Study of possibilities of aquaculture activities in the Gorgan Bay

The Gorgan Bay has situated in the South east of the Caspian Sea and water entersthe Bay from the Sea .it covers an area about 450 squar kilometers that is connected to the sea only by the passage of Ashouradeh in the north east of the bay . The water balance is almost constant and is not tidal. In this study, a model made for the bay on the basis of its water quality and quantity. Its reactions evaluated under different qualified scenarios and its surrounding water quality survey during next 29 years. Mike 21 software was used for 2 dimensional modeling . At first hydrodynamic modeling of the bay was done .one of the important factor was water depth which calculated by hydrography method of the bay. Then, a model made for the salinity of the bay. Since, salinity is a stable parameter, a sub-program TM (Mike 21) which has the ability to make a model from the process of advection – dispersion was used. The amount of Manning (0.025) and Dispersion (50) coefficient calculated simultaneously with calibration of salinity model (D:square meter / second). Results from data verification of salinity model indicated about 3 percent mean error. The pollution dispersion type in the bay evaluated at six points of the bay using the method of dot constant source of pollution. Results showed that around 99.9 percent of pollution decreases under the effect of dilution process till the 100 m distance. Then modeling of dissolved oxygen, Ammonia, nitrite and nitrate was done by using of subprogram ECOLAB at the Mike software To make these models, first the sensitivity analysis of these