Recent advances in sturgeon nutrition

Dietary resveratrol improves the flesh quality of Siberian sturgeon (Acipenser baerii) by enhancing myofiber growth, nutrient accumulation and antioxidant capacity

BACKGROUND

In aquaculture, sturgeons are generally maintained in the confined spaces, which not only hinders sturgeon movement, but also threatens their flesh quality that seriously concerned by aquaculture industry. As a typical antioxidant, resveratrol can improve the flesh quality of livestock and poultry. However, the mechanism of resveratrol's effect on the muscle of Siberian sturgeon is still unclear.

RESULTS

In this study, the dietary resveratrol increased the myofiber diameter, the content of the amino acids, antioxidant capacity markers (CAT, LDH and SOD) levels and the expression levels of mTORC1 and MYH9 in muscle of Siberian sturgeon. Further transcriptome analysis displayed that ROS production-related pathways ("Oxidative phosphorylation" and "Chemical carcinogenes-reactive oxygen species") were enriched in KEGG analysis, and the expression levels of genes related to the production of ROS (COX4, COX6A, ATPeF1A, etc.) in mitochondria were significantly down-regulated, while the expression levels of genes related to scavenging ROS (SOD1) were up-regulated.

CONCLUSIONS

In summary, this study reveals that resveratrol may promote the flesh quality of Siberian sturgeon probably by enhancing myofiber growth, nutritional value and the antioxidant capacity of muscle, which has certain reference significance for the development of a new type of feed for Siberian sturgeon.

Supplementation of Siberian sturgeon (Acipenser baerii) diet with different zinc sources: effects on growth performance, digestive enzymes activity, hemato-biochemical parameters, antioxidant response and liver histology

An 8-week feeding trial was carried out to examine the effect of different sources of dietary Zn on some physiological responses (performance, digestive enzymes activity, hemato-biochemical parameters, antioxidant status and liver histology) of Siberian sturgeon, Acipenser baerii. For this purpose, fish with an average weight of 100 g ± 5 were randomly allocated into four groups including control, inorganic zinc (Zn-sulfate), organic zinc (Zn-gluconate), and zinc-oxide nanoparticles (ZnO-NPs) at 50 mg Zn kg- 1 feed. Improved growth indices, namely weight gain (WG) and specific growth rate (SGR) and feed conversion ratio (FCR) were observed in fish fed Zn-gluconate supplemented diet (P < 0.0.5). The highest digestive enzymes activity was recorded in fish fed Zn-gluconate supplementation (P < 0.0.5). Hematological indices significantly increased in fish fed diet containing ZnO-NPs (P < 0.0.5). Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) of fish fed ZnO-NPs contained diet were the highest (P < 0.0.5). The highest serum superoxide dismutase (SOD) and catalase (CAT) enzymes activity were observed in fish fed ZnO-NPs and inorganic/organic Zn contained diets, respectively. While liver tissue SOD and glutathione peroxidase (GPx) enzymes activity Zn were significantly increased in fish fed inorganic/organic Zn supplemented diet (P < 0.0.5). Based on liver histological results, a severe tissue changes such as necrosis and pyknosis were observed in fish fed with Zn-sulfate in comparison to other forms. In conclusion, the data of the present study confirmed that organic Zn (mainly) and nano-Zn (to some extent) could be more efficient Zn sources in Siberian sturgeon.

Mechanism of Chinese sturgeon IFN-γ inhibition on Mycobacterium marinum (Acipenser sinensis)

