Clupeonella Cultriventris Research Articles

Effect of Global Warming on the Fish Population Parameters in the Upper Volga Reservoirs

As a result of global warming, the average annual water temperature has significantly increased in the Upper Volga reservoirs. Warming and the subsequent deterioration of the oxygen regime had a significant effect on most of the fish populations inhabiting temperate waters. This led to changes in the population structure of many fish species. Such phenomena as the disappearance or a sharp decline in the abundance of cold-water species (European smelt, vendace, burbot and pike) in the Rybinsk reservoir coincided with the period of warming. The disappearance of European smelt in the Rybinsk Reservoir and the favorable temperature regime contributed to the appearance and rapid increase in the abundance of the Caspian invader, the Black Sea sprat, which occupied the empty niche of the European smelt and became instead the dominant species in the pelagic zone of the Upper Volga reservoirs. Warming resulted in a decrease in the abundance and the growth rate of burbot and pike. Climate warming had an indirect effect on many species through oxygen deficiency or transformation of the forage base (ruff, zander, perch, roach), which also led to a decrease in abundance and the growth rate.

Influence of Sea Surface Temperature Changes on the Development of Sprat (Sprattus sprattus phalericus) (Pisces: Clupeidae) Living on the South-Western Shelf of Crimea

A study of changes in sea surface temperature (SST) on the South-Western shelf of the Crimea in 2000–2020 was conducted. The equations of trends in the change of SST are found. It is shown that according to the nature of changes in the average annual sea temperature, three periods can be divided: 2000–2007, 2008–2013 and 2014–2020. The influence of changes in the average annual SST on the development of pelagic fish of the cold-waters complex (on the example of the Black Sea sprat) is considered. Changes in the main parameters of populations and their relationship with the change in the average annual SST were found. It was found that the observed increase in sea temperature negatively affected the development of the sprat population, the average age of the population decreased by 1.3 times, in general, the population was rejuvenated, the average size and weight of individuals decreased.

Modeling the structure changes of cold-water copepods Calanus euxinus population under the influence of the black sea depths deoxygenation

The paper presents the results of modeling the possible changes in the structure of the population of Calanus euxinus Hulsemann, 1991 copepods in the Black Sea under the influence of deoxygenation that began in the late 1980s. Over the past 50 years, the depth of oxygen penetration in the deep sea has decreased by almost 50 m. The lower “life limit” of zooplankton in the Black Sea corresponds to the upper boundary of the suboxic layer, where intense copepod aggregation occurs at an oxygen concentration of 10 μM /L. In 1955–1976, this boundary was 130–140 m across the sea, but due to eutrophication and climate change since late 1980s, it has risen in deep water areas to 70–80 m. As a result, the dense copepod layers near the redoxcline and especially their reserve population stock, consisting of non-migrating individuals in diapause, may have been subjected to intensive eating by the Black Sea sprat, which lives to a depth of 100 m and can tolerate hypoxia. To explore this process, we created a new population dynamics model for C. euxinus, which makes it possible to assess changes in the abundance and structure of the population under conditions of a quasi-stationary state and during intensive predation of individuals in diapause. The model describes the dynamics of the Сalanus population based on a statistical description of the relationship between the growth of individuals, their fecundity, the duration of diapause, mortality, and environmental conditions: the concentration of food suspension and temperature in the layer of vertical migration. We put forward the hypothesis that the access of small pelagic fish to the concentration layers of copepods in diapause has a key effect on significant changes in the Black Sea ecosystem, associated with a decrease in the supply of forage plankton and fluctuations in the abundance of pelagic fish.

Complete Mitochondrial Genome of Clupeonella abrau (Maliatsky, 1930) (Clupeiformes), an Endemic Freshwater Fish from the Lake Abrau (Russia).

