Juvenile Sterlet Research Articles

Trophological studies for calculating the receiving capacity in the interests of artificial reproduction of sterlet in the Volga-Caspian Fisheries Subdistrict

The article presents the results of trophological studies of pass-through and riverine fish species in the root channel and delta of the Volga River. The aim of the work was to establish food competitors of juvenile sterlet from artificial reproduction in the places of its release and feeding. As a result, the nutrition spectra and the degree of filling of the digestive tracts of a number of cyprinid, catfish and goby fish species were studied. Based on the conducted studies, the daily rations and the frequency of occurrence of forage organisms in the food of each fish species were determined. The obtained materials are included in the calculation of the receiving capacity and serve as the basis for determining the optimal volume of release of factory sterlet juveniles into the watercourses of the Volga River in the Astrakhan region.

Влияние кормовой пробиотической добавки «Ветоспорин-Ж» (Bacillus subtilis) и минеральной добавки «Цеолит» (опока) на проявление генотоксических эффектов в клетках крови молоди стерляди (Acipenser ruthenus) в условиях аквакультуры

In modern conditions of declining natural sturgeon populations in the Volga-Caspian basin, the role and importance of aquaculture is increasing. In the Astrakhan region, due to the presence of a large natural water fund, cage farming of fish, including sterlet, is widely developed. Cage farming of sturgeon in natural water bodies is associated with the impact of anthropogenic pollution, in this area it is associated with water pollution in the river delta Volga, and the deterioration of the hydrochemical regime, which directly affects fish farming. One of the factors of the negative impact of these changes in the aquatic environment is genotoxicity, the degree of manifestation of which can be assessed using accessible and modern methods, which include micronuclear and DNA comet tests. A serious consequence of the genotoxic effect of pollution is the formation of damage to the DNA of the fish body. The purpose of this work was to assess the frequency of appearance of micronuclei and the degree of DNA damage in the blood cells of juvenile sterlet, as well as the selection of functional additives in food that will reduce the effects of genotoxic pressure from a natural water source. In a scientific laboratory, a series of experiments was carried out on feeding juvenile sterlet delivered from a fish farm in the Volga delta. All juvenile sterlet, both at the beginning and at the end of the experiment, were characterized by a normal physiological state, low levels of DNA comets, and the number of erythrocytes with micronuclei was slightly higher than normal. As a result of experimental feeding, reliable data were obtained that food with the addition of the probiotic drug “Vetosporin-Zh” based on the bacteria Bacillus subtilis contributed to a significant increase in weight gain and body length. All analyzed indicators of DNA comets were significantly lower in the group that was fed with the introduction of a probiotic (the micronucleus test turned out to be less sensitive in this case). The mineral additive “Zeolite” did not show such effectiveness. Thus, the addition of Bacillus subtilis-based preparations when feeding juvenile sturgeon can be reasonably recommended to effectively reduce genotoxic stress for fish, mainly to reduce DNA damage.

Effects of selenomethionine on the growth, oxidative potential, digestive enzyme activity, and immune status of juvenile sterlet (Acipenser ruthenus)

Abstract In a 56-day experiment, the effects of selenium-enriched yeast (SeY) on the growth, enzymatic activity of the gastrointestinal tract, oxidative stress parameters, and selected immunological parameters of sterlet, Acipenser ruthenus (L.), were analyzed. The concentration of selenomethionine (SeMet) from SeY in the feed was 0 mg kg−1 (C), 0.7 mg kg−1 feed (S1), 1.4 mg kg−1 feed (S2), and 2.1 mg kg−1 feed (S3). Statistically significant differences were found in the final fish body weight between the control and groups S1 and S3. A significant increase in lipase activity was found in the initial section of the small intestine of fish from group S3. The highest activity of the antioxidant enzymes glutathione peroxidase and superoxide dismutase was recorded in the liver of fish from group S2. Analyses of non-specific humoral response parameters showed an increase in ceruloplasmin activity in group S1. The lowest active dose of SeMet derived from yeast tested in this study that stimulated humoral immunity and fish growth was 0.7 mg kg−1 feed (S1).

