فصلنامه شیلات
سال هفتاد و پنجم شماره 2 (تابستان 1401)

Wastewaters contain nutrients that can be used as culture media for microalgae. In this study, density, growth, and biochemical compositions (protein, lipid and carbohydrates) of Tetraselmis tetrathele were investigated using mollasse and beer wastewater. A completely randomized experimental design was performed containing treatments; Conway, mollasse, and beer wastewater in two concentrations of diluted (5 ml per liter of culture medium, v/v), and concentrated (10 ml per liter of culture medium, v/v) over a 11-day period. The highest cell density was obtained in the concentrated mollasse treatment (96.7×103 cells per ml) and the highest specific growth rate obtained in the dilute Conway treatment (15.5 per day). In addition, the highest amount of protein and lipid (39.5% and 8.1%, respectively) was measured in the concentrated beer treatment and the lowest recorded in the concentrated Conway treatment (10.70% and 2.98%, respectively). The highest amount of carbohydrates (28.92%) was obtained in diluted mollasse treatment. Therefore, based on the results of growth rate and biochemical compositions of T. tetrathele, it can be concluded that the beer and mollasse wastes are suitable media for growth of T. tetrathele..

In this study, phycocyanin pigment extraction from Arthrospira platensis microalgae was carried out using various solvents (distilled water, phosphate buffered saline) and methods (sonication, microwave and freezing & thawing) for comparison and determine the best solvent and method in order to achieve higher extraction yield. Rate of 0.1 g A. platensis powder in 10 cc of solvent (distilled water and phosphate buffered saline) was similar in each three extraction method whereas the conditions of extraction methods sonication, microwave and freezing & thawing as follows, respectively: 50% amplitude and 15 min, 100 W and 3 min, frozen at -20 ± 2 °C for 24 h and thawing at room temperature. The analysis of variance was obtained for data mean ± SD (standard deviation) using SPSS in confidence level of (P < 0.05). Most extraction yield was obtained by phosphate buffered saline (PBS) and method Freezing & Thawing (pc= 146/3 ± 1/55 mg/g) and least by distilled water and method Microwave (pc= 94/4 ± 2/68 mg/g).

Strengthen defense mechanisms with immune system stimulants like probiotics, it is a good way to prevent diseases and increase the efficiency of reproduction and breeding in fishers. Bacillus and Lactobacillus are a group of gram-positive bacteria and previous studies have shown that the use of these bacteria improves immunity and reproductive factors in aquaculture. In this study, the combined effects of optimal concentrations of two probiotics, Bacillus and Lactobacillus, on qualitative indicators including: larval stage index (LSI), larval condition index (LCI), larval dry weight, larval survival, Simultaneity of larval maturation to post larvae, time of emergence of first post larvae, duration of larval period and salinity and formalin stress tests in order to investigate Improvements in qualitative growth indices and immune system of Vannami shrimp larvae were examined. For this purpose, two concentrations of 3×105 (B1) and 6×105 (B2) CFU/g from of bacterial suspension mixtures Bacillus probiotic and two concentrations of 3×106 (L1) and 6×106 (L2) CFU/g from of bacterial suspension mixtures probiotic Lactobacillus in combination includes: B1L1, B1L2, B2L1 and B2L2 were added to the water of Vannami shrimp larval reservoirs. The results showed that the larval quality indices at different levels of combined probiotics differed significantly from the control treatment and the best results were at level 4, respectively: Survival was 61±3.41, dry weight was 143±5.48, larval maturation reached was 1.26±0.02, the time of emergence of the first larval post was 7.5±0.82, the length of the larval period was 8.4±0.15. The two indices of larval stage index and larval status index were examined on the third, sixth and ninth days. The results showed a significant difference between the control group and other combination treatments, and no significant difference between combination treatments for both indices. Salinity and formalin stress tests also showed significant differences between the control group with different levels of combined probiotics for all indicators. Finally, the most important quality indicators of larvae 31% increase in survival, 30% increase in dry weight, 33.8% improvement in the synchronization index of larvae reaching post-larvae, 14.7% decrease in the time of emergence of the first post-larvae and 20% reduction in larval duration was observed at level 4.

