نشریه بهره برداری و پرورش آبزیان
سال یازدهم شماره 2 (تابستان 1401)

Effluents from fish farms have high levels of nitrate and phosphate. In the present study, the removal of nitrate and phosphate from aquatic farm effluent was investigated by nanosilica adsorbent modified with mineral pumice. For this purpose, the desired adsorbent was added to 250 ml of effluent (with 50% and 100% concentration) in laboratory conditions (adsorbent doses of 0.01, 0.05, 0.1, 0.5 and 1 g/l). Nitrate and phosphate concentrations in the effluent were measured before the experiment. According to the results, the highest amount of nitrate and phosphate removal at a dose of 0.5 g/l was selected as the optimal dose, so the nitrate and phosphate removal efficiency was decreased at concentrations higher than this amount, because the available active ingredient was reduced at doses higher than 0.5 g. In this experiment, the optimum contact time of the adsorbent with the contaminant was 45 minutes. It seems that modified nanosilica with mineral pumice has a high ability (86% efficiency) to remove nitrate and phosphate from aquaculture effluents and can be used to purify effluents from aquaculture farms before reuse in the return system or before entering to the environment.

Proper nutrition is one of the most important pillars of success in the aquaculture industry, which accounts for about 50% of costs and on the other hand ensures survival, proper growth and aquatic health. The aquaculture industry always has stressors such as high density, transportation, manipulation and changes in water quality that have an adverse effect on fish health and growth. In fish, stressors initiate hormonal cascades along the hypothalamic-pituitary-internal (HPI) and hypothalamic-sympathetic-chromaffin (HSC) axes to trigger several physiological reactions to regulate and maintain homeostasis and adversely affect various fish physiological processes such as Grows growth, reproduction and immunity. In fish farming, several ways are used to prevent the negative effects of stress and achieve maximum animal health without affecting production performance, and the use of new feeding strategies is an easy and practical way to improve the health of fish. Changes in the ratio of proteins, fats and carbohydrates in the diet, the use of vitamins, especially ascorbic acid, new substances in biotechnology such as probiotics, nucleotides and polysaccharides have been studied. Fatty acids, probiotics and minerals. Immunosuppressants are prescribed as food additives, which usually increase innate (non-specific) defense mechanisms and resistance to certain pathogens, and increase inhibition of stress-induced immune suppression. In this review, different physiological responses were assessed among fish species fed stress-reducing diets.

Yersiniosis is one of the most important bacterial diseases that cause a lot of economic losses to cold-water fish farms in the country. Therefore, the use of effective vaccination is one of the best ways to control this disease. In this study, the vaccine efficacy of different methods of bathing in these fish has been evaluated. In this regard, 300 fish with an average weight of 3 ± 0.35 were divided into 12 tanks after adaptation. In this study, 6 experimental groups including a positive control group, negative control group, single dose vaccinated fish group, two-dose vaccinated fish group, hyperosmotic environment + single dose vaccinated fish group, and hyperosmotic environment + two-dose vaccinated fish group. Fish from different groups were exposed to 4.3 10 107 bacteria intraperitoneally after vaccination and the survival rates of the fish was evaluated.Based on the results, the white blood cells counts (WBC) in the vaccinated groups were significantly higher than the control group. Yersinia ruckeri antibody titers by microagglutination method were also measured significantly higher in the vaccinated groups compare to the control, in the othe hand, in the fish that received the vaccine twice, this titer was significantly higher than the other groups. According to the bacterial exposure results, 100% of the fish in the control group died during 5 days. In all vaccinated groups, the mortality rate was significantly lower than the control group, while the lowest mortality rate was recorded for fish in the hyperosmotic environment + twice vaccine. In this study, vaccination significantly reduced fish mortality after exposure to Yersinia rockeri bacterium, and based on this study, the use of hyperosmotic environments with vaccination is recommended to increase vaccine efficacy.

