Aim The objective of this study was to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from the intestinal ecosystem of rainbow trout. Methods and Results Among LAB isolates, 10 of them were selected and screened for resistance to acid and bile salts, pancreatin, sodium chloride and temperature, hydrophobicity, growth profile and antimicrobial activity against fish pathogens. Then, biosafety assessments were investigated. Selected LAB tolerated to gastrointestinal physiological conditions, pancreatin and a range of sodium chloride and temperature. They also exhibited hydrophobicity and showed antagonistic activity against Streptococcus iniae and Yersinia ruckeri. Results of 16S rRNA gene sequencing showed that selected LAB belonged to the Lactococcus lactis (n = 5) and Weissella oryzae (n = 5) species. They exhibited no β‐haemolytic activity, while six selected LAB were resistant to some antibiotics. None of them harboured virulence factors. Conclusions This study revealed probiotic characteristics of indigenous LAB isolated from the intestinal ecosystem of rainbow trout. However, further studies are required to confirm the effectiveness of these isolates as probiotics in aquaculture. Significance and Impact of the Study To the best of our knowledge, for the first time, the presence of probiotic candidates belonging to W. Oryzae was confirmed in fish intestinal microbiota.

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.

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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. K E Y W O R D Sbiochemical indices, body composition, fasting, growth, haematology, restricted feeding, sturgeon | 283 SHIRVAN et Al.