In this study, the effects of different levels of dietary supplementation with vitamin C, astaxanthin and lecithin on some biochemical indices of ovarian fluid (Total protein, ACP, ALP, LDH and AST enzymes) and reproductive performance (fecundity and fertilization rate) of Caspian brown trout (Salmo trutta caspius) were investigated. For this purpose, nine experimental diets were formulated and supplemented with different combinations of vitamin C at levels of 0, 300 and 700 mg kg-1 diet, astaxanthin at levels of 0, 50 and 100 mg kg-1 diet and soybean lecithin at levels of 0, 6 and 9% (C0A0L0, C300A50L0, C700A100L0, C0A50L6, C300A100L6, C700A0L6, C0A100L9, C300A0L9, C700A50L9) and broodstocks (2.51±0.05 kg) were fed for four months. After maturation and stripping, ovarian fluid was separated for biochemical indices and oocytes used for reproductive performance. Based on the results, a significantly increase was observed in the total protein content of ovarian fluid of fish fed with the treatments C300A100L6, C700A50L9, C700A0L6, C0A100L9 and  C300A0L9 compared to the control (p<0.05). Also, the lowest LDH ​​were obtained in treatments C300A100L6, C0A100L9 and C0A50L6, which were significantly different from the control (p<0.05). Treatments C700A0L6 and C0A100L9 had the lowest AST ​​and the highest ALP values, both of which were significantly different from the control (p<0.05). The highest fecundity and fertilization rate were observed in C0A100L9 and C300A100L6 treatments which were significantly different from the control (p<0.05). In conclusion, dietary supplementation of 300 mg kg-1 vitamin C with 100 mg kg-1 astaxanthin and 6% lecithin led to a decrease in AST and LDH enzymes activity and improvement of fecundity and fertilization rates.

The aim of this study was to enrich the rotifer with microscopic algae as a feed in order to investigate their effects on growth indices and survival rates of rainbow trout larvae. For this purpose, Chlorella vulgaris and Scenedesmus quadricauda were used as foods, separately and together, for feeding the rotifer Brachionus plicatilis. In treatment 1, the larvae fed the enriched rotifers with chlorella, in treatment 2 fed the enriched rotifers with Scenedesmus algae and in treatment 3, fed the enriched rotifers with a combination of chlorella and Scenedesmus (50%). The control was performed using commercial feed. The density of algae cells per milliliter of water kept at 10 × 107 cells in each medium. In each experimental unite, a 60 liter of fish tank, 30 rainbow trout (Oncorhynchus mykiss) were stored. The mean (± SD) larvae weight reached to 409.66 ± 2.51 and 594.66 ± 4.93 mg on days 14 and 21 in the control group and the maximum weight was 694.33 ± 7.50 mg on day 21 in treatment 3. The specific growth, feed conversion ratio and protein efficiency and survival rates were also significantly different among treatments 1, 2 and 3 (P <0.05). The body composition analysis showed significant (P <0.05) differences in crude protein and crude fat indices in treatments 1 and 3 on day 21. The results of this experiment showed that the enriched rotifers with Chlorella and a combination of Chlorella and Scenedesmus could significantly improve the growth and survival indices in Larvae of Rain bow trout.

The present study estimated relative frequency index of Purpleback flying squid and Oman cuttlefish also evaluated the effect of depth, distance, and time of capture (before & after noon) on them. Sampling was in the west of the Gulf of Oman at the spring of 2019. The depth of the Gulf was 208 to 285 meters. The vessel used was an industrial Myctophid trawler and the sampling gear was a rope trawl that operated with the fishing technique in a water column (the bottom panel was maximum 6 meters higher than the bottom of the Gulf). According to field observations, the average catch per unit of effort index in Purpleback flying squid and Oman cuttlefish was estimated to be 7584.22 and 1345.066 gram / hour based on weight and 19.062 and 18.250 number / hour based on number, respectively. Based on the selected models, the variables of depth and distance had a significant effect on catch per unit of effort for Purpleback flying squid (P<0.05). With increasing depth and distance, the catch per unit of effort for squid increased. However, based on the results, no significant effect of the studied variables on the relative abundance index of Oman cuttlefish was observed, given the lack of sufficient research on this theme and the discard caught of these species in Iranian waters, more extensive research to manage their stock in the Gulf of Oman is a need..

The aim of this study was to investigate the effects of iron nanoparticles and the LactobacillusThe aim of this study was to investigate the effects of iron nanoparticles and the Lactobacillus probiotic on the activity of digestive enzymes and the intestinal microbial flora of the common carp (Cyprinus carpio). For this purpose, 180 carp with an average weight of 40±5 g were fed with 6 experimental diets with different levels of iron nanoparticles and Lactobacillus, including: treatment 1 (control group) (commercial food without adding any iron nanoparticles and probiotics), treatment 2 (commercial food containing 108 CFU/g probiotics), treatment 3 (commercial food containing 0.25 mg/g iron nanoparticles), treatment 4 (commercial food containing 0.50 mg/g iron nanoparticles), treatment 5 (Commercial food containing 0.25 mg/g iron nanoparticles with 108 CFU/g probiotics) and treatment 6 (commercial food containing 0.50 mg/g iron nanoparticles with 108 CFU/g probiotics). The results of this study showed that the use of iron nanoparticles and Lactobacillus probiotic had a significant increase in the activity of digestive enzymes alpha amylase, trypsin, chymotrypsin, alkaline phosphatase, protease and lipase (P <0.05). The results of bacterial analysis of fish intestine showed that while in probiotic treatments, Lactobacilli occupied the dominant flora, the addition of iron nanoparticles also increased the total number of intestinal bacteria. What can be concluded in general is that increasing the activity of carp digestive enzymes by adding iron nanoparticles and probiotics along with its establishment in the fish digestive tract will be able to provide better conditions for fish growth and improve nutritional factors.s.