Search

Pikeperch, Sander lucioperca (L.) is a valuable species that is in high demand among consumers due to its nutritional features such as delicious meat, white and soft texture and lack of intermascualr bones. The main barriers in the development of pikeperch aquaculture are the challenges of its larviculture. A major problem in the larval period is that pikeperch must feed on live food, which imposes high costs on producers. Therefore, substituting live food with formulated diets is necessary, but this process cannot be performed easily and it requires an action plan to be successful. The aim of this study was to provide a brief overview of different aspects related to pikeperch nutrition including its natural feeding habits, nutritional requirements, digestive tract ontogeny, and the most common live foods used in pikeperch first feeding. Moreover, different weaning methods in pikeperch culture are provided to introduce an appropriate strategy to assist this fish in adapting to formulated diets.

The present study was conducted to understand key biochemical, physiological, and molecular changes associated with ovarian growth and with lipid transfer and/or accumulation into the ovary during oogenesis in captive beluga sturgeon. Plasma levels of triacylglycerides, cholesterol, phospholipid, and sex steroid hormones were determined and all were found to increase notably throughout development from the perinucleolar to the tertiary yolk stage. Using fast protein liquid chromatography, we recognized three major lipoprotein peaks in chromatograms from all samples. These peaks were characterized as containing very low-density lipoprotein (Vldl), low-density lipoprotein/high-density lipoprotein (Ldl/Hdl), and plasma proteins. While Ldl/Hdl represented the most abundant lipoprotein fraction, the relative abundance of different lipoprotein classes did not change with the stage of oogenesis. Eluted lipoproteins were separated using sodium dodecyl-sulfate polyacrylamide gel electrophoresis and sequenced. The peptide sequence spectra for 66-kDa, 205-kDa, 29-kDa, and 70-kDa bands matched with albumin, vitellogenin (Vtg) AB2b, immunoglobulin light-chain precursor, and immunoglobulin heavy-chain, respectively. The large amount of albumin in the plasma protein peak and the confined presence of Vtg AB2b to within Ldl/Hdl reinforce the lipoprotein classification. Lastly, transcript levels of genes encoding ovarian lipoprotein lipase ( lpl), apolipoprotein E ( apoe), very low-density lipoprotein receptors ( vldlr), and low-density lipoprotein receptor-related protein 8-like ( lrp8) were estimated using quantitative RT-PCR. The high mRNA levels of lpl, apoe, and lipoprotein receptors vldlr and lrp8 in previtellogenic females suggest that sturgeon oocytes need to be prepared to accept and traffic Vtg and lipids internally, before the start of vitellogenesis.

The in vivo effect of 11-ketotestosterone (11KT) on transcript levels of the gonadotropin receptors (fshr and lhr) and sex differentiation-related genes (dmrt1 and foxl2) was examined in the ovaries of immature female beluga. For this purpose, six fish were treated with implants containing 2.5 mg 11KT and a placebo group of six females of the same age and gametogenic stage were given a blank implant. The implants were intraperitoneally inserted into 4-year-old females at the previtellogenic stage (mean body weight 5580 ± 165 g) and maintained under culture conditions for 8 weeks. Ovary samples for gene expression analysis of lhr, fshr, dmrt1 and foxl2 were collected by biopsy at 3 and 8 weeks post implantation. Diameters of oocytes increased in response to 11KT treatment, both at 3 and at 8 weeks post implantation, but no obvious changes were evident in cytology. Three weeks of 11KT treatment did not affect target gene expression, but a tendency for a time-dependent decrease of lhr and dmrt1 mRNA levels was observed in both treatment and placebo groups. By 8 weeks of treatment, however, 11KT implants provoked the upregulation of fshr and foxl2 transcript levels. Furthermore, lhr and dmrt1 transcript abundances recovered by 8 weeks of exposure in both blank- and 11KT-implanted beluga. These results suggest that 11KT, either directly or indirectly, may affect gametogenesis and regulate some key components of the reproductive axis in female beluga.

Thyroid hormones (THs) play important roles in regulating growth, development and physiological functions in vertebrates. To study the role of short‐term effects of thyroxine (T4) on metabolism and growth in female Sterlet sturgeon, thirty fish with a weight of 707.97 ± 37.15 g were divided into six tanks. Fish were injected intraperitoneal with (a) coconut oil alone (control), (b) 1 mg T4 kg per BW in coconut oil (T₁) and (c) 10 mg T4 kg per BW in coconut oil (T₁₀). Blood samples were collected at 0, 4, 7, 14, 28 and 60 days for plasma biochemical analysis, and body length and mass were determined at day 60. Based on results, higher growth was indicated in T₁₀ group. The highest T4 levels were observed on day 4 in the T₁ and T₁₀ treatments and gradually declined during the trial. Plasma T3 levels were highest on days 4 and 7 in the T₁ and T₁₀ groups, respectively. Plasma triglyceride levels were significantly elevated on day 28 in the T₁ group and on day 60 in the T₁₀ group. Plasma glucose concentrations were significantly elevated on days 7 and 14 in T₁₀ group. Overall, the present results suggest that a single injection of T4 can improve growth via changes in the metabolic profile of Sterlet sturgeon.