Physiological and biochemical studies of young sterlet sturgeon (Acipenser ruthenus L.) in the lower reaches of the Volga river

In conditions of a decrease in the number of rolled sturgeon larvae in the lower reaches of the Volga River, an urgent issue is the study of the physiological and biochemical parameters of the fish organism. The purpose of this work is to conduct physiological and biochemical studies of juvenile sterlet (Acipenser ruthenus L, 1758). The study of fish was carried out using the methods of classical histology and biochemistry. The degree of damage to the gills and liver was assessed on a scale from 1 to 5 points. The content of total lipids and water-soluble protein in the muscle tissue of sterlet fingerlings was studied as biochemical parameters. The morphological picture of the gills of 80% of the fish corresponded to a weakly pronounced character of changes (2 points), while in others it was characterized by the presence of a borderline state between weakly pronounced changes and moderate injuries (2–3 points). Six types of disorders were found in the gills: hyperplasia of the respiratory epithelium of lamellae, dilation of the blood vessel of the filament, goblet-shaped swellings of the apical part of the filament, invasions, expansion of the apical part of the lamellae, proliferation of connective tissue of lamellae. In the liver of 80% of fish, a borderline state was recorded between mild changes and moderate damage (2–3 points), in 13.3% of individuals the liver had mild damage (2 points), in 6.7% there were medium damage (3 points). Four types of disorders were found in the liver of juvenile sterlet: fullness of the liver capillaries, pronounced venous fullness, cavities, capillary dilation. In the muscle tissue of fingerlings, the concentrations of total lipids were in the range of 1.39–5.28%, and water-soluble protein — 45.59–57.97 mg/g. The study of the physiological and biochemical parameters of juvenile sturgeon in the lower reaches of the Volga River is very important for the biology of the species and monitoring the natural reproduction of these valuable fish species.

Early nutritional programming in sterlet sturgeon (Acipenser ruthenus) with dietary soybean meal: Assessment of growth performance, body composition, and expression of GH, IGF-I, and Ghrelin genes.

This study was performed to assess the impacts of introducing diets containing different levels of soybean meal (SBM) to sterlet sturgeon (Acipenser ruthenus) larvae on growth performance, body composition, and molecular responses in the juvenile stage. The sterlet larvae (57.68 ± 0.66 mg) were weaned onto the formulated diets as follows: a control diet containing 60% fishmeal (FM), and three experimental diets with replacement levels of 15% (SBM15), 30% (SBM30), and 45% (SBM45) of FM with SBM. Then, a total of 260 fish (initial weight: 323.33 ± 11.76 mg) were fed the four different diets for 28 days in triplicates (phase 1, nutritional programming, NP). All treatments were then fed with the FM diet in phase 2 (common phase), and in phase 3 (challenge phase), all experimental groups (6.14 ± 0.08 g) were transitioned to SBM45 for 28 days. At the end of phases 1 and 2, growth performance showed no significant differences among the groups (P > 0.05), while significantly improved in SBM45 than the control at the end of phase 3 (P < 0.05). No significant differences were found among the groups in any phases for whole body composition (P > 0.05). Additionally, the total saturated fatty acids were significantly higher in SBM-based diets than FM at the end of phase 3 (P < 0.05). The mRNA of GH, IGF-I was significantly affected by variation of FM replacement level (P < 0.05). The expression level of Ghrelin was up-regulated in fish fed SBM at the end of phase 3 (P < 0.05). Our findings revealed that NP can positively enhance the adaptation of juvenile sterlet sturgeon to 45% SBM when exposed to the same diets at the larval stage. Further research is being carried out to provide valuable insights into the underlying mechanisms of digestive performance for this species.

