مجله علمی شیلات ایران
سال سی و دوم شماره 4 (پیاپی 138، مهر و آبان 1402)

Given the concerns regarding the use of synthetic antiviral compounds in the pharmaceutical industry, it seems necessary to pay attention to natural sources with antiviral activity. Sea cucumbers are one of these sources that numerous physiological properties are discussed in the scientific community. The present study aimed to produce bioactive peptides from Holothuria leucospilota using two microbial enzymes, alcalase and flavourzyme, and to evaluate their antiviral activity against Herpes simplex types 1 and 2, Chikungunya, and Dengue viruses. The results showed that the whole body of the sea cucumber has about 13% protein, which this amount reached more than 67% in the resulting hydrolyzed powders. The amount of protein, as well as the degree of hydrolysis in the hydrolyzed protein using alcalase enzyme (71.58±0.16 and 48.37±0.3%, respectively) was higher than the powder produced with flavourzyme (67.88±0.26 and 41.42±0.6%, respectively) (p<0.05). It was further found that both types of peptides produced at both concentrations of 4 and 5 mg/ml have antiviral properties. In this study, the type of enzyme used to produce bioactive peptides and also the concentration of peptides had a significant effect on their antiviral activity (p<0.05). The peptides produced using alcalase enzyme had significantly more antiviral activity against the studied viruses, while increasing the concentration of peptides from 4 to 5 mg/ml led to a significant increase in the antiviral activity (p<0.05). Among the studied viruses, Herpes type 1 and Dengue virus were the most resistant and susceptible viruses, respectively (p<0.05). According to the results of the present study, bioactive peptides extracted from the sea cucumber have the potential to be used in the pharmaceutical industry as a natural antiviral compound, however, it is necessary to carry out additional tests to evaluate their possible toxicity effects.

The most important limitation of the mass production of Spirulina microalgae in the world is the high cost of its culture medium. The present study was carried out with the aim of evaluating the cultivation mediums based on chemicals and commercial fertilizers and comparing the growth  characteristics, pigments, and the amount of protein in the produced spirulina in comparison with the Zarrouk’s medium. In order to meet the nutritional needs of Spirulina species, low-cost fertilizers were used in the form of 18 treatments and three replications. In all treatments, commercial sodium bicarbonate at 16.8 g/L, sea salt at 0.5 g/L, and the commercial liquid fertilizer (K:P, 20:20) were used to meet the phosphorus and potassium needs of the microalgae. To supply nitrogen in the treatments, three sources of sodium nitrate, urea, and a 50:50 combination of both were used. In all three groups, 6 substances were used in the form of 6 treatments (control, potassium, iron, a combination of potassium and iron, magnesium, and micronutrients). According to the results, the growth of Spirulina was higher in the control group (Zarrouk’s medium) than other treatments until the 20th day, but after that, the sodium nitrate -magnesium (N-Mg) treatment showed a higher growth rate than the control group. Also, the highest specific growth rate, cell density of algae, and the lowest doubling time were measured in the treatment containing sodium nitrate source. The highest algal cell density and specific growth rate were significantly (p<0.05) observed in sodium nitrate-magnesium (N-Mg) and sodium nitrate-micronutrients (N-Mic) treatments, which were significantly different from the control group (Zarrouk’s medium). The maximum chlorophyll a, chlorophyll b, and total pigment were obtained significantly in sodium nitrate-micronutrients (N-Mic) treatment (p<0.05). The highest amount of protein was obtained in the combined sodium nitrate-urea group with iron and potassium sources. To sum up, the highest growth rate and the highest cell density were obtained in the culture medium containing sodium nitrate, which is comparable to Zarrouk’s culture medium that can be used on a commercial scale.

Aquaponic system, which is a combination of recycling aquaculture and hydroponic plant cultivation, is consistent with the goals of sustainable development in the aquaculture industry. This experiment was conducted in the form of a completely randomized design with five experimental treatments and each treatment with three replications, which includes the control group: 30 carp (Cyprinus carpio) in a 300-liter tank (without lettuce), A1: 10 lettuce (Lactuca sativa) per m2 (without fish) along with liquid fertilizer, A2: 30 lettuce plants per m2 (without fish) along with liquid fertilizer, A3: 10 lettuce per m2 and 30 fish, and A4: 30 lettuce per m2 along with 30 fish for 60 days. The average weight of the fry fish (50.18 ± 1.23 g) and lettuce plant (10.32 ± 1.49 g) at the beginning of the experiment was the same in the experimental groups. The amount of dissolved oxygen in all experimental treatments was significantly higher than the control group (5.76±1.18 mg/liter) and the highest leve was obtained in A2 treatment (6.80±1.24 mg/liter) (p<0.05). At the end of the experiment, the average total suspended solids (1245.8±60.84 mg/liter), alkalinity (133.64±15.7 mg/liter), nitrite (0.18±0.04 mg/liter), and nitrate (62.40±2.15 mg/liter) were significantly higher in the control group (p<0.05) and the lowest values were seen in A2 treatment. There was no statistically significant difference regarding the performance of growth and feed utilization of the fish between the experimental treatments and the control group (p>0.05). However, the length and final weight of the plant and the relative growth rate of lettuce showed a significant difference between the experimental treatments and the control group (p<0.05) and the highest amount of the mentioned indicators was recorded in A4 treatment. To sum up, the results of this experiment showed that in the aquaponic system containing carp with a density of 100 carp per m2 and a density of 30 lettuce plants per m2, it leads to an improvement in the productivity of carp and lettuce production with proper water quality.

