Sturgeon Fry Research Articles

The possibilities of using of captive and domestic broodstocks for saving of natural populations: 1. Acipenseriformes (part 1)

In last years the stocks of Russian species of sturgeons decreased to critical level which can be followed by their complete extinction in nature. As a result, the number of sturgeons beginning spawning migration into rivers are extremely small, but Astrakhan sturgeon hatcheries continue release annually about 35 mln fry using own broodstocks of two types — captive and domestic ones. However the releases of offspring of domestic broodstock are extremely discussible. On one hand, creation of such broodstocks could avoid the complete extinction of natural populations of Adriatic sturgeon Acipenser naccari in Po River and European sturgeon A. sturio in Gironde estuary. On other hand, long-term practice of commercial fish farming had shown that even the accidental refugees from sea cages or fresh-water ponds caused great harm to natural populations of same species. Hatchery individuals were undergoing different selection than fish in wild nature and had poorly formed reflexes (searching for food and avoiding predators). Besides a progressive decrease in genetic diversity with each generation could be seen in such fry due to limited number of parents (the Ryman-Laikre effect). However the creation of captive and domestic broodstocks of endangerous species and subspecies (Azov beluga Huso huso maeotica, fringebarbel sturgeon Acipenser nudiventris, Sakhalin sturgeon Acipenser mikadoi) and extinct populations (Baltic sturgeon Acipenser oxyrinchus) remains the only way to release hatchery juveniles. The first part of presented review is devoted to creation and using of captive and domestic broodstocks for conservation-type sturgeon fry releases in Russia and other countries.

The possibilities of using of captive and domestic broodstocks for saving of natural populations: 1. Acipenseriformes (part 2)

In last years the stocks of Russian species of sturgeons decreased to critical level which can be followed by their complete extinction in nature. As a result, the number of sturgeons beginning spawning migration into rivers are extremely small, but Astrakhan sturgeon hatcheries continue release annually about 35 mln fry using own broodstocks of two types — captive and domestic ones. However the releases of offspring of domestic broodstock are extremely discussible. On one hand, creation of such broodstocks could avoid the complete extinction of natural populations of Adriatic sturgeon Acipenser naccari in Po River and European sturgeon A.sturio in Gironde estuary. On other hand, long-term practice of commercial fish farming had shown that even the accidental refugees from sea cages or fresh-water ponds caused great harm to natural populations of same species. Hatchery individuals were undergoing different selection than fish in wild nature and had poorly formed reflexes (searching for food and avoiding predators). Besides a progressive decrease in genetic diversity with each generation could be seen in such fry due to limited number of parents (the Ryman-Laikre effect). However the creation of captive and domestic broodstocks of endangerous species and subspecies (Azov beluga Huso huso maeotica, fringebarbel sturgeon Acipenser nudiventris, Sakhalin sturgeon Acipenser mikadoi) and extinct populations (Baltic sturgeon Acipenser oxyrinchus) remains the only way to release hatchery juveniles. The first part of presented review is devoted to creation and using of captive and domestic broodstocks for conservation-type sturgeon fry releases in Russia and other countries.

Dietary Mentha piperita essential oil loaded in chitosan nanoparticles mediated the growth performance and humoral immune responses in Siberian sturgeon (Acipenserbaerii)

Siberian sturgeon (Acipenser baerii) fry often face environmental stressors that can compromise their immune system, rendering them susceptible to opportunistic pathogens in intensive aquaculture systems. In this study, we explored the innovative use of chitosan nanoparticles loaded with Mentha piperita essential oil (MPO/CNPs) as a dietary supplement to improve the growth and immune responses of A. baerii. The results demonstrated that the addition of MPO/CNPs to the diet led to significant improvements in growth, as evidenced by increased red blood cell count, hematocrit, haemoglobin concentration, and reduced triglyceride levels. Furthermore, significant differences were observed in the immune parameters for the treatment groups receiving Mentha piperita essential oil loaded in chitosan nanoparticles (MPO/CNPs), including enhanced lysozyme activity, immunoglobulin M (IgM) levels, respiratory burst activity, and ACH50 activity. Additionally, gene expression analysis revealed upregulation of key immune-related genes in the MPO/CNPs-treated groups. These findings suggest that the use of MPO/CNPs can enhance the growth and bolster the immune defences of Siberian sturgeon fry, contributing to more sustainable production in intensive aquaculture environments.

