نشریه پژوهش های ماهی شناسی کاربردی
سال هفتم شماره 1 (بهار 1398)

The present investigation considered retina structure in embryos, larvae and adult Alburnus chalcoides. Histological samples of retina were provided from adult fish, different stages of embryonic and larval development. Eye primordia formed from ectoderm at 16 hours after fertilization (16hAF) and then developed to eye cups. Initial eye cup which contained undifferentiated retina began to form before 26hAF. Epithelial pigmented cells were first to be distinguished from other cells at 36hAF where as pigmentation initiated by delay at 68hAF. Larvae were hatched with undifferentiated retina at major part (~72hAF). First distinct stratification was observed at 96hAF (1DAH) with 5 strata including: retina pigmented epithelium, photoreceptor cell layer, inner nuclear layer, inner plexus layer and ganglion cell layer. At 144hAF (3DAH) outer plexus layer was distinguished. The stratification was completed at early 4DAH when photoreceptor cell layer divided into two layers i.e. outer plexus layer and photoreceptor layer,. Retina was stratified completely before yolk sac depletion was completed at late 7DAF. The strata order in adult was similar to 4DAH larva, but its thickness was different. As inner nuclear layer thickness was decreased but photoreceptor layer thickness was increased.

Five hundred and ninety two Siberian sturgeon fingerlings (average weight, 11.1±0.9 g) were randomly distributed in 16 tanks (150 L) at a density of 35 fish per tank and fed different treatments (Control, degrading bacteria, 2% PHB, degrading bacteria + 2%PHB) for 60 days. At the end of the experiment, no significant difference was observed in case of final weight in fingerlings but fish fed PHB and degrading bacteria had lower FCR then the others (P<0.05). Also dietary treatments affected on the lipid percentage in fish muscle and lowest lipid content was observed in supplemented diets (P<0.05). The bacterial metabolic activity of fingerlings hindgut was investigated by biological oxygen demand (BOD5) method using Oxitop® bottles and the results showed that the highest bacterial metabolic activity was seen in fish fed PHB. Also, at the end of the BOD test, bottles pH was measured and the results indicated that the lowest pH was observed in PHB and degrading bacteria treatments. The results in this experiment show that PHB and degrading bacteria have beneficial effects on growth performances and bacterial metabolic activity of Siberian sturgeon fingerlings. Such effects could be considered for new applications in aquaculture.

Abstract
This study was conducted to investigate the effect of different levels of phospholipids on fatty acid profile, lipid content of body and lipase activity in stellate fish (Acipenser stellatus) fed different levels of lecithin as phospholipid source. The fish with average weight of 11.25 ± 0.06 g were fed seven different diets having identical levels of protein and lipid content but different levels of soy bean lecithin (1, 2, 4, 6, 8 and 10 percent) for 11 weeks. The fish were fed at satiety during experimental period. The results showed that using up to 10% soy bean lecithin in the fish diet increased linoleic, saturated fatty acids (SFA) and n-6 highly unsaturated fatty acids (n-6 HUFA) significantly in the fish body (p<0.05), whereas there was no significant difference in EPA and DHA levels. The results revealed that the body fat composition is significantly influenced with the fat content in the diet, however, maximum lipid was observed in fish fed 6% lecithin. The lipase activity in the digestive system of stellate fish increased significantly in the groups fed 2-4% lecithin. Therefore, we can conclude that increase in soy bean lecithin level of diet up to 4 and 6% can significantly increase the lipase activity and SFA, al MUFA and n-6 HUFA fatty acids level in the stellate fish at this weight range respectively.

Selenium is an essential nutrient for physiological function, including immunity, Reproduction and nervous systems. This element as glutathione peroxidase enzyme cofactor, improve fish growth and propagation index via reducing of free radicals. In the present study, the effect of different levels of organic selenium were evaluated on some antioxidant indices, such as total antioxidant capacity (TAC) and malondialdehyde (MDA) and Reproduction indices including, gonadal development, histology evaluation, fertilization rate and survival of the treated fish larva. Adult goldfish were fed with 0 and 0/5 mg of organic selenium (Selplex) per kg food for 8 weeks, and HCG hormone was injected Intraperitoneally to induce the gonadal development in the treated broodstocks. Results showed that the TAC in blood serum treated with selenium broodstocks was increased and MDA levels were also significantly reduced. Histological studies showed selenium treated testicular tissue broodstocks, the level of mature spermatozoa are significantly higher than the control group and in the ovarian tissue, sexual maturation in the control group and treated group were in stage 2 and 5 respectively. In addition, rates of fertilization (%91/17), deformity (%8/45) and survival (%87) in the Selenium treatment compared to the control group showed significant improvement. Therefore, Significantly higher body weight, antioxidant function, gonadal development in the fish treated with 0.5 mg selenium were shown in compare to the control group, to which no organic selenium was fed.