Providing a non-invasive procedure to track fish maturity remains a priority in broodstocks' management. In the present study, the main goal was to assess reproduction status by measuring sex steroids and vitellogenin (VTG) in the skin mucosa, as a non-invasive method. For this purpose, the present study compared the levels of estradiol-17β (E2), testosterone (T), 11-ketotestosterone (11-KT), VTG and calcium (Ca) in skin mucosa and blood plasma of goldfish (Carassius auratus). Skin mucosal and blood samples were collected, as well as gonad tissues, from goldfish, as a seasonal spawner. Histological analysis confirmed the gender and maturity status from females' ovaries (as primary-growth, cortical-alveoli, initial and late-vitellogenesis) and males' testes (as spermatogenesis and spermiation). Furthermore, vitellogenin (vtg) expression was observed in skin, liver and gonads. The results indicate that mucosal E2 concentrations were significantly higher during initial and late vitellogenesis than the other stages. Mucosal 11-KT concentrations significantly increased at spermiation (P < 0.05). E2/T and 11-KT/E2 ratios significantly increased at early vitellogenesis and spermatogenesis, respectively (P < 0.05). Females' mucosal VTG levels were significantly fluctuated according to the maturity stage. Ca showed a similar trend, but Ca was more accurate for sex identification than the VTG. Although mucus showed high levels of VTG, ovarian vtg expression was strongest while liver and skin had the similar results. These results show that measuring the mucosal androgens could be considered as an accurate, non-invasive method to monitor fish maturity.

An 8‐week study was applied to evaluate the effects of feed restriction and starvation on growth, proximate composition, haematological and biochemical factors in juvenile Siberian sturgeon Acipenser baerii with an average weight of 54 ± 0.6 g. Fish were randomly divided into nine indoor tanks (1,050 L volume) with 30 fish per tank in a flow‐through system at 18 ± 0.4°C. Three feeding strategies were considered: I) fed at satiation (F), II) restricted feeding at the rate of 1% body weight per day (R) and III) starvation (S) each with 3 replicates. Fish were fed with commercial pellets 4 times daily, but no feed was considered for S group throughout the trial. Basal level at the start, 4 and 8 weeks after initiation of the experiment, blood samples were taken from 5 fish/tank to measure the haematological and biochemical parameters. Moreover, growth performance was recorded every 2‐week interval. At the end of the experiment, the growth parameters and proximate composition were significantly different among the treatments. As expected, the highest weight (164.7 ± 2.1 g) was observed in F group compared to R (101 ± 1.7 g), or S (42.4 ± 0.8 g) groups. The highest (12.07 ± 0.14%) and lowest (5.37 ± 0.42%) fat contents were observed in F and S groups, respectively, while the protein was not affected in R group compared with F group. In addition, most haematological and biochemical indices of Siberian sturgeon were affected by starvation at week 4 and 8, while few changes were observed in restricted feeding. The highest mean corpuscular volume, mean corpuscular haemoglobin, plasma total protein, cholesterol and triglyceride was found in S group, while the lowest value of plasma glucose was observed in this group. It can be concluded that Siberian sturgeon adjusts the physiological condition in short‐term (4 weeks) feed restriction using stored metabolites to have basal metabolism and due to this, a short period of feed restriction strategy recommends to the optimum nutritional management of Siberian sturgeon to cost‐saving during unsuitable conditions.

The aim of this study was to determine the effects of dietary probiotics on reproductive performance, growth, haematological and biochemical parameters of female rainbow trout broodstock. A total of 60 broodstocks with an average initial weight of 2,267.4 ± 54.9 g were divided into four groups and three replicates in raceway ponds. Fish were fed with diets containing 0 (control), 1 × 10⁹ (P1), 2 × 10⁹ (P2) and 4 × 10⁹ (P3) CFU probiotic per kg diet twice a day for 8 weeks before spawning season. Results revealed that higher levels of dietary probiotics (P3) enhanced protein efficiency ratio and decreased feed conversion ratio (p

This study investigates the basis of the stimulatory effects of thyroxine (T4) on the growth and physiological changes in Sterlet sturgeon broodstock and their larval offspring. Groups of fish received four injections of 0, 1 or 10 mg kg BW−1 of T4 over a 170-day period. At the end of trial, blood was taken and plasma biochemical parameters, sex steroid and thyroid hormone (THs) levels were measured. Broodstock were induced to ovulate by the injection of LHRHa2 and ovarian fluid (OF) and eggs were obtained through a minimally invasive surgical technique. The eggs were fertilized and resulting larvae were assessed after 14 days of grow out. Weight gain, protein and lipid efficiency and food efficiency of broodstock in T10 were higher than the other treatments (P

A 7-month feeding trial was conducted before spawning induction in sterlet (Acipenser ruthenus) broodstock (initial weight 990.3 ± 20.05 g). The effects of dietary fish and vegetable oils were investigated on fatty acid profiles in eggs, hematological characteristics, serum lipid indices, and expression of some lipid metabolism and transport-related genes. Three experimental diets with different levels of fish and vegetable oils were formulated as: FO (100% kilka oil), VO (100% rapeseed oil), and FO + VO (50% kilka oil + 50% rapeseed oil). At the end of the feeding trial, egg samples from ovulating females were collected to examine fatty acid profiles and transcriptional mechanisms involved in lipid metabolism and transport. The broodstock physiological condition was assessed using hematological and biochemical indices. Similar to the diets, oleic acid (18:1n-9) was the most predominant monounsaturated fatty acid among all lipid classes in sterlet eggs. Results revealed that the eggs of the broodstock fed VO diet had the highest ratio of DHA/EPA, while the eggs of the broodstock fed FO + VO or FO diet showed higher ratios of EPA/ARA and DHA/ARA. No changes were observed in the levels of lipoproteins, blood lipid indices or hematological parameters in broodstock. This implies that the examined oil sources did not have any adverse effects on fish health during the feeding trial. Feeding different dietary ratios of VO and FO resulted in altered expression of ApoE and PPARα in the eggs, suggesting that lipid metabolism pathways can be influenced by dietary lipid sources. Compared with broodstock fed FO or FO + VO diet, in eggs from the broodstock fed VO diet the expression of ApoE gene was significantly up-regulated and the expression of PPARα was down-regulated. However, the expression of PPARγ was not significantly different among the dietary treatments. Different expression levels of related genes in treatment with various oil sources demonstrate that ApoE, PPARα, and PPARγ play key roles in lipid metabolism, such that they might perform different functions in lipid metabolism and utilization.