Protective effects of HSP Inducer on diazinon-exposed stellate sturgeon (Acipenser stellatus) fry: Insights on HSP70 gene expression, immune response, and enzyme indices.

Aquatic environments face frequent exposure to organophosphate pesticides, such as diazinon, which are frequently utilized in agriculture. The goal of this study was to evaluate the effects of diazinon exposure on fish and to investigate the potential of the HSP inducer (HSPi) in developing a defense mechanism. To achieve this, several factors were analyzed, including the HSP70 gene expression, levels of immunity markers (lysozyme, IgM, and C3), antioxidant status, and the activity of acetylcholine esterase (AChE). Stellate sturgeon (Acipenser stellatus) fry, was exposed to diazinon (25, 50, and 75% of 96h-LC50) for 6 days after pre-treatment with an HSP inducer (HSPi), TEX-OE® (a prickly pear cactus extract), for 4 hours. Two HSPi concentrations, 100 and 200 mg.L-1, were used. Pre-treatment with HSPi significantly enhanced HSP70 gene expression in the gill and liver, as well as immune markers in the blood of Acipenser stellatus. Diazinon-treated groups exhibited higher antioxidant activities of SOD, CAT, and T-AOC. Increased activity also observed in control fish pre-treated with HSPi. However, stellate sturgeon receiving both diazinon and HSPi+diazinon experienced a significant decrease in AChE activity in comparison with control group. Cortisol levels were elevated in the fish that were subjected to diazinon. Those subjected to diazinon after receiving HSPi showed a significant decrease in cortisol levels. In conclusion, the study suggests that HSPi-mediated HSP70 induction may have a protective effect. The presence of an HSP inducer offers a potential strategy to mitigate the consequences of diazinon exposure in stellate sturgeon.

Біологічні особливості організму молоді осетрових (Acipenseridae Bonaparte, 1831) риб за дії синтетичного та органічного імуностимуляторів

Purpose. To analyze the productive-biological and biochemical parameters of sturgeon larvae and fry under conditions of introduction of synthetic (Levamisole) and organic (Chitosan) immunostimulants into their diet. To evaluate the effect of supplements on the stability of homeostatic processes based on the analysis of enzyme activity. Methodology. The study was carried out on juvenile hybrid besters (♀ Huso huso х ♂ Acipenser ruthenus) and sterlet (Acipenser ruthenus) (BSS). Larvae and fry were fed with Artemia nauplii, which were the transfer of immunostimulants after a six-hour enrichment in the respective solution. Pre-larvae, larvae and fry of sturgeon were reared in a RAS at the Lviv Research Station of the Institute of Fisheries of the National Academy of Sciences of Ukraine. During cultivation, the main productive parameters were studied, which included: weight, body length, growth rates, mortality, output from each stage of cultivation. The activity of α-amylase was determined by the Karavey’s method. Alanine aminotransferase activity was determined by the Reitman–Frenkel’s method. Alkaline phosphatase activity was determined by reaction with phenylphosphate. Gamma-glutamyltranspeptidase activity was determined by reaction with L-gamma-glutamyl-p-nitroaniline. All data were statistically processed using Statistica 6.0 and MS Excel. Findings. Addition of Levamisole to the diet during the first week of exogenous feeding had a positive effect on the growth processes of sturgeon larvae. The average weight of experimental fish in the experimental group No. 1 increased during the week by 3.96 times, which was 9% higher than the control values. In the experimental group No. 2, which consumed Chitosan, no significant difference was found compared to the average weight of the control group. Average daily growth was 24.9% in the experimental group No. 1 and 20.7% in the group No. 2, and 22% in the group No. 3, which served as a control. After 21 days of the experiment, the average body weight of juvenile sturgeons in the group No. 1, which consumed Levamisole, increased to 0.794 g, which exceeded the control values by 50.5%. The average weight of juveniles in the experimental group No. 2 was 0.661 g, which was 25.28% higher than the control group. The average growth rates were 9.3% in the group No. 1, 12.1% in the group No. 2, and 11.3% in the group No. 3. The short-term positive effect of immunostimulants on the activity of digestive enzymes of sturgeons in the juvenile period was shown. The activity of α-amylase in the body of fish for 21 days under the action of both Levamisole and Chitosan was higher than in the control by 88.2 and 91.4%, respectively. The analysis of the effect of immunostimulants on the activity of transferases (AlAT, LF, GGTP) of the tissues of internal organs confirmed the strengthening of the nonspecific resistance of the body in the short period of their action due to the activation of the transport processes of dephosphorylation and transamination. In addition, the activity of none of the enzymes indicated the impairment of homeostasis. Originality. The advisability of using synthetic and organic immunostimulants in raising sturgeons has been demonstrated. The effect of these supplements on the productive and biochemical parameters of juvenile sturgeons was evaluated. Practical value. The obtained results will be useful for improving the technology of early rearing of sturgeon larvae and fry. The application of the acquired knowledge will allow reducing mortality during critical periods of their cultivation and will allow strengthening the non-specific immunity of these valuable fish species. Key words: sturgeons, enrichment, non-specific resistance, immunostimulants.