The effect of a complex bajillary microbiological preparation on the growth and indicators of the internal environment of the body in juvenile siberian sterlet Acipenser ruthenus marsiglii Brandt

Probiotic drugs are a product of agricultural biotechnology. Their use for feeding fish and other aquatic organisms, especially coldwater ones, is currently insufficiently studied. The addition of a bacillary probiotic preparation (based on two species of bacteria of the genus Bacillus in fish feed) was carried out. These microorganisms are symbionts of many warm-blooded animals and are not a specific intestinal microflora of sturgeon. Experimental work was carried out in the UZ of the Aquaculture Research Center of the Novosibirsk State Agrarian University. Studies have shown that the addition of a bacillary probiotic drug in doses of 500 and 1000 mcg per kg of feed when feeding juvenile sterlet weighing 0.27–0.29 kg to a weight of 0.375–0.384 kg for 40 days did not have a positive effect on fish growth in experimental groups. All physiological parameters, such as oxygen consumption, the state of white and red blood, lay within the limits typical for sturgeon fish contained in the ultrasound. At the same time, there is an increase in leukocytosis in fish in the group receiving 1000 mcg/kg of feed within 106,7±16,7–143,8±56,3×103/mcl by an average of 22.3% compared to the control. The oxygen consumption level in the fish in the control group was 18.7–28.31% lower than in the experimental ones. There were no significant changes in the growth rate of fish receiving different doses of the drug. The average daily increase in the group receiving 500 mcg/kg of feed was 4.52 g per day, 1000 mcg/kg — 4.44 g per day. On average, on the 30th day of observations, when compared with the control, the growth rate of juvenile sterlet in the experimental groups was lower by 25.16 and 38.6%. At the same time, the safety of fish in the control group was 96.55, and in the experimental group it was 100%.

How does induced polyploidy affect the swimming and physiological performance of juvenile sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baerii) and their reciprocal hybrids?

How does induced polyploidy affect the swimming and physiological performance of juvenile sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baerii) and their reciprocal hybrids?

Dietary effect of actinidin enzyme on growth, digestive enzymes activity, immunity, liver and intestine histology of juvenile sterlet sturgeon (Acipenser ruthenus)

This 56-day experiment examined the effect of actinidin added to commercial feed at concentrations of 0 g (control group C), 10 g (A1 group) and 20 g (A2 group) kg−1 diet on growth, feed utilization, intestinal morphology, digestive enzyme and immune response of juvenile sterlet (Acipenser ruthenus). A total of 270 juvenile sterlet with an average body weight of (46.21 ± 0.37 g) were divided into nine tanks (280 L for each), with 30 fish per tank (three replicates each) under a recirculating aquaculture system (RAS). At the end of the experiment, distinct differences in the mean body weights of the fish were observed, with the greatest differences (P < 0.05) noted in A1 group (112.88 ± 1.20 g). The mean body weight in group A2 (106.40 ± 1.37 g) was statistically significantly (P < 0.05) higher compared with control group C (87.80 ± 1.51 g). A significant decrease in the activity of alkaline phosphatase (ALP) was noted in the liver in A2 group (57.72 IU g−1) compared with the control group (127.38 IU g−1). In the hindgut part of the intestine, a significant increase in the activity of alkaline phosphatase (ALP) was noted in A2 group (179.06 IU g−1) compared with the control group (92.44 IU g−1). An analysis of the immunity response showed an increase in the lysozyme value in A1 and A2 groups. In these groups, the immunoglobulin (Ig) content increased statistically significantly compared with the control group. A significant increase was noted in the phagocytic killing activity in the pronephros of fish fed feed supplemented with actinidin. A higher metabolic activity of macrophages and a higher phagocytic killing activity were also noted in the spleen in A1 and A2 groups. Based on the experiment, it can be concluded that the actinidin has a positive effect on Sterlet growth and stimulates its immune system.

