نشریه بهره برداری و پرورش آبزیان
سال یازدهم شماره 4 (زمستان 1401)

According to researches, the continuation of the trend of lowering the water level as a new round of oscillating features of the water level in the Caspian Sea is not unexpected. Due to the separation of Gorgan Bay from the Caspian Sea, many irreparable environmental and economic risks will affect micro and macro management in regional and supra-regional dimensions. According to studies, Gorgan Bay is not endangered and the decrease in water level is considered part of the natural behavior of Gorgan Bay against the fluctuation of the Caspian Sea water level. The proposed option is dredging the Ashuradeh canal after the water level reaches minus 27.5 meters. However, according to the results of the current study, declining water levels have caused nutritionalism, destructive ecological substitutions, changes in the structure of biological communities, morphological changes, increased sedimentation, bay drought and increased salinity, damage to ecotourism and marine infrastructure and reduced the depth of inputs in Gorgan Bay. Accordingly, the issue of urgency and crisis in Gorgan Bay is obvious. Therefore, finding a solution that can save Gorgan Bay from the emergencies and crises ahead is inevitable. It is suggested that short-term action be taken to align the Caspian Sea basin countries to determine water rights from rivers and dredge traditional canals to prevent the Gulf from being cut off from the sea. In the long-term action, the construction of a new canal is proposed to increase self-purification and prevent the emergence of degraded ecosystems.

In this study to investigate the relationship between length and weight of Leaping Mullet (Chelon saliens) 177 fish samples (91 Female and 86 Male) of leaping mullet were caught by fin nets from June 2020 to July 2020. sex ratio of male to female was 1:1 that showed no significant difference between sex ratio of male and female in population (〖 x〗^2=0.141 , P > 0.05 ). Maximum total length and weight were 28 cm and 186 g for females, 22cm and 137 g for males. The length-weight relationship of female was W=0.0048 〖Tl〗^3.167 (r^2 = 0.78) and the length-weight relationship of male was W=0.0313 〖Tl〗^2.542 (r^2 = 0.80) and the total relationship was W=0.0123 〖Tl〗^2.856 ( r^2 = 0.78. ( The results showed negative allometric growth for males and isometric growth for both population and female groups (t-test,t_male=3.350,t_female=0.959,t_population=1.290 ,p<0.05)

The objective of this study was to investigate the effect of different levels of Lactobacillus plantarum probiotic on estradiol hormone and gonad tissue in zebrafish (Danio rerio). So, six hundred healthy zebrafish (0.15+0.01 gr) were randomly distributed in 12 glass aquariums and fed experimental diets contain different levels of L. plantarum (0%, 105, 106 and 107CFU/gr ) for 3 months . After this period and sex determination, males were seprated and females fed probiotic for 1 month more. At the end of the experiment, the whole body of the fish was used to measure the hormone, the amount of esteroid hormone was measured by RIA method. Also of the histological point of view were studied by light microscope. The results of this study showed an increase in the amount of estradiol hormone during vitellogenesis in fish fed 106 CFU/gr L. plantarum which had a significant difference with other treatments (P <0.05). However, 107 CFU/g fed L. plantarum treatment had a decreasing trend. In tissue sections, the most of the eggs in control were clearly in the second and third stages of sexual maturation while in the 106 CFU/gr fed treatment, most of the eggs were in the third and fourth stages and even at the end of the fourth stage of maturation.These stages were more common than treatments fed 105 CFU/g and 107 CFU/g L. plantarum. The results of the present study indicated that the use of probiotics L. pentarum in the effective amounts can be considered as a new strategy to improve reproductive performance.

Macroinvertebrates of running water are affected by their environment and their distribution in the habitat is affected by changes in environmental factors of the habitat. The aim of this study was to investigate the effect of some environmental factors on the large diversity of benthic invertebrates in Shahrestanak River, Karaj. Sampling of benthic invertebrates was conducted using a sorber sampler at six stations (with four replications per station) in 1397 and in two seasons of spring and autumn by measuring 10 environmental variables. A total of 12 families of large benthic invertebrates were identified in spring and 13 in autumn, in which the larvae of aquatic insects had the highest frequency. According to the results, station three (middle of the river) had the highest frequency and also the families Heptageniidae and Baetidae had a high frequency. In spring, the highest diversity, dominance and species richness was in station four (downstream) and the highest uniformity was in station six (downstream). The highest amount of diversity, dominance and uniformity in autumn was related to station one (upstream of the river) and the highest amount of species richness was related to station two (middle). Changes in environmental variables of resistance, electrical conductivity and total soluble solids (spring), flow rate and height (two seasons) were significantly different. In addition to the mentioned variables, the factors of width, depth, height and speed of water flow were among the factors affecting the frequency and composition of large species of benthic invertebrates. It seems that effective environmental factors in the study area have affected habitat conditions, diversity, abundance and species composition. Conducting these studies, while understanding the needs of aquatic organisms, contributes to effective conservation planning, determination of appropriate ecological water rights and sustainable abstraction of river resources.

