Incubation rate and larvae size of Persian sturgeon (Acipenser persicus Borodin 1897) in relation to sperm restripping

In this study, 11 wild male brood fish were used and their mean ages were 15.08 ± 1.66. The luteinizing hormone‐releasing hormone analogue (LH‐RH‐A₂) was used to stimulate twice in few days interval (3–7 days) and then semen samples were stripped. The results showed that there was significant difference among the percentage of motile spermatozoa, sperm density and spermatocrit during two strippings (P < 0.05). The duration of sperm motility in first and second stripping was 315/83 ± 162.16 and 212.5 ± 110.53 s respectively. Also, sperm pH was 8.41 ± 0.53 and 8.05 ± 0.33 in first and second stripping respectively. There was significant differences between hatching rate, as well as larvae size significantly changed in both hatching and initiation of active feeding (P < 0.05).     

Improvement in wild endangered Persian sturgeon,Acipenser persicus (Borodin, 1897) semen cryopreservation by 2‐hydroxypropyl‐beta‐cyclodextrin (HβCD)

In this study, cryopreservation feasibility of Persian sturgeon (Acipenser persicus) and the effect of different doses of 2‐hydroxypropyl‐beta‐cyclodextrin on thawed spermatozoa quality (motility duration and motility percentage) were investigated. For freezing, semen of seven male individuals was pooled in equal volumes and diluted with 4°C [Tris‐HCl (100 mM), pH = 8, DMSO 10%] extenders containing 0, 5, 10, 15 mM of HβCD in a ratio of 1:1(semen/extenders). Then semen was filled into 0.5‐mL straws, and was frozen with vapour of liquid nitrogen at 4‐cm above surface of liquid nitrogen. After 3 min, straws were plunged in to liquid nitrogen. Thawing was performed at 40°C water baths for 15 s. Motility duration of the 10 mM HβCD treated spermatozoa at days 14 (228.98 ± 16.39) and 56 (199.66 ±21.78) were longer than other treatments. In day 56, the motility percentage in treatment with 10 mM was significantly higher (16.14 ± 2.54) (P < 0.05) compared with 5 mM treatment (8.75 ± 2.47) (P < 0.05). Therefore, it is recommended that 10 mM of HβCD can be used as an additive cryoprotectant for increasing cryopreserved spermatozoa quality in this species.     

Effects of the dietary protein levels and the protein to energy ratio in sub‐yearling Persian sturgeon,Acipenser persicus (Borodin)

A 3 × 4 factorial design was used to evaluate the dietary protein requirement and to determine the optimum dietary protein to energy (P/DE) ratio in sub‐yearling Persian sturgeon, Acipenser persicus, reared in the indoor system. Twelve experimental diets (₄₀P₁₆, ₄₀P₁₇, ₄₀P₁₈, ₄₀P₁₉, ₄₅P₁₉, ₄₅P₁₇, ₄₅P₁₈, ₄₅P₁₉, ₅₀P₁₆, ₅₀P₁₇, ₅₀P₁₈ and ₅₀P₁₉) were formulated and prepared to contain three protein levels (40%, 45% and 50%) and four digestible energy levels (16, 17, 18 and 19 kJ g^?1 diet) at each protein level. Fish averaging 103.3 ± 3.5 (mean ± SD) were fed one of the experimental diets for 14 weeks. At the end of the experimental period, there were significant energy effects (P < 0.05) on weight gain (WG) and specific growth rate (SGR). Weight gain and SGR tended to decrease, although non‐significantly, with increase in dietary protein levels. Furthermore, there were significant protein and energy interaction effects on WG, SGR, hepatosomatic index and protein efficiency ratio. However, there were no significant dietary protein, energy or their interaction effects on feed efficiency for fish fed all diets. Weight gain and SGR of fish fed ₄₀P₁₉ were significantly higher than those of fish fed ₄₀P₁₆, ₄₅P₁₆, ₄₅P₁₇, ₅₀P₁₆ and ₅₀P₁₇ diets (P < 0.05). There were no significant differences in WG and SGR among fish fed ₄₀P₁₇, ₄₀P₁₈, ₄₀P₁₉, ₄₅P₁₈, ₄₅P₁₉, ₅₀P₁₈ and ₅₀P₁₉ diets. These results may indicate that the optimum dietary protein requirement and the P/DE ratio could be 40% protein and 22.0 mg protein kJ^?1 (₄₀P₁₈), respectively, in Persian sturgeon, based on growth performance and feed utilization.     