The present study was conducted to determine the appropriate level of protein in diet of Cyprinus carpio fry based on biofloc technology. The experiment was designed based on triplicate of four bioflocs treatments (BFT) and one control treatment (CW). 450 specimens of C. carpio fry with mean weight of 17±0.08 g were stocked in 15 fiberglass tanks. Fish were fed in biofloc treatments with diets containing 23% crude protein (CP) (BFT-23%), 27% CP (BFT-27%), 31% CP (BFT-31%) and 35% CP (BFT-35%). Sugar beet molasses was added as a carbon material to development the biofloc. Fry were fed with 35% CP (CW-35%) in non-biofloc control treatment. According to obtained results, weight gain, specific growth rate, daily growth and protein efficiency rate were significantly higher in BFT-31% and BFT-27% than other treatments (P<0.05). Protein level of diet had significant effect on some parameters of blood and serum biochemistry (red blood cells, white blood cells, hematocrit, hemoglobin, total protein and albumin) in bifloc treatments and their rates in BFT-31% and BFT-35% treatments were significantly higher than other treatments (P<0.05). Results of this research indicated that diet protein level can decrease from 35% to 27% without any effect on survival, growth, feed conversion ratio and some parameters of blood and serum chemistry when Cyprinus carpio fry culture in biofloc system, and shows that biofloc system can help to protein feeding and physiological health of Cyprinus carpio.

This study aimed to investigate the effect of commercial phytase (SMIZYME PHYTASE) between diets containing 20 and 40 percent soybean meal on growth and body composition of rainbow trout. For this experiment, 300 Rainbow trout with an average initial weight of 6.5 ± 0.43 g were randomly distributed in 18 aquariums (15 fish per tank). Three replicates per treatment were considered. The fish were fed for eight weeks at a rate of 3% of body weight. To analyze the carcass some fish were randomly sampled and for growth characteristics, all fish from each tank were used at the beginning and end of the experiment. The result of this study indicated that phytase enzyme had a significant increase on some growth indices (p <0.05). Also in each levels of soy bean meal, adding 1,000 and 2,000 units of phytase could significantly increase protein content of carcasses. Adding commercial phytase to diet containing higher levels of plant protein with 40% soy replacement increased phosphorus, calcium and magnesium of carcasses. With increasing the level of phytase, the results of soy bean meal replacement is better and using 2,000 units of phytase per kg diet and 40% soy bean meal is recommended.

Abstract
In the present study, 180 Persian sturgeon fries at releasing weight with average weight of 1.8 ± 0.6 g were exposed to three different salinity levels including 0 (fresh water), 6 and 12 ppt in 96-hour and 10-day periods for measuring their gill metabolites by H-NMR based metabolomics. The results showed that changes in salinity caused changes in the metabolites involving in osmotic regulation, such as betaine, methionine, and threonine and also changes in energy metabolites such as alanine, DMA, and glutamine. After studying the metabolites, it was found that alanine, betaine, serine, glutamine, threonine, dimethylamine, fumaric acid, methionine, tyrosine, leucine, acetone, isoleucine, serine and formic acid showed significant differences between fresh and 12 ppt water. The metabolites including alanine, betaine, glutamine, threonine, dimethylamine, fumaric acid, methionine, acetic acid, and choline were significantly different between fresh and 6 ppt water, and the metabolites including lactic acid, formic acid, and serine showed significant differences between 6 and 12 ppt water (P<0.05). The need to provide energy and immunity in conditions of increasing salinity caused significant increasing in branched amino acids, lactate and alanine in 12 ppt salinity water in compare to fresh water (P<0.05). Methionine and taurine which are responsible for coping with salinity stress, as well as glutamine and fumaric acid, which change at oxygen stress, also significantly increased (P <0.05) between fresh and 12 ppt salinity water. The betaine metabolite which acts as osmotic regulator in salinity conditions and prevents intracellular water loss, showed a significant reduction (P <0.05) in 12 ppt water in compare to fresh water. The results of this study indicate that fumaric acid, methionine and branched chain amino acids are the most important biomarkers of salinity tolerance in Persian sturgeon fries.

