Study of microbiocenosis of fish gills and intestines in their cultivation using preparations based on bacteriophages

Nowadays bacteriophages are widely used in veterinary medicine, bio-technology, agriculture and in particular in aquaculture. Narrow specificity affecting the bacterial microflora and selective influence on the pathogenic and opportunistic microorganisms allow using the bacteriophages for diagnosing, preventing and treating the diseases of farm animals and fish. The emergence of antibiotic-resistant strains of microorganisms involves the search for new drugs to combat them. In this regard, phage therapy is an alternative to antimicrobial treatment of bacterial diseases of animals and fish. Despite the lack of data on the bacteriophage-based drugs applications in aquaculture, this direction is found to be promising and relevant. There is given a comparative analysis of the microbiocenosis of the gills and intestines of two-year-olds of red tilapia farmed in the water with adding the poly-valence pyobacteriophage and fed by compound feed treated by the preparation. It has been found that the dominant position in the intestinal microbiocenosis of red tilapia belongs to Micrococcus bacteria, whose share made 45.7% of all isolates of the gastrointestinal tract. By the frequency of occurrence, the second place is taken by the Bacterium species (33.2%), the third place - Staphylococcus (16.1%) species. The remaining groups of intestinal microorganisms are presented by a significantly number of isolates. It has been stated that the gills microflora was represented by a smaller species composition compared to the digestive tract microbiota. Isolates of the Bacterium and Staphylococcus bacteria were dominating, while the Actinomycetales and Bacillus microorganisms were represented in smaller numbers (1-2 colonies). The addition of a bacteriophage to water and its processing of compound feed helps to reduce the contamination of gills and reduce pathogenic microflora in the intestines of fish.

Current state of bacterioplankton in Northern Caspian

Microbiological monitoring of the Northern Caspian proved that for the research period in 2013-2018 the average annual value of the total number of bacteria (TBN) was 1.35 million cells/ml. The TBN maximum value (1.46 million cells/ml) was recorded in 2013, the minimum (1.19 million cells/ml) - in 2014. Concentration of saprotrophic bacteria in the waters of the Northern Caspian during the research period varied from 50.94 thousand CFU/ml in 2013 to 1.66 thousand CFU/ml in 2014. The concentration of saprotrophic bacteria remained practically unchanged within 2014-2018. The values of the ratio of the total abundance of microorganisms and saprotrophic bacteria show the eutrophication of the waters of the North Caspian in 2013 and in 2016, in other periods the water quality corresponded to the readings of an oligotrophic reservoir. The maximum number of oil-oxidizing bacteria (OOB) (8.28 thousand CFU/ml) in the waters of the Northern Caspian was recorded in 2013, the minimum (0.21 thousand CFU/ml) - in 2014. Starting from 2015 there was recorded an increasing number of OOBs and its stabilization until the end of the research period. The ratio of NOB and saprotrophs in water varied from 16.47 to 52.47%. Analysis of microbiological and hydrological-hydrochemical indicators revealed positive correlations of TBN and annual runoff (r = + 0.77), TBN and the content of mineral forms of nitrogen (r = + 0.60), the number of saprotrophic bacteria and nitrogen (r = + 0.83), the amount of NOB and mineral nitrogen and silicon (r = + 0.81). In the long-term aspect, an improvement in the microbiological situation was recorded against the background of a growing total number of bacterioplankton under a simultaneous decrease in the number of saprotrophic and oil-oxidizing bacteria.

Assessing state of water protection zones of Volga River within Ilyinka village area (Astrakhan region)

Anthropogenic pollution of water basins may become a serious threat for ecosystems and human health. Pollutants are transferred through food chains or directly when untreated water is used, released to soil through subsoil waters or during floods. The increased anthropogenic load on rivers’ hydrosystems, especially in their del-tas, is becoming rampant these days. The goal of the research is to study the coastal areas and to assess the state of vegetation. To achieve this goal, standard methods of biotesting and bioindication were applied in the territories of two water-protection zones – those of the Volga River and the Nozhovskiy erik (shallow channel in the Volga delta – translator’s note) near the Ilyinka village. The water quality in the Volga River, within the examined range, is stably characterized as “dirty” (4th class). The exceeded level of maximum permissible concentrations for petroleum products, heavy metals (mercury, zinc, molybdenum), sulfides and phenols is observed. The research has not revealed the impact of the quality of water on phytotoxicity of the soil and indices of abundance of the vegetation that grows in this territory. Toxicity of soils is weak in the area of the Nozhovskiy erik, it is very weak in the area of the Volga River: the germination capacity of the test object (watercress) ranges between 67 and 88%, morpho-metric indices of plants do not differ much from those in control groups. Within the summer period the monitoring sites were characterized by the maximum frequency-abundance indices of typical representatives of the local flora, which are camel thorn (Alhagi pseudalhagi) and greater burdock (Arctium lappa). Vegetation in these areas is abundant, its state is assessed as satisfactory.

