نشریه آبزیان دریای خزر
سال چهارم شماره 1 (بهار و تابستان 1398)

The use of cage structures due to the advantages of increasing production capacity with the size of the sea, the ability to self-purify in marine environments, water ventilation, lack of oxygenation, reduction of depreciation costs, repair and maintenance and the use of natural environment has provided good conditions for aquaculture. The performance and production of cage-based structures depend on a variety of factors, such as the type of design, size and material used in structures, environmental diversity including relatively protected and closed locations, open or exposed areas, and types The cage includes floating and immersed cages. Therefore, the necessity of designing the structure in accordance with the environment is of special importance and the present article, in line with the above objectives, examines the considerations of choosing and designing cage structures. The goal is to determine the parameters such as effective wave height, wind velocity, wave motion and wave pattern, cage, in accordance with the climatic conditions of each region. It is also possible to predict the amount of force on the structure caused by the abovementioned factors. Therefore, by identifying undesirable consequences and choosing the type and method of deployment of the cage structure in accordance with the region conditions, destructive effects can be minimized and a significant improvement in the performance of cage structures. The results of the research showed that the force generated by the flow of waves in comparison to other factors predominates and plays a decisive role in the design of the cage

The aim of this study was to investigate the performance of antioxidant and antimicrobial activity of hydroelectric extract of Anethum graveolens. In this study, the well test and paper discs were conducted to investigate the anti-microbial activity, and to determine the total phenolic compounds by the Folin-Siouketto method and for DPPH radical scaling activity by measuring the capacity Radical scaling of 1-1-2 pecril of hydazine as well as total antioxidant activity (TAC) were performed by the mentioned method. The results of the antibactrial performances showed that the plant had no inhibitory effect on the growth of Aeromonas hydrophila at concentrations of 125, 250, 500 and 1000 micrograms per milliliter. Also, the amount of phenolic, DPPH and total antioxidant compounds in the plant were 49.85 ± 8.92, 62.51 ± 1.6 65.6 and 84.69 ± 3.65, respectively. generaly, the results of this study showed that the hydroalcoholic extract of the plant has a significant antioxidant effect, and even the antioxidant power of the hydroalcoholic extract in different methods has shown a different level in comparison with the similar work of other researche.

The Nodularia microalga has the potential for bloom at low salinity, brackish and saline waters. The algal bloom is endangered as a serious problem of living aquatic organisms in the southern part of Caspian Sea. In this study, the effect of algal bloom inhibition were investigated with three species of Pseudomonas spp. including aeruginosa, putida and fluorescence, which were isolated and identified from the estuaries of the Tajan River in basin of the southern of Caspian Sea, in a laboratory scale. Also, fluctuation of chlorophyll-a, dissolved oxygen, phosphate and nitrate were simultaneously evaluated. The results showed that the trend of chlorophyll-a, dissolved oxygen and nitrate were significantly reduced in all treatments containing bacteria, especially aeruginosa (68%) and mixture of bacteria (71%) (p<0.05) and this trend of the parameters was almost constant in the control treatment. Although, phosphate concentrations decreased relative at different times, but there was no significant difference (p>0.05). In addition, the rate of phosphate consumption was higher than nitrate at different times. As a result, these species can be used as indicator bacteria for inhibiting of the algae bloom in a larger ecosystem.

The aim of this study was to promoting fish production in floating cages on the southern shores of the Caspian Sea by increasing fish density per unit volume of water. Because the capacity of fish production in floating cages is 15 kg / m3, but for 6 years (2011-2017), the production rate of rainbow trout (Oncorhynchus mykiss) in cages in this coasts were 7-8 kg / m3 have been. The weight of introducing fish to cages (100-220 g), time and rearing period (December to April for 5 months) in this method did not change in comparison to previous years. But the initial density of fish stock has increased by 70 to 90 percent. In this method, two types of floating cages with a diameter of 16 and 20 meters were carried out in two sites in Mazandaran province and in the city of Noshahr (5 cages) and Abbas Abad (10 cages). Harvesting of fish from cages was done step by step from March to April. The final weight of fish during harvesting of cages was 1100-400 g in each two site. By implementing this method, the fish production in the floating cage increased to about 100-90 percent and was produced at 15 kg / m3. Aquacultures can use this method to increase the production of fish in a cage floating on the coasts of the Caspian Sea.

Disregarding the degraded ecosystems, especially the regional rivers, threatens biodiversity in the Caspian Sea basin. The purpose of this study is to promote the co-ordination of research, implementation, promotion and education on the conservation of natural reproduction of Caspian Sea fish in the Kheirud River. This study was conducted in the Kheirud River in the years 2017-2018 as a model site from September 2017 in one year. The Kheirud River with a latitude of 51 ° 34 ° 51 and a latitude of 40 ° 37 ° 36 are divided into three upper parts of the hands, the middle section and the lower part. In this survey, 15,000 Rutilus kutum breeder entered the river, which female numbers were of at least 5000-3000. On average, the capacity of 10 million larvae (7.5-7.5 million) from natural reproduction entered the production chain. The penetration rate of the river reached about 0 to 7.5 million larvae. More than 70 fishermen were covered by this study, with a penetration rate of from 0 to 3.5%. More than 450 women and 500 students and teenagers were covered by this study and their penetration rate in this region was estimated at 30% and 16%, respectively. With this view, and in light of the experience gained from the present study, the importance of the greater participation of the public and the public in the pursuit of the goals of similar studies becomes more eviden

The Caspian rivers has importance roles in spawing sites of fishes and regeneration of anadromous fishes in natural proliferation. Lavandvil, Chelvand, Lemir, Hevigh and Chowbar rivers are located in west of Guilan province. These rivers are important for having the special fish population, spawning of migratory fishes and feeding of estuary fishes. Main purposes of this paper is to the role of these rivers in restoring of Caspian Sea anadromous fish species. So diversity and abundance of fishes has been studied in these riveres. Sampling has been done in 5 stations of studied rivers with electrofishing and small-meshed beach seine gears in 2007. Results showed 25 fish species belong to 10 families exist in the rivers and Cyprinidae with 12 species and 82.6% of total populations was dominant. 19 fish species were native or endemic and 6 species alein, too. The study showed 5 species belong to anadromous fishes: Alburnus chalcoides, Cyprinus carpio, Leuciscus aspius, Rutilus kutum and Vimba persa,and they migrate from sea into these rivers for spawning, and the abundance of A. chalcoides and R. kutum was realtively good but the others, few. Thus, it is essential to have an extensional programm for protecting rivers with popular corporation in responsible fishery management system, for conservation and long sustainable exploitation of valuable and commercial fish sepecies.