IFN-γ plays a crucial role in both innate and adaptive immune responses and is a typical Th1 cytokine that promotes Th1 response and activates macrophages. When macrophages were incubated with IFN-γ, their phagocytosis ratio against Mycobacterium marinum increased significantly, as observed under fluorescence microscopy. The macrophages engulfed a large number of M. marinum. The proliferative ability of macrophages treated with IFN-γ was significantly weaker on the 4th and 7th day after phagocytosis and subsequent re-infection with marine chlamydia (P < 0.001). This suggests that IFN-γ enhances the phagocytosis and killing ability of macrophages against M. marinum. IFN-γ protein also significantly increased the production of reactive oxygen species (H2O2) and nitric oxide (NO) by macrophages. Additionally, the expression levels of toll-like receptor 2 (tlr2) and caspase 8 (casp8) were significantly higher in macrophages after IFN-γ incubation compared to direct infection after 12 h of M. marinum stimulation. Apoptosis was also observed to a higher degree in IFN-γ incubated macrophage. Moreover, mRNA expression of major histocompatibility complex (MHC) molecules produced by macrophages after IFN-γ incubation was significantly higher than direct infection. This indicates that IFN-γ enhances antigen presentation by upregulating MHC expression. It also upregulates tlr2 and casp8 expression through the TLR2 signaling pathway to induce apoptosis in macrophages. The pro-inflammatory cytokine showed an initial increase followed by a decline, suggesting that IFN-γ enhances the immune response of macrophages against M. marinum infection. On the other hand, the anti-inflammatory cytokine showed a delayed increase, significantly reducing the expression of pro-inflammatory cytokines. The expression of both cytokines balanced each other and together regulated the inflammatory reaction against M. marinum infection.

Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

Neuropeptides and hormones in hypothalamus-pituitary axis of Chinese sturgeon (Acipenser sinensis)

The hypothalamus and pituitary serve as important neuroendocrine center, which is able to secrete a variety of neuropeptides and hormones to participate in the regulation of reproduction, growth, stress and feeding in fish. Chinese sturgeon is a basal vertebrate lineage fish with a special evolutionary status, but the information on its neuroendocrine system is relatively scarce. Using the transcriptome data on the hypothalamus-pituitary axis of Chinese sturgeon as reference, we found out 46 hypothalamus neuropeptide genes, which were involved in regulation of reproduction, growth, stress and feeding. The results of sequence alignment showed that the neuroendocrine system of Chinese sturgeon evolves slowly, which confirms that Chinese sturgeon is a species with a slow phenotypic evolution rate. In addition, we also isolated six pituitary hormones genes from Chinese sturgeon, including reproductive hormones: follicle-stimulating homone (FSH) and luteinizing hormone (LH), growth-related hormones: growth hormone (GH)/prolactin (PRL)/somatolactin (SL), and stress-related hormone gene: proopiomelanocortin (POMC). Similar to teleost, immunostaining localization analysis in Chinese sturgeon pituitary showed that LH and FSH were located in the pituitary proximal pars distalis, SL was located in the pituitary rostral pars distalis, and POMC was located in the pituitary pars intermedia and pituitary rostral pars distalis. This study will give a contribution to enrich our information on the neuroendocrine system in Chinese sturgeon.

Feeding Strategies for Adapting Lake Sturgeon (Acipenser fulvescens) Larvae to Formulated Diets at Early Life Stages

Cost-effective feeding management is required to support conservation hatcheries for lake sturgeon (Acipenser fulvescens), an ecologically important species in the Great Lakes region. This study investigated an approach to transition lake sturgeon larvae from live feed (Artemia) to formulated feed and its effect on growth performance, survival, and response to acute hypoxia stress. The first experiment showed that sturgeon had similar (p > 0.05) growth and survival when fed Artemia or the combined feeding of Artemia with the commercial diet (crude protein, 551 g/kg diet). Feeding solely on the commercial or lab-made (crude protein, 491 g/kg diet) diet significantly reduced growth and survival (p < 0.05). In the second experiment, the growth performance of sturgeon (14 days post-hatch, DPH) fed with either Artemia only or combined feeding different feeding durations of two, three, and four weeks followed by a complete transition to the commercial diet. At the end of six weeks, the 3- and 4-week combined feeding periods resulted in significantly higher body weight and survival compared to the 2-week combined and the Artemia only feeding treatments. In the last experiment, sturgeons (27 DPH) were fed only with Artemia or combined feeding of Artemia with the commercial diet for four weeks followed by the complete transition to the commercial diet for two weeks. Eighteen fish from each treatment were investigated the response to acute hypoxic conditions (gradual decrease in dissolved oxygen level from 8 to 2.3 mg/L at the rate of 1 mg/L per hour). When the dissolved oxygen was between 3 and 4 mg/L, the mortality rate of the combination-fed sturgeon (11.7%) was significantly lower than those fed only Artemia (83.3%). These results clearly demonstrate that a commercial diet can partially replace Artemia at early life stages to improve growth, survival, and hypoxia tolerance and thus its co-feeding with Artemia is recommended.