Effects of Dietary Taurine on Growth, Body Composition, Blood Parameters, and Enzyme Activities of Juvenile Sterlet (Acipenser ruthenus)

To evaluate the effects of dietary taurine on Acipenser ruthenus, a total of 180 fish with an initial weight of 14.13 ± 0.10 g, were stocked into 15 (300 liters) tanks (12 fish/replicate) for 70 days. Five experimental diets (38.60% crude protein and 18.78% crude lipid) supplemented with 0 (T0), 5 (T5), 15 (T15), 30 (T30), and 50 (T50) g/kg taurine were used. The experimental fish were fed to visual satiation four times daily. At the end of the experimental period, weight gain, thermal growth coefficient, and survival in fish fed T30 diet was higher ( P &lt; 0.05 ) than other experimental fish. Food conversion ratio in all treatments containing taurine was significantly lower than T0 treatment ( P &lt; 0.05 ). The highest and the lowest total essential amino acids of muscle were found in T50 and T0 treatments, respectively. The highest serum cholesterol and low-density lipoprotein levels were observed in the T30 treatment ( P &lt; 0.05 ). An increasing trend was observed in the values of alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase activities of serum from T0 to T30 treatments and the highest level was recorded in T30 ( P &lt; 0.05 ). The highest lysozyme, trypsin, chymotrypsin, alkaline phosphatase, lipase, and amylase activities were also observed in T30. Catalase activity in T15 was higher than other treatments ( P &lt; 0.05 ). Malondialdehyde activity in T0 was significantly higher than other experimental treatments ( P &lt; 0.05 ). The highest total numbers of bacteria and lactic acid bacteria of the gut was recorded in T30 and T5, respectively. The overall results indicate that the T30 experimental diet induced the improvement of growth performance, hepatic, digestive, and antioxidant enzyme activities in A. ruthenus.

Technological factors in the cultivation of sterlet sturgeon planting material in a recirculation aquaculture system

Recently, it has not been possible to engage in natural reproduction of sturgeons in Dagestan, because the spawning rivers Terek and Sulak are regulated, and the passage to the spawning grounds is completely closed by dams. There is only one way out for the restoration of sturgeon stocks it is artificial reproduction through industrialization and the creation of complex, closed regulated fish farms that can function both in the form of small fish farms and in the form of large holdings. The purpose of the work was to study technological factors in the cultivation of sterlet sturgeon planting material in a recirculation aquaculture system. The object of the study was a population of sterlet sturgeon (Asirepseg ruthenus Linnaeus, 1758) – a freshwater fish species of the sturgeon family. The study material was normally pigmented and albino (colored) sterlet with an average initial weight of 60 g. Under the conditions of the Republic of Dagestan studies have been carried out to establish the influence of a complex of biotic and abiotic factors (temperature, oxygen, planting density, feed grade, meat and bone attractant, probiotic Subtilis) on the growth, morphometric indicators and survival of juvenile sterlet sturgeon in the recirculation aquaculture system. The fish-breeding and biological characteristics of pigmented and albino sterlet have been given. It has been established that the design features of the recirculation aquaculture system did not allow to meet the biological needs of sterlet in water. The flow rate of water entering fish tanks was limited to 10 l/min per 1 m³, which provided a water change in 1 hour 40 minutes at a standard of 20–60 minutes. The optimal planting density of sterlet with an initial body weight of 58–64 g under conditions of limited water supply (10 l/min/m³) was the density of 250 pcs. /m³. The effectiveness of using two formulations of compound feed when growing both normally pigmented fish and their albinos showed that the highest fish-breeding indicators were obtained in normally pigmented sterlet when feeding with Sturgeon Grower No. 4 (47/13). The economic effect amounted to 373,5 rubles/m³. In albinos, the highest fish-breeding indicators were obtained when feeding productional feed Sturgeon grower 46/18 with. The economic effect was 285,0 rubles/m³.

