Blue Bream Research Articles

Effect of Different Water Salinities on the Larvae of the Blue Bream Ballerus ballerus (Linnaeus, 1758) during Rearing

The influence of water salinities of 3, 5, and 7 ppt on the growth and survival of Ballerus ballerus (L.) larvae was studied. The control group was fish reared in freshwater (0 ppt). The larvae showed high tolerance to water salinities of 5-7 ppt. The mean final weight of the larvae ranged from 48.6 to 64.1 mg, with corresponding mean total lengths from 18.9 to 22.6 mm, depending on the water salinity level. The best larval length increments were recorded in water with salinity of 3 ppt. They were only slightly lower in 0 ppt water, and there were no statistically significant differences between the breeding rates calculated for larvae reared in 3 ppt water. Depending on the salinity level of the water, the final survival rate of the blue bream larvae ranged from 83.5 to 98.6%. The blue bream larvae reared in water with salinity levels of 5 and 7 ppt were statistically smaller than the others, but the results obtained were equally satisfactory.

VETERINARY AND SANITARY EXAMINATION OF FISH OF THE UPPER VOLGA BASIN IN THE YAROSLAVL REGION

В статье представлены результаты исследований ветеринарно-санитарной экспертизы рыбы Верхневолжского бассейна Ярославской области. В ходе патологоанатомического исследования установлено, что у образца синца № 3 из устья реки Ильдь, синца № 1 и леща № 1 и № 4 из устья реки Сунога, а также у образца синца № 1 из устья реки Латка наблюдается гидремия мышечной ткани, истощение, брюшко вздуто, в брюшной полости видны лигулы. В остальных образцах изменений не обнаружено. При гельминтологическом исследовании рыбы установлено заражение лигулами образца синца № 3 из устья реки Ильдь, синца № 1 и леща № 4 из устья реки Сунога, а также образца синца № 1 из устья реки Латка. Образцы леща № 4 из устья реки Ильдь и № 3 из устья реки Латка заражены метацеркариями описторхиса, а образцы щуки № 3 из устья реки Сунога – плероцеркоидами дифилоботриума. Органолептические исследования рыбы показали, что все образцы, предоставленные для исследования, соответствуют нормативным значениям. Поверхность образцов без посторонних примесей, ровная, чистая, плотной консистенции, естественного розового цвета, со специфическим запахом, свойственным для данного вида. Бульон, при пробе варки, прозрачный, ароматный, содержит на поверхности блёстки жира (жира нет в бульоне и образцах синца № 3 из устья реки Ильдь, синца № 1 и леща № 4 из устья реки Сунога, а также образца синца № 1 из устья реки Латка). Физико-химические испытания показали, что во всех образцах рыбы, представленных на исследование, показатели порчи и гниения мяса рыб отсутствуют. Реакция на пероксидазу положительная. При микроскопическом исследовании единичные кокки и палочки обнаружены в образце леща № 4 из устья реки Ильдь, образце щуки № 3 из устья реки Сунога, образце леща № 3 из устья реки Латка. В мазках из поверхностных слоёв мускулатуры обнаружены микроорганизмы в количестве 31 штука. The article presents the results of the research on the veterinary and sanitary examination of fish of the Upper Volga basin in the Yaroslavl region. It was in postmortem examination revealed that samples of blue bream № 3 from the mouth of the Ild river, blue bream № 1 and bream № 1 and № 4 from the mouth of the Sunoga river as well as the sample of blue bream № 1 from the mouth of the Latka river had muscular tissue hydremia, exhaustion, the abdomen is swollen, ligules are visible in abdominal cavity. No changes were found in the remaining samples. During helminthological examination of fish ligula infestation was found in the sample of blue bream № 3 from the mouth of the Ild river, blue bream № 1 and bream № 4 from the mouth of the Sunoga river, as well as in the sample of blue bream № 1 from the mouth of the Latka river. Samples of bream № 4 from the Ild river mouth and № 3 from the Latka river mouth were infested with opisthorchis metacercaria and samples of pike № 3 from the mouth of the Sunoga river were infested with diphilobothrium plerocercoides. Organoleptic examinations of fish showed that all the samples proposed for examination corresponded to regulatory values. The surface of the samples without foreign impurities, smooth, clean, of dense consistency, natural pink color with a specific smell peculiar to this species. The broth when cooked is transparent, aromatic, contains spangles of fat on the surface (there is no fat in the broth and samples of blue bream № 3 from the mouth of the Ild river, blue bream № 1 and bream № 4 from the mouth of the Sunoga river, as well as a sample of blue bream № 1 from the mouth of the Latka river). Physicochemical tests showed that all samples of fish submitted for the study there are no indicators of spoilage and decay of fish meat. The reaction to peroxidase is positive. During microscopic examination single cocci and bacillus were found in bream sample № 4 from the mouth of the Ild river, pike sample № 3 from the mouth of the Sunoga river, bream sample № 3 from the mouth of the Latka river. Microorganisms in the amount of 31 pieces were found in smears from the surface layers of the musculature.