Changes in HSP70 Gene Expression, Immune Response, and Enzyme Indices in the Stellate Sturgeon (Acipenser Stellatus) Fry Exposed to an Organophosphate Pesticide in the Presence of HSP Inducer

Changes in HSP70 Gene Expression, Immune Response, and Enzyme Indices in the Stellate Sturgeon (Acipenser Stellatus) Fry Exposed to an Organophosphate Pesticide in the Presence of HSP Inducer

Effects of heat shock protein inducer on Hsp70 gene expression and immune parameters during Streptococcus iniae infection in a Persian sturgeon fry.

Heat shock proteins (HSPs) as stress-related factors play a fundamental role in innate and adaptive immune responses in fish, which can be considered as strong candidates for the development of new methods for fish disease prevention. It has been proven that Pro-Tex® as a heat shock protein inducer (HSPi) reduces harmful effects of cellular stress by increasing the Hsp70 protein production. We evaluated the effects of Pro-Tex® as an HSPi in a Persian sturgeon, (Acipenser persicus) exposed to a pathogenic bacterium. Therefore, A. persicus fries were pre-treated with 25.00, 50.00 and 100 mg L-1 of Pro-Tex® and then, injected with Streptococcus iniae ATCC29178. The Hsp70 gene expressions were determined in various organs including liver, gill and intestine and lysozyme (LYZ) activities along with supplemental levels of complement component 3 (C3) and immunoglobulin M (IgM) were also determined in sturgeon blood in days 3 and 7 after infection. Expression of Hsp70 gene was increased during the first three days of infection and then, it was found to be down-regulated during the infection process. Also, levels of LYZ activity, C3 and IgM increased in a concentration-dependent manner; but these parameters decreased after 7 days. Our data suggest that induction of Hsp70 is a promising approach in modulation of immune response in A. persicus and it might be employed to confer protection in fish against bacterial infections.