The effect of dietary taurine on growth performance and liver histopathology in Persian sturgeon,Acipenser persicus (Borodin, 1897) fed plant‐based diet

This experiment was conducted to illustrate the effect of dietary taurine levels on Persian sturgeon, Acipenser persicus (mean weight of ~35 g) fed plant‐based diet. A basal diet containing low level of fishmeal (19%) was formulated containing 0.05% endogenous taurine (control diet). To this diet were added five levels of exogenous taurine: 0.25 (0.25T), 0.5 (0.5T), 0.8 (0.8T), 1.2 (1.2T) and 1.6% (1.6T). These diets were fed to the experimental fish for 42 days. Results showed that growth performance decreased and food conversion ratio increased as dietary taurine increased, although no significant difference was observed between the control and 0.25T treatments. Increased dietary taurine led to increased carcass moisture and decreased carcass lipid percentages. Feed intake was significantly and negatively correlated with dietary taurine. Carcass taurine content significantly increased with dietary taurine elevation up to 1.2% and then decreased. Hepatic taurine content showed a significant increase in 0.25T treatment and then decreased along with dietary taurine elevation and reached the control values at 1.6% taurine level. Dietary taurine elevation led to more hepatic damages compared to the control. In conclusion, although within the range reported for other studied fish, the tested taurine levels in this study might be supra‐optimal causing adverse effects in Persian sturgeon and further study with lower taurine levels is encouraged.     

Physiological,ionoregulatory, metabolic and immune responses of Persian sturgeon,Acipenser persicus (Borodin, 1897) to stress

The physiological ionoregulatory, metabolic and immune responses of Persian sturgeon, Acipenser persicus, to acute stress were investigated. Water levels were lowered to the fish dorsal scutes, and fish were blood‐sampled before stress (pre‐stress), and 0, 6, 24 and 72 h after stress. Results showed that serum cortisol rapidly increased after stress, returning to initial levels at 24 h. Serum glucose significantly increased at 6 h, declining to the pre‐stress levels at 72 h. Serum triglyceride and cholesterol showed significant decreases at 0 h, then increasing to higher than the initial levels at 72 h. Serum T₃ and T₄ significantly decreased at 0 h and recovered at 72 h. Serum chloride levels showed no significant changes while serum calcium showed a significant increase at 0 h and a further increase until 72 h poststress. Serum total protein and alternative complement activity showed a significant initial decrease and recovery at 24 h with further increase at 72 h. Serum lysozyme activity increased significantly at 24 and 72 h after stress. Serum total immunoglobulin significantly increased at 0 h and peaked at 24 h. This is the first work showing thyroid hormone and immunological responses in Persian sturgeon subjected to stress, and the results show that this species follows a classical hormonal and energetic stress response, although, in the low range among the sturgeons. Although transient and moderate, confinement stress can induce significant changes in the innate immune response.     

Tuna viscera protein hydrolysate: nutritive and disease resistance properties for Persian sturgeon (Acipenser persicus L.) larvae

The effect of fish protein hydrolysate (FPH) on the growth, feed utilization, digestive enzymes, gut microflora and resistance to bacterial challenge in Persian sturgeon (Acipenser persicus) larvae during a 45‐day feeding trial has been investigated. Artificial diets containing different levels of tuna visceral protein hydrolysate (PH0, PH10, PH25 and PH50) and live foods (Artemia: 5 days, Daphnia: 40 days) were fed to Persian sturgeon larvae. Larvae fed on the PH10 and PH25 had growth, feed utilization, protein content and trypsin activity significantly better than PH0 and PH50 groups (P < 0.05). Condition factors, survival rate and pepsin activity were not significantly different (P > 0.05). Brush border membrane enzymes to cytosolic enzyme ratio revealed that maturation had been occurred in 41 days post hatch (dph) at moderate FPH levels. In 54 dph larvae, this ratio was not affected by the level of FPH in the diet. No significant differences were observed in the total number of gut microflora or in the resistance to Aeromonas hydrophila (P > 0.05), whereas lactic acid bacteria was significantly higher in PH50 (P < 0.05). The results of this study show that application of moderate levels of FPH in Persian sturgeon diets could enhance larvae performance due to the early maturation in intestinal.     