This experiment was designed to investigate the use of live Eisenia fetida as a nutritional supplement on growth performance and carcass composition The purpose of this study was to evaluate the nutritional efficiency and changes in digestive enzymes of rainbow trout (Oncorhynchus mykiss). Fish were placed with average weight 58 g in a completely randomized design in 4 treatments and each with 3 replications. Rainbow trout with different levels of 0, 25, 50 and 75% (control, T1, T2 and T3) diet (including 50% moisture) of live worm for 8 weeks. At the end of the experiment, growth performance and body biochemical analysis were and of the experiment, nutritional function and digestive enzyme analyzes were performed. There was a statistically. Comparison of mean values obtained from final weight, weight gain, daily growth rate and specific growth rate showed a significant difference between experimental treatments. The highest amount of final weight was obtained in treatment 2 (109.24 ± 0.96 g) and the lowest in control (89.22 ± 1.21 g). The protein and lipid content of carcass was significantly different between the control and experimental treatments. The highest amount of protein and lipid in treatment 2 and 1 were 66.12 ± 0.29 and 25.73 ± 0.07 respectively. There was a statistically significant difference in the amount of feed conversion ratio (FCR) between different treatments, so that was obtained the lowest in W2 (1.50 ± 0.01) and the highest in W3 (1.95 ± 0.03). The analysis of gastrointestinal enzymes showed that amylase, protease and lipase had a statistically significant difference between control treatment and experimental treatments. The highest values obtained from them in W2 treatment were 732.68 ± 50.16, 79.33 ± 4.50 and 34.33 ± 5.35, respectively. The lowest amount of these enzymes was observed in control treatment. The results showed that using 50% of worm instead of the base diet can improve growth and carcass composition and of the base diet could lead to increased food productivity and activation of digestive enzymes.

Rutilus kutum , one of the most important and valuable is the bony fishes of the Caspian Sea and the use of gill net fishing is one of numerous methods and the use of gill net fishing is one of the main ways that likely to more die the large number of fish during captured in net. In this study, sensory and the appearance changes white fishes after fishing by gillnetting was performed to determine two treatments of live fish caught (choking in the air), and treatment of dead fish caught (death in water) in 30 samples.  Color measurements on the skin and fillet, fillet texture analyzer machine and sensory evaluation was conducted for 12 days. The results showed that the amount of hue of color measurements the fillet, texture analysis factors in hardness and chewiness, texture and the appearance of gills and sensory evaluation parameters were significant differences (p<0/05)  between two treatments. Existence of a decreasing-increasing trend observed in the results of  colorimetry to be associated with enzymatic -microbial and changes in texture analysis with changes in the sarcomeres and adhesion between fibers.

This study showed that there is no significant difference in the appearance characteristics and skin color parameters, still the most important challenges ahead for consumers to distinguish and identify the dead fish caught with contraindicated to religious,However, with the passage of time and more attention to the gills appearance and tissue factors may be reduce the problem somewhat. Thus, The results of appearance and sensory properties showed that a more desirable at live fish caught than the dead fish captured.

Knowledge on the fish species is important in habitat protection management. This study was conducted to compare the morphological characteristics of two populations of Rhinogobius similis from Hariroud basin based on landmark morphometric truss network system. A total of 60 individuals from Polkhatoun (30 specimens) and Tafrihgah dam (30 specimens) stations were caught by electrofishing 220 volts. 15 landmarks set were selected and 105 distances were measured between the landmarks on the left side of each specimen. Then principal components analysis and discriminate function analysis were applied to identify influential truss variables to differentiate between the two populations. Based on principal components analysis results, there were 15 principal factors in morphometric characters. The linear discriminant analysis gave an average percentage of specimens classified of 100% for morphometric characters indicating a high rate of correct classification of individuals into their original populations. These populations are distinguished especially by head shape, eye diameter, and pre-dorsal, pre-pelvic and pre-anal distances.