Temporal variability of catches, distribution and dynamics of length of Russian sturgeon in waters of the Caspian Sea in 2015 –2020

The paper presents long-term data on catches, distribution and length dynamics of Russian sturgeon in the waters of the Caspian Sea for the summer-autumn periods in 2015-2020. When considering the catches in the different parts of the sea there is found their annual variability, which is especially noticeable in the shallow zone in the North Caspian (0.31-2.0 specimens/trawl) and in the Middle Caspian (0-1.31 specimens/trawl). In the course of determining the reasons for the interannual dynamics of catches there were revealed several decadal rises. The dependence of decadal catches on the temperature of the bottom water layer was analyzed. The highest rise in catches was observed in the first decade of September when the temperature of water lowered up to 20.0-15.0 °C. The increase was observed due to migrating individuals to the shallow zone of the Northern Caspian Sea from shallow waters. Despite the variability of catches, the localization of Russian sturgeon schooling in the northern and middle part of the sea during the summer-autumn periods of 2015-2020 has certain similar features and trends. Sturgeon species fed mainly on shallow banks and deep dumps, where the largest catches of sturgeon were recorded from 5.0 to 12.0 specimens/trawl. The absence of sturgeon at depths of up to 3.0 m isobath in the last five years is due to the water heating up to 27.6-28.8 °C. The decrease in the length of the Russian sturgeon observed in recent years is due to an increase in the proportion of youngsters (19.2-70.0%) against the background of a decrease in the adult population. It should be noted that from 2017 to 2019 there were not found the adult species in the catches by fishing nets, which indicates their continued re-moval from the population.

Studying sanitary and hygienic conditions of bream and water in its habitat

The article highlights the data on microbiological monitoring of fish raw materials and water of the Volga-Caspian fishing channel in 2020-2021. The most indicative organisms for assessing the quality of the aquatic environment are benthos-eating fish. Bream Abramis brama (Linnaeus, 1758) is one of the valuable objects of fishing in the Astrakhan region. As a commercial object of river coastal fishing, bream has a higher bacterial contamination than fish caught in the sea. In this regard, studying the conditions for bacteriocenosis of fish raw materials, as well as the factors that determine the pathogenicity of its microflora and sanitary and epizootic monitoring by the microbiological tests remain the most relevant research of aquatic organisms. Quantitative and qualitative indicators of the bream microflora were estimated, according to the analysis of 180 species. The indicators of the water microflora were analyzed using the results of studies of 90 samples. The species identification of the isolated microflora was carried out according to the Bergey identification keys. In the samples of bream muscles there was determined the total number of facultative anaerobic microorganisms and aerobic mesophylls, presence of coliform microorganisms, as well as a causative agent of Staphylococcus aureus, pathogenic bacteria Salmonella and Listeria, and parahemolytic vibrios Vibrio. The study results were processed, according to the methods of biological statistics in the Microsoft Excel 2010 software. The results are presented as mean values and standard errors (M ± m). The general microbiological analysis of the fish muscle tissue confirmed the satisfactory sanitary state of bream Abramis brama (L., 1758) caught in the fishing area of the Volga-Caspian Canal during the study period. Pathogenic microflora in the form of E. coli bacteria, bacteria Salmonella, L. monocytogenes and St. aureus were not found

Aquatic bioresources of artificial water bodies in Republic of Mordovia (case of Turgenev Reservoir)

On the territory of the Republic of Mordovia there are found more than 220 multi-purpose ponds and water reservoirs built on the watercourses. The Turgenev Reservoir on the Alatyr River is a typical channel artificial reservoir. The results of comprehensive fisheries research for the period of 2009–2015 are presented. Analysis of the fod der base showed a significant underutilization of zoobenthos and phytoplankton. Using the average indicators of the fodder base over the above period, the production capacity of the reservoir fodder base was calculated, which amounted to 39.69 tons or 405 kg/ha. According to the results of research fishing with fry seine, the ichthyomass of small fish species and juveniles under the age of two years is estimated by years at the level of 8 tons or 73–91 kg/ha. According to the results of net catches, the ichthyomass of the commercial fish fauna is at the level of 6.3 t or 64 kg/ha; the total ichthyomass is 146 kg/ha. The possible catch of mainly small fish in the Turgenev Reservoir can make 5–7 tons, and in total in the Republic of Mordovia in the multi-purpose water reservoirs - about 260 tons. Due to the reconstruction of ichthyofauna at the expense of a free food base, reproduction, fish- and water protecting measures the catches of marketable fish in ponds and water bodies of Mordovia can reach 1000 tons. The artificial reservoirs of the republic have a significant regulated potential of the aquatic biological resources for the low-water regions of Central Russia both providing the population with freshwater fish and creating the conditions for active and useful recreation on the territory near the water reservoirs: developing facilities for sport and amateur fishing and tourism.