Influence of environmental factors on the development and conservation of sturgeon young

Commercial sturgeon breeding is one of the promising areas of aquaculture. This is not only an integral part of the production of valuable protein products, but also the main source of replenishing the number of sturgeon fish, especially rare and endangered species. This paper examines studies on the influence of environmental factors on the development and safety of sturgeon fry in a sturgeon breeding enterprise in the Krasnodar Territory, carried out on juvenile Russian sturgeon. It was found that the control group was reared for 213 days, the experimental group for 152 days. The average water temperature during the growing period was 20.39°C for the control group and 21. 19°C for the experimental group. The oxygen concentration was at the level of 73.6% in the control group and 76.6% in the experimental one. The pH level in water for the control group was 8.15, for the experimental one – 7.51; the concentration of nitrites for the control group was 0.025, for the experimental group it was 0.017. The average nitrate index is 0.96 and 0.84, in the control and experimental groups, respectively. The weight growth of sturgeons of the first group was higher, with the same initial weight, the final weight of juveniles in the experimental group was 97.4 grams, which is 14.8 grams more than juveniles in the control group. And the weight gain was 174.4% in the control group, and 222.5% in the experimental group. The average linear growth was also higher in the experimental group – 25.8 cm, in the control group – 24.1 cm. The increase in length was 76.7% in the experimental group, 68.5% in the control group. The survival rate of juveniles in the experimental group was 90.7% (136 specimens of Russian sturgeon out of 150), in the control group it was 86%.

Assessment of food intensity and growth rate young sevryuga (Acipenser stellatus Pallas, 1771) depending on from the terms of fishing of growing ponds

Artificial reproduction of sturgeon fish in the Volga-Caspian basin in modern conditions is the only real opportunity to replenish natural populations with juveniles, therefore, increasing its efficiency is the key to restoring the stocks of these relict fish species. Improving the technological processes of growing juvenile sturgeon fish, including the Caspian stellate sturgeon, the number of which has been rapidly decreasing in recent years, is one of the main tasks at present. We studied the conditions for growing stellate sturgeon larvae in the nursery ponds for artificial reproduction at different periods of their watering. It is known that the stocking of ponds with larvae that have switched to exogenous feeding occurs at the end of June or the beginning of July, this coincides with the time of maximum water heating in nursery ponds to extreme (26–28 °C) values and with a depletion of the food supply in them. Hydrobiological studies were carried out to assess the food supply in water bodies that were watered in the traditional (June 12–14) terms (control option) and earlier (May 28) 2 weeks earlier than usual (experimental option). In addition, the intensity of feeding and the growth rate of juvenile starred sturgeon in the indicated ponds was studied for 20–24 days. The results of the studies performed showed that the food supply in the experimental pond was higher, so the zooplankton was represented by four orders, the biomass on average ranged from 2,8 to 4,6 g/m³, and in the control variant, planktonic organisms were represented by three orders, total biomass from 0,3 to 2,5 g/m³. The same tendency can be traced for zoobenthos. The feeding intensity of stellate sturgeon fry reared in ponds of early watering had indicators in terms of the gastrointestinal tract filling index, fatness coefficient and growth rates higher than the juveniles kept in water bodies of traditional watering periods.

Effects of feeding <italic>Bacillus subtilis</italic> on growth and intestinal microflora of hybrid sturgeon

