Limnology and Freshwater Biology

Diversity of fishery resources and catch efficiency of fishing gears in the Feni River (Bangladesh)

2024-07-26T16:00:32+08:00

A thorough examination of fish diversity indices, gear efficiency, catch composition, and decline causes of fish diversity was carried out in the Feni River (Bangladesh). Monthly data collection took place from July to December 2023 at three stations of the river. A total of 8 fish species under 7 orders and 8 families were recorded. The order Perciformes was the most prevalent, representing 30% of the total. Approximately half of the identified species are classified as least concern, while the remaining 4 species are classified as Not Threatened (12.5%), Vulnerable (12.5%), Endangered (12.5%), and Critically Endangered (12.5%). The mean values of the Margalef’s richness (d), Pielou’s evenness (J), Simpson’s index (1-D), Shannon-Weaver diversity (H), and 0.973±0.002 were calculated as follows: 1.720±0.139, 0.699±0.112, and 0.248±0.034, respectively. Based on the Bray-Curtis similarity matrix, two groups were observed at a similarity of 58% within six months across the three sites. The chandi net and ghera net recorded the highest CPUE (kg gear^-1day^-1) at 5.93±0.966 and 0.53±0.041, respectively. The highest fish catch was recorded in July (2249 ± 668.71 kg), while the lowest was in October (1564 ± 465.05 kg). There was no significant difference (p>0.05) in the monthly fish catch. Fish biodiversity in the Feni River is declining day by day as a result of pollution, overfishing, the use of harmful gear, and a lack of optimal water and pollution. To improve and conserve fish species in the Feni River, it is strongly advised that appropriate fishery management techniques should be applied, that overfishing be closely monitored, and that fishermen be made more aware of their rights.

The first detection of coccidia (Conoidasida: Eimeriidae) DNA in Godlewski’s sculpin Abyssocottus (Limnocottus) godlewskii (Dybowski, 1874)

2024-06-19T10:20:40+08:00

For the first time, fragments of the cox1 gene of a representative of the family Eimeriidae were obtained by high-throughput sequencing in the digestive tract of Godlewski’s sculpin Abyssocottus (Limnocottus) godlewskii (Dybowski, 1874). The nucleotide sequences of the coccidia, which accounted for less than 0.01% of the total data set, belonged to a single genotype and were significantly different from all previously known. Phylogenetic reconstruction based on the translated amino acid sequences reliably revealed the basal location of branches belonging to representatives of the family Eimeriidae among fishes. The question of the genus of the detected organism remains unresolved due to the limited nucleotide data for representatives of the genera Eimeria, Calyptospora, and Goussia from fish.

Intragroup variability of growth in perch, Perca fluviatilis L., 1758 (Percidae) in waterbodies in the watershed of the Middle Ishim

2024-08-05T16:01:23+08:00

As a result of the research carried out in 2016-2021 on the lakes of the Shchuchinsk-Borovoe resort area and on the Ishim River, material was obtained on the intragroup variability in the growth of perch. The absence of sexual variability was noted, which is explained by the relative stability and positive influence of environmental factors. The revealed generational variability of growth showed both a noticeable decrease in its rates in Lake Shchuchie and a significant increase in Lakes Borovoe, Katarkol and Tekekol. These processes of linear growth dynamics are caused by the interaction of hydrological and trophic factors. In all samples, a division of the general population into two clusters (incremental morphs) with different growth characteristics was observed. They correspond to the traditionally identified “coastal” and “pelagic” morphs of perch from the largest bodies of water (e.g. the former Aral Sea), but their differences are revealed statistically and not visually. Perch populations differ in the proportion of these clusters, which largely determines the average length per generation in general samples. Based on the characteristics of the back calculation of linear growth for clusters, all samples can be divided into two types, which in miniature resemble species-specific evolutionary r- and K-strategies (but not identical to it).

Long-term dynamics of spectral water transparency in the surface layer of Lake Teletskoye in summer