Hypoxia stress is an unfavorable environmental condition for fish that can have several effects on immunity and antioxidant. The aim of the present study investigated the impact of hypoxia stress (Chronic; 2 to 2.5 mg/L for 36 hours) and (acute; 0.013 and 0.017 mg/L for 1.5 hours) compared to control (6 to 7 mg/L) on survival, immune and oxidative status Common carp (Cyprinus carpio) in biofloc conditions. In the first stage, the fish (21.90 ± 0.75 g) were stored in 9 tanks (50 liters) in the biofloc system for 7 weeks. In the second stage, the fish were subjected to hypoxia stress (chronic and acute) and control (normoxia). After hypoxia stress, serum lysozyme, total immunoglobulin, and ACH50 activities were significantly lower, and red blood cells (RBC), hemoglobin, and hematocrit were higher in chronic and acute stress treatments. The activity of SOD, CAT, and GPX in the fish serum exposed to hypoxic stress was significantly reduced compared to the control. In general, the results show that both chronic and acute hypoxic stress weakened the blood parameters of common carp in the biofloc system.

This study was designed to determine the effect of rainbow trout culture in floating cage on the distribution and structure of Phytoplankton community in the Abbas Abad area, southern basin of the Caspian Sea. For this purpose, water and phytoplankton samples were collected by a distances of 5, 50, 100 and 1000 m from the cage culture during December 2014 (pre cage), March and April (production period) and August 2015 (post cage). The results of physicochemical factors of water showed that most of the measured parameters had significant differences only among different sampling periods (P<0.05). In this study, 42 taxa of phytoplankton belonging to five phyla (with the dominance of Bacillariophyta) were identified. The results showed that the abundance of most dominant phytoplankton samples had a significant difference during different periods (P<0.05), but this significant difference between different stations was observed for few species studied only. Also, the results of determining the effect of environmental factors using CCA test on the Bacillariophyta abundance showed a minor impact and a positive correlation with turbidity and total nitrogen, While the effect of temperature and ammonium on its abundance was negative. It seems that the rainbow trout cage culture in the Abbas Abad region had a minor impact on water quality factors and nutrients concentration probably due to short duration of cage culture activity and high velocity currents, but no remarkable effect on phytoplankton structure in the vicinity of fish cages, so that the observed changes were more associated with seasonal fluctuant.

Many marine invertebrates, such as sponges, produce secondary metabolites that have some pharmaceutical uses. This study was carried out to determine the antibacterial properties and the effect of seasonal variations on methanolic extracted from sponge Niphates furcata against Gram-positive bacteria Bacillus subtilis, Staphylococcus aureus and Gram negative bacteria Escherichia coli and Pseudomonas aeruginosus using broth dilution method. The experiment results showed that methanolic extracts of sponge extracted in summer did not show any antibacterial effect on E. coli and P. aeruginosus and did not have the ability to inhibit the growth of the mentioned bacteria, and naturally the concentrations determined could not have any bactericidal effect on the gram-negative bacteria of E. coli and Pseudomonas aeruginosus. In winter, this extract had an inhibitory effect on all four gram positive and gram negative bacteria used in this study, In contrast to methanolic extract from summer, methanolic extract of winter season on Escherichia coli had a bactericidal effect, although it did not show any bactericidal effect, similar to that of summer on Pseudomonas aeruginosus. Comparison of the data shows that the methanolic extract of Niphates furcata sponge has a more severe inhibitory effect on the bacteria than in the winter, although the comparison of the bacterial pathogenic effects in both summer and winter shows similar results, and the concentrations have not shown any bactericidal effect on Pseudomonas aerosinosis.

In order to investigate the resistance of shrimp against white spot disease by Gracilaria corticata algae, 300 Vannamei shrimp in two groups were fed with and without algae extract for 14 days. At the end of the experiment, half of the shrimp of each group were exposed to the white spot virus. After the challenge, during days 0, 3, 9, 18 and 25, the survival rate and immune factors of shrimp were examined. According to the results, survival rate of shrimp fed with algae extract was higher than the shrimp were fed by commercial pellet without the algae extract (positive control) significantly (P < 0.05). Immune system enhancement from the first to twenty fifth day and the highest levels of THC, TPP, SOD, POD and PO were observed in group Algae on twenty fifth day of the experiment. This condition was also observed in group AV, but less than group A with a significant difference (P <0.05). Considering the function of algae in stimulating the immune system, it seems that during the culture period, algae supplementation in the diet can be used as a proposed strategy to control white spot disease.