Antimicrobial activities and mechanism of sturgeon spermary protein extracts against Escherichia coli

This study aimed to evaluate the antimicrobial activities and mechanism of sturgeon spermary protein extracts (SSPE) against Escherichia coli. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. Cell structural change was analyzed using scanning electron microscopy-energy dispersive X-ray spectrometry and transmission electron microscope. Moreover, pH, zeta potential, membrane potential, intracellular ATP concentrations and the interaction of SSPE with genomic DNA were analyzed. Results showed that molecular weight of SSPE is 13.4 kDa, the content of basic amino acids is the highest, in which arginine accounts for 73.2%. The MIC and MBC of SSPE for E. coli were 0.05 and 5 mg/mL, respectively. After SSPE treatment, cell membrane permeability changes, zeta potential decrease and genomic DNA lysis occurred in E. coli, which indicated it exerted bacteriostatic effects either independently or simultaneously by destroying the cell membrane and genomic DNA. These findings indicated that SSPE has potential to be a natural antiseptic.

Phosphorus Absorption and Excretion in Hybrid Sturgeon (Huso dauricus♀ X Acipenser schrenckii♂) Intubated with Different Ca/P Ratios

To study the effect of Ca/P ratio on the P and Ca absorption and excretion in hybrid sturgeon (Huso dauricus♀ X Acipenser schrenckii♂), five groups of fish were intubated with 100 mg P·kg−1 BW with the Ca/P ratios of 0:1, 0.25:1, 0.5:1, 1:1, and 2:1. Plasma P concentrations were significantly elevated at Ca/P ratios below 2:1, and the highest value was obtained at Ca/P ratio of 0.5:1. Plasma Ca content was significantly increased at the highest Ca/P ratio. Urine P excretion rate in the fish intubated with Ca/P ratio of 0.5:1 was significantly higher than that of the groups with Ca/P ratios of 0:1 and 2:1. The highest urea excretion rates were observed at Ca/P ratio of 0.5:1 and 1:1. The total P excretion at 48 h post intubation reached about 30 mg·kg−1 BW, which was recorded for the group with Ca/P ratio of 0.5:1. The present study showed that P absorption efficiency was improved in hybrid sturgeon at Ca/P ratio of 0.5:1, indicating that P inclusion level in sturgeon feed can be further optimized to reduce dietary P input and lower the excessive undigested P discharge into the rearing water.

Generation and Evaluation of Novel Biomaterials Based on Decellularized Sturgeon Cartilage for Use in Tissue Engineering

Because cartilage has limited regenerative capability, a fully efficient advanced therapy medicinal product is needed to treat severe cartilage damage. We evaluated a novel biomaterial obtained by decellularizing sturgeon chondral endoskeleton tissue for use in cartilage tissue engineering. In silico analysis suggested high homology between human and sturgeon collagen proteins, and ultra-performance liquid chromatography confirmed that both types of cartilage consisted mainly of the same amino acids. Decellularized sturgeon cartilage was recellularized with human chondrocytes and four types of human mesenchymal stem cells (MSC) and their suitability for generating a cartilage substitute was assessed ex vivo and in vivo. The results supported the biocompatibility of the novel scaffold, as well as its ability to sustain cell adhesion, proliferation and differentiation. In vivo assays showed that the MSC cells in grafted cartilage disks were biosynthetically active and able to remodel the extracellular matrix of cartilage substitutes, with the production of type II collagen and other relevant components, especially when adipose tissue MSC were used. In addition, these cartilage substitutes triggered a pro-regenerative reaction mediated by CD206-positive M2 macrophages. These preliminary results warrant further research to characterize in greater detail the potential clinical translation of these novel cartilage substitutes.