Beneficial effects of dietary papain supplementation in juvenile sterlet (Acipenser ruthenus): Growth, intestinal topography, digestive enzymes, antioxidant response, immune response, and response to a challenge test

Juvenile sterlet (Acipenser ruthenus) were fed commercial feed (group C) and experimental feed supplemented with papain in doses of 10 g kg−1 feed (P1) and 20 g kg−1 feed (P2) for eight weeks. Growth, digestive enzyme activity, immunity parameters, pathological changes of the liver and intestine, proximate body composition, and oxidative response were assayed. A challenge test with Yersinia ruckeri was also performed. The final body weights of groups P1 (107.07 ± 7.66 g) and P2 (111.98 ± 1.93 g) were significantly (P < 0.05) higher compared to the control group (99.73 ± 2.71 g). The height of the intestinal enterocytes was the greatest in group P2, and the highest supranuclear surface of the intestinal enterocytes was noted in groups P1 and P2. The activities of α-amylase, trypsin, lipase, and leucine aminopeptidase were significantly (P < 0.05) higher in the posterior intestine of the fish from group P2 than in the other dietary treatment groups. Ceruloplasmin, total immunoglobulin (Ig), the metabolic activity of splenic macrophages (PMA), and the potential killing activity of splenic phagocytes (PKA) were significantly higher in groups P1 and P2 compared with the control group. The proliferative activities of spleen T and B-lymphocytes were significantly (P < 0.05) higher in group P2 in comparison to the control group and group P1. Total antioxidant status (TAS), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were significantly increased in groups P1 and P2 compared with the control group. The glutathione reductase (GLURED) activities decreased significantly (P < 0.05) with increasing levels of papain supplementation. Furthermore, during the challenge test, fish survival was significantly higher in groups fed feed supplemented with papain. Finally, the current study indicated that supplementing feed with doses of 10 g and/or 20 g papain kg−1 for a period of 56-days improved growth efficiency and feed utilization and also stimulated immunity in aquaculture conditions.

Effects of different levels of combo multi-enzyme on growth performance, blood factors and immunity of juvenile Sterlet (Acipenser ruthenus)

Effects of different levels of combo multi-enzyme on growth performance, blood factors and immunity of juvenile Sterlet (Acipenser ruthenus)

The role of ichthyopathological observations in the industrial reproduction of sterlet for the tasks of release into the Kuibyshev reservoir

The features of the industrial reproduction of sterlet in the Middle Volga region are considered. The necessity of further increasing the volume of production and release of juvenile sterlet to the Kuibyshev reservoir is shown. An increase in the relevance of research works in the field of sturgeon ichthyopathology has been noted. The importance of carrying out ichthyopathological observations is shown both for ensuring the stability and efficiency of production, and for preserving the natural population of sterlet in the Kuibyshev reservoir. The article considers the relative novelty of ichthyopathology as a science and the discrepancy between normative legal acts regulating ichthyopathological observations in Russia. The industrialization of aquaculture forms is shown. The emergence of new sturgeon diseases specific to high-intensity fish farming was noted. The results of experiments on the use of inorganic drugs for the treatment of sturgeon nutritional diseases are presented.

Immunohistochemical mapping of thymic microenvironment in sterlet (Acipenser ruthenus)

In this study, we describe the immunohistochemical characterisation of the thymus, the main lymphoid organ, in sturgeon. The wide range cytokeratin, vimentin, S-100 protein, LCA (CD45) and CD3 were selected as the immunohistochemical markers to map the thymus in juvenile sterlet (Acipenser ruthenus). The epithelial cells and Hassall’s corpuscles were labelled with a wide range cytokeratin. The fibroblasts and connective tissue within the thin fibrous capsule on the thymic surface expressed vimentin positivity. The stromal reticular cells were S-100 protein positive. The Leukocyte Common Antigen LCA (CD45) was negative on the thymic lymphocytes. The CD3 was negative on the thymic lymphocytes with cross-reactivity on the non-targeted structures. In conclusion, the commercially available antibodies against the wide range cytokeratin, vimentin and S-100 protein can be used to differentiate components of the sturgeon thymus, while the LCA (CD45) and CD3 application failed. We suggest that further studies are needed to generate fish specific antibodies.

