فصلنامه فیزیولوژی و بیوتکنولوژی آبزیان
سال دوازدهم شماره 3 (پاییز 1403)

Artemia is the most important live food in aquaculture. Considering its mass cultivation, easy usability, and nutritional value in fish farming, the effect of Spirulina platensis and Dunaliella salina algae on the growth, survival, and total protein of Artemia franciscana were evaluated. For this purpose, Artemia was cultured in laboratory conditions with a combination of yeast and Spirulina powder in five different treatments (20, 40, 60, 80 and 100% Spirulina powder and yeast) compared to the control treatment (100% Dunaliella algae and yeast). The results showed that there were significant differences in growth in treatments with 40, 60, 80 and 100% Spirulina powder, and survival in the 100% Spirulina powder treatment, compared to the control (P<0.05). The investigation of the first molt in each treatment revealed that the 100% Spirulina powder treatment had the earliest molting time, which was consistent with the total protein content of the treatments. According to the results, the best treatment in terms of growth, survival, time to first molt and total protein content was the 100% Spirulina powder treatment. Therefore, Artemia cultivation with Spirulina is scientifically and economically justified.

Microalgae are used to produce valeable natural compounds. Low yield and high cost limit the commercial potential of microalgae. Recently, the techniques of immobilization and increasing production efficiency have been noticed. In the present study, the effect of salt concentration, stabilization and growth period on growth, biomass, carbohydrate, carotenoid, chlorophyll a and b in Dunaliella salina was evaluated. The results showed that the growth of microalgae in free conditions was more than in stabilization condition. At salinity of 150 and 300g/L algae growth was significantly reduced. The maximum biomass was measured at 75g/L salinity and free condition. Carotenoid in salinity of 75g/L and unstabilized condition was more than other treatments. Carbohydrate in salinity of 30g/L was significantly higher than other treatments. In the concentration of 150g/L, carbohydrate was significantly higher in stabilization condition. It seems that the composition of the substrate as well as the method of application of stabilization is an effective factor. Salt stress is a simple method to induce carotenoid synthesis. Research in the field of optimization of the material used as well as the method of applying stabilization to increase the production efficiency of valuable compounds seems necessary.

Garlic can improve the immune system, growth indicators and be effective in the prevention of infectious diseases. To study the effect of garlic powder on growth factors and the survival of black tetra larvae, this survey was performed using 6 aquariums and 50 fish per aquarium, completely randomized design (CRD). The larvae were divided and reared into three treatments including the control group fed with basic diet, the first group fed diet with 5g/kg garlic powder and the second group fed diet with 10g/kg. The larvae rearing continued for five weeks. The results showed that the survival rate and growth factors such as specific growth rate, body weight index and daily growth rate in the first and second groups were better than the control group. However, in most cases, the changes were not statistically significant (P>0.05). But the mean weight changes of the studied groups in the second, third and fourth weeks were statistically significant (P<0.05). Therefore, feeding with the diet complemented by garlic powder can improve the survival and growth factors in black tetra.

The migration of fish to the sea requires the ability of osmoregulation to exposure to salinity, and changes in the structure and function of many organs, including the kidney, are involved in the developing this process. In this study, quantitative and qualitative changes in the kidney tissue of Caspian kutum (Rutilus frisii) fingerlings exposed to water salinity in the coastal and estuarine areas of the Caspian Sea were investigated. Three weighing groups 0.5, 1, and 1.5g were treated for 10 days in the three natural environments of the river (freshwater), the estuary (6-7‰), and the coast of the Caspian Sea (11-12‰) in the Kiasher beach area. At the beginning (0h) and end of the experiment (240h), 6 individuals from each weight group in each treatment were caught. After dissecting and separating the kidney tissue, the area and diameter of the glomerulus and Bowman's capsule were measured. The results showed that at the end of the experiment, the size of the kidney tissue indices significantly decreased (P<0.05) with the increase in salinity in all treatments. So that, the extent of this decrease in 1 and 1.5g weight groups was significantly more than the 0.5g group (P<0.05). Qualitative changes, including a decrease in the width of the proximal and distal convoluted tubule after exposure to salinity, were observed in all weight groups. The decrease in the size of the glomerulus in the estuary and coastal environments can be because constant drinking of water in these environments causes enough ions to be provided to the body and there is no need for large glomeruli for filtration. In the present research, two weights of 1 and 1.5g can compromise with the conditions of increased salinity of the environment when released and placed in the estuary and coastal environments of the Caspian Sea.

The present study was conducted with the aim of investigating the effect of salinity changes on the activity of liver enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and the biomarker malondialdehyde (MDA) in gray mullet. Fish samples, after acclimatization, were studied in treatments of 28, 34, 50g/L and control (36.5g/L) in three periods of 7, 14 and 21 days. Results showed that malondialdehyde biomarker was the highest on the 7th and 14th days in 50g/L salinity treatment, but the highest value was recorded on the 21st day in 34g/L salinity. The statistical test showed a significant difference between days and treatments (P<0.05). Alanine aminotransferase had the highest value on the 7th day at 50g/L salinity, 14th day at the control and 21st day at 28g/L salinity, and the difference between the data was significant. Aspartate aminotransferase enzyme had the highest amount on the 7th and 21st days of the control treatment and on the seventh day of 34g/L salinity. The control treatment had always a significant difference with other treatments. Alkaline phosphatase enzyme had the highest value on the 7th day at 34g/L salinity, 14th day at 28g/L salinity and 21st day at 50g/L salinity, and except for 50g/L salinity, the concentration of the enzyme decreased significantly from day 7 to 21 in other treatments. No significant correlation was observed between any of the measured parameters and salinity. The general result showed that in most of the treatments, due to the increase in salinity, the concentration of enzymes had a decreasing trend, which indicated the inhibition of enzyme activity in high salinity. In addition, reducing salinity showed an increasing effect to deal with stress and create adaptation.

Catla (Catla catla) is one of the main species of Indian carp that was introduced to the country in order to diversify the species. In order to increase the population, the propagation of the Catla species was carried out. In this study, 16 female spawners with an average weight and total length of 3183.33±76.01g and 568.33±1.05mm, respectively, were examined. The appropriate temperature was recorded as 29-29.5°C. The synthetic spawning-inducing hormone OvaPAS was used to stimulate spawning in the spawners. The injection was done intramuscularly and in one stage. The injection amount in female spawners was 0.5mL/kg of fish weight. The injection of male spawners was done 2 hours after the injection of the female at a dose of 0.2mL/kg. 100% of the spawners reached to spawning stage. The latent period lasted 6.11±0.08h. Catla had non-adhesive eggs. The number of eggs per gram and the number of eggs per milliliter were 1271.16±21.29 and 1259.83±22.35, respectively. The average number of eggs collected from the broodstock was recorded as 581.33±52.62g. The size of collected eggs, fertilized eggs and hatched eggs were 1080.17±9.64, 1641.62±14.39 and 3370.46±24.65µm, respectively. The average fertilization percentage was calculated as 91.01±2.33, hatching percentage was 80.66±1.7 and larval survival percentage was 70.81±2.83. The time of larval emergence from the eggs was calculated after 16 hours and 20 minutes. The size of the newly hatched larvae was 4.55±0.06mm. The results obtained from this study can be used in breeding centers for mass production.