Preliminary study on the activity of protease enzymes in Persian sturgeon (Acipenser persicus Borodin, 1897) larvae in response to different diets: effects on growth and survival

The specific activity of alkaline protease, trypsin and pepsin‐like enzymes was measured in yolk sac stage Acipenser persicus larvae and over a 1‐month feeding experiment using live Artemia nauplii (ND), formulated feed (FD) or mixed food (MD). Artemia nauplii group larvae showed significantly higher growth and survival during the first 15 days while FD larvae showed the lowest growth and survival. At day 30, MD larvae exhibited significantly higher growth than the ND group. Alkaline protease activity showed the lowest activity on day 15; the highest activity was observed in the MD group larvae. Pepsin‐like activity showed a drastic increase from day 1 to 5 in all treatments, but remained stable throughout the next 25 days, with the lowest and the highest activity in the FD treatment on day 10 and in the MD treatment on day 30 post‐feeding respectively. Trypsin‐like activity in group ND remained almost the same from day 5 to 30, whereas in groups MD and FD, it decreased significantly from day 10 to 30. The contribution of the naupliar proteases was moderate but effective. Additionally, better performance in Artemia fed sturgeon larvae may also be due to the structure and digestibility of proteins and the food intake stimulation by the nauplii.     

The effect of lactic acid bacteria administration on growth,digestive enzyme activity and gut microbiota in Persian sturgeon (Acipenser persicus) and beluga (Huso huso) fry

The aims of this study was to assess the effect of two lactic acid bacteria (LAB), Lactobacillus curvatus and Leuconostoc mesenteroides, originally isolated from gastrointestinal (GI) tract of beluga (Huso huso) and Persian sturgeon (Acipenser persicus), respectively, on growth, survival and digestive enzyme (amylase, lipase and protease) activities and the population level of LAB in the GI tract. The treatments included 10 different groups; control, separate supplements of L. curvatus and Leu. mesenteroides at three different counts [2 × 10⁹, 5 × 10⁹ and 9 × 10⁹ colony forming units (CFU) per gram food] and three combinations of the two LAB (2 × 10⁹ + 2 × 10⁹, 5 × 10⁹ + 5 × 10⁹ and 9 × 10⁹ + 9 × 10⁹ CFU per gram food). The bacteria used in this study were added in lyophilized form to chopped Chironomidae. In the beluga study, highest specific growth rate, survival and improved intestinal enzyme activities were noted in the rearing group fed 9 × 10⁹ L. curvatus per gram food. In Persian sturgeon, the inclusion level of 2 × 10⁹ Leu. mesenteroides had similar positive effect. The ability of LAB to colonize the digestive tract seems to involve host specificity, and our bacteriological results are relevant to initiate future probiotic studies in sturgeons and future directions will be discussed.     

Effects of enriched Artemia by fish and soybean oils supplemented with vitamin E on growth performance,lipid peroxidation,lipase activity and fatty acid composition of Persian sturgeon (Acipenser persicus) larvae

This study aimed to evaluate the effects of enriched Artemia by fish and soybean oils supplemented with vitamin E on growth performance, lipid peroxidation, lipase activity and fatty acid composition of Persian sturgeon (Acipenser persicus) larvae. For this purpose, five experimental diets including non‐enriched Artemia (control diet), Artemia enriched with soybean oil supplemented with 15% and 30% vitamin E (S15 and S30 diets) and fish oil supplemented with 15% and 30% vitamin E (F15 and F30 diets) were used. The larvae were fed to apparent satiation four times per day for 22 days. The results indicated that fish fed enriched Artemia had no significant differences compared with those fed non‐enriched Artemia in terms of growth and survival, but increase in vitamin E levels from 15 to 30% improved growth performance of larvae. Vitamin E content in fish fed S15 and S30 diets was significantly higher. Fish fed non‐enriched Artemia had significantly higher thiobarbituric acid and lower lipase activity. The highest HUFA and n‐3/n‐6 ratio were observed in fish fed F15 and F30 diets. Our results demonstrated that fish oil can completely replace with soybean oil in larval diets. Therefore, using S30 diet is recommended for feeding of Persian sturgeon larvae.     