The Abrau sprat (tyulka or sardelka) Clupeonella abrau (Maliatsky, 1930) is an endemic fish of the Lake Abrau (Krasnodar Krai, Russia). The full C. abrau mitochondrial genome (16 650 bp) showed a gene arrangement conserved in Clupeidae and 98.8% similarity with the mitochondrial genome of the related species Black and Caspian Sea sprat C. cultriventris from the Black Sea. The COX1 gene sequence was additionally studied in a museum specimen collected in the Lake Abrau in 1938. Variability in modern Abrau sprat COX1 gene locus was estimated at approximately 0.15%, the difference between C. abrau and C. cultriventris was 1.2%, and the difference between the museum and modern C. abrau specimens from the Lake Abrau was 0.92%. The study confirmed that the Abrau sprat is present in the fish community and is capable of reproducing in the lake. Various scenarios were proposed to explain colonization of the Lake Abrau by C. abrau.

Production of Omega-3 Fatty Acid Concentrates from Common Kilka Oil: Optimization of the Urea Complexation Process.

There has been an increase in interest in the application of ω-3 PUFAs, especially EPA and DHA, in the development of various food products owing to their myriad health benefits. However, most fish oils do not contain more than 30% combined levels of EPA and DHA. In this study, through the urea complexation procedure, the production of EPA and DHA concentrate in their free fatty acids (FFAs) form was achieved from an enzymatic oil extracted from common kilka (Clupeonella cultriventris caspia). To gain the maximum value of EPA and DHA, the response surface methodology (RSM), which is an effective tool to categorize the level of independent variables onto the responses of an experimental process, was also used. Different variables including the urea-fatty acids (FAs) ratio (in the range of 2-6, w/w), the temperature of crystallization (in the range of -24-8 °C), and the time of crystallization (in the range of 8-40 h) were investigated by response surface methodology (RSM) for maximizing the EPA and DHA contents. Following the model validation, the levels of the variables at which the maximum desirability function (0.907 score) was obtained for response variables were 5:1 (urea-FAs ratio), -9 °C (the temperature of crystallization), and 24 h (the time of crystallization). Under these optimal conditions, increases of 2.2 and 4.4 times in the EPA and DHA concentrations were observed, respectively, and an increase in the concentrations of EPA and DHA from 5.39 and 13.32% in the crude oil to 12.07 and 58.36% in the ω-3 PUFA concentrates were observed, respectively. These findings indicate that the urea complexation process is efficient at optimizated conditions.

Image Segmentation Based On U-Net and Adjusted U-Nets

Image segmentation, the process of dividing an image into various areas is quite crucial recently. Numerous industries, including robotics, remote sensing, and medical imaging, have applications for this task. In recent years, deep learning techniques, especially U-shaped networks (U-nets), have shown remarkable success in solving image segmentation problems. This paper provides an overview of image segmentation using neural networks, introduces different types of adjusted U-nets used for this task, including the implementation of attention gates and the use of residual neural network as the encoder path based on the original encoder-decoder structure, and then uses U-net and adjusted U-nets to conduct image segmentation on the black sea sprat. The study uses dice similarity coefficient and binary cross entropy loss function to compare the model training results and further judges the functionality of the models by the predicted segmented images. According to the test results, the Res34-UNet with attention gates performs most efficiently in segmenting this image dataset, although it's more unstable compared to the basic U-Net.

УСОВЕРШЕНСТВОВАНИЕ ТРАЛОВОГО ПРОМЫСЛА ТЮЛЬКИ В АЗОВСКОМ МОРЕ В СОВРЕМЕННЫХ УСЛОВИЯХ ВОССТАНОВЛЕНИЯ ПОПУЛЯЦИЙ ОСЕТРОВЫХ РЫБ