This study set out to examine the effects of thyroxine (T4) on reproductive success of female Sterlet sturgeon broodstock and subsequent growth and development of the larval offspring. Fish received four intraperitoneal injections of coconut oil (controls), 1 mg T4/kg body weight (BW) in coconut oil (T1) or 10 mg T4/kg BW in coconut oil (T10) over a 170-day treatment period. Ovulation was induced by intramuscular injection of luteinizing hormone-releasing hormone (LHRHa2). Fish in the control group ovulated quicker and had higher fecundity than the fish in experimental groups. Oocyte diameter was highest in the T10 group. Hatching rate in the control group was lowest among the groups. Larval survival at 3 days post hatch in T10 group was 92.2% and was highest among the treatments. Larval survival and the specific growth rate were greater in T10 than in the other treated groups. The T4 concentrations in unfertilized eggs, pre-larvae and post-larvae were higher in the T10 group than the others. These results showed the maternal injection of T4 has stimulatory effects on larval hatching rates, survival, and growth which make it a valuable treatment in sturgeon aquaculture.

International audience; In the present study, the biological function of recombinant gonadotropin-releasing hormone associate peptide (rGnRH) was tested for the induction of ovulation and spawning in Sterlet sturgeon (Acipenser ruthenus) broodstock. For this purpose, Sterlet sturgeon broodstock were divided into four treatments and treated with following preparing procedure: 0.9% NaCl (C); 2.5 mu g kg body weight(-1) (BW) LHRH-A2 (luteinizing hormone-releasing hormone-A2, L2.5); 2.5 mu g kg BW-1 rGnRH (rGn2.5); 10 mu g kg BW-1 rGnRH (rGn10). The capability of the rGnRH for eliciting biological response was studied in vivo by evaluating the changes of 17 beta estradiol (E2), progesterone (P) and testosterone (T) and by its ability for inducing final maturation. Blood samples were collected at the time of first injection, 10 h after the first injection and at ovulation time. The L2.5 or rGn10 treatments led to significantly lower E2 concentration 10 h after the first injection and at ovulation time compared to the baseline measures. E2 levels increased in the rGn2.5 treatment 10 h after the first injection and by ovulation time compared to the time of first injection. T levels were significantly increased in the L2.5 or rGn10 treatments 10 h after the first injection compared to the time of first injection and it further decreased at ovulation time. No significant differences were found in C and rGn2.5 treatments between the different sampling times. P secretion was significantly higher in the rGn10 or L2.5 treatments compared to C and rGn2.5 treatments 10 h after the first injection and at ovulation time. No significant difference was found in P secretion in the C and rGn2.5 treatments at different sampling times. The results showed that the rGnRH at the highest dose (10 mu g kg BW-1) was more efficient than the other treatments in the induction of spawning and this dose caused P secretion and spawning in vivo. Our results present the possibility of using rGnRH in artificial reproduction of sturgeons and it can be introduced as a specific homologue to treat reproductive disorders in fish.Highlights: 1. rGnRH had a positive effect in final maturation in Sterlet sturgeon. 2. rGnRH at the dose of 10 µg kg body weight-1 was efficient in spawning induction. 3. rGnRH can stimulate the secretion of sex-steroids in vivo. 4. rGnRH can be used as a specific homologue to treat reproductive disorders in fish.

This study was conducted to assess the effects of photoperiod on growth and spawning of zebrafish. Two hundred and forty zebrafish (120 males and 120 females) were maintained under four different light dark cycles: shortened light regime (08L:16D), control (12L:12D), extended light regime (16L:08D), and continuous light regime (lights on continuously for 24 h). The fish were kept in these conditions for 42 days, during which growth and reproduction were measured. The best growth was achieved at the ELR group, with the greatest final mean weight (P

International audience; GnRH is a neuropeptide known to regulate reproduction in vertebrates. The purpose of this study was to design and produce recombinant gonadotropin-releasing hormone associated peptide (rGnRH/GAP) as an alternative of the previous GnRHs and native extracted hormone from tissue, to induce final maturation in fish. Decapeptide as well as GAP area sequences were compared between GnRH1, GnRH2, and mGnRH from Acipenser sp and Huso huso, respectively. Considering the conserved amino acids and the replacement of un-stable amino acids with those that were more stable against proteolytic digestion as well as had a longer half-life, the sequence was designed. The sequences of decapeptide and GAP region were synthesized and then cloned on pET28a expression vector and transformed into expression host Escherichia coli BL21(DE3). The supernatant of cultured recombinant bacteria was used for purification using TALON Metal affinity resin. The purity of the GnRH/GAP was confirmed by single 8 kDa band on SDS-PAGE and Western blot. Bioinformatics studies were performed for evaluation of homology between GnRH protein sequences and prediction of 3D protein structure using Swiss Model. The result showed that the structure prediction of the recombinant GnRH decapeptide was relatively similar to decapeptide of GnRH2 from Beluga (Huso huso). The GAP structure was similar to GAP1 of Nile tilapia (Oreochromis niloticus) and sturgeon and GnRH2 of Chinese sturgeon (Acipenser sinensis). The mass analysis showed that the sequence was exactly the same as designated sequence. Biology activity of rGnRH/GAP was tested in mature goldfish (Carassius auratus) and results showed that rGnRH/GAP had a positive effect in final maturation. Indeed 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) was increased 17 h and 24 h after injection with rGnRH/GAP and spawning stemmed from that injection. These novel findings introduce the potential of utilizing rGnRH/GAP in aquaculture.