Influence of temperature and stocking density during rearing on larval blue bream, Ballerus ballerus (L.)

Abstract This study determined the effects of stocking density and water temperature on the rearing parameters and survival of larval blue bream under controlled conditions. Two experimental larval blue bream rearing variants were conducted. In the first experiment, larval blue bream were reared at different stocking densities of 20, 40, 80, and 120 indiv. dm−3 at 25°C. In the second experiment, larvae were reared in water at 15, 20, 25, and 30°C at a stocking density of 40 individuals per dm3. The larval blue bream achieved the highest growth rate at the lowest density tested (20 indiv. dm−3; 69.4 mg at an average length of 26.8 mm) and at the highest temperature tested (30°C; 80.1 mg at an average length of 28.4 mm). The final larval survival rate during rearing at different temperatures ranged from 95.2 to 97.6%, while the final larval survival rate at different stocking densities ranged from 91.4 to 94.6%. The lowest growth and survival rates were recorded for larvae reared in water at 15°C and at a density of 120 indiv. dm−3.

Fishes in the economy of Ancient Greek colonies (600 BC – 300 AD) on the Northern Black Sea Coast – new touches to an old portrait

The article presents the results of a thorough study of fish remains recovered during the excavations of three ancient Greek cities (Olbia, Berezan and Chornomorka) in the northern part of the Black Sea coast. These materials are dated in the range of 600 BC – 300 AC (in the case of Olbia and Berezan), and 500–400 BC for Chornomorka. Fish bones were processed for the identification of species used by the inhabitants of these ancient cities for food. The remains of about ten fish species are present in the studied sample. Of them, sturgeons (Acipenser spp.) were the most numerous in the region at that time. The other species which were usually caught in these ancient Greek cities are mostly represented by carp fishes (roach, common bream, white bream, blue bream, common carp, and crucian carp), but also European catfish Silurus glanis, pike Esox lucius, and pikeperch Sander lucioperca. The weight and size of some fish individuals were reconstructed based on complete bones. Comparison of the specimens from individual samples (series) showed no significant differences in their total length and weight. The economic activity of ancient settlements of the Northern Black Sea region is of interest to archaeologists for a long time. Many of the aspects of this activity, such as agriculture, crafts, and architecture, have been explored quite well (e.g., Christodoulou 2016 and references therein). At the same time, fishery, an important direction of the economy of coastal cities providing a valuable animal protein, often falls out of the scope of research interests. A significant amount of materials collected by archaeologists in the north of the Black Sea coast during the 20th century is still not processed and remains unpublished. Therefore, it is difficult to create a holistic picture of the economy of ancient Greek cities. A valuable information about fishing and fish consumption in ancient cities of the Northern Black Sea region according to archaeological data and osteological collections is presented in Lebedev (1960), Zhiteneva (1964), Hojte (2005), Morales et al. (2007) and Odrin (2010). A few recent publications are focused on the fish osteological material from ancient Greek cities discovered on the Northern Black Sea coast. Archaeozoological studies can show how important fish was in the diet of people, which species were preferred, and how intensive was fishing in this region in different periods. In addition, it is possible to find out whether there was a fish trade between these cities using the ratio of cranial and postcranial elements of the skeleton. Such studies can prove or disprove the statements of Strabo or Herodotus, who wrote about the culinary preferences of ancient Greeks. Therefore, the aim of this article is to present in detail the results of the study of fish bone samples from Olbia, Berezan and Chornomorka in the range from their formation (600 BC) until the end of the Roman period (300 AD). By comparing data from different periods, it is possible to track the role of fishery in the economy of these settlements and its dynamics over time. Key words: Olbia, antiquity, Berezan, archaeozoology, fishing, ancient Greeks, Black Sea