2024-06-03T12:57:51+08:00

The article presents the long-term experimental data on spectral water transparency in the surface layer of Lake Teletskoye (21 sampling stations) obtained in summer of 2017‒2022. During the study period, values of the light attenuation index calculated at the natural logarithmic base at four wavelengths (430, 450, 550 and 670 nm) ranged within 0.2‒4.0 m^‒1. The index of light absorption by yellow substance varied from 0.1 to 3.2 m^‒1. Relative transparency measured with the use of a white Secchi disk made up 0.8‒11.7 m at its average of 6.3 m. Over a 6-year study period, the content of chlorophyll-a in the surface layer was 0.1‒4.1 mg/m³ that corresponded to the oligotrophic type of lakes. The concentration of yellow substance in the lake, optically determined through measuring light absorption by yellow substance at a wavelength of λ=450 nm, ranged from 0.9 to 15.0 g/m³. Calculations of the spectral contribution of the main optically active components of lake water to light attenuation in the surface layer of Lake Teletskoye in various sampling sites indicated that yellow substance and suspension had the greatest optical effect on the total attenuation. It is shown that the optic structure of the study reservoir (dynamics of major primary hydro-optical properties) depends on spatial-temporal variability of concentrations of different optically active components influenced by the in-water processes closely related with those occurred in the lake catchment.

Role of the invasive amphipod Gmelinoides fasciatus (Crustacea: Amphipoda) of littoral macrozoobenthos of the Zaonezhye area of Lake Onego

2024-06-27T02:37:12+08:00

The results of research of bottom biocenoses of the Zaonezhye area (Zaonezhsky Peninsula in the northeastern part) of Lake Onego in 2023 are presented. Insignificant differences in the spatial distribution of quantitative characteristics of macrozoobenthos were revealed. Quantitative indicators such as abundance and biomass of macrozoobenthos ranged from 1.56-4,01 thousand ind/m² and 0.35-3.19 g/m², respectively. It is shown that the invasive species Gmelinoides fasciatus (Stebbing 1899) (Crustacea: Amphipoda) has naturalized in the littoral. Amphipoda <i>G. fasciatus</i> plays a dominant role in the abundance of the bottom community in Keften-Guba and in the vicinity of Padmozero village. It was noted that the native species Gammarus lacustris Sars 1863 was not recorded anywhere. Quite rapid dispersal of the Baikal species G. fasciatus on the littoral of the reservoir suggests that in the coming years these amphipods may colonize the Lizhemskaya Guba (Bay) of the lake, where there are habitats not subject to its invasion, according to the literature.

Spectral properties of the horizontal irradiance vertical distribution in Lake Teletskoye in August 2023: processing methodology and regional features

2024-06-17T18:07:04+08:00

The sunlight spectral composition, penetrating to different depths in the upper water layer, on the one hand, depends on the optically active components contained in the water, on the other hand, it is important for the functioning of phytoplankton, and therefore plays an important role in the functioning of the aquatic ecosystem in general. When studying the spectral composition of light at different depths, a new instrument was used, made on a modern elemental basis. Analysis of the obtained spectra of the vertical attenuation coefficient made it possible to identify regional features of the penetration of natural sunlight characteristic of Lake Teletskoye.

The Complete Mitochondrial Genome of Chlorella sp. isolated from Lake Baikal

2024-10-31T17:13:40+08:00

We report here the mitochondrial genome sequence of Lake Baikal green alga extracted from complete genome of Chlorella sp. strain BAC9706. Sequenced mitochondrial genome of strain BAC9706 has 90.8-kbp containing including 34 protein-coding genes. Phylogenetic analysis using the mitochondrial genomes of algae of Chlorellales order indicated that the strain BAC9706 belongs C. vulgaris clade and is Baikal ecotype of C. vulgaris.

Benthic Macroinvertebrates as Indicators of Water Quality and Ecological Health in a Tropical Lake, Southern Nigeria

2024-07-22T22:21:32+08:00

This study assesses the community structure and diversity of benthic macroinvertebrates in Ozomu Lake, Southern Nigeria, to evaluate the water quality and ecological health. Sampling was conducted twice monthly from March to August 2020, at three stations using bottom sediment grabs and bank-root zone sampling. A total of 23 taxa and 427 individuals were recorded. Diptera (25%) and Odonata (22%) were the most abundant, followed by Coleoptera (18%) and Ephemeroptera (12%). In terms of diversity, the stations were ranked as follows: Station 2, Station 1, and Station 3. The Shannon-Wiener index indicated that Station 2 had the highest species diversity (2.896), followed by Station 1 (2.828) and Station 3 (2.472). Pielou’s Evenness index revealed that Station 2 had the most even distribution of species (0.7871), while Station 1 had the lowest (0.6235). Pollution-sensitive taxa at station 1 comprised 40.8% of the benthic fauna (58 individuals), indicating relatively good water quality. Moderately tolerant taxa represented 28.9% (41 individuals), while pollution-tolerant taxa accounted for 30.3%. Station 2 recorded similar results for pollution-sensitive taxa at 40.3% (52 individuals). However, moderately tolerant taxa dominated this station, making up 41.1% (53 individuals), with pollution-tolerant taxa at only 18.6%, suggesting lower environmental stress. Pollution-tolerant taxa predominated at 40.4% at station 3 (65 individuals), indicating greater environmental disturbance. Moderately tolerant taxa constituted 33.5%, while pollution-sensitive taxa were reduced to 26.1%, reflecting the most stressed environment among the stations. Overall, the lake’s ecological health appears stable, but localized stressors may require targeted management.