Comparative assessment of amateur fishing influence on water bioresources of Lake Tsatsa in Volgograd region

The paper presents the results of research conducted in 2020 on the impact of amateur fishing on the aquatic bioresources of Lake Tsatsa, which is part of the Sarpin Lakes located in the Volgograd region. On the basis of field studies (direct accounting), the number of amateur fishermen who visited the lake, as well as the qualitative and quantitative composition of their catches, was established. According to the data obtained, the total catch of fish by amateur fishermen, as well as the average catch per fisherman, was estimated. The size and weight composition of amateur fishing catches was determined based on the analysis of 2912 fish species. During the observation period 9 fish species were marked as part of amateur fishermen’s catches. The assessment of compliance of aquatic biological resources catch by amateur fishermen with the norms of the current Fishing Regulations was carried out. An assessment of the scale of amateur fishing impact on the aquatic bioresources of Lake Tsatsa is given, according to the analysis of the collected data. The catch of amateur fishermen in 2020 in Lake Tsatsa is amounted to 8.8232 tons, which can account for up to 15% (about 65-70 tons) of the total stock of commercial fish species in the lake. The forecast values of the production volume for industrial fisheries, for which the total allowable catch (TAC) is established and the species for which the recommended catch is determined, are 5.9 and 18.6 tons, respectively. Out of the forecast volumes amateur fishermen additionally catch fish species for which the total allowable catch (TAC) is established (carp, bream, pike) in the amount of 2.858 tons, and species for which the recommended catch value is determined as 5.643 tons.

Growth of tench (Tinca tinca L., 1758) (Cyprinidae) in reservoirs of K. Satpayev canal

The reservoirs of the K. Satpayev canal are the important fishery water bodies in the Central Kazakhstan. Some of these reservoirs are inhabited by tench, a fish species relatively widely represented in other water systems of the region. In the reservoirs of the canal this species is not the main commercial one but it has a fairly high commercial value due to its popularity with consumers. As part of the research, the growth indicators of Tinca tinca from 4 reservoirs were evaluated, and the data on its growth from 3 more reservoirs were also provided. These samples differ in efficiency and growth rates. It has been found that there is no sexual or generation variability. Growth rates in successive fish generations strongly correlate with each other, which may indirectly indicate the stability of living conditions. The R. Lee’s phenomenon was not marked. In this regard, the calculation of variables of the von Bertalanffy growth equation was carried out without additional data processing. The highest rates of linear growth were characteristic of Tinca tinca from the reservoir of HS No. 9. However, the effectiveness of its growth scheme was the lowest. Population with a longer age range from the reservoir HS No. 3 did not have high linear growth rates, but its growth efficiency was higher. In this case, it is obvious that any assessment of growth will be relative and depend on the goals set for it. In the reservoirs of the canal there are more or less similar conditions for tench populations living due to the specifics of its functioning. The main limiting factor for the growth rate, in our opinion, will be abundance of the species in the reservoir and related trophic factors with a certain influence of withdrawal (fishing, predators).

Force performance of trawl system – III: mathematical modeling (part I)

The force performance of trawl systems directly depends on the work performed by these forces.The mechanical work of a trawl system is a physical quantity that depends on the vectors of force (hydrodynamic, tension, compression, etc.) and displacement. Thermodynamic work is the amount of energy transmitted or received by the trawl system by changing its external parameters. There is also the work of the forces of the electrostatic field when the charge moves from one point of the field to another. Equations are obtained for ideal flexible steel ropes and rope-rope products, characterizing the direct proportionality of the ratio of the productivity of forces that are directed perpendicular to each other and depend on the Poisson's ratio and the constructive elongation of ideal flexible steel ropes and cordage products. The ratio of the capacities of the forces or the ratio of the moduli of elasticity in the transverse and longitudinal directions, which arise when steel ropes and rope-rope products are stretched, are inversely proportional to the square of the coefficient k connecting the elongation λ, Poisson's ratio μ and the relative elongation ε at a constant volume of the product and its mass. There has been described an example of stretching perfectly flexible steel ropes and cordage. Such constructive parameters as lay, the number of strands, wire and fiber thickness, type of weaving were not taken into account.

Characteristics of perch fish diet in small lake of Lake Onega catchment area

Fish feeding process is studied as one of the links in the transformation of the energy of a water reservoir, as one of the factors that determine the ecology of fish and make an imprint on the morphology, physiology and behavior of fish, or as one of the criteria, which help the most rationally use natural resources of the water bodies. The results of work carried out by the Northern Water Problems Institute (NWPI KarRC RAS) and Petrozavodsk State University (PetrSU) within the framework of state assignments, forecast problems and economic contractual topics on assessing the nutrition of perch species (perch, ruff) in some lakes of the Konchezero group (South Karelia), in particular Lake Munozero, which is part of the lower reaches of the river Shuya belonging to the catchment area of Lake Onega. The work was carried out by the experts from the IWPS KarRC RAS and PetrSU in 2018-2020. Its main hydrological and ichthyological indicators have been studied. The reconnaissance fish productivity of Lake Munozero based on the development of the forage base at the present stage is estimated as 9 kg/ha. The feeding spectra of ruff and perch in the lake overlap only with respect to eggs, the ruff using eggs more actively. Predation is peculiar only to perch, while even fish whose size is less than 14 cm (the average size of the transition to predation for Karelia) hunt at a time when there is a lot of other food in the reservoir. As the perch passes to summer feeding, its diet becomes more diverse. Some benthic organisms are replaced by others, an air fraction appears, the perch's diet includes fish in summer and spring; nutrition becomes more active: the average stomach fullness index increases from 7.3 to 145.6‰.