Background. At present, the Black and Caspian Sea sprat (tyulka) is the least exploited species of the aquatic biological resources in the Azov and Black Sea Fishery Basin, although it has always been a valuable fishing target and a possible reserve pool for the increase of fish catches in the Basin. In the recent years, with the increasing number of midwater trawls allowed for using in the Black and Caspian Sea sprat (tyulka) fishery, all vessels transitioned to its trawl fishing; however, its total catch is decreasing, and the fishing results of these vessels are on the decline. Relevance. Taking into consideration the stock restoration occurring to the sturgeon fish species in the Azov Sea Basin in the recent years, it is necessary to take measures for maintaining this trend, as the Black and Caspian Sea sprat trawl fishing can result in increased mortality or injury of sturgeon fish and considerably damage their population. With a substantial decrease in the Black and Caspian Sea sprat fishing stock, the matter of stock restoration of the sturgeon fish species in the Azov Sea can induce the prohibition of the trawl operations in this water body, including the complete ban of the insufficiently profitable trawl fishing of the Black and Caspian Sea sprat in its current form. The aim of this article is to examine the design of the midwater trawls used in the Black and Caspian Sea sprat fishing in the Azov Sea, to investigate the global best practices in the trawl selectivity improvement, and to substantiate the main design characteristics for the specialized tyulka midwater trawls and means of their selectivity improvement. Methods. The standard methods of sample collection and data processing that could characterize fishing methods, gears and techniques for harvesting aquatic bioresources have been used. Results. The designs for the specialized trawls for the Black and Caspian Sea sprat fishing (exploitation) and methods for their selectivity improvement have been developed. Conclusion. These specialized trawls with the sorting units and a new principle of using otter boards (trawl doors) can increase fishing selectivity and mitigate possible damage inflicted by trawling to the populations of sturgeon fish species in the Azov Sea.

РАСПРЕДЕЛЕНИЕ И ДИНАМИКА ЧИСЛЕННОСТИ ИХТИОПЛАНКТОНА И РАННЕЙ МОЛОДИ ТЮЛЬКИ И ХАМСЫ В АЗОВСКОМ МОРЕ В 1993–2023 ГГ.

Background. Natural and anthropogenic factors have a major influence on the fish population status. In the Azov Sea, for the last 30 years, substantial changes in the environment have been observed and new exotic species of aquatic living organisms have been introduced, which affected reproduction of fish species. Relevance. To identify the driving forces behind the present dynamics of population abundance of European anchovy and Black and Caspian Sea sprat (tyulka), it is crucial to summarize the data collected during the annual ichthyoplankton surveys of the Azov Sea. This work is aimed at the assessment of the distribution of the ichthyoplankton and early juveniles of Black and Caspian Sea sprat (tyulka) and European anchovy in the Azov Sea area over time with regard to various environmental factors. Methods. Ichthyoplankton surveys are customarily conducted over the entirety of the Azov Sea in the middle of June, when eggs and larvae of Black and Caspian Sea sprat (tyulka) and European anchovy are caught at the highest quantities. Results. The dynamics of distribution and abundance variations for the early developmental stages of Black and Caspian Sea sprat (tyulka) and European anchovy under the influence of environmental factors, including ctenophores and scyphozoan jellyfishes, has been identified; a decrease in the survival rates of their jellyfishes juveniles in the present period of the Azov Sea salinization has been observed. Conclusion. In the context of increasing salinity of the Azov Sea waters, the main factors contributing to the reduced survival rates of the Black and Caspian Sea sprat (tyulka) larvae and fingerlings are the decrease in spawning ground area and competition for food resources with scyphozoan jellyfishes and ctenophores. In the case of the European anchovy larvae and fingerlings, the main factor affecting their abundance is a small number of breeders; food competition and predation of the scyphozoan jellyfishes and ctenophores are of secondary importance.