China is the world’s largest sturgeon farming country. In recent years, the disease of sturgeon has been frequent, which has a serious impact on sturgeon farming industry. The sturgeon disease mainly occurrs in juvenile stages, especially the juvenile opening stage and the juvenile feeding stage, which are two sensitive stages in the breeding of sturgeon seedlings and it often results in massive death. How to improve the survival rate of sturgeon fry has become an important problem restricting the development of sturgeon industry. The effect of <italic>Bacillus</italic> in promoting the healthy growth of cultured animals is mainly reflected in three aspects: promoting the digestion and absorption of animal nutrients, regulating the micro-ecological balance of animal digestive tract, and enhancing the immunity and disease resistance of animals. Therefore, probiotics have attracted more and more attention as an effective feed additive and disease control substance. However, there are few reports on probiotics in sturgeon farming. In this study, the commercialized <italic>Bacillus subtilis</italic> with concentrations of 0.00%(control), 0.10%, 0.20% and 0.40% were added to the feed of juvenile hybrid sturgeon (<italic>Acipenser baeri</italic> ♀ × <italic>A</italic>. <italic>schrenkii</italic> ♂) for 90 days, with breeding time from August 23rd, 2018 to November 23rd, 2018. The application effect of <italic>B</italic>. <italic>subtilis</italic> were evaluated by observing growth performance, blood biochemical indices and the intestinal microbial flora of juvenile hybrid sturgeon. The results showed that the feeding rate and feed coefficient first decreased and then increased with the addition of <italic>B</italic>. <italic>subtilis</italic> but all significantly lower than that of the control group(<italic>P</italic><0.05), and the addition of 0.22% into the feed could improve the feed utilization for sturgeon. Compared with the control group, the addition of <italic>B</italic>. <italic>subtilis</italic> to feed increased the serum glucose content, and the its content in 0.10% addition group was significantly higher than that of the control group (<italic>P</italic><0.05). The analysis of intestinal microbial species composition among four groups showed that at genus level, <italic>Cetobacterium</italic> was the dominant bacterium in each experimental group. With the increase of the amount of <italic>B</italic>. <italic>subtilis</italic>, the content of <italic>Cetobacterium</italic> decreased, and the lowest proportion (74.29%) was obtained in the 0.40% group. While the content of <italic>Plesiomonas</italic> increased. When the amount of <italic>B</italic>. <italic>subtilis</italic> reached 0.40%, the content of <italic>Plesiomonas</italic> reached the highest 23.64%. Adding <italic>B</italic>. <italic>subtilis</italic> to feed can reduce the abundance of <italic>Streptococcus</italic>, <italic>Lactobacillus</italic> and <italic>Lactococcus</italic>. In conclusion, feeding different doses of commercial <italic>B</italic>. <italic>subtilis</italic> to hybrid sturgeon can significantly reduce the feeding coefficient, enhance the fish body’s ability to use blood sugar and fat and improve the intestinal microecological environment to a certain extent. The recommended dosage of <italic>B</italic>. <italic>subtilis</italic> (Gutcare^a, DSM32315) in sturgeon feed is 0.10%-0.20%.

Drift Netting for Lake Sturgeon Fry

Drift Netting for Lake Sturgeon Fry

Effects of Pro‐Tex® on the expression of Hsp70 gene and immune response parameters in the Persian sturgeon fingerlings, Acipenser persicus, infected with Aeromonas hydrophila

The induction of Hsps (heat shock protein) recognized as a promising approach to limiting disease and improving health in aquaculture. This investigation aimed to study the impacts of Pro‐Tex®, an extract from the prickly pear cactus (Opuntia ficus indica), on the expression of Hsp70 gene and induction of immune response parameters in Acipenser persicus infected with Aeromonas hydrophila ATCC®7966ᵀᴹ. Fish were pretreated with 25, 50 and 100 mg/L of Pro‐Tex and then injected in the intra‐peritoneal cavity with A. hydrophila. The expression level of Hsp70 gene, lysozyme activity (LYZ) and complement C3 (C3), and immunoglobulin M (IgM) levels were assessed in liver, gill, and intestine on the days 3 and 7 post‐infection. Tex‐OE® increased expression of Hsp70 in a dose‐dependent way in A. persicus, but this expression significantly reduced on the 7‐days post‐injection. The Hsp70 expression pattern was variable in each tissue, also, LYZ activity, C3, and IgM increased, depending on the concentration, and showed a decreasing trend in a time‐dependent way. In conclusion, our data indicated that Pro‐Tex as an Hsp70 inducer increases the resistance of sturgeon fry against fish pathogens by induction of different immunity factors.