Effect of dietary taurine and methionine supplementation on growth performance,body composition,taurine retention and lipid status of Persian sturgeon,Acipenser persicus (Borodin, 1897), fed with plant‐based diet

The aim of this study was to investigate the effects of dietary taurine and methionine on Persian sturgeon (Acipenser persicus) fed with plant‐based diets. To this purpose, sturgeons were fed with either of methionine + taurine‐supplemented (MT), without taurine supplementation (M) or without methionine supplementation (T) diets. Growth performance, body composition, tissue amino acids and serum glucose and lipids were studied at the end of the experiment. Results showed that the treatments T and MT had similar growth performance and feed efficiency, which were significantly higher than the treatment M. Dietary taurine and methionine significantly altered carcass and liver taurine and methionine contents. The highest serum glucose was observed in the treatment M and the lowest in treatment MT. Serum cholesterol and triglyceride levels in the treatments T and MT were similar and significantly higher than those of the treatment M. This study showed that Persian sturgeon needs taurine supplementation when fed with plant‐based diets, but the supplemented level seems to be lower than those of the other species. Taurine has hypoglycaemic and lipidogenesis effects on Persian sturgeon. However, further studies are required to illustrate taurine and methionine metabolism in Persian sturgeon.     

Replacement of fish meal with blend of rendered animal protein in diets for Siberian sturgeon (Acipenser baerii Brandt), results in performance equal to fish meal fed fish

An 8w growth trial was conducted to determine the effect of partial replacement of fish meal (FM) by a blend of rendered animal protein (BAP, comprised of 40% meat and bone meal, 40% poultry by‐product meal, 20% hydrolyzed feather meal in diets for juvenile Siberia sturgeon (Acipenser baerii Brandt). Five experimental diets were formulated. The control diet (C) contained 48% FM, whereas in the remaining four diets, FM were replaced by BAP at 25% or 50% level balanced by crystallized amino acid (AA) or spray‐dried blood meal (BM), which named as BAP25‐AA, BAP25‐BM, BAP50‐AA and BAP50‐BM, respectively. Weight gain rate of BAP50‐AA group was significantly higher than that of C group, while other BAP diets did not show negative effect on growth performance. The BAP25‐BM group exhibited the lowest feed conversion rate (FCR) (P < 0.05). FM replacement by BAP did not affect chemical composition of the whole body and crude fat level of the liver, but significantly affect the fillet lipid content. Hepatic aspartate aminotransferase and serum total protein, total cholesterol and triglyceride were reduced in fish fed diet BAP50B. Siberian sturgeon showed high efficiency on utilization of crystalline amino acid as good as those from BM.     

The effect of time‐dependent protein restriction on growth factors,nonspecific immunity,body composition,fatty acids and amino acids in the Siberian sturgeon (Acipenser baerii)

The effect of time‐dependent protein restriction (PR) and refeeding were investigated on growth, body composition, fatty acids (FA), amino acids (AA) and nonspecific immune functions in the juvenile Siberian sturgeon (Acipenser baeri; 75 ± 5 g). Test diets included: T1 (control) and T2 fish fed diets containing 400 and 300 g/kg protein respectively during the whole experimental period, T3 (every other day) and T4 (every other week) fish were fed diets containing 300 g/kg protein (PR) and refeeding with diet containing 400 g/kg protein respectively, and T5 fish fed a diet containing 300 g/kg protein for 3 weeks and a diet containing 400 g/kg protein for 5 weeks, were fed to the fish for 56 days by visual satiation. Unlike ration T2 and T5, feeding treatments of T3 and T4 showed an increase in fish growth and body composition (p < 0.05) and they were very close to the control group (p > 0.05). Regarding the fatty acid profile, although the percentage of highly unsaturated fatty acids (HUFA) and polyunsaturated fatty acids (PUFA) declined significantly in the T2 and T5 groups, the saturated fatty acid (SFA) and monounsaturated fatty acids (MUFA) indicated no change among the treatments. In addition, the T2 and T5 groups demonstrated a reduction in essential amino acids (EAA) with a simultaneous increase in nonessential amino acids (NEAAs), which was significant from that of controls and other groups (p < 0.05). In terms of nonspecific immune parameters (serum lysozyme activity and alternate complement activity [ACH50]), treatment 3 has an appropriate result that did not have a significant difference with the control group (p > 0.05), but there was significant difference with other groups (p < 0.05). As a result, the T3 treatment can be used in sturgeon aquaculture practically without any negative impacts on biological or physiological indices.