Black Soldier Fly Full-Fat Larvae Meal as an Alternative to Fish Meal and Fish Oil in Siberian Sturgeon Nutrition: The Effects on Physical Properties of the Feed, Animal Growth Performance, and Feed Acceptance and Utilization

Simple Summary

Research for alternative protein sources that may replace fish meal and fish oil in fish diets is one of the ongoing tasks for aquaculture. Sturgeons role captive fish production increases due to the rapid decrease in its wild stocks during the 20th century. Insect meals are a novel group of feed materials rich in nutrients that are produced in an environmentally sustainable way. Therefore, the aim of the study was to assess the effects of black soldier fly larvae full-fat meal (BSFL) usage as fish meal and fish oil replacement in Siberian sturgeon diets. The experimentally obtained data showed the possibility of extruded feed production with up to 30% of BSFL and physical parameters suitable for fish feeding. Moreover, feed acceptance increase was observed in treatments containing than 10% and higher shares of BSFL. In the groups whose feed contained 5 to 30% of BSFL in the diet, the growth of experimental fish as well as their feed utilization parameters were improved; however, with no effects on feed digestibility. All presented data make BSFL a suitable nutrient source alternative to fish meal in Siberian sturgeon nutrition.

Abstract

This study provides data on the use of black soldier fly (Hermetia illucens) full-fat meal (BSFL) in Siberian sturgeon (Acipenser baerii) nutrition, examining pellet physical properties, growth performance, feed acceptance and utilization, apparent protein, and fat digestibility. The study consisted of: feed quality assessment; a growth performance; feed acceptance; digestibility trials. The effect of the use of BSFL as a replacement for fish meal (FM) and fish oil (FO) was investigated. The applied BSFL shares were 5%, 10%, 15%, 20%, 25%, and 30% of the diet, replacing up to 61.3% of FM and allowing us to reduce FO use by up to 95.4% in the case of 30% incorporation. The applied substitution affected feed quality, increasing the expansion rate, and decreasing feed density, sinking speed and water stability. However, body weight gain, specific growth rate, feed, and protein conversion ratios, were improved in groups fed BSFL. Moreover, feed acceptance was increased with treatments containing 10 to 30% BSFL. No effects on nutrients digestibility were observed. The results show that the use of BSFL as an FM and FO replacement may have positive effects on sturgeon growth performance, and BSFL can be developed as a promising alternative feed material.

Plant protein diet-induced hypoimmunity by affecting the spiral valve intestinal microbiota and bile acid enterohepatic circulation in Amur sturgeon (Acipenser schrenckii)

An 8-week growth trial was conducted to study enterohepatic recirculation of bile acid metabolism and the intestinal microbiota of Amur sturgeon (Acipenser schrenckii) fed with three diets, including 540 g/kg, 270 g/kg or 0 g/kg fishmeal, which was correspondingly replaced by a plant protein blend (named P0, P50 and P100, respectively). The diets were designed to be isonitrogenous, isoenergetic and essential nutrients balanced. With rising levels of dietary plant protein, disruption of the spiral valve intestinal microbiota and more morbidity with liver disease were observed in the P100 group, although there were no haematological abnormalities observed. An obvious bile acids enterohepatic circulation disorder was found with phenotypes of increased liver bile acids compensatory synthesis, and reduced expression of bile acid receptors (FXR and TGR5), which induced BA accumulative toxicity. Accompanied by increased oxidative stress, it further induced hepatic lesions and hypoimmunity, which were non-negligible reasons for the high mortality and low utilization ability of plant protein by Amur sturgeon.

Multifactorial Causes of Chronic Mortality in Juvenile Sturgeon (Huso huso)

This investigation focused on an episode of chronic mortality observed in juvenile Huso huso sturgeons. The examined subjects underwent pathological, microbiological, molecular, and chemical investigations. Grossly severe body shape deformities, epaxial muscle softening, and multifocal ulcerative dermatitis were the main observed findings. The more constant histopathologic findings were moderate to severe rarefaction and disorganization of the lymphohematopoietic lymphoid tissues, myofiber degeneration, atrophy and interstitial edema of skeletal epaxial muscles, and degeneration and atrophy of the gangliar neurons close to the myofibers. Chemical investigations showed a lower selenium concentration in affected animals, suggesting nutritional myopathy. Other manifestations were nephrocalcinosis and splenic vessel wall hyalinosis. Septicemia due to bacteria such as Aeromonas veronii, Shewanella putrefaciens, Citrobacter freundii, Chryseobacterium sp., and pigmented hyphae were found. No major sturgeon viral pathogens were detected by classical methods. Next-generation sequencing (NGS) analysis confirmed the absence of viral pathogens, with the exception of herpesvirus, at the order level; also, the presence of Aeromonas veronii and Shewanella putrefaciens was confirmed at the family level by the metagenomic classification of NGS data. In the absence of a primary yet undetected biological cause, it is supposed that environmental stressors, including nutritional imbalances, may have led to immune system impairment, facilitating the entry of opportunistic bacteria and mycotic hyphae.