Репродуктивные характеристики синца Ballerus ballerus (Linnaeus, 1758) Камского водохранилища

This paper presents the age and sex structure of the spawning part of the blue bream population in the Kama reservoir in 2019–2022. The age structure of the blue bream is characterized by a high number of older groups, which is associated with the peculiarity of fishing in the Kama reservoir. In comparison with earlier data on the reservoir, a reduction in the timing of fish puberty has been established, currently timed to the 5-year-old age for males, and to the 6-year-old age for females. It was revealed that the life expectancy of fish increased to 17 years of age. A study of fertility of blue bream was carried out on 87 females represented by 11 age groups. The limits of variation of individual absolute fecundity have been determined to exceed the earlier data, the minimum of individual absolute fecundity is 8.6 thousand eggs, the maximum of individual absolute fecundity is 78.8 thousand eggs. It is shown, that the reproductive ability of the females of the blue bream in the Kama reservoir remains at a high level and is characterized by increase in the average values of individual relative fertility up to 10 years of age, the maximum average values of relative fertility are observed in 15-year-old fish.

Мониторинг естественного воспроизводства популяций рыб озера Едильсор

The article presents the results of monitoring the commercial fish populations of Edilsor Lake. Edilsor is one of the large lakes of the West Kazakhstan region of fishery importance, in connection with which the monitoring of the natural numbers of populations of aboriginal commercial fish species of the studied reservoir is relevant. Control catches were used to analyze the state of natural fish populations. As tools for catching biological objects, commercial fish, lake plug-in nets with mesh sizes of 30–70 mm were used. Control catches of aboriginal commercial fish were carried out during the period of field studies. The captured biological objects were subjected to the analysis of such biological indicators as species, age composition, ratio of females and males in the catch, weight, length of the whole body of fish, according to the results obtained, the average values were determined. As a result of control catches, the species composition of the ichthyofauna of Lake Edilsor included the following species of aboriginal commercial fish: carp — 7.1 %, bream — 16.7 %, blue bream — 7.1 %, crucian carp — 4.8 %, perch — 64.3 %. The largest population was characterized by the perch population, which amounted to 27 individuals, the bream was less common — 7 individuals, the carp and blue bream — 3 individuals, the smallest number was observed in the population of crucian carp, which amounted to 2 individuals. According to the weight ratio, fish species are located as follows: perch — 40 %, carp — 32.5 %, bream — 15.8 %, crucian carp — 8.5 %, blue bream — 3.2 %. The largest mass falls on representatives of perch — 6.94 kg, followed by carp — 5.63 kg, bream — 2.73 kg, crucian carp — 1.47 kg, blue bream — 0.56 kg.