The effects of replacing fish meal (FM) with corn gluten meal (CGM) on growth and physiological performance were evaluated in common carp (Cyprinus carpio). Six experimental diets were formulated by substituting 0 (control), 20, 40, 60, 80, and 100% CGM protein for FM protein. The concentrations of dietary protein in the experimental diets were 27.8–29% and the P:E ratios were 14.7–15.46 mg/kJ. Eighteen fish with an initial weight of 13.5 ± 0.1 g were allocated to each of 18 circular tanks (450 L) to give triplicate groups for each dietary treatment. The fish were fed to satiation for 8 weeks. At the end of the feeding trial, growth indices, body proximate composition, and hematological and biochemical parameters were measured. Blood samples were taken from six fish in each tank. Final weight and total length were significantly higher in fish fed 100% CGM (27.8 ± 1.2 g and 11.9 ± 0.3 cm) than for those fed the control (22.7 ± 1.4 g and 10.9 ± 0.5 cm) or 20% CGM (22.3 ± 1.2 g and 11 ± 0.4 cm) diets. No effect of FM replacement by CGM was observed for condition factor or hepatosomatic index (P > 0.05). The highest value of protein productive value (14.31 ± 0.65) was observed in fish fed 20% CGM (P

The effect of various feeding strategies was evaluated on growth performance and biochemical parameters in two sizes of Siberian sturgeon (465.75 ± 11.18 and 250.40 ± 12 g) during 45 days. Fish were distributed into six experimental treatments including large fish with satiation feeding (LA), small fish with satiation feeding (SA), large fish with 50% satiation feeding (LR), small fish with 50% satiation feeding (SR), large starved fish (LS), and small starved fish (SS). Differences in final weight between LA and LR treatments were not noticeable, whereas SA and SR treatments showed significant differences. Growth parameters were more affected in small fish. In condition factor and weight gain in starved treatments, a considerable reduction occurred by interaction between feeding strategies and fish size, so the lowest values were obtained in SS treatment. Glucose levels significantly decreased in small fish during the starvation. Interaction between feeding strategy and fish size indicated the highest and lowest albumin level in SA and SS treatment, respectively. Cholesterol, triglyceride, total protein, and globulin showed no significant differences. It can be deduced that small fish are more sensitive to starvation than the large fish. Since glucose and albumin showed significant decrease in starved small fish, these parameters can help to monitor nutritional status and feeding practices. It was indicated that in both sizes of Siberian sturgeon, feeding 50% satiation reduced the food cost without negative impact on physiological condition, and it can be considered as an appropriate strategy to face unfavorable circumstances.

The aim of the present study was to evaluate the effects of replacing fish meal with sunflower meal had on common carp, Cyprinus carpio L. fingerlings. A total of 455 fish with an average weight of 3.03 ± 0.36 g were distributed in 15 fiberglass tanks and fed five isonitrogenous and isoenergetic diets with replacement levels of 0 (control), 25, 50, 75, and 100% of fish meal with sunflower meal for 10 weeks. Based on the results, the highest and lowest final weights were observed at 25 and 100%, respectively, although the differences at 50 and 75% were not significant compared to the control. Significant differences were observed in body composition excluding ash content. Differences in all hematological indices among treatments were not significant, but in plasma biochemical indices, there was a significant decline in triglyceride levels at 100%, and cholesterol was significantly higher in the control. The results of the current study demonstrate that replacing fish meal with sunflower meal is possible up to 75% for common carp fingerlings without negative impacts on growth, body composition, or hematological and plasma biochemical indices.

A 2-factorial experiment was conducted to investigate the effect of clay turbidity on ventilation frequency (VF) in juvenile beluga sturgeon Huso huso. Ninety fish (initial mean weight 27.2 ± 0.1 g) were exposed to six levels of turbidity (0.0, 2.5, 5.0, 10.0, 20.0 and 40.0 g clay/l) for three min. Then, the fish were gently transferred to a recovery tank and monitored to record the VF for 3 min. Results indicated that clay turbidity significantly affected the VF of the fish. The highest VF was observed in the first minute after the exposure. VF increased with increasing clay turbidity levels. In addition, the obtained results showed that VF of the beluga decreased through the time. Based on the result, it can be concluded that the beluga has the ability to adapt to clay turbidity in a short time; although they had an acute stress at first.

This study examined the effects of thyroxine (T4) on hematological indices, immune parameters and the stress markers of female sterlet sturgeon. Adult broodstock (708 ± 37 g) were assigned to three groups each consisting of ten females. Fish were injected with coconut oil (control), 1 mg T4 kg body weight−1 in coconut oil (T1) or 10 mg T4 kg body weight−1 in coconut oil (T10). Injections were given intraperitoneally four times over a 170-day treatment period. At the end of the experiment, hemato-biochemical and immunological changes were measured. Treatment with the high concentration of T4 led to a significant increase in weight gain at the end of the experiment. The number of red blood cells, hemoglobin content and hematocrit were also significantly higher in the T10 group compared to the other groups (P 0.05). The highest levels of total protein, albumin, complement component 3, complement component 4, and immunoglobulin M were found in the T10 group (P

The reduction of Aflatoxin B 1 (AF) in juvenile rainbow trout ( Oncorhynchus mykiss ) diet was analyzed after supplementing Nanostructured Zeolite (NZ) in a 56-day experiment. Two hundred and seventy juveniles with an average weight of 23 ± 3.7 g were placed in 6 different groups of C (control as a basal diet), NZ 0.5 (basal diet + 0.5% NZ), NZ 1 (basal diet + 1% NZ), AF 5 (basal diet + 5 mg AFB 1 ), AF 5 NZ 0.5 (basal diet + 5 mg AFB 1 + 0.5% NZ), AF 5 NZ 1 (basal diet + 5 mg AFB 1 + 1% NZ) with three replications and were fed four times a day based on their satiation. No significant differences were observed in terms of growth performance among the experimental groups ( P > 0.05). However, hepatosomatic index in fish fed by AF 5 NZ 0.5 was reduced compared with NZ 0.5 group ( P 5 NZ 0.5 compared to the control group ( P 5 compared to that of the control group ( P P P > 0.05). Concentrations of C 3 , C 4 and immunoglobulin M together with serum lysozyme activity showed no significant differences among all treatments ( P > 0.05). No considerable histopathological lesions were observed in liver, kidney and spleen for all treatments. Based on the results, NZ showed some effects on physiological functions in juvenile rainbow trout fed by 0.5% dietary NZ which could improve performance in this species.

