The percentage determination of Rutilus frisii kutum (200, 500 and 1000 mg) resistance to salinity, turbidity and decrease of oxygen by usage of the river water at the releasing meantime

The survey effect of salinity, turbidity and dissolved oxygen performed on Rutilus frisii Kutum juveniles with aim, which was determined about survival rate and histological changes in gill and kidney tissues. Juveniles provided from the Rajai's fish propagation center and then examined in Caspian Sea Ecology Research Center laboratory. The juveniles were investigated on three weight group (200-75%) had shown in 400-<600mg weight group with dissolve oxygen: 3.8±0.15SE mg/l. In addition, the lowest survival rates under turbidity stress (95.83%) had shown that in weight group less than 400 mg with turbidity 15600 FTU. Therefore, survival of juveniles was high. However, gill tissue of juveniles under turbidity and salinity stress became short (necrosis) and thick (edema and hyperplasia) in the end of experiments. The juveniles gill tissues were not changes in the river clear freshwater. Therefore, the factors of gill tissue deformation were salinity and suspended particles in the water. However, the structures of kidney in the different groups of juveniles were similar. Nevertheless, juveniles glomerular diameter increased with increasing weight (p<0.05, Duncan test). Furthermore, there was a increasing the internal cavity of the proximal and distal tubules and decreasing of glomeruli in diameter in the transfer of juveniles from freshwater to brackish water. Although the survival rate of juveniles is acceptable in this study, but there was abnormal changes in the structure of them gills. It appears that this change will cause a disruption in trend of juvenile's growth

Evaluation of stocking density vannamei shrimp Litopenaeus vannamei (Boone, 1931) in culturing with brackish water of Caspian Sea

Recently, the development of aquaculture has focused on the use of seawater, because of freshwater crisis in the world. Whiteleg shrimp (Litopenaeus vannamei) is one of the most important species for aquaculture development, because of tolerance and adaptation to different ecological conditions. One of the advantages of species in aquaculture, compatibility status is dense in the rearing period. In this study, the effect of different densities (45/m^2 , 50/m^2 , 55/m^2 and 60/m^2 ), of primary stock whiteleg shrimp postlarvae (PL12) on the growth and survival rate were evaluated. Brackish water (10.52±0.43 ppt) was providing from Caspian Sea. The experiments were performed in 12 circular concrete pond with a sandy bed (area: 78m^2 ) in four treatments and three replications for each treatment. The experiments performed in a 75-day period. In this study, the water temperature was 27.4±1.79°C. The results showed statistically difference in growth parameters and survival rate among experimental treatments (Duncan test, P<0.05). Therefore, with high levels of density, has decreased the amount of weight gain and survival rate (SR), specific growth rate (SGR) and average daily growth (ADG). In addition, the treatments were different variations of FCR (P<0.05) and not depend on the primary stock density of postlarvae. In low density (45/m^2 ) were observed the highest growth (SGR=11±0.04 and ADG=0.25±0.01 gr/day/ind.), survival rate and calculate the amount of production per 78m2 equal 43.6±3.3kg (5596±433kg/ha). Therefore, It is possibility that there is commonly increasing primary stocking of density about L. vannamei postlarvae culture in Iran

Survey and feasibility study for the introduction of native fish and non- native fish for cage culture in the southern part of Caspian Sea

The aim of this study is the feasibility of introducing suitable species of fish (native and exotic) for rearing in cages in the southern region of the Caspian Sea. This study from the perspective of economic efficiency and maintaining ecology were analyzed. The results showed that the southern Caspian Sea has the ability to aquaculture fish. However, due to the yearly temperature variations of water (from surface to a depth of 50 meters), the talent of aquaculture area is preferred for fish in cold water than warm water fish due to possibility rearing over the years. The survey showed that the current conditions and due to unfavorable changes in the ecology of the area in the last decade, the use of non-native fish culture in cages is not recommended. Many species of native fish are suitable for rearing in cages. Nevertheless, there is no infrastructure suitable for the production of all of them. Therefore, respectively species of Salmo caspius, Huso huso and Common carp of Caspian Sea for cultivation of in cages was suggested. In the current situation, this fish for their ability to grow faster than the need for selectivity. It is noteworthy that detailed environmental assessments and species risk assessments before the final introduction of any fish species (native and exotic) for rearing in cages in the Caspian Sea ecosystem is essential