The use of bromelain as a feed additive in fish diets: Growth performance, intestinal morphology, digestive enzyme and immune response of juvenile Sterlet (Acipenser ruthenus)

Bromelain is a proteolytic enzyme extracted from Ananas comosus and has great potential to affect several physiological functions. The current study examined the effect of bromelain added to commercial feed at concentrations of 0 g (control), 10 g (B1) and 20 g (B2) per kg diet on growth, feed utilization, intestinal morphology, digestive enzyme and immune response of juvenile Sterlet (Acipenser ruthenus) for 56 days. At the end of this experiment, the highest final body weight was detected in fish fed diet of B2 compared to control. The protein content of whole fish was higher in fish fed diet of B1 and B2, but the content of calcium, iron, copper and zinc was noted lower in fillets of fish fed diet of B1 and B2. Supplementation with bromelain significantly increased the height of mucosal folds, enterocytes and the supranuclear zone of the epithelial cells compared to control diet. The enzymatic activity of lipase and pepsin was significantly (p 0.05) difference was found in ceruloplasmin, metabolic activity of spleen macrophages and potential killing activity of spleen phagocytes between different treatments.

Sedative Efficacy of Tobacco Extract, Clove Oil, Tricaine Methanesulfonate, and Ketamine: Effects on Hematological Parameters and Blood Biochemical Profile in Sterlet

AbstractThis study was carried out to evaluate the efficacy of four sedatives, including tobacco extract, clove oil, tricaine methanesulfonate (MS‐222), and ketamine, in juvenile Sterlet Acipenser ruthenus by use of two experiments. First, fish with an average weight (±SD) of 64.1 ± 3.4 g were exposed to immersion at six concentrations of each sedative, including clove oil at 14, 35, 56, 77, 98, and 119 mg/L; MS‐222 at 45, 50, 55, 60, 65, and 70 mg/L; ketamine at 35, 37.5, 40, 42.5, 45, and 50 mg/L; and tobacco extract at 375, 450, 525, 600, 675, and 700 mg/L. Induction time (deep induction) and recovery time were measured, and the concentrations inducing lower induction time and recovery (i.e., optimum concentrations) of each sedative were obtained as follows: 56 mg/L for clove oil, 60 mg/L for MS‐222, 45 mg/L for ketamine, and 675 mg/L for tobacco extract. To evaluate the impact of the selected concentration of each sedative on physiological responses of Sterlet, the hematological indices, plasma cortisol, glucose, and lactate concentrations were measured. Additionally, one nonexposed group was considered as a control group. Significant changes were revealed in all hematological parameters except for mean corpuscular hemoglobin concentration and monocytes percent. Biochemical parameters were measured at 0, 1, 3, and 6 h after induction. Significant changes were found in cortisol and lactate levels for all treatments except clove oil. Glucose concentration changed significantly only in the control group. Given that fish sedated with clove oil did not indicate changes in blood chemistry, clove oil may be the more effective sedative according to our results.

Na+/K+-ATPase ACTIVITY IN VARIOUS ORGANS OF THE STERLET (ACIPENSER RUTHENUS L.) UNDER CHANGES IN ENVIRONMENTAL FACTORS

Studies of the mechanisms regulating the ion-salt and acid-base balance in the organism of juvenile sterlet acquire special relevance in connection with its possible acclimation to habitats with varying salinity and acidity. In aquarium conditions, two series of experiments were carried out, investigating the effect of ambient salinity and pH on the activity of Na + /K + -ATPase in the gills and muscles of juvenile sterlet, Acipenser ruthenus L. (average body mass ~ 50 g): in the first series juvenile sterlet were reared in three aquariums with different salt concentrations (control – 0.3, 3, 6 ‰); in the second series juvenile fish were kept in water with 0.3 ‰ salt concentration in three aquariums with different pH values: 7.0, 8.0, and 9.0. A significant (р < 0.05) increase in Na + /K + -ATPase activity was observed in the gills and muscles of fish under salinity increase to 6 ‰, and when the water pH in the aquariums increased from 7.0 to 9.0, the activity of the enzyme declined significantly (p < 0.05). It is shown that activation / reactivation of Na + /K + -ATPase in the gills and muscles of fish is one of the important mechanisms of biochemical adaptation in juvenile sterlet, aimed at maintaining homeostasis when acclimating to a change in ambient salinity and pH.

How do long-term effects of temperature influence sex ratio, somatic and gonadal development in juvenile sterlet (Acipenser ruthenusL.)-An additional climate change consequence?

In this paper, the effects of temperature on the production performance values, as well as on sex differentiation and gonad development, of juvenile sterlet were investigated. For this purpose, fry were reared in the recirculating aquaculture system at three different temperatures (15, 20, and 25°C) in four replicate groups each for 140 days (10–150 dph). Fish were fed mainly with commercial diet. The growth rate in this period was significantly affected by temperature. The best performance values in terms of daily growth rate, thermal growth coefficient, and yield were registered at 20°C, indicating that this value to be near, or close to, the optimal for juvenile sterlet. Gonad samples were taken for histological analysis which revealed that the increased temperature did not cause significant differences in the sex ratio between treatments, but at 25°C resulted in significant deviation from the theoretically expected 1:1 gender ratio to favouring males. We have also found that increased temperature at 25°C accelerated germ cell development. These results indicate that rearing of sterlet juveniles at about 20°C temperature could be considered optimal both from aquaculture, as well as from species conservation viewpoints.

Effects of dietary administration of purple coneflower on growth, hematology and non-specific immune parameters in juvenile sterlet (Acipenser ruthenus)

This study was conducted to evaluate the effects of purple coneflower (Echinacea purpurea) (EP) on growth and blood parameters in juvenile sterlet (Acipenser ruthenus). One hundred and eighty fish (mean weight 75±1SDg) divided into 12 tanks (n=15) after adaptation period. Base diet was supplemented with 0 (control), 0.5, 1 and 2g/Kg EP to formulate experimental diets. Fish were fed daily at a rate of 3% of body weight. After 60 days, all fish were weighted for growth analysis and blood samples were collected to assess hematological parameters. Results showed that growth indices were not significantly affected by EP extract (p>0.05). There was no notable differences in hematological parameters, including red blood cell, white blood cells, hemoglobin, lymphocyte and neutrophil percentage in treatments compared to the control group (p>0.05). Total protein, albumin, globulin and albumin to globulin ratio did not reveal any differences between experimental and control groups (p>0.05). Lysozyme and Immunoglobulin M in fish fed with EP were higher, compared to the control group (p<0.05). It could be concluded that diet supplementation with EP improved immune system function in A. ruthenus, but had no effect on growth in this species.

Effects of feeding, digestion and fasting on the respiration and swimming capability of juvenile sterlet sturgeon (Acipenser ruthenus, Linnaeus 1758).

The objective of this study is to provide information on changes in swimming capability and respiration of the sterlet sturgeon (Acipenser ruthenus, Linnaeus 1758) caused by different levels of fasting. Before testing, the four groups of sturgeon (body length: 12.1-15.4cm, body mass: 10.0-20.2g) fasted for 6h, 2days, 1 and 2weeks, respectively. Swimming tests were then performed to measure critical swimming speed and oxygen consumption at 20±0.5°C. Results show: (1) Fasting times shorter than 2days has little effect on swimming capability, but it decreases significantly when the fasting time is longer than a week. (2) After 2weeks of fasting, swimming efficiency is significantly reduced. (3) Anaerobic capacity increases when digestion nears completion.