Results of synchronous measurements of the content of nitrogen and sulfur oxides in the atmosphere of Southern Baikal in July 2023

2024-10-03T12:11:32+08:00

The paper presents the results of synchronous measurements of the content of small gas impurities at the three atmospheric monitoring stations located on the shore of Southern Baikal, July 2023. The measurements were carried out using automatic gas analyzers, which enabled to obtain data on the content of sulfur and nitrogen oxides in the atmospheric air with high temporal resolution. The studies showed that in spite of a small distance between the observation stations, the fluctuations of concentrations of small gas impurities on different shores of Southern Baikal occur independently of each other. We suggested that an increase of nitrogen and sulfur oxide concentrations on the western shore in summer is probably correlated more with the impact of regional thermal power plants (TPP) and on the eastern shore with the orographic features of the southern basin of the lake and local sources. The influence of meteorological conditions on the content of gas components in the atmosphere of Southern Baikal was estimated using multivariate statistical methods, namely, NWR and PSCF.

Hydroacoustic studies of the structure of the Baikal omul feeding stock in the Selenga shallows of Lake Baikal

2024-10-31T17:39:07+08:00

A comparative analysis of hydroacoustic data from 2011 to 2024 allowed us to determine the distribution characteristics of Baikal omul in the spring in the water area of the Selenga shallows under a significant decrease in stocks. Test trawling provided analysis of the length-at-age data on Baikal omul, revealed an increase in the stock abundance owing to the 2019-2023 generations, and confirmed the possibility of the correct use of the length-weight relationship (LWR), W=10.9(SL_dm)^3.02, based on long-term data. The obtained data predict a growth of biomass, as a more inert indicator, in four-six years. To formulate a more accurate forecast, it is necessary to adjust the natural mortality rates.

First reports on the genetic diversity and phylogenetic relationships of bathynellids (Malacostraca: Bathynellidae) from Lake Baikal

2024-10-23T14:08:09+08:00

Within the fauna of Lake Baikal, two species of bathynellids are known: Bathynella baicalensis Bazikalova, 1954 and Baicalobathynella magna (Bazikalova, 1954), both originally described from the southern basin of the lake. The authors’ findings indicate that bathynellids are prevalent across all three basins of the lake, occuring on habitats such as methane seeps, mud volcanoes and hydrothermal vents. A comprehensive analysis of the COI (mtDNA) and 18S rRNA (nuclear DNA) gene fragments from bathynellids collected at tectonic fault sites in the northern basin of the lake revealed the absence of any representatives of the genus Bathynella Vejdovsky, 1882 among them. Instead, individuals identified as Baicalobathynella cf. magna comprise two genetic lineages at the species level, which diverged from a common ancestor approximately 7 Ma. The genus Altainella Camacho, 2020, whose representatives inhabit the interstitial hyporheic zone of the Onon river in Mongolia and Aktru mountain river of Altai, is designated as the closest relative of the Baikal bathynellids studied.

Current assessment of nitrogen and phosphorus content in the river water and snow cover of the Southern Baikal basin

2024-10-01T09:39:02+08:00

The paper presents the results of long-term studies of chemical composition of water of tributaries and snow cover of the south-eastern and south-western coasts of Lake Baikal. The content of different forms of nitrogen and phosphorus in river water and snow cover was analyzed. A quantitative assessment of total nitrogen and phosphorus input from the atmosphere to the Southern Baikal catchment area for 2019-2023 is given. The south-western coast of the lake experiences a great load in terms of the content of various forms of nitrogen and phosphorus in the snow cover and water of tributaries. Nitrogen in the snow cover and tributaries of Southern Baikal is represented mainly by its mineral form. The rivers of the south-eastern coast, which are exclusively atmosphere-fed, are generally not subjected to anthropogenic impact. In contrast, the minor watercourses of the south-western coast of the lake (Listvyanka settlement) are significantly influenced by economic activities. The organic form of phosphorus predominates in the snow cover of Southern Baikal and in river waters of the south-eastern coast. In the water of tributaries of the south-west coast phosphorus is found in its mineral form. A comparison of current data with the results of previous years was carried out.