The effect of different water hardness levels on growth indices, survival rate, hematological parameters, and water quality of Caspian Kutum (Rutilus kutum) fingerlings was investigated in a completely randomized design with six water hardness treatments (350, 600, 650, 700, 800, and 900 mg of calcium carbonate (CaCO3) each with three replications containing 13 pieces of fish (n = 300 in total) with an average weight of 2 g for 56 days. The highest final weight, body weight gain, and daily growth rate were estimated in the treatment with a hardness of 650 mg/L CaCO3 (P < 0.05); the same treatment represented the minimum feed conversion ratio and the lowest daily food intake (P < 0.05). The highest values of hardness and alkalinity of water were measured in the treatment with a hardness of 900 mg/L CaCO3 (P < 0.05). The highest levels of red blood cells were counted in well water treatment (600 mg/L CaCO3) + distilled water with a hardness of 350 mg/L CaCO3 (P < 0.05). The highest and lowest hemoglobin levels were estimated in treatments containing 700 and 900 mg/L CaCO3, respectively (P < 0.05). The highest levels of cortisol and glucose with significant differences between treatments were recorded in the treatment containing 15 g of CaCO3 with a hardness of 900 mg/L (P < 0.05). The highest amounts of sodium and calcium in fish meat were obtained in the treatment with a hardness of 650 mg CaCO3 (P < 0.05). Therefore, water hardness of 650 mg/L CaCO3 led to the highest values of final weight, body weight gain, and daily growth rate in R. kutum fingerlings in the laboratory (P < 0.05), which can be used for the culture of this valuable fish species.

Rearing of sturgeon is of great importance in Iran, and diet is one of its important factor. A lot of research has been executed on the nutrition of these fish, but more researches are needed to complete this knowledge. The purpose of this research was to investigate the effect of adding glycine to the diet on hematological parameters, protein concentration and plasma enzyme activity in beluga (Huso huso). For this purpose, the fish were fed diets enriched with 0 (control), 0.25, 0.5 and 1% glycine for 8 weeks. The results showed that the number of red blood cells, hematocrit percentage and hemoglobin concentration in 0.25% and 0.5% glycine treatment were significantly higher than the control (P < 0.05). Also, these treatments had lower alkaline phosphatase and aspartate aminotransferase activities than the control (P < 0.05). 1% glycine treatment showed a significant increase in total plasma protein concentration, compared to the control treatment (P < 0.05). Also, there was no significant difference in MCV, MCH, MCHC, albumin, globulin, ammonia, and alanine aminotransferase and lactate dehydrogenase activities among the treatments (P > 0.05).. Based on these results, adding 0.25-0.5% glycine to the diet of beluga can improve hematological indicators.

The aim of this study was to investigate the physiological response of young beluga to different levels of sodium butyrate in the diet. For this purpose, 360 young beluga (average weight of 15 ± 0.56 g) with 6 experimental diets containing 0, 0.1, 0.2, 0.3, 0.4 and 0.5% sodium butyrate were fed for 8 weeks. The number of red blood cells (RBC) and MCV, MCH and MCHC indices were significantly higher in the 0.3% treatment than in the other treatments (p <0.05). The number of white blood cells (WBC) and the amount of hemoglobin and hematocrit in fish fed with 0.3% sodium butyrate in the feed were higher than other treatments, although there was no significant difference with the treatment of 0.4% and the control group (p >0.05). Lysozyme activity and IgM level in 0.3% treatment was significantly higher than other treatments (p <0.05). Cortisol and glucose levels in fish fed diets containing 0.3% sodium butyrate increased slightly less than other groups after acute density stress and a significant difference was observed between treatments (p <0.05). Overall, this study indicates that including 0.3% sodium butyrate in the diet of young beluga can improve fish health, innate immune response and resistance to density stress.

Nowadays, plastic pollution is regarded as one of the most threatening environmental pollution. In this regard, microplastics may enter the food web and produce some negative impacts in aquatics. The goal of the present study was to study effects of polystyrene microplastic on antioxidant and immune genes expressions in gold fish (Carasius aurata). For this, polystyrene microplastic was synthetized via suspension and emulsion polymerization method in two sizes of 0/25 and 8 µm. The fish were exposed to the microplastic with sizes of 0.25 and 8 µm and concentrations of 0.05, 0.5 and 5 mg/L during 28 days under 6 treatments. Based on the results, polystyrene microplastic induced gene expression of SOD, CAT and HSP70 that were dependent on the microplastic concentration and size. Smaller size of microplastic showed higher induction effect on the studied genes expressions so that in most cases, the highest level in the same concentrations was observed in the treatments exposed to 0.25 µm microplastic. With increase in microplastic concentration from 0.05 to 5 mg/L, a similar decreasing-increasing trend was observed in the investigated genes expressions but the CAT gene reaction was slightly different. Overall, more studies seem necessary to understand polystyrene microplastic effects on aquatics and its potential mechanisms. With respect to the results from the present study indicating the changes in antioxidant and immune genes expressions under microplastic exposure, establishing some strategies seem to be obligatory to manage the effluents entered to the aquatic ecosystems and prevent more microplastics increase in the environment. Totally, based on the results, it could be said that polystyrene microplastic as a pollutant can induce the antioxidant and immune system of gold fish.

In this study, the biological indicators (length, weight, age) and the stock of the common kilka (Clupeonella caspia) in the Iranian waters of the Caspian Sea were investigated in 2020 and 2021. The results showed that the amount of kilka caught was 20050 tons in 2020, reached 20138 tons in 2021, and presented fairly stable. The catch per unit effort (CPUE) was 2.298 and 2.321 tons per vessel per night, respectively. The average fork length (± standard deviation) of common kilka (male and female) was 100.9 ± 11.1 mm, and the minimum and maximum were 62.5 and 137.5 mm, respectively. In the catch composition, age groups of 3 and 4 years dominated the catch, representing 78.9% and 77.9%, respectively. In the years 2020 and 2021, the total biomass was estimated to be 92653 and 78135.3 tons, age 3 had the highest biomass (31615.1 and 22672.6 tons, respectively). The biomass of mature individuals were 44277.6 and 41606.5, respectively. The ratio of matures to the total biomass was 47.8% and 53.2%, respectively. The acceptable biological catch (ABC) of this species was estimated at 18,000 tons with a precautionary approach. During the last decade, the average catch of this species was 22769 ± 1904 tons, which is more than the estimated ABC.