Impact of replacing natural food with commercial feed on the growth and survival of blue bream larvae (Ballerus ballerus) under controlled conditions

Abstract The effect of replacing natural food with commercial feed on the growth and survival of blue bream, Ballerus ballerus (L.), larvae reared under controlled conditions was investigated. Live food, brine shrimp, Artemia sp. (A), nauplii, was replaced after four (A4P17), eight (A8P13), and 12 (A12P9) days with commercial feed (P). The control groups were larvae fed nauplii (A21) or feed (P21) exclusively for throughout the experiment. The density of larvae was 40 ind. dm−3, and the rearing temperature was 25 ± 0.5°C. The highest blue bream larval growth rate in the groups fed the commercial feed tested was in group A12P9, in which larvae reached an average body weight of 56.1 mg with an average total length of 21.1 mm. These values were only slightly lower than those obtained in the A21 control sample. Final larval survival in each of the feeding groups ranged from 67% (A4P17) to 93% (A12P9). The larval lowest survival and growth parameters were recorded in control group P21, in which larvae received only commercial feed; this indicated the necessity of using natural food when rearing blue bream larvae.

Differences in the infection of different fish species in the European part of Russia with opisthorchid metacercariae as a basis for additions to veterinary and sanitary regulatory documents

Studies carried out and many literary data indicate that the ide, roach, rudd and bleak fish are infected with opisthorchid metacercariae much stronger than the main commercial fish, such as bream, blue bream and silver carp. Therefore, the latter are proposed to be assigned to the "potentially dangerous" group and allowed to be sold in fresh or cooled form, but only according to the results of a preliminary veterinary examination that confirmed their parasitic purity. This approach should be limited only to the European part of Russia, where the intensity of fish invasion by opisthorchid larvae is lower than in Western Siberia.

NATURAL AND SOCIAL FACTORS OF OPISTORCHOSIS CIRCULATION IN WEST KAZAKHSTAN REGION

The formation and course of epidemic and epizootic processes of opisthorchiasis is influenced by natural-ecological and socio-economic factors. Geographical position of the Ural River basin, the proximity of the Volga focus, species diversity and abundance of commercial species of cyprinids, ecological conditions in the Ural basin, in floodplain water bodies and in small rivers of West Kazakhstan region, connected with the Ural River, the dietary habits of people, intensive migration of population create optimal conditions for the functioning of parasitic system of opisthorchiasis and contribute to the spread of this invasion among the population of the Ural region.The risk of infection with opisthorchiasis at the natural and social levels remains high. The territory of West Kazakhstan region has the following natural and ecological conditions: it is confined to the Ural-Caspian lowland. Surface waters of West Kazakhstan region are represented by rivers, lakes and reservoirs. In the Ural River and its basin, there are many mollusks Bithynia leachi and fish species, among which there are potential carriers of opisthorchian metacercariae – bream, ide, dace, redfin, tench, wild carp, carp, white bream, roach, asp, prussian and crucian carp, chub, minnow, sabre fish, blue bream. In the region, the incidence of opisthorchiasis in people is annually recorded. A significant part of the infected population lives in settlements located along the banks of the Ural River and its floodplain reservoirs.

Artificial Reproduction of Blue Bream (Ballerus ballerus L.) as a Conservative Method under Controlled Conditions

