The research was accomplished in order to study the efficiency of natural zeolite to prevent acute toxicity of ammonia on Huso huso. The study was performed using Water static method for 96 h. Fish with average weight 46 ± 5 g and total length 22 ± 4 cm were exposed to four different concentrations (15, 30, 50, 75 mg L -1 ) of ammonia salt. A group of fish was considered as control. Under stable condition, the lethal concentration of ionized ammonia was 50 mg L -1 during 96 h. In the lethal concentration of total ammonia, different amounts of 5, 10, 15 g L -1 granulated clinoptilolite zeolite were used. Results indicate significant differences between treatments and also with control (p < 0.05). With increasing clinoptilolite zeolite in each treatment, the survival rate of fish also increased significantly (p < 0.05). In lethal concentration of ammonia, the use of 15 g L -1 zeolite could prevent the mortality rate. Histopathological findings showed that major lesions were hemorrhage, hyperemia, hyperplasia, epithelial cells necrosis, degenerated tubules of kidney, expansion of Bowman's capsule and hepatocytes necrosis.

A 4 days study was conducted to determine the effects of Different concentration of bioaugmentor bacterial strain Bacillus licheniformisi, B. subtilis, B. polymyxa, B. laterosporus and B. circulans (Protexin Aquatech, UK) on adjustment of parameters of water quality as TAN, NO2-N, NO3-N and turbidity from the effluent of Common Carp ponds. Effects of time and concentration were studied as a completely randomized split-plot design. Time and concentration and their interaction had a significant difference (P<0.05)on changes of total ammonium nitrogen, nitrate nitrogen, nitrite nitrogen and turbidity. The total counts of bacteria recorded in the water of bioremedated tanks were also lower than that in the control tank.

Community structure and biodiversity of benthic macro fauna in around pen culture of Sturgeon fish in Gorgan Bay were studied for period of one year from August 2015 to July 2016. Seasonal samplings were carried out at 5 stations in 3 transects. In addition, depth (D), water temperature (Toc), dissolved oxygen (DO); pH, total dissolved solid (TDS), biological oxygen demand (BOD5), chemical oxygen demand (COD), phosphorus (PO4-3), nitrite (NO2-) and total ammonia (NH3+) were measured in each station. Results of season variations of Physico &ndash; chemical factors of water showed that, there were no significant differences between PO4-3 (p&gt;0.05). However, there were significant differences between BOD5, COD, NO2-, NH3+ and TDS (p&lt;0.05). Totally, 11 genus&#39;s and 10 families belong to 3 phyla as Mollusks, Arthropods and Annelids were identified. The results showed, there were the maximum abundance percent belong to Hydrobiidae and Cochliopidae with 33.83% and 26.25% and the minimum abundance percent belong to Gammaridae with 0.05% respectively. However, the maximum abundance belongs to Pyrgohydrobia sp., from Hydrobiidae with 3410 n/m2. The results showed, there were the maximum and minimum abundance percent in autumn and spring with 1.07 and 0.88 % respectively. The results of distance-based redundancy analysis (db.-RDA) revealed that environmental factors such as depth, DO and TDS are all important in determining the distribution of macro benthic species in Gorgan Gulf. However, there were significant differences between abundance, species number (S), diversity (as Shannon&ndash;Wiener&rsquo;s, H&acute;), species richness (as Margalef&rsquo;s, D), and evenness (as Pielou&rsquo;s, J) (p&lt;0.05). There were the most diversity species in 2 and 5 stations.