Структурні показники та динаміка промислових уловів риб дніпровських водосховищ

Purpose: to establish and analyze the dynamics of the species composition and amounts of commercial fish catches over the past 10 years in the context of assessing the overall efficiency of the fishery exploitation of Dnieper reservoirs. Methodology. As primary materials, data from official commercial fishery statistics and the results of field monitoring studies carried out by the Institute of Fisheries of the National Academy of Sciences on Dnieper reservoirs in the period of 2012‒2022 were used. The intensity of commercial fish harvest was assessed by the annual fishing mortality rate, which was defined as the difference between the total and natural mortality. The total mortality rate was determined graphically by the natural logarithms of the number of age groups in catches; natural mortality — based on the parameters of the von Bertalanffy equation. Statistical data processing was carried out in MS Excel. Findings. The dynamics of commercial catches in the cascade of Dnieper reservoirs in the last 10 years has been characterized by instability with a minimum of 8.9 thousand tons in 2013 and a maximum of 14.0 thousand tons in 2019. The majority of commercial catches was Prussian carp (28.2% of the total catch), common bream (21.1%), roach (20.5%) and silver bream (8.3%). The catch dynamics of all limited species had the same features — a growth in the period 2014‒2016, stabilization until 2019 and a further decrease, which was due to the determining influence of organizational factors. The distribution of fishing pressure by the objects of fishing does not fully correspond to the quantitative parameters of their ichthyomass; the average (2019‒2021) coefficients of annual fishing mortality were: pikeperch — 32.0%, common bream — 22.8%, roach — 24.2%, silver bream — 22.7%, Prussian carp — 19.0%. The maximum catches per unit effort of the gill net in the studied period were recorded for the Kamianske reservoir (348.9±73.4 kg), the lowest (152.0±44.5 kg) — for the Kaniv reservoir. The average fish catch per one gill net per cascade was 245.1±36.3 kg; a trend towards its growth during 2012‒2021 was observed. Originality. Original data on the modern dynamics of the amount and structure of commercial fish catches as a component of scientific support for fisheries exploitation of the Dnieper reservoirs were obtained. Practical value. It has been found that the fluctuations of fish catches in Dnieper reservoirs are largely determined by the influence of external (organizational) factors, which makes it possible to effectively manage the use of fish stocks. It is shown that for some species (in particular, pikeperch), the intensity of fishery exploitation exceeds the optimum, for others (Prussian carp, Black Sea sprat), on the contrary, an increase in the fishing pressure is possible.

Population Dynamics and Distribution of the Lake Smelt, a Dwarf Form of the European Smelt Osmerus eperlanus (Osmeridae), and the Black Sea Sprat Clupeonella cultriventris (Clupeidae) while Cohabiting the Rybinsk Reservoir

The data for a 23-year period (2000–2022) on the population dynamics and distribution of the lake smelt (a form of the European smelt Osmerus eperlanus) and the Black Sea sprat Clupeonella cultriventris in the Rybinsk Reservoir have been summarized. The lake smelt dominated the reservoir pelagial from the 1950s to the mid-1990s. An anomalously low water level in the reservoir in 1996 and abnormal (for this reservoir) water warming in subsequent years led to elimination of the species from the reservoir ichthyofauna in 2002. The Black-Sea sprat invaded the reservoir in the mid-1990s; its population irruption occurred in the early 2000s (during the depressed state of the smelt population). Currently, this species dominates in the pelagial of the reservoir. Since the early 2000s there were noted two periods when the lake smelt was found in practically all parts of the Rybinsk Reservoir and the sprat abundance was also high. However, high water temperatures in 2010 and 2021, as well as low level in 2014, resulted in almost complete disappearance of the lake smelt disappeared. During the periods of cohabitation of the studied species, a significant similarity in the diet of individuals of both species with the size of up to 80 mm has been noted. The larger smelt fed on larger plankton, and in the summer also on fish. Currently, the main limiting factor negatively affecting the recovery of the smelt population in the Rybinsk Reservoir is the abnormal heating of the water column in some years.

Screening of Lesser-Known Salted–Dried Fish Species for Fatty Acids, Tocols, and Squalene

The fillets and roes of 29 species of dry-salted fishes consumed in Eurasian countries were analyzed for fatty acids (FAs), tocols, and squalene, looking for derived health benefits. FAs were analyzed by GC-FID, and tocols and squalene were analyzed by HPLC-DAD. With some exceptions, docosahexaenoic (DHA, 22:6n-3), eicosapentaenoic (EPA, 20:5n-3), and arachidonic (ARA, 20:4n-6) acids were the prominent polyunsaturated fatty acids (PUFAs). The fillets of Scardinius erythrophthalmus reached the highest amounts of total FAs, ARA, and DHA (23.1, 1.82, and 2.49 mg/100 g). The fillets of Seriola quinqueradiata showed the highest percentages of DHA (34.4% of total FAs). Nutritional quality indices for fish lipids were favorable in all samples, especially the n-6/n-3 PUFA ratio, which was below 1 in most cases. α-Tocopherol was found in all fillets and roes, especially in Cyprinidae and Pleuronectidae species, and the highest value was found in the roes of Abramis brama (5.43 mg/100 g). Most samples contained tocotrienols at trace levels. The fillets of Clupeonella cultriventris contained the highest amounts of squalene (1.83 mg/100 g). Overall, dry-salted fish stand out due to their high concentrations of ARA, EPA, and DHA, as well as for α-tocopherol concentrations in roes.

