Ulnaria acus, U. danica and U. ulna was established.

In Mustalakhti Bay of Lake Ladoga, which is used for placing trout farms, a study was conducted on the structure of bottom landscapes and the transformation of the lakebed surface under the influence of aquaculture activities. Field data for mapping bottom landscapes were collected using hydroacoustic surveys with the SOLIX 10 SI MEGA CHIRP side-scan sonar and underwater photography with the Limnoscout ROV. Standard sedimentological and biological studies of the lakebed were also carried out. The identification of distinct facies elements was based on morphometric features (depth zones, bottom slopes in different parts of the bay, and terrain elements), characteristics of bottom sediments (sediment type, fluid mud composition), surface appearance, and benthic biological communities (dominant benthic groups, presence/absence of macrophytes). The study resulted in bathymetric and landscape maps of the investigated bay, highlighting the characteristic features of individual landscape facies. A total of 8 facies were identified. The study demonstrated a significant negative impact of trout farms on the bay’s bottom. This is confirmed by: 1. substantial changes in the lakebed appearance detected through video footage; 2. visual changes in the surface observed in acoustic images (sonograms) from the side-scan sonar; and 3. increased sediment thickness and higher accumulation of organic matter, evidenced by sonar data and previously conducted chemical analyses of sediments in the farm areas. The data indicates that the features of the bay’s basin, specifically its steep slopes and the extensive shallow area with relatively large depths (20-35 m), create conditions for the accumulation of anthropogenically transformed sediments within the farm area and extending outwards by several tens of metres (a 100 m diameter zone around each farm). Conclusion: The use of a landscape approach with modern research tools, including acoustic and underwater photography, has provided a spatial assessment of the impact of trout farming on the condition of the studied section of the freshwater body.

This study examines the spatial distribution of horizontal currents within under-ice anticyclonic eddies that lead to the formation of ring structures on the spring ice of Lake Baikal. Horizontal geostrophic current fields were calculated using the dynamic method, with a focus on comparing various approaches to determining water density, including a package specifically adapted for Baikal conditions, TEOS-10. Measured water temperature and conductivity data from the 2009 ring structure area served as the primary dataset, while reference data comprised velocity and direction profiles from a similar 2020 eddy, measured for the first time. Comparisons revealed that outdated methods, such as the Krotova method or the Chen-Millero equation, result in significant discrepancies from actual measurements, whereas the adapted TEOS-10 package shows the best agreement. Overall, the dynamic approach proved effective and can be successfully applied to study current fields in Lake Baikal. The research also identified and described several characteristic features of current structures within the examined under-ice circulations for the first time.