Summary The study evaluated the effects of dietary carbohydrate levels on growth performance and digestive enzyme activities in juveniles Caspian Kutum, Rutilus frisii (Kamenskii, 1901). Fish with an initial average weight of 0.8 ± 0.2 g (means ± SD) were fed five isonitrogenous and isoenergic formulated diets with different carbohydrate levels of 15%, 20%, 25%, 30% and 35% in triplicate groups for 10 weeks (fifteen 45-L aquaria with 30 fish per tank and water temperature of 21.5–23.5°C). Based on the results, growth performance of Caspian Kutum was significantly improved by increasing carbohydrate levels from 15% to 35% (p

Calcitonin (CT) has a potential function in calcium (Ca) regulation, but there are conflicting observations in fishes. Because of the lack of calcified endoskeleton, sturgeons have low Ca circulating compared with teleost fish and the function of CT on Ca in sturgeon is very less understood. The purpose of this study was to investigate the impact of injection of salmon CT on plasma Ca, magnesium (Mg), phosphate (PHO), and glucose levels of juvenile Siberian sturgeon Acipenser baerii. Sixteen-month-old fish (429.6 ± 12.1 g) were intraperitoneally injected with a single dose of CT (5 μg kg−1 BW) and saline solution as a control group. Thereafter, blood sampling was performed at 0, 1, 2, 4, 6, 12, 24, and 48 h after injection. CT produced marked increases in all variables measured. The highest levels of Ca (6.77 ± 0.53 mg dL−1), Mg (9.79 ± 0.16 mg dL−1) and PHO (1.74 ± 0.05 mg dL−1) were recorded at 2 h after CT injection and showed significant difference compared with control treatment (Ca 4.75 ± 0.12 mg dL−1; Mg 5.47 ± 0.16 mg dL−1 and PHO 1.23 ± 0.06 mg dL−1). It also likely produced hyperglycemia. However, the differences with the controls were not statistically significant, possibly due to interference with the hyperglycemia induced by the stress of injection. Our results showed that the injection of 5 μg kg−1 BW CT to Siberian sturgeon has an incremental effect on plasma Ca, Mg, and PHO. The increase in plasma Ca level indicated that CT has a potent hypercalcemic effect in sturgeon under laboratory condition, in contrast to the hypocalcemic effects reported for teleosts.

To determine the influence of density on the hybrid of Leuciscus aspius ♀ × Rutilus frisii ♂, fish performance was evaluated at densities of 2, 4, 6, 8 and 10 kg m–3 for a 56-day period. Fish (60.41 ± 0.04 g; mean ± SEM) were maintained in 15 circular concrete tanks under natural photoperiod and were fed with a commercial diet (40% protein and 18% fat) three times a day. Growth performance was assessed at the end of the experiment by measuring the length and weight of all fish. Hematological and biochemical parameters were analyzed following blood sampling at day 0, 7, 28 and 56 of the experiment. At the end of the experiment, body weight, specific growth rate and feed intake at 10 kg m–3 were significantly greater (72.55 ± 0.81 g) than 2 kg m–3 (67.58 ± 1.33 g). Hematocrit, hemoglobin, erythrocytes, mean corpuscular volume and mean corpuscular hemoglobin indicated significant changes among different densities and sampling times. Leukocytes, lymphocytes, neutrophils and monocytes variations were statistically significant at different sampling times; however, they were not affected by experimental densities. Plasma cortisol concentrations showed a significant elevation over time at 4 and 8 kg m–3. Plasma glucose and lactate increased significantly on day 28 and then decreased. Plasma cholesterol decreased at 10 kg m–3 from day 7 to day 56 and it was higher at 10 kg m–3 compared with 8 kg m–3 at day 7. Improved growth performance by increasing the density and changes in blood parameters among different densities revealed that the density of 10 kg m–3 or probably more can be applied for rearing Leuciscus aspius ♀ × Rutilus frisii ♂ hybrid to achieve an optimal production under commercial culture conditions. Keywords: Asp, Caspian Kutum, Growth, Hematology, Stress, Density, Cyprinids

An effect of 11-ketotestosterone (11-KT) on growth of previtellogenic (PV) ovaries of eel, salmon and Atlantic cod has been demonstrated. The purpose of this study was to investigate the effects of 11-KT treatment (in vivo) on ovarian growth, on hormonal and biochemical changes in blood, and on ovarian mRNA levels of lipidation-related genes in captive beluga with PV oocytes. In addition, the potential involvement of lipoprotein lipase (Lpl), an important enzyme for extracellular hydrolysis of lipoprotein-associated lipids, was evaluated. Twelve beluga (4-year olds) were treated with an intraperitoneal slow-release implant of either 11-KT (2.5 mg) or a compressed matrix (control). Ovarian biopsy was done to obtain pre- (day 0: T0) and post-treatment (day 21: T21) data on histology and target gene expression. Three weeks of exposure resulted in an increase in serum 11-KT levels from 2.2 ng/mL to 83 ng/mL but did not yield significant changes in serum levels of triacylglycerides and cholesterol. Furthermore, 11-KT implantation increased oocyte diameters from 259 μm (T0) to 309 μm by T21. Regardless of the increase in oocyte size, ovaries remained in the PV stage, mostly as late perinucleolar oocytes. Meanwhile, at the molecular level, the expression of lipidation-related transcripts [lpl, apolipoprotein E (apoe), very low density lipoprotein receptors (vldlr), low-density lipoprotein receptor-related protein 8-like (lrp8)] was significantly up-regulated after three weeks. Immunostaining for Lpl by Western blotting indicated three immunoreactive bands (70, 58 and 37 kDa) in ovarian homogenates from beluga, but signal intensity was not affected by treatment. Altogether, the administration of 11-KT increased 11-KT serum levels, oocyte size, and the expression of genes associated with lipid uptake. However, this treatment did not advance ovarian development beyond the PV stage.