Fish reproduction in Krasnoarmeysk district of Saratov region in 2022

One of the main factors influencing the efficiency of reproduction of limnophilic fish is the height of water level and the duration of spring flood with uniform water heating. Work was carried out to assess the natural reproduction of fish in the area of the middle zone of the Volgograd reservoir, near the villages Akhmat and Zolotoye, Krasnoarmeysk district, Saratov region, in 2022. In total, juveniles of 11 fish species were caught in the surveyed areas in 2022. There is a significant decrease in species diversity compared to previous years. Due to the unfavorable level regime during the spawning period, very unfavorable conditions for the reproduction of fish have developed in 2022. For the first time in 6 years of research in the waters under consideration, it was possible to record the reproduction of catfish (Silurus glanis) and carp (Cyprinus carpio). In 2022, in the area near Akhmat village, an anomaly was observed: underyearlings of bleak (Alburnus alburnus), which usually dominates catches, and perch (Perca fluviatilis), which is also common in this area, were absent in the catches (despite the fact that individuals of these fish of older ages were encountered). In the water area near Zolotoye village still recorded the reproduction of Black Sea-Caspian sprat (Clupeonella cultriventris), the early larvae of which are common there in the catches and are not found in the water area near Akhmat village. In the water area near Zolotoye village underyearlings of asp (Aspius aspius) are still common, and they dominate the catches in 2022. In the water area near Akhmat village, the catches of 2022 are dominated by crucian carp (Carassius gibelio).

Polyunsaturated Fatty Acid Content in the Muscles of Alien Fish Species of the Rybinsk Reservoir

The biochemical composition of the muscles of two fish species, European smelt Osmerus eperlanus and the Common (Caspian) kilka Clupeonella cultriventris, that were successively invaded and naturalized in the Rybinsk Reservoir in the second half of the 20th century, differs significantly in the fatty acid content. The sum content (mg/g) of eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) polyunsaturated fatty acids in the muscle tissue of the kilka is almost four times higher than that in European smelt. Given that smelt and the kilka are similar in their ecological and morphological characteristics and do not differ significantly in the composition of their diet in the Rybinsk Reservoir, it is obvious that the observed differences primarily result from the phylogenetic aspect. The obtained data on the composition of the fatty acids of the invaders show that the replacement of one alien species with another (European smelt with the kilka) significantly changed the quality of production of an important link in the trophic web of the reservoir.

The adventive species community changes in the Cheboksary reservoir during 2001-2021

Generally publications devoted to invasive fish species in the Volga-Kama cascade of reservoirs represents relative indicators and do not provide data on the abundance, numbers and invasive communities’ single species dynamics. It does not allow providing a correct assessment of population’s state and changes in the nonindigenous species composition. In this work, changes in the abundance and species structure of the Cheboksary reservoir’s invasive fish community during 2001-2021 were estimated. The total fish count was determined on data of active fishing gears catches and precise reservoir area. Differentiation into mass, widespread and relatively numerous and locally found with a small average abundance species was noted. A decrease in the species evenness of the invasive community was recorded in consequence of the Black Sea-Caspian sprat Clupeonella cultriventris (Nordmann, 1840) and the round goby Neogobius melanostomus (Pallas, 1814) domination rise. The Black Sea-Caspian sprat and the round goby put together for 98.7% of the total number of invasive fish in the current period. Due to this two dominant species there is a tendency to increase the relative abundance of invasive fish species in the reservoir up to 561 unit/ha despite a significant decrease in the abundance of some other invaders.

