Juvenile Sterlet Research Articles

Effects of acute temperature change on the metabolism and swimming ability of juvenile sterlet sturgeon (Acipenser ruthenus, Linnaeus 1758)

The objective of this study was to provide information on changes in the metabolism and swimming ability of juvenile sterlet sturgeon, Acipenser ruthenus, caused by acutely low or high temperatures. Changes in critical swimming speed (Ucrit), oxygen consumption rate (MO2), tail beat frequency (TBF) and tail beat amplitude (TBA) were observed with a Steffensen-type swimming respirometer, an oxygen electrode and a camera at different swimming speeds at three temperatures: 5°C, 15°C, and 25°C. Fish tested at 5°C and 25°C were maintained at 15°C (near optimal) for one week to simulate conditions below a dam. The Ucrit value decreased significantly during acute temperature changes at 5°C and 25°C; Ucrit was highest near the optimal temperature. Oxygen consumption rate (MO2) increased with the swimming speed at 15°C; however, at 25°C and 5°C, the MO2 decreased with the swimming speed. Both TBA and TBF decreased at 5°C and 25°C compared to values at 15°C. The slopes of the regression lines (TBF/U) at 5°C and 25°C seemed lower compared to 15°C.

Effect of temperature on the activity of proteinases in potential food items of fish

The effect of temperature on some characteristics of proteinases functioning in the tissues of food items of fish (juvenile sterlet Acipenser ruthenus L., Black Azov Sea tyulka Clupeonella cultriventris (Nordm.), perch Perca fluviatilis L. and fish of fam. Cyprinidae) was studied for the first time. The differences in the shapes of curves describing the temperature dependence of prey-tissue enzymes hydrolyzing casein and hemoglobin were revealed. As a rule, the values of the energy of activation of caseinolytic proteinases of prey tissues are higher than those of hemoglobinolytic proteinases. The lowest values of this parameter are the characteristic of tissue hemoglobinolytic proteinases of perch and cyprinids. This suggests better adaptability of these fish tissues for functioning at low temperatures. Revealed differences show that thermal characteristics of tissue proteinases of potential food items of fish depend on species phylogenetic specificity.

Growth and feeding of juvenile sterlet Acipenser ruthenus L. (Acipenseridae) in a pond after various durations of being preliminarily kept in tanks

It is shown that the level of information richness of the environment in which the juvenile fish were raised at early stages of ontogenesis is one of the determining factors for the development of the most important adaptive patterns of behavior. Minimal values of fullness index, lower body weight, and shorter length, along with a feeding spectrum strongly differing from that in natural conditions, are characteristics of juvenile fish kept preliminarily in the hatchery. The food of this group of fish is dominated by organisms of epibenthos, which may have been detected by the fish using gustatory and tactile receptors. At the same time, the proportion of infaunal invertebrates, the detection of which is only possible using olfaction and electric reception, is minimal. The prolonged development of juvenile fish under conditions of sensory deprivations leads to inadequate behavioral skills, making the process of conventionally reflective “switching” upon the release of such juvenile fish in the wild more difficult.

Effects of Dietary Garlic Extracts on Whole Body Amino Acid and Fatty Acid Composition, Muscle Free Amino Acid Profiles and Blood Plasma Changes in Juvenile Sterlet Sturgeon, Acipenser ruthenus.

A series of studies were carried out to investigate the supplemental effects of dietary garlic extracts (GE) on whole body amino acids, whole body and muscle free amino acids, fatty acid composition and blood plasma changes in 6 month old juvenile sterlet sturgeon (Acipenser ruthenus). In the first experiment, fish with an average body weight of 59.6 g were randomly allotted to each of 10 tanks (two groups of five replicates, 20 fish/tank) and fed diets with (0.5%) or without (control) GE respectively, at the level of 2% of fish body weight per day for 5 wks. Whole body amino acid composition between the GE and control groups were not different (p>0.05). Among free amino acids in muscle, L-glutamic acid, L-alanine, L-valine, L-leucine and L-phenylalanine were significantly (p<0.05) higher in GE than in control. However, total whole body free amino acids were significantly lower in GE than in control (p<0.05). GE group showed higher EPA (C22:6n3) and DHA (C22:5n3) in their whole body than the other group (p<0.05). In the second experiment, the effects of dietary garlic extracts on blood plasma changes were investigated using 6 month old juvenile sterlet sturgeon averaging 56.5 g. Fish were randomly allotted to each of 2 tanks (300 fish/tank) and fed diets with (0.5%) or without (control) GE respectively, at the rate of 2% of body weight per day for 23 d. At the end of the feeding trial, blood was taken from the tail vein (n = 5, per group) at 1, 12, and 24 h after feeding, respectively. Blood plasma glucose, insulin and the other serological characteristics were also measured to assess postprandial status of the fish. Plasma glucose concentrations (mg/dl) between two groups (GE vs control) were significantly (p< 0.05) different at 1 (50.8 vs 62.4) and 24 h (57.6 vs 73.6) after feeding, respectively, while no significant difference (p>0.05) were noticed at 12 h (74.6 vs 73.0). Plasma insulin concentrations (μIU/ml) between the two groups were significantly (p<0.05) different at 1 (10.56 vs 5.06) and 24 h (32.56 vs 2.96) after feeding. The present results suggested that dietary garlic extracts could increase dietary glucose utilization through the insulin secretion, which result in improved fish body quality and feed utilization by juvenile sterlet sturgeon.

Effects of Dietary Garlic Extract on Growth, Feed Utilization and Whole Body Composition of Juvenile Sterlet Sturgeon (Acipenser ruthenus).