The first step for rearing the newly produced hybrid of Asp, Leuciscus aspius ♀, × Caspian Kutum, Rutilus frisii ♂ (so-called “Aspikutum”) is to understand essential production requirements such as stocking density. For this purpose, fish (60.4 g) were held at five stocking densities of 2, 4, 6, 8, and 10 kg/m3 in circular concrete tanks (603 L) for a period of 56 d. The culture system was maintained at natural temperature and photoperiod. Fish were fed thrice a day using a commercial diet. At the end of the trial, growth indices, including final mean weight, weight gain, and specific growth rate, were significantly higher at the density of 10 kg/m3 compared with 2 kg/m3 (P 0.05). Increased stocking density caused significant increase in body protein and fat contents (P< 0.05). Condition factor in higher densities (8 and 10 kg/m3) was significantly higher compared with 2 kg/m3 (P< 0.05). The results indicated that rearing this hybrid in the studied weight range at high density of 10 kg/m3 or more is possible without negative impacts on growth performance and body composition.

Juvenile beluga sturgeon, Huso huso (initial weight 50 ± 0.2 g), were fed with two lipid levels (120 g kg−1 lipid as low-energy diet, LE; 240 g kg−1 lipid as high-energy diet, HE) at different feeding times for 8 weeks, and the effects on growth, hematology, muscle composition, and apparent digestibility coefficients of dry matter, lipid, and protein were examined. Feeding times were as follows: (1) at 09:00 and 16:00 (under light regime), (2) at 21:00 and 04:00 (under dark regime), and (3) at 13:00 and 20:00 (under light–dark regime). Dietary lipid levels did not affect the hematological indices or apparent digestibility coefficients of dietary nutrients (P > 0.05); however, they affected the growth and muscle composition (P 0.05). Accordingly, juvenile beluga sturgeon can be fed at different times of the day without suffering growth loss, because probably, they have a low dependency on vision to detect food.

This study was planned to investigate the effects of immersion of Sterlet sturgeon (Acipenser ruthenus) eggs by thyroxine hormone (T4) on the embryonic survival rate (ESR), hatching rate (HR), larval survival rate (LSR), and thyroid hormone levels. Hence, oocytes of six females were pooled, fertilized with pooled semen of three males and 45 min after fertilization process, the eggs were placed 120 min in four batches that were immersed in T4 solutions as follows: D1 (the control treatment: T4-free, hatchery water), D2 (0.01 mg L−1 of T4), D3 (0.05 mg L−1 of T4), D4 (0.1 mg L−1 of T4), and D5 (1 mg L−1 of T4). Next, the eggs were transferred to the incubator. The ESR was recorded 6 h after fertilization while HR, and LSR were measured at 1 day post hatching. In addition, the levels of thyroid hormones were measured using the competitive enzyme immunoassay method three hours and three days after fertilization and at the five-day pre-larval stage. The highest ESR was obtained following D5 treatment (P

Summary The study aimed to investigate changes in serum concentrations of sex steroids, thyroid hormones, stress indices, cholesterol, triacylglycerol, calcium and phosphorus, as well as the growth in the 3-year old previtellogenic stage of great sturgeon, Huso huso over a 6-month period. Forty individually marked fish (mean weight 6913 g) were divided among three circular tanks under a natural temperature and photoperiod. Every 1.5 months fish were weighed and blood samples taken for serum analysis. Fish showed significant changes in 17β estradiol, testosterone, triiodothyronine (T3), thyroxine (T4), adrenocorticotropic hormone, cortisol, cholesterol, and phosphorus, but not in triacylglycerol and calcium concentrations. From the January onset of the experiment to the end of the trial in July, there was a decrease in sex steroids and cortisol concentrations as well as a decline in T3 concentrations from March and in T4 from February to July. The mean weight of fish increased significantly from the beginning to the end of the experiment. Although the oocyte diameter increased from 197 to 202 μm, the difference was not significant. The histological data on oocytes suggest that the great sturgeon, like the other sturgeons, has a heterogeneous asynchronous ovarian development in the early stage of reproduction. This data might be useful to the further understanding of the physiology of Huso huso and/or to improve its culture. Moreover, it leads to a general increase in the understanding of the basic reproductive biology of this valuable chondrostean species.

A study was performed to investigate the influence of dietary lactoferrin (LF) on growth and stress responses of juvenile Siberian sturgeon. Fish were fed six experimental diets (0, 100, 200, 400, 800, and 1600 mg LF/kg diet) for 10 wk. At the end of the experiment, fish were exposed to an acute stressor of 2-min air exposure. The levels of cortisol, glucose, and lactate were measured before and at 1, 3, 6, 9, 12, and 24 h after stress. LF supplementation did not influence the fish growth. Cortisol and lactate, but not glucose level, were significantly affected by dietary LF. Cortisol levels in the control group rose twofold 1 h after stress and were significantly higher than that in LF groups. Moreover, the lowest level of cortisol at all sampling times (prestress and poststress) was observed in fish fed 400 mg LF/kg diet. Lactate concentrations in sturgeon fed 400 mg LF/kg markedly rose 1 h after stress, albeit changes in other LF groups were not significant. Results of this study show that dietary LF can suppress the stress responses in Siberian sturgeon, while 400 mg LF/kg diet appears to be an effective dietary level for this species to reduce stress.

Sturgeon aquaculture grows fast with 465% increasing through 2003–2013. Unfortunately, there is no special culture system or nutritional requirements for these valuable species. Among 27 different sturgeon species, Siberian sturgeon Acipenser baerii is one of the best sturgeon fish for culture in different environments with high growth rate and adaptation to captivity. With growing Siberian sturgeon aquaculture, nutritional requirements at any life stage and culture condition should be considered. This chapter provides basic information and recent data on nutrient requirements of Siberian sturgeon to illuminate the way for sturgeon aquaculturists, feed factories, and researchers to improve and provide appropriate specialized feeds for the fish. Hence, this chapter is focused on macro- and micronutrients, feeding practices, and starvation effect of Siberian sturgeon.