Histological Evaluation of Gonad Impairments in Russian Sturgeon (Acipenser gueldenstaedtii) Reared in Recirculating Aquatic System (RAS)

Simple Summary

The growing interest in sturgeon aquaculture necessitates the constant development of rearing techniques with special emphasis on the maintenance of high fish reproduction performance. However, there is a substantial lack of knowledge regarding gonadal impairments in sturgeons, even though the occurrence of such disorders poses a significant threat to the future of both commercial and conservation farming. Therefore, the aim of the research was to determine potential pathologies in the gonads of over-four-year old Russian sturgeon (Acipenser gueldenstaedtii) reared in the controlled conditions of recirculating aquatic systems (RAS). RAS have gained popularity in recent years, as they are considered the most environmentally friendly way of producing fish. Nevertheless, there are many issues that need to be resolved regarding sturgeon RAS farming, including its effect on gonadal development and, therefore, fish reproduction capacity. A detailed histological analysis revealed multiple gonadal disorders in the analyzed sturgeon, some of which can contribute to decreased fish fertility or even sterility. The female-biased sex ratio and the character of the identified impairments indicates that the observed germinal tissue disruptions might originate from estrogenic endocrine disturbances. Therefore, for the further sustainable development of sturgeon RAS aquaculture, there is an urgent need to identify and eliminate the causes of such disruptions.

Abstract

The aim of the study was to raise an issue concerning gonadal impairments in sturgeon reared in recirculating aquatic systems (RAS). In the present study, an in-depth histological evaluation in terms of gonadal pathologies was performed on over-4-year-old (1600 days post-hatching) Russian sturgeon (Acipenser gueldenstaedtii) reared under indoor RAS. A female-biased sex ratio, intersex occurrence, ovarian fat overgrowth, T-cell infiltration and follicle atresia were the most commonly observed disorders in the analyzed gonads. The combined processes of oocyte autophagy and follicular cell apoptosis were engaged in follicular atresia; however, atretic follicles showed a varied morphology, whereas oogonia and oocytes in the early stages of meiosis, as well as spermatogonia, underwent degeneration by apoptosis. The most severe pathology was observed in females with abundant intra-ovarian fat deposition. The extremely fatty ovaries were noted to lose the majority of ovarian follicles, which directly leads to fish sterility. The identified impairments might be related to estrogenic endocrine disruption, as feminization and unspecific vitellogenin synthesis were detected, although the sources of the observed pathologies can be diverse. Therefore, the presented research lays the groundwork for further studies on reproductive disorders in this prized and endangered fish species.

Effect of different cooking methods on sensory quality assessment and in vitro digestibility of sturgeon steak

Sous vide can keep the nutritional properties and improve taste of food compared with other conventional methods. In addition, this method may reduce the risk of recontamination after cooking and during storage. The purpose of this paper was to study the effects of four cooking methods (steaming, microwaving, baking, and frying) on the sensory and digestibility on sturgeon steak pretreated by sous vide during the cold storage (0-25 days). The results showed that the digestibility of steaming and microwaving groups (range from 80.34% to 90.12%) significantly higher than that of the other treatment groups (p < .05); however, the overall acceptability of the two groups was lower. What more, the frying group has the highest acceptability and the lowest digestibility (range from 65.12% to 70.89%). The springiness (4.12-6.56 mm) and chewiness (1.75-3.12 mm) of the frying group were significantly higher than those of the other treatment groups, which was consistent with the results of scanning electron microscopy (SEM) that frying treatment group has a denser structure and smaller pores. With the prolonged refrigeration time, especially between 15 and 25 days, the volatile flavor components (nitrogen oxide, methane, and alcohol) and stagnant water (T21) were significantly decreased. Principal component analysis showed that the moisture content was the main factor affecting the overall acceptability and best consumption time of the sturgeon was within 15 days. Simulating the effects of home cooking conditions and refrigeration storage time on the quality of sturgeon steak provided a reference for consumers using similar products.