In this research, 30 farms from five cities of Markazi province were assessed and biosecurity audited. The forms for examining danger crossings, mechanization equipment used on the farm, and biosecurity audit (standard of the country's veterinary organization) were completed for each farm. The relationship between mechanization and the level of biosecurity was done using correlation analysis and a semi-quantitative model was used to assess the probability of risk. The obtained results showed the maximum probability of risk with a numerical index of 0.40 for the trout farms of Arak and Farahan and the maximum mean probability of risk (± standard error) with 0.205±0.022 in Farahan city and the minimum probability of risk with a numerical index of 0.03 for Arak and Shazand, the mean of risk probability (± standard error) was obtained with 0.15±0.016 in the trout rearing farms in Shazand. The mean probability of risk at the level of all the selected farms of certain studied cities of Markazi province was calculated as 18.009 ± 0.009, which indicated that all the selected farms studied were in the category of medium possible risk (level B). In order to test the relationship between two variables, the probability of risk and the degree of mechanization from Pearson's correlation test were used. No significant correlation was observed between the probability of risk and the degree of mechanization (P = 0.41, n = 30, and r = 34). As a result, from the statistical point of view, it was determined that the variables of risk probability and the degree of mechanization were not related to each other. This component was also similar for production capacity and mechanization level. The obtained results showed that due to the weakness of biosecurity equipment in the mechanization of dual-purposed agricultural farms for fish farming in the Markazi province, the risk in some of these farms has increased to the level of being placed at probability of high risk (level C), which can easily reduce the risk in these farms significantly by taking necessary measures and establishing biosecurity plans.

By broodstocking and propagating of specific pathogen-free (SPF) rainbow trout in Iran, the need to create a cryopreserved sperm bank from the breeders was deemed necessary. In this study, after evaluation of four different extenders for rainbow trout sperm cryopreservation, the best extender (0.6M sucrose and 8% DMSO) has been selected. The sperm samples were obtained from 24 breeders, including four breeders from each of the selected specific pathogen-free farms of the country in Mazandaran and West Azerbaijan provinces (Sarshar, Maroufi, Fakhari, Hadidi, Malekitabar, and Qorbani) were cryopreserved after qualitative evaluation. The fertilization test of sperm samples on the day of sampling and comparison of their fertilization percentage with frozen-thawed sperms in three time intervals (4, 24 and 48 hours) did not show any significant differences between the sperm of the control group and the frozen-thawed samples. The results indicated that the method used in this research can be well used in cryopreservation the sperm of SPF rainbow trout breeders and if needed, the sperm obtained from the best breeders can be transferred to other centers with this method.

The purpose of this study was to investigate the infestation of Portunus segnis with symbiotic organisms to determine the abundance, prevalence, and intensity of the infestation. A total of 86 blue swimming crabs were collected from Bandar Abbas coast during Summer and Autumn, 2018. Totally, 473 symbionts including Lepas anserifera, Chelonibia testudinaria, Philometra sp., Microstella norvegica, two unidentified species of order Cyclopoida, unidentified species of Ostracoda and Bivalvia were isolated. The prevalence of infection was 66.59, 1.47, 53, 13.5, 5.91, and 12.47%, respectively. Except for C. testudinaria, other taxa are reported for the first time in P. segnis and the Persian Gulf during this study. The intensity of infestation in both males and females did not show a significant difference, therefore, it can be concluded that this factor is not affected by gender in blue swimming crab. The intensity of infestation in autumn was approximately, four times more than summer (21 and 5.84, respectively). It is probably because of the suitable conditions and the larger size of the host in this season. Moreover, intensity of infestation in cluster 2 was almost four times more than in cluster 1, confirming the positive effect of size on the abundance of symbionts in P. segnis.