Simple SummaryQuite severe biological imbalances have been caused by the often ill-conceived and destructive actions of humans. The natural environment, with its flora and fauna, has been subjected to a strong, direct or indirect, anthropogenic impact. In consequence, the total population of wild animals has been considerably reduced, despite efforts to compensate for these errors and expand the scope of animal legal protection to include endangered species. Many animal populations on the verge of extinction have been saved. These actions are ongoing and embrace endangered species as well as those which may be threatened with extinction in the near future as a result of climate change. The changes affect economically valuable species and those of low value, whose populations are still relatively strong and stable. Pre-emptive protective actions and developing methods for the reproduction and rearing of rare species may ensure their survival when the ecological balance is upset. The blue bream is one such species which should be protected while there is still time.The blue bream Ballerus ballerus (L.) is one of two species of the Ballerus genus occurring in Europe. The biotechnology for its reproduction under controlled conditions needs to be developed to conserve its local populations. Therefore, a range of experiments were performed to obtain valuable gametes from blue bream following hormonal stimulation with carp pituitary homogenate (CPH), Ovopel and Ovaprim. CPH and Ovopel were injected twice and Ovaprim—once, under a pectoral fin. The spawners were inspected 12 h after the last injection, and the gametes were collected. Eggs were collected from spawning females and fertilized with sperm from three males. The smallest number of ovulating blue bream (four females) was obtained from individuals stimulated with Ovaprim. There were six to nine ovulating females in the other groups, accounting for 60–90% of the females in the respective groups. The latency period was the shortest in the spawners stimulated with Ovopel. The fish in this group ovulated 14 h after the hormonal injection. Spawning was synchronized and all females spawned simultaneously. The highest average weight of eggs per fish (75.4 g) was obtained from the females stimulated with Ovopel, whereas the individuals stimulated with Ovaprim provided the smallest average amount of eggs (49.5 g). The study showed that blue bream spawners are not very sensitive to reproduction-related handling under controlled conditions.

Level of natremia as an index of the condition of the organism of animals under stress

In the diagnosis of stressful conditions in humans and other animals, ionic indicators remain practically unused. In this work, we studied the changes in the concentrations of sodium ions in the blood plasma of freshwater fish under stress caused by stressors of different quality and quantity. Most of the experiments were carried out on adult bream (Abramis brama L) from the Rybinsk Reservoir. Separate experiments were duplicated on adult individuals of roach (Rutilus rutilus L.), pike (Esox lucius L.), and blue bream (Abramis ballerus L.). The concentration of cations in the blood plasma was determined using a Flapho-4 flame photometer. Under the action of mild and short-term stressors of different qualities, the sodium concentration in the internal environment altered toward an increase in concentration gradients on the cell membrane (eustress or physiological stress). Hypernatremia was approximately 10%. Under the action of strong and/or prolonged stressors of different strength, the sodium concentration in the internal environment changed toward a decrease in concentration gradients on the cell membrane (distress or pathological stress). Hyponatremia was 50% in the conditions of acute lethal stress, 20% in subacute lethal stress, 10% or more in chronic lethal stress. During strong acute reversible stress, hyponatremia could reach 30%. Analysis of the material on mammals allowed us to conclude that the adaptation mechanisms in fish and higher vertebrates are similar. In this work, for the first time, the state of the system of electrolyte balance of animals under stress was analyzed from the standpoint of the leading role of ionic concentration gradients on the cell membrane (mainly sodium) in the energetics (level of disequilibrium) of the organism. We propose a concept that in normal and extreme conditions fish use two different defense reactions (or adaptation strategies): active and passive, consisting, respectively, in increasing or decreasing the level of disequilibrium (energy) in the organism. The hyponatremia recorded by numerous authors, which accompanies diseases in humans, is evidently a nonspecific reaction of the organism and serves as an indicator of reduced energy of the organism. It is suggested that the sodium level in the internal environment of the organism be used for diagnosing the stress state of animals.

The epidemiological significance of parasites of fishes in the Volga-Caspian fishery subdistrict (Astrakhan region)