Plant protein diet suppressed immune function by inhibiting spiral valve intestinal mucosal barrier integrity, anti-oxidation, apoptosis, autophagy and proliferation responses in amur sturgeon (Acipenser schrenckii)

An 8-week growth trial was conducted to investigate the effects of replacing dietary fishmeal with a plant protein blend on the growth performance, mucosal barrier integrity and the related regulation mechanism in Amur Sturgeon (Acipenser schrenckii) with initial weight of 87.48 g. Three isonitrogenous and isoenergetic diets were prepared. A basal diet containing 540 g/kg fishmeal (P0), whereas the other two diets were formulated by replacing 50% and 100% of FM with plant protein blend (soybean protein concentrate and cottonseed protein concentrate), and named as P50 and P100, respectively. Although essential amino acids, fatty acids, and available phosphorus had been balanced according to the nutrient requirement of sturgeon, compared with the fish of P0 and P50, the full plant protein diet (P100) significantly reduced growth performance and survival, and accompanied with serious spiral valve intestinal (SVI) damage. The increased tissue necrosis and failed responses in anti-oxidation, programming apoptosis, autophagy and cell proliferation system were regulated by inhibiting ERK1 phosphorylation, which indicated that SVI hypoimmunity and functional degradation were the main reasons for the high mortality and low utilization ability of plant protein in Amur sturgeon.

Effects of dietary soybean lecithin on growth performance, blood chemistry and immunity in juvenile stellate sturgeon (Acipenser stellatus)

An eleven weeks feeding trial was conducted to determine the effects of different levels of dietary soybean lecithin (SBL) on growth performance, blood chemistry and immunity in juvenile stellate sturgeon (Acipenser stellatus). Fish were fed seven isoproteic (44% crude protein) and isolipidic (17% crude fat) diets containing graded levels of SBL: 0 (control), 1, 2, 4, 6, 8 and 10%. Results showed that dietary SBL supplementation significantly improved the final body weight (BW) and weight gain (WG). Fish fed 6% SBL showed the highest BW and WG values in comparison to fish fed the control diet (P < 0.05), whereas increasing SBL levels above 6% had little practical benefit in terms of somatic growth performance. The inclusion of SBL in diets significantly improved the immune response as data from lysozyme, total Ig levels, alternative complement, phagocytic and bactericidal activities indicated (P < 0.05). The broken-line regression analysis of immunological variable revealed that depending on the parameter considered, the optimal SBL levels in diets for stellate sturgeon juveniles varied. In particular, dietary SBL levels requirements in stellate sturgeon when considering the phagocytic activity rate were determined at 3.3%, whereas 4.1-4.2% were recommended when considering data from lysozyme, alternative complement and bactericidal activities. In contrast, the highest minimum dietary SBL content was estimated at 6.9% when data from total Ig levels were considered. These results indicated that dietary PLs are required for boosting innate immunity in stellate sturgeon, although their minimal level changed depending on the immunological parameter considered. Therefore, we assume that SBL levels comprised between 3.3 and 6.9% may be used as a prophylactic measure to improve the health status in stellate sturgeon. Red blood cell count, hemoglobin and hematocrit levels increased with increasing dietary SBL levels, especially in those sturgeons fed the diet with 6% SBL (P < 0.05). In addition, white blood cell counts significantly increased as dietary SBL levels increased from 4 to 8% in comparison to the control group. Blood biochemistry was also affected by different dietary SBL levels. In particular, significantly higher levels of glucose, cholesterol, HDL and triglycerides were detected in fish fed >6%, >4%, >2% and 2% SBL, respectively (P < 0.05). Based on somatic growth parameters, blood chemistry and systemic immunity parameters, diets containing ca. 6% SBL are recommended for juvenile stellate sturgeon.