Polyunsaturated Fatty Acid Content in the Muscles of Alien Fish Species of the Rybinsk Reservoir

The biochemical composition of the muscles of two fish species, European smelt Osmerus eperlanus and the Common (Caspian) kilka Clupeonella cultriventris, that were successively invaded and naturalized in the Rybinsk Reservoir in the second half of the 20th century, differs significantly in the fatty acid content. The sum content (mg/g) of eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) polyunsaturated fatty acids in the muscle tissue of the kilka is almost four times higher than that in European smelt. Given that smelt and the kilka are similar in their ecological and morphological characteristics and do not differ significantly in the composition of their diet in the Rybinsk Reservoir, it is obvious that the observed differences primarily result from the phylogenetic aspect. The obtained data on the composition of the fatty acids of the invaders show that the replacement of one alien species with another (European smelt with the kilka) significantly changed the quality of production of an important link in the trophic web of the reservoir.

ЛЕЙКОЦИТЫ И ТРОМБОЦИТЫ ПЕРИФЕРИЧЕСКОЙ КРОВИ ТЮЛЬКИ ЧЕРНОМОРСКО-КАСПИЙСКОЙ (CLUPEONELLA CULTRIVENTRIS, NORDMANN 1840) ИВАНЬКОВСКОГО И УГЛИЧСКОГО ВОДОХРАНИЛИЩ

For the first time, the hematological parameters of tyulka (Clupeonella cultriventris, Nordmann, 1840) in the reservoirs of the Upper Volga were studied. The composition of leukocytes and thrombocytes, morphometric characteristics of cells were studied by routine methods of light microscopy. It was shown that blood of tyulka has a lymphocytic character, but an increase in the number of granulocytes and their size was found against the background of a decrease in the number of lymphocytes in tyulka a in the lower section of the Ivankovo ‒ the upper section of the Uglich reservoirs, which may indicate the presence of anthropogenic pressure. The proportion of thrombocytes was approximately three times higher than the proportion of leukocytes, which indicates a high blood clotting of the tyulka. Correlations between the characteristics of leukocytes and platelets and the content of basic cations and anions in water were studied.

DISTRIBUTION PATTERNS OF METACERCARIAE OF THE TREMATODA <i>APOPHALLUS </i><i>MUEHLINGI</i> (JÄGERSKIÖLD, 1899) IN UNDERYEARLINGS IN AN INVASIVE POPULATION OF <i>CLUPEONELLA CULTRIVENTRIS</i> (NORDMANN, 1840) FROM THE GORKY RESERVOIR (UPPER VOLGA BASIN)

After the successful naturalization of the prosobranch mollusk Lithoglyphus naticoides (C. Pfeiffer, 1828) and a number of associated trematodes in the Gorky Reservoir (in 2005-2015) an intensive spread of apophallesis in fish of this water body has been observed. As one of the second intermediate hosts of the trematode causing this disease, Apophallus muehlingi (Jägerskiöld, 1899), a freshwater form of the Black Sea-Caspian kilka Clupeonella cultriventris (Nordmann, 1840) was recorded. The aim of the work is to study the consequences of dispersal of C. cultriventris for the formation of large permanent foci of apophallesis in the Upper Volga. For comparison, data on the spread of this type of "black-spot" disease in the populations of C. cultriventris from the Gorky Reservoir and an unregulated area of the Lower Volga (downstream the cascade of Volga reservoirs, pelagic trawl coordinates from 47°08ʹN, 47°17ʹE to 46°51ʹN, 47°41ʹE) were used. The high rates of occurrence of A. muehlingi metacercariae (the infection prevalence P, %) are recorded in the fall along the entire area of the Gorky Reservoir: from the northernmost site near Rybinsk (58°01ʹN, 39°06ʹE) to the dam area (56°41ʹN, 43°21ʹE). It is found that the distribution pattern of A. muehling metacercariae varies in the sections of the reservoir differing in hydrological characteristics. In the middle (transitional type) section of the reservoir the prevalence of A. muehlingi metacercariae in groups of the smallest Black Sea-Caspian kilka fingerlings (with a body length of up to 45 mm), is close to the maximally possible (30.00-94.49%). In the upper (river-type) section of the reservoir, the prevalence of metacercariae in this group of fish does not exceed 24.39%. The minimum values of this indicator are found in the lower (lake-type) section of the reservoir (6.76-14.84%). Judging by the values of the abundance index and the coefficient of variation in the infection intensity, the aggregation of metacercariae is more pronounced in the groups of faster growing underyearlings and the Black Sea-Caspian kilka yearlings as compared to the groups of the smallest fingerlings. In the Black Sea-Caspian kilka fingerlings samples from the Lower Volga in 2020 reveals no statistically significant differences between the infection prevalence values (13.33-18.11%) in the different size groups. Thus, although the main second intermediate hosts of A. muehlingi are various fish species of the Cyprinidae family, in some cases the presence of C. cultriventris in the water body ecosystem can significantly increase the likelihood of apophallesis spread. In conditions of the Upper Volga, due to the high migration activity of large individuals of the Black Sea-Caspian kilka, a continuous zone of apophallesis can form without clearly defined boundaries between the individual foci of disease.