Introduction. The epidemiological situation of parasitic diseases among the population of the Volga-Caspian fishery subdistrict within the Astrakhan region continues to be stressful. To cancel or prolong the restrictions on biohelminthoses in the region, it is necessary to conduct regular studies on the parasitic purity of fish and fish raw materials. Material and methods. In accordance with methods generally accepted in parasitology, in the period of 2013-2017, 7,671 mature specimens of thirteen species of fish of five families (carps, pikes, sheatfishes, perches, herrings) were examined. Results. In the parasitic fauna of all types of hydrobionts examined there were sanitary-significant parasites, represented by eight types of systematic groups: nematodes (Anisakis schupakovi, Contracaecum bidentat, Estrongylides excisus), trematodes (Apophallus muehlingi, Rossicotr.ema donutses), acanthocephalans (Corynosoma strumosum). The dominant group in prevalence in the population of the Volga fish were roundworms, small - acanthocephalus. The maximum quantitative indices were characterized by trematodes, the number of which in the single fish amounted to thousands. Discussion. The level of infestation of pike, catfish, bream, carp, pike-perch, perch, white bream, rud, roach, Caspian roach, sichel, Caspian anadromous shad, blue bream, parasites dangerous to humans has remained relatively stable for a number of years. The majority of fish in the eastern part of the delta (with respect to the western part) have a higher percentage of infected individuals, and therefore, aquatic animals caught in the first specified area should be subjected to more thorough veterinary examination when preparing it for sale to the population. Conclusion. The data on the annual invasions of fish and people (along with other warm-blooded animals) with epidemiologically significant parasites indicate the active functioning of natural foci of apophallosis, rosicotremosis, opisthorchiasis, pevdoamphistomosis, anizakiosis, contratsekoleza, eustrongilidosis, and corynozomosis in the Volga delta. For the prevention of biohelminthoses, it is necessary, in addition to state control (ensuring proper product quality), to establish a direct informational notification of the population in order to clarify the importance of the issue of parasitic invasions transmitted through fish.

The epidemiological significance of parasites of fishes in the Volga-Caspian fishery subdistrict (Astrakhan region)

Introduction. The epidemiological situation of parasitic diseases among the population of the Volga-Caspian fishery subdistrict within the Astrakhan region continues to be stressful. To cancel or prolong the restrictions on biohelminthoses in the region, it is necessary to conduct regular studies on the parasitic purity of fish and fish raw materials. Material and methods. In accordance with methods generally accepted in parasitology, in the period of 2013-2017, 7,671 mature specimens of thirteen species of fish of five families (carps, pikes, sheatfishes, perches, herrings) were examined. Results. In the parasitic fauna of all types of hydrobionts examined there were sanitary-significant parasites, represented by eight types of systematic groups: nematodes (Anisakis schupakovi, Contracaecum bidentat, Estrongylides excisus), trematodes (Apophallus muehlingi, Rossicotr.ema donutses), acanthocephalans (Corynosoma strumosum). The dominant group in prevalence in the population of the Volga fish were roundworms, small - acanthocephalus. The maximum quantitative indices were characterized by trematodes, the number of which in the single fish amounted to thousands. Discussion. The level of infestation of pike, catfish, bream, carp, pike-perch, perch, white bream, rud, roach, Caspian roach, sichel, Caspian anadromous shad, blue bream, parasites dangerous to humans has remained relatively stable for a number of years. The majority of fish in the eastern part of the delta (with respect to the western part) have a higher percentage of infected individuals, and therefore, aquatic animals caught in the first specified area should be subjected to more thorough veterinary examination when preparing it for sale to the population. Conclusion. The data on the annual invasions of fish and people (along with other warm-blooded animals) with epidemiologically significant parasites indicate the active functioning of natural foci of apophallosis, rosicotremosis, opisthorchiasis, pevdoamphistomosis, anizakiosis, contratsekoleza, eustrongilidosis, and corynozomosis in the Volga delta. For the prevention of biohelminthoses, it is necessary, in addition to state control (ensuring proper product quality), to establish a direct informational notification of the population in order to clarify the importance of the issue of parasitic invasions transmitted through fish.

Оценка состояния пресноводной ихтиофауны Волго-Ахтубинской поймы на современном этапе (в 2018–2019 гг.)