Морфологічні параметри травної системи молоді російського осетра (Acipenser gueldenstaedtii Brandt &amp; Ratzeburg, 1833) за дії пекарських дріжджів, згодовуваних з основним кормом

Морфологічні параметри травної системи молоді російського осетра (Acipenser gueldenstaedtii Brandt &amp; Ratzeburg, 1833) за дії пекарських дріжджів, згодовуваних з основним кормом

SEASONAL CHANGES IN INFECTION OF INTRODUCED FISH SPECIES BY INVASIVE BACTERIA IN FISH FARMS OF BELARUS

The material for this report was the results of bacteriological examination of fish of various species (silver carp (Carassius gibelio); silver carp (Hypophthalmichthys nobilis); white cupid (Ctenopharyngodon idella); common carp (Cyprinus carpio); rainbow trout (Oncorhynchus mykiss), fry of sturgeon of Lena (Acipenser baeri) and sterlet (Acipenser ruthenus)) and various age groups in 2016–2018. in 7 fish farms in Belarus. As a result of research, 21 species of bacteria have been registered in introduced fish species in pond farms that are potential causative agents of bacterial diseases of introduced fish. Two types of bacteria – Shewanella putrefaciens and Aeromonas hydrophila – are invasive and harm the fish industry. Studies have shown seasonal changes in the frequency of occurrence of Sh. putrefaciens and A. hydrophila in introduced fish. During January-March, the infection of fish with A. hydrophila bacteria was not high, increasing sharply in April-May. In June-July, a decrease is observed, and in August is a sharp decrease in the infection of the internal organs and blood of fish with aeromonads. Bacteria Sh. putrefaciens were found in fish much less frequently than A. hydrophila, however, some seasonal dependence in the change in the frequency of its occurrence in introduced species is observed. The peak of occurrence is in June. The maximum values of the frequency of occurrence of pathogens of bacterial infections were noted for A. hydrophila in April (80.0%), for Sh. putrefaciens – in June (33.0%). It should be noted that the active consumption of mixed fodder and natural feed by the fish leads to the restoration of the body’s immune status after winter.

Genetic monitoring of natural sturgeon spawning in the lower Volga for the period 2017-2018

Genetic monitoring of natural sturgeon spawning in the lower Volga for the period 2017-2018

Analysis of the influence of ecological parameters on the results of growing fry of russian sturgeon in ponds

Analysis of the influence of ecological parameters on the results of growing fry of russian sturgeon in ponds

ОЦЕНКА БИОГЕННОЙ НАГРУЗКИ И ЭФФЕКТИВНОСТИ ВЫРАЩИВАНИЯ РУССКОГО ОСЕТРА ПРИ СОЛОНОВАТОВОДНОМ РЕЖИМЕ В УСЛОВИЯХ ЗАМКНУТОГО ВОДООБЕСПЕЧЕНИЯ

Fry of Russian sturgeon ( Acipenser gueldenstadtii Brandt et Ratzeburg, 1833) was an object of research in the course of studying the influence of different concentration of water salinity onto the operation of a closed water supply unit and on the intensity of fish growth. Salt medium (3; 5; and 7‰) was made using sodium chloride solution, whose osmotic force corresponded to water salinity in the Northern Caspian - from 0 to 7‰. Temperature and oxygen condition changed within 20.0-22.0°C and 85.0-100.0% of saturation. Maximum fish growth was registered in salinity of 5 and 7‰, increase made 8.0-21.0%. The intensive growth rate proved that sturgeon breeding in brackish waters facilitated more efficient digestion of food components in the fish gastrointestinal tract. Blood indices corresponded to parameters specific for fishes in the natural habitat: haemoglobin - 30.0-45.0 g/l; cholesterol and crude protein - up to 3.5 mmol and 26.0 g/l. Level of lipids was high - 4.8-6.5 g/l, which is characteristic to fish fed with complete dry feed. Osmolality of fish blood serum was within 219.0 ± 2.41 - 239.0 ± 0.94 mmol/kg of H2O and corresponded to the parameters of sturgeons of different age groups in desalinated area in the Northern Caspian. However, increase of water temperature and salinity up to 7‰ affected operation of biological filter and raised the concentration of ammonium nitrogen in water, which lowered viability to 10.0%. Parameters of hydrochemical condition of a closed ecosystem were within normal values under salinity of aqueous medium up to 5‰, which should be taken as optimal for creating brackish regime in the closed water supply units of sturgeon breeding.

Features of the effect of a complex probiotic with Bacillus bacteria and the larvae of Hermetia illucens biomass on Mozambique tilapia (Oreochromis mossambicus × O. niloticus) and Russian sturgeon (Acipenser gueldenstaedti) fry

A study of the effect of a complex probiotic preparation with bacteria of the genus Bacillus and a microdose of larvae of the fly Hermetia illucens on the physiological. parameters of fish has been carried out. It was established that introduction of the complex into artificial feeds for tilapia and Russian sturgeon juveniles during their incubation in recirculating aquaculture systems improves the digestion efficiency and increases the rate of fish growth and body mass accumulation. In tilapia, a decrease in the cholesterol level was revealed, while in sturgeon, an increase in the hemoglobin content was found. It was noted that a probiotic with biologically active agents H. illucens had a stimulating effect on the development of sexual gonads in female sturgeon fry, promoted an increase in the ovary mass, and provided for the development of eggs without morphological disturbances.

Feeding Rates Affect Expression of Heat‐Shock Protein 70 in Green Sturgeon Fry

AbstractTwo growth trials were conducted to determine the effect of feeding rate on the responses of a heat‐shock protein (hsp70) in the fry of Green Sturgeon Acipenser medirostris. Four tanks were randomly assigned to each feeding treatment: 2.5, 5.0, 7.5, 10.0, 12.5 and 15.0% of body weight/d in trial I and 2.0, 3.0, 4.0, 5.0, 6.0 and 7.0% of body weight/d for trial II. The fry were raised indoor at 18°C and fed a commercial salmonid soft‐moist diet. Densities were 50 fry/tank in trial I fed for 49 d posthatch (dph) and 30 fry/tank in trial II fed for 70 dph. At the end of 1 week of feeding, five fish from each tank were subjected to heat shock by increasing the water temperature from 18°C to 28°C at a rate of 4°C/h and then holding at 28°C thereafter for 4 h before tissue samples were collected. Heat shock induced significant changes in the levels of hsp70 in the liver and white muscle of fish in all feeding treatments. However, feeding rate treatments had no significant effect on the basal and heat‐shocked levels of hsp70 in the liver of these fish. The lowest feeding rate significantly depressed the induced level of hsp70 in the muscle of Green Sturgeon. A feeding rate of 10.0% of body weight/d is suggested for Green Sturgeon at 49 dph and 6.0% at 70 dph, based on their maximum responses of hsp70 in white muscle tissue. This study indicates that the response of hsp70 in the liver and muscle of Green Sturgeon is sensitive to heat‐shock stress. The effect of different feeding rates on the response of hsp70 is also tissue‐dependent. This variation should be considered when hsp70 is used as a biomarker to evaluate heat‐shock response.

The effect of feeding rate on the growth performance of green sturgeon (Acipenser medirostris) fry

Four one-week growth trials were conducted on green sturgeon fry to determine the effect of feeding rate on their growth performance at 18 °C when they were fed a salmonid soft moist feeds containing 445–457 g kg−1 of crude protein and 201–207 g kg−1 of lipid. The fry used in Trials I-IV were 5–8 weeks after their initiation of exogenous feeding. Their average initial body weights were 1.63 ± 0.01, 2.63 ± 0.03, 5.08 ± 0.08 and 7.49 ± 0.05 g, respectively. Six feeding rates used were as follows: 2.5–15.0% body weight per day (% BW day−1) with a 2.5% increment in Trial I; 1.25–7.50% BW day−1 with a 1.25% increment in Trial II; and 2.0–7.0% BW day−1 with a 1.0% increment in Trials III and IV. Four replicates with 50 fry per tank in Trials I-III and 30 fry per tank in Trial IV were assigned randomly to each feeding rates. The final body weight, specific growth rate, feed efficiency, protein retention, and whole-body moisture, lipid, and energy contents were significantly (P < 0.05) affected by the feeding rates. The optimum feeding rates determined by the broken-line model were 7.1, 5.7 and 5.3% BW day−1 for Trials I, II and IV, when the fry were 5, 6 and 8 weeks after their initiation of exogenous feeding, respectively.