Summary This study describes the sex steroid profiles and hematological indices of 5-year-old reared female Siberian sturgeon, Acipenser baerii, at perinucleolus and migratory stages to ascertain whether they are influenced by the maturity stage. Fish of 2923 g mean weight and 89 cm mean length were reared in rectangular concrete tanks (25 × 3 × 0.6 m, mean water temperature 16.2 ± 2.2°C, fed a diet with 38.2% crude protein and 7% crude fat in 10 kg m−2). Blood samples were taken for serum steroid levels, including 17-β estradiol (E2), testosterone (T), 17α-hydroxy progesterone (P) and hematological indices (packed cell volume, hemoglobin, red blood cells, white blood cells, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration as well as leukocyte differential counts). Hematological indices and the leukocyte differential count showed no significant differences among fish at the perinucleolus and migratory stages. The results indicated significant differences in E2 levels among fish at the perinucleolus and migratory stage, but the T and P levels showed no significant differences between stages. This study indicates that serum sex steroid measurements and histological observations can segregate females effectively at the perinucleolus and migratory stages; however, the hematological parameters did not discriminate females at these stages. Such observations provide basic information to achieve a method to determine with high accuracy the stage of sexual maturity, for better sturgeon aquaculture management.

The present study made an attempt to measure the cortisol content, as an indicator of stress response, in rainbow trout embryos which were exposed to different densities and handling stress (air exposure) during incubation. The three densities of experimental embryos at early development stages were considered as 2.55 embryos/cm(2) (low density), 5.10 embryos/cm(2) (normal density) and 7.65 embryos/cm(2) (high density). The cortisol content of eggs (5.09 ± 0.12 ng/g) decreased to 3.68 ± 0.14 ng/g in newly fertilized eggs. Resting level of cortisol dropped at three densities by day 18 of post fertilization. Then, cortisol increased at hatching stage to 1.16 ± 0.11, 1.20 ± 0.12 and 1.21 ± 0.14 ng/g at low, normal and high densities, respectively. There were no statistically significant differences between cortisol concentrations in three densities. The acute handling stress test (5-min out-of-water), conducted on embryos (48 h post fertilization, organogenesis and eyed stage) in three densities, revealed no differences in whole-body cortisol levels between stressed and unstressed experimental groups. At hatching stage in low-density group, level of cortisol increased but the difference with the pre-stress levels was not statistically significant. Furthermore, significant differences in cortisol levels of stressed and unstressed embryos were detected on hatching in normal and high density groups [1.20 ± 0.12 at time 0-1.49 ± 0.11 ng/g at 1 hps (hours post stress) and from 1.21 ± 0.14 at time 0 to 1.53 ± 0.10 ng/g at 3 hps, respectively]. The results showed no difference in profile of cortisol in different densities, but acute stress conducted on embryos, incubated in different densities, revealed differences in cortisol stress response at hatching between normal and high density, which lead to cortisol increase at hatching time. It indicates that the lag time in the cortisol response to stressors immediately after hatching does not occur when the siblings were stressed during the embryo stage. Results, finally, indicated that hypothalamus-pituitary-interrenal axis was active and responded to an acute stressor under normal and high density, but it is unresponsive to a stressor around hatching under low density.

Due to the importance of ascorbic acid (AA) in fish larval development and performance, chironomid (midge) larva were enhanced with AA using chicken manure mixed thoroughly with a stable form of ascorbic acid (L-ascorbyl-2-polyphosphate). AA was used in three doses (0, 100, and 1,000 mg/kg) each with three replicates. The chironomid culture was maintained for 18 days. There were no significant differences (P > 0.05) in average biomass and growth of chironomid larva among the treatments. Spectrophotometric analysis of AA content of chironomids demonstrated that 1,000 mg/kg produced larvae with significantly (P < 0.05) higher AA content (779.86 ± 31.81 μg/g) than 0 (74.2 ± 15.45 μg/g) or 100 mg/kg (325.03 ± 116.61 μg/g). This result indicated that using chicken manure as substrate mixed by high doses of stable form of AA is an efficient method of enriching and enhancing the nutritional value of this kind of live feed.

Chironomid larvae have a high reproduction capacity. Because of their excellent nutritional quality, they have great potential in larval fish nutrition, specially bottom feeders like sturgeons. In this study, indoor production of Chironomus riparius was performed by controlling the physicochemical factors and developing an appropriate condition for this insect to complete the life cycle. Enrichment of lava was conducted by adding 0 (C0), 100 (C100), or 1000 (C1000) mg of ascorbic acid to 1 kg of chicken manure (as substrate). Ascorbic acid analysis of chironomid larva showed significant differences among the groups: 74.2 μg/g for C0, 325.0 μg/g for C100, and 779.9 for C1000. In the second experiment, enriched chironomids were fed to larval Persian Sturgeon Acipenser persicus and were compared with sturgeons fed live cladocerans, Daphnia, which are regulary used in hatcheries. Length and weight measurements after 14 d of the experimental period showed no significant differences in growth performanc...