The article assesses the state of freshwater ichthyofauna of the Volga-Akhtuba floodplain (VAP) in the modern period. A retrospective analysis of the dynamics of the composition of the ichthyofauna of the floodplain under the influence of different fishing regimes was carried out. The increasing role of amateur fishing in this process has been defined. There has been defined the orientation of changes including increasing pressure on the most valuable fish species (perch, brim, pike perch, sazan and perch), unstable hydrological regime of the Lower Volga during the repro-duction period, growth of illegal, unreported and unregulated fishing, etc. The values of the qualitative and quantitative composition of net catches of fish are given. The extrapolation method assuming 
 a uniform distribution of the ichthyofauna calculated the commercial stock of freshwater ichthyofauna of the floodplain. It has been noted that in the stock structure of the Volga-Akhtuba floodplain there dominate the typical river species, more than 50% of which are presented by bream, crucian carp, sabrefish and blue bream. In the context of the limited extraction (catch) of aquatic biological resources by industrial fisheries, the commercial stock of semi-migratory and river fish in the Volga-Caspian and North Caspian fishery subareas due to the unaccounted stocks of the Volga-Akhtuba floodplain can be increased by 10%, and for such fish as pike perch – by 13%, crucian carp – by 15%, silver breeds, bersh, silver carp and grass carp – by 50%, zope and sabrefish – by 100%, roach – by 200%. The commercial stock is currently being developed by amateur fishing, the volumes of which do not undermine the reproductive potential of the freshwater ichthyofauna of the Volga-Akhtuba floodplain.

Особенности биологии и промысла плотвы (Rutilus rutilus L.) в некоторых водоемах Республики Карелия

The article summarizes the results of long-term observations of the status of roach stocks in the main fishing waters of the Republic of Karelia (Lake Onega, Lake Ladoga, Vodlozerо and Topo-Pyaozerо reservoirs, Lake Syamozero). New data on its biology (distribution, linear and weight indicators, abundance, biomass) have been presented. There has been shown the dynamics of roach catch for a long-term period (1950–2017). It has been found that the fishing capacity of the represented roach populations corresponds to the production capabilities of its mature part and to the value obtained by biomass growth. The results of observations showed that in the studied water bodies the number and stocks of roach allow for greater volumes of catch than it is currently available and the total catch can be increased up to the calculated values of the allowable catch subject to rational fishing in the water bodies. Roach should be commercially caught at the age of 4+ years old. Given the interspecific contradictions of roach and bream, intensive fishing is recommended during the period of spawning in the straits, bays and mouths of rivers. For catching roach, it is necessary to use coastal-type fishing gear (trap nets, seines). The intensity of fishing and the increase in catches in reservoirs should be considered as mandatory measures in terms of biological reclamation in water bodies. When allocating catch quotas, the priority should be given to the most productive roach suppliers. The accompanying factor for the wide distribution of roach, along with other spring-spawning carp species (blue bream, bream), in our opinion, is warming of the climate in the region. In this regard, it is necessary to take measures to force catching the above fish species.

Effect of triiodothyronine on the activity and sensitivity of glycosidases to heavy metals (Cu, Zn, and Pb) in juvenile blue bream Ballerus ballerus (L.)

The influence of exogenous triiodothyronine (0.25 ng/mL) on the activity glycosidases (maltase, amylolytic activity) and their sensitivity to Cu, Zn and Pb ions (25 mg/L) has been studied in the whole organism of juvenile blue bream Ballerus ballerus (L.). We have found that the treatment of fish with triiodothyronine resulted in an increase in amylolytic activity. Maltase activity is not affected. In addition, the exposure to exogenous triiodothyronine results in a decrease in the sensitivity of glycosidase to the in vitro action of the ions of biogenic metals Cu and Zn and in an increase in the sensitivity of the maltase to the action of Cu, Zn, and Pb ions.

Pleiotropic effect of thyroid hormones on gene expression in fish as exemplified from the blue bream Ballerus ballerus (Cyprinidae): Results of transcriptomic analysis.