Экология, состояние запаса и перспективы промысла одного из видов - вселенцев Чебоксарского водохранилища – черноморско-каспийской тюльки Clupeonella cultriventris

Based on long-term materials, the ecology, the current state of the reserve and some features of the biology of the Black Sea-Caspian Sea sprat in the Cheboksary reservoir are considered. A brief biological characteristic of its age and size-weight indicators is given. The prospects of industrial development are shown.

Fishing and biological characteristics of the common sprat near the Dagestan coast of the Caspian sea

The fishing and biological characteristics of the common sprat (Clupeonella cultriventris caspia Svetovidov, 1941), caught along the coast of the Caspian Sea in the area of Makhachkala, the Republic of Dagestan, were obtained. Examination of the fish showed that the individuals were in a spawning state. In the muscles, the content of the main reserve and energy substances of the body — total lipids and water-soluble protein — was studied. A significant (p < 0.05) positive correlation was registered in females and males between fish weight and fishing length: (r = +0.87) and (r = +0.85), respectively. The physiological state of the common sprat in terms of the content of total lipids and water-soluble protein in the muscle tissue is satisfactory. The tendency of the highest content of total lipids in the muscles of females compared to males was registered, since individuals need a larger energy reserve to ensure oogenesis than for spermatogenesis. This is due to the use of muscle lipids to build the gonads and supply with the necessary nutrients for the embryo, and later the larva. In a comparative aspect, there were no significant differences in the content of water-soluble protein in the muscles of males and females during the spawning period. Analysis of the coastal fishery for common sprat with fixed seines in the period 2011–2021 showed that its catch on the Dagestan coast of the Caspian Sea increased from 302.7 tons in 2012 to 1815.0 tons in 2021, which was in direct proportion to the number of fixed seines. In this regard, the most actual task is the development of fishing reserves of this species, which will contribute to the development of the fish extraction and fish processing industry of the Republic of Dagestan.

Влияние эффекта глобального потепления на качественные характеристики популяции черноморского шпрота на Крымско-Кавказском шельфе Черного моря

The Black Sea sprat Sprattus sprattus phalericus (Risso) and temperature factor impact have been investigated. Statistical assessment of the long-term dynamics (1951–2019) of a relationship between the temperature factor and sprat mean weight in fishery catches used as a population quality characteristic has been performed. Pearson product-moment correlation and cross-correlation was evaluated, then data series was smoothed by the local polynomial regression and, finally, a linear model was fitted. The correlation test shows significant relationship between the temperature factor and sprat mean weight-at-age (mean weight in 3+ age group and SST in the port of Yalta resulted in r = -0.86, whereas average SST and average mean weight by age classes led to r = -0.74). The fitted linear model by smoothed data of average SST and average weight-at-age successfully passed diagnostics (R2 = 0.87, RSE = 0.34), with the equation: w = f(sst) = 22.23 - 1.263*sst. As a result, this study allows to emphasize the temperature factor as a main driver of the sprat fishery quality characteristics. The global warming effect, starting since the 1990’s has had a significant negative impact on the sprat population.