Effects of dietary ascorbic acid (AA) supplementation were carried out on growth performance and physiological indices in juvenile beluga Huso huso fed different levels of dietary L-ascorbyl-2-polyphosphate as AA source consisting of 0 (control), 100, 200, 400, 800 and 1600 mg AA kg−1 diet for 16 weeks. No significant differences were found in growth performances between treated groups except for condition factor. Using AA caused significant differences in haemoglobin, number of red blood cells, white blood cells, aspartate aminotranspherase and lactate dehydrogenase, while no significant difference was found in haematocrit, mean corpuscular haemoglobin concentration, differential white blood cells count and alkaline phosphatase activity at the end of the experiment. Lysozyme activity after 8 weeks was significantly affected by dietary treatments with the lowest value in fish fed control diet, but not at completion of 16-week feeding trial. Liver AA concentration showed a significant increase in correlation with dietary AA increase. Air exposure stress test showed significant differences among the treatments in case of cortisol and glucose concentrations. Also between pre- and post stress, significant changes were observed in some of treatments. The lowest and highest levels of cortisol were 9.2 ± 3 (in 200 mg kg−1) and 16.8 ± 5.1 ng mL−1 (in control), 6 h post stress (P

The present study aimed to investigate the effect of thiamine on growth, hematological, egg thiamine content and oocyte nucleus migration indices in sterlet sturgeon (Acipenser ruthenus). A total of 45 female fish (698.6 ± 8.9 g) were distributed in nine fiberglass tanks with three treatments (each in three replicates). Experimental fish were fed once a day with practical diet supplemented with 1 g kg−1 amprolium hydrochloride (as the antithiamine) for 5 months before spawning. Thiamine hydrochloride was injected to fish with one of three doses at 0, 5 and 50 mg kg−1 body weight (BW) at three different stages. At the end of each month, fish were weighed and growth parameters such as weight gain, specific growth rate, feed efficiency and final weight were determined. At the end of the 5-month period, hematological parameters and egg thiamine content were measured. The results showed no significant differences in terms of growth performance. Hemoglobin, number of red blood cells and white blood cells were not significantly different among the treatments, but hematocrit was significantly higher in fish injected with 5 mg kg−1 BW thiamine. The mean corpuscular volume and mean corpuscular hemoglobin were not significantly different, but lower value of mean corpuscular hemoglobin concentration was observed in fish injected with 5 mg thiamine. Percentage of lymphocytes, neutrophils, eosinophils and monocytes were not significantly different among treatments. The results of the germinal vesicle migration index at different stages showed no significant differences in different groups. Results showed that free thiamine, thiamine pyrophosphate and total thiamine in eggs significantly increased at 50 mg kg−1 injection dose compared with the control, but no significant different was found in thiamine monophosphate. The results revealed that thiamine injection to sterlet broodstocks has positive accumulation in egg thiamine content and some hematological parameters but have no effect on growth and ovarian maturation. We conclude that thiamine can affect some physiological features of broodstock, which needs to be specified in further studies.

This study was carried out to investigate the effect of an acute stressor on the variation of some physiological and immunological parameters of Siberian sturgeon (Acipenser baerii) juveniles. Fish, reared in 3 tanks for 10 weeks, were used for this study. The acute stress of fish consisted of 2 min of air exposure stress. Plasma levels of cortisol, glucose, and lactate as well as lysozyme activity in plasma were measured before stress and 1 hr, 3 hr, 6 hr, 9 hr, 12 hr, and 24 hr after stress. The plasma cortisol significantly increased in the highest level 1 hr after stress, yet it gradually declined after 3 hr. The glucose significantly increased only 1 hr after stress. There was no significant difference between plasma lactate prestress and poststress. Moreover, lysozyme activity was enhanced by stress, thus reaching the highest level 9 hr after stress. The results of this study indicate that Siberian sturgeon not only have a rapid response to acute stress, but also a great capacity for recovery from stress, thus returning physiological parameters to prestress levels after 6 hr.

Cortisol level changes in response to stocking density in the early stages of rainbow trout were measured. Eggs were exposed to low, normal, and high (2.55, 5.10 and 7.65 eggs cm(-2)) densities during the incubation period. Cortisol of maternal origin was found in pre-fertilized eggs (5.09 ± 0.12 ng g(-1)) of rainbow trout. In newly fertilized eggs, resting Cortisol levels (3.68 ± 0.14 ng g(-1)) decreased to 0.58 ± 0.08, 0.60 ± 0.12, and 0.57 ± 0.16 ng g(-1) at low, normal and high densities by day 10 (organo-genesis), respectively. Resting Cortisol levels remained constant until the eyed stage (day 18). Then, Cortisol showed an increase at hatching to 1.16 ± 0.11, 1.20 ± 0.12, and 1.21 ± 0.14 ng g(-1) at low, normal, and high densities, respectively. The pattern of change in Cortisol level was similar in all three densities. Interrenal cells were observed in 1-day old alevins at all three densities. Hematopoietic tissue, renal tubules and nucleated red blood cells were clarified through the head part of kidney. Higher numbers and larger interrenal cells were observed at high-density groups. Chronic density stress test conducted on embryonic stages of rainbow trout revealed no differences in Cortisol levels, but had an effect on the abundance and size of the interrenal cells. Densities were equaled after hatching (200 alevins per replicate) to investigate the different densities of eggs on stress indices in rainbow trout alevins. An acute stress (air exposure of eggs for five minutes) was applied in three treatments two weeks after hatching, and samples were taken at 0, 1, 3, 6, and 24 hps (hours post stress). Cortisol content increased under low density in 1 hps and reached from 5.21 ± 0.13 ng g(-1) to 6.01 ± 0.18 ng g(-1) (P0.05). Cortisol levels increased under normal density in 1 hps from 6.03 ± 0.28 ng g(-1) to 10.84 ± 0.18 ng g(-1) (P0.05). In high density also Cortisol increased from 6.83 ± 0.23 ng g(-1) to 8.86 ± 0.26 ng g(-1) (P0.05). At 3 hps;, Cortisol level was returned to basal level under low (P0.05) and normal (P0.05) densities, but significantly decreased (P0.05) under high density. Results revealed that the Cortisol biosynthesis was observed in rainbow trout between eyeing to the hatching stage. An increase in the density of eggs until 7.65 egg cm(-2) impaired Cortisol secretion and feedback system in alevins. However, more studies are needed to identify the exact time for Cortisol synthesis ability from eyeing to hatching in this species.