A pronounced pleiotropic effect of thyroid hormones on the regulation of gene expression in fish in postembryogenesis was demonstrated for the first time using larvae and juveniles of the blue bream Ballerus ballerus as an example. Genome-wide transcriptome sequencing (RNA-seq) identified 1212 differentially expressed genes in the brain and liver of fish kept in triiodothyronine solution (0.25 ng/mL). Our data show that the regulation of gene expression by thyroid hormones is widespread in nature: it involves not only the structural genes but also the regulatory genes. A significant number of genes under the control of thyroid hormones are involved in the determination of morphological traits.

Role of peptidases of the intestinal microflora and prey in temperature adaptations of the digestive system in planktivorous and benthivorous fish.

Many fish enzymatic systems possess limited adaptations to low temperature; however, little data are available to judge whether enzymes of fish prey and intestinal microbiota can mitigate this deficiency. In this study, the activity of serine peptidases (casein-lytic, mainly trypsin and hemoglobin-lytic, mainly chymotrypsin) of intestinal mucosa, chyme and intestinal microflora in four species of planktivorous (blue bream) and benthivorous (roach, crucian carp, perch) was investigated across a wide temperature range (0-70 °C) to identify adaptations to low temperature. At 0 °C, the relative activity of peptidases of intestinal mucosa (<13%) and usually intestinal microflora (5-12.6%) is considerably less than that of chyme peptidases (up to 40% of maximal activity). The level of peptidase relative activity in crucian carp intestinal microflora was 45% of maximal activity. The shape of t°-function curves of chyme peptidase also differs in fish from different biotopes. Fish from the littoral group are characterized by a higher degree of adaptation of chyme casein-lytic peptidases to functioning at low temperatures as compared to fish from the pelagic group. The role of intestinal microbiota and prey peptidases in digestive system adaptations of planktivorous and benthivorous fish to low temperatures is discussed.

Thyroid hormone divergence between two closely related but ecologically diverse cyprinid fish species (Cyprinidae)

Thyroid hormones (THs) are involved in regulation of many life history traits of fishes. Development, growth, reproduction and shaping the adult phenotypes were found to be regulated by THs. Regulatory evolution is one of the main factors driving morpho-ecological diversification and speciation. We tested a hypothesis whether closely related but ecologically diverged species may have a diverse level of THs. We compared seasonal levels of plasma concentrations of triiodothyronine (T3) in two cyprinid species, benthophagous bream Abramis brama and zooplanktivorous blue bream Ballerus ballerus. Significant differences in T3 concentrations were detected. B. ballerus had substantially reduced T3 levels as compared to most other species of fish. Two hypotheses explaining the thyroid divergence are discussed. Despite differences in absolute T3 concentrations, both species manifest similar seasonal cycling with increased plasma T3 levels in warmer seasons and decreased T3 in colder seasons. Several peaks of plasma T3 level were registered: at pre-spawning periods, at mid-summer and in the early autumn. The pre-spawning peak noted in cyprinids was a novel observation. Significant positive correlations were detected between water temperature and plasma T3 concentrations, as well as between the duration of daylight and T3 plasma concentrations in both species.

Characterization of intestinal digestive glycosidases in planktofagous and benthofagous fish species of the genus Ballerus (Cyprinidae)

The activity of hydrolases (maltase, sacharase, amylolytic activity) in the intestinal mucosa of the planktofagous blue bream Ballerus ballerus and benthofagous white-eye bream Ballerus sapa were investigated. The thermal characteristics of maltase hydrolysis (Topt and Eact) are similar in both species. The lower KM of maltase hydrolysis in the white-eye bream reflects a higher enzyme/substrate affinity and indicates a more effective carbohydrate hydrolysis in the bentho-versus planktofagous species. The glycosidase activity in the white-eye bream is twice as high as in the blue bream. This may be due not only to different feeding spectra and biochemical food composition but also to differencies in the thyroid status of species under consideration.