The main purpose of this research was to identify the most appropriate strategies for the development of aquaculture businesses in the downstream of Taleghan dam in Alborz province through the evaluation of the internal and external environment of the development of these businesses in 2019. The statistical population of this study was 15 fish farm operators who work in the studied area and were investigated by census method. The main tool for collecting information in this research was a questionnaire. The face and content validity of the questionnaire was examined and finally confirmed by experts in the field of fisheries as well as agricultural extension. The data was analyzed using the SWOT method. The results showed that in the internal environment of the development of aquaculture production and rearing, the most important strengths of aquaculture in the downstream of Taleghan Dam were: high-quality product production and suitable topography and slope of the land for the construction of aquaculture farms. On the other hand, the high cost of water and electricity for the aquaculture farms and the old technologies and equipment used in these farms were among the most important weaknesses. Examining the external environment of aquaculture development and production showed that the most important threats to this industry were the high cost of inputs in the market and inability of producers, especially the small producers to afford them. On the other hand, the high adaptability of fish species to the climatic conditions of the region, the low per capita consumption of aquatic products and the need to increase it, and the suitable and available market for marketing products are among the most important opportunities for the development of this industry in the studied area. The comparison of the internal and external environment of the development of aquaculture businesses in the downstream of Taleghan Dam showed that the internal and external environment was with total weighted scores of 0.35 and 0.03, respectively. In other words, the strength points were dominant in the internal environment and the opportunities were dominant in the external environment. The results of the situation evaluation and strategic action matrix also showed that the most suitable strategies for the development of the aquaculture industry under the Taleghan Dam are in the competitive field. Some of the most important strategies presented in this area include branding products and sending them to capital markets and international markets, using the capacity of the private and public sectors to provide inputs, quick market access to fishery products, and training the producers.

In this study, due to the importance of Doiraj Dam Lake, which supplies an important part of agricultural water of Dehloran and Mosian, the assessment of the lake water was carried out in order to develop aquaculture activities and investigate the possibility of fish farming in the lake behind the dam. For this, 4 stations selected, the entrance, before and ater the lake and sampling were done in three seasons by using Van veen grab with with 0.0625 m2. The results of this study were determined based on the biological indicators. In benthic indices, the quality of water was evaluated by determining the species composition and biological value of different species using Shannon-Wiener diversity indices and Hilsenhoff Family Biotic Index (HFBI). The HFBI index in the studied stations ranged from 3.07 to 6.07. In general, based on the biological indicators, in most of the stations and seasons, moderate pollution was observed, which was more evident in the stations before the dam due to its without move nature than the entry and after stations.

In this study, some aspects of the reproductive biology of Caspian Roach caught by beach seining were investigated along the southeast coats of the Caspian Sea in the period of 2019-2021. From a total of 317 samples of caught fish (144 males and 173 females), the sex ratio of male to female was 1:1/2, which was not statistically significant with the expected ratio of 1:1 (p>0.05). The average fork length (± standard deviation) was 15.6 ± 2.63 cm (with a range of 10.6-25.5 cm) for males and 18.7 ± 3.70 cm (with a range of 11.3-32-5 cm) for females. The range and average weight for males were 18-214 g and 60.7 ± 36.20 g, respectively, and 22-502 g and 120.5 ± 74.76 g for females, respectively. The minimum, maximum, and average absolute fecundity of R. caspicus were estimated as 6707, 51438 and 18773 ± 9800 eggs, respectively. The mean relative fecundity was estimated to be 152 ± 33 eggs/g and 967 ± 367 eggs/cm in relation to the total weight and fork length, respectively. The absolute fecundity of the species increased with an increase in the length and weight of fish with coefficients of determination of R2= 0.62 and 0.68, respectively, so that the range of fecundity in the length range of 14.5-15.5 cm is equal to 6707-11807 eggs and in the length range of 27-32 cm was estimated as 35813-42693 eggs. According to the results, sexual maturity at stages IV and V is present in all sampling months for females of R. caspicus. The mean length (fork length) at first maturity (Lm50%) of females R. caspicus was 13.8 cm. The highest value of Gonadosomatic index (GSI) for males was observed in February with a value of 7.08, and for females in March with a value of 16.06 which decreased to 15.96 in April. Considering that the peak value of GSI and the high percentage of V maturity stage of R. caspicus is observed in March and April; it can be prohibited to catch this species in this time.

In coldwater-fish farms, 50-60% of current expenses is for feed suplly. High-lipid feed may cause an increase in the lipid storage in body. In most fish, fat storage is limited and excess fat can accumulate in liver tissue that causes lipoidosis. All salmonid fish and especially rainbow trout are susceptible to fatty liver degeneration. Fatty liver is a serious and even lethal disease in farmed fish. In this study 200 farmed rainbow trout were collected in two seasons, autumn (100 samples) and winter (100 samoles) from 20 farms and 10 samples from each farm in Shahrood city of Semnan province in 2021. After biometry the fish were classified into 300-400, 400-500- and 500-600 g weight groups and immediately transferred into the lab under chilled conditions. The livers with discoloration (yellow, milky white and light brown), enlargement, swelling, rounded edges and even fragility, hemorrhagical spots and hyperemia on the surface were selected as suspected livers. After preparing histological slides, totally, five liver samples were confirmed as positive samples that showed aggregation of fat vacuoles, cytoplasm changes and eccentric nucleus, bigger hepatocytes compare to normal ones and restricted necrosis as coagulative necrosis. No significant difference was observed between the occurrence and non-occurrence of fatty liver in autumn and winter and also in different farms.