This study was carried out to investigate the supplemental effects of dietary garlic extract (GE) on growth performance of juvenile sterlet sturgeon (Acipenser ruthenus). The first experiment was designed to determine the optimum levels of garlic extract as growth promoter during 10 weeks. Three groups (two replicates/group) of 240 fish with mean body weight of 85 g were fed with diets containing 0 (control), 0.5 and 1.0% of GE. The highest weight gain (%) and feed efficiency (%) were found in fish groups fed with diet containing 0.5% GE. Subsequently, the supplemental effects of dietary GE was studied on growth of juvenile sterlet sturgeon (Acipenser ruthenus) with an average body weight of 59.6 g. Fish cultured in freshwater were randomly allotted to each of 10 tanks (two groups of five replicates, 20 fish/tank) and fed diets with 0.5% GE or without GE (control), respectively, at the level of 2.0% of fish body weight per day for 5 weeks. Weight gain (51.1%), feed efficiency (79.1%), specific growth rate (1.18%) and protein efficiency ratio (1.50) of fish fed 0.5% GE were significantly (p<0.05) higher than those fish fed the control diet. Significantly higher protein (PRE 20.4%) and lipid retention efficiencies (LRE, 74.5%) were also found in 0.5% GE group (p<0.05). The present results suggested that dietary GE could improve growth and feed utilization of juvenile sterlet sturgeons.

Feeding of juvenile sterlet (Acipenser ruthenus, Acipenseridae) in the Danube River midstream

The present paper provides the results of the study on feeding of juvenile (underyearlings and age 2+) sterlet (Acipenser ruthenus) caught in the Danube River in 2002–2003. The full spectrum of food items found in the fish stomachs was identified. The seasonal patterns of food composition are revealed. It is shown that juvenile sterlet in the Danube feeds mainly on larvae of chironomids and trichopterans, amphipods, and leeches. The organisms typical for lithophilic and lithorheophilic biocenoses play considerable role in the feeding of sterlet. Mean daily gains of body length and weight in the sterlet underyearlings are calculated.

Effects of Starter Diets on Pancreatic Enzyme Activity in Juvenile Sterlet (Acipenser ruthenus)

Nine-day-old sterlet (Acipenser ruthenus) larvae were reared for 21 days on one of three commercial diets with different protein and fat contents: Bio Kyowa, Aglo Norse, or Perla Larva Proactive. At the end of the experiment, the sterlet juveniles were sampled for histological analysis of the pancreas and evaluation of lipase, trypsin, and amylase activity. Fish fed the Bio Kyowa and Aglo Norse diets were the largest. Survival was highest in the Aglo Norse group. There were no differences between groups in histologi- cal analysis of the pancreas, and no histological anomalies. The highest lipase activity was observed in fish fed the diet with the highest lipid content (21%) - the Aglo Norse diet. Trypsin activity was higher in fish fed Bio Kyowa with a protein content of 55% than in fish fed Aglo Norse with a pro- tein content of 59%.

Seasonal changes in condition, hepatosomatic index and parasitism in sterlet (Acipenser ruthenus L.)

Measurements of biomarker responses in fish from contaminated sites could provide valuable data for environmental risk assessment. Biomarkers are sensitive to both environmental pollution and confounding factors that are not related to pollution (e.g., season, nutritional status, and population density). Unfortunately, data about the latter group are scarce. Therefore, juvenile sterlet (Acipenser ruthenus L.) specimens were collected on a monthly basis from the Danube River from September 2002 through August 2003 to determine if seasonal changes exist in condition, hepatosomatic index, and parasitism. Fulton condition factor (FCF range: 0.27 - 0.79), hepatosomatic index (HSI range: 1.14 - 6.67) and Skrjabinopsolus semiarmatus parasite prevalence (range: 37.9 - 85.7 %), intensity (range: 1 - 337 parasites per fish) and the mean intensity (range 9.6 - 89.2) in sterlet showed significant seasonal variations. This study pointed out that biomarker sampling on different locations has to be performed within the short time frame in order to avoid differences generated by confounding factors. Better understanding of the life cycle of S. semiarmatus and sensitivity of different phases to pollution is needed.

Alteration of thermoregulation behavior in juvenile fish in relation to satiation level

Thermoregulation behavior of satiated and hungry juvenile sterlet Acipenser ruthenus, the Siberian sturgeon Acipenser baeri, and the goldfish Carassius auratus was studied. Significant alterations of thermoregulation behavior appear in juvenile fish one day after food deprivation. Hungry fish preferred, on average, lower temperatures, their temperature range was broader, and the locomotor activity was higher than in satiated fish.

Comparative analysis of morphometric characters of juvenile sterlet Acipenser ruthenus L. from natural population and aquaculture

A comparative analysis was performed on sixteen morphometric characters, in three different juvenile sterlet Acipenser ruthenus L. populations. Specimens were collected from a wild population in the Serbian part of the Danube River (n = 46), from aquaculture stocks in the Czech Republic originating from Russia (n = 40), and aquaculture stocks in the Slovak Republic originating from Slovakian part of the Danube River (n = 28). Average values for total length were 29·9 ± 3·9 cm, 29·1 ± 3·7 cm and 27·3 ± 7·7 cm for Serbia, Czech Republic and Slovak Republic, respectively. Populations were compared using t‐test and sequential Bonferroni correction for multiple comparisons was applied in order to determine significant differences between them. Results of analysis showed that all three populations differed in prebarbel length, interocular distance and maximum head width. Although all these characters are head‐related, head length itself was very uniform among all populations. The natural population from the Serbian part of the Danube River differed from the populations reared in aquaculture in seven morphometric characters. The two populations reared in aquaculture consistently showed lower morphological variability than the wild population, even though they had different genetic backgrounds (Russia and Slovakia). Future genetic studies will show if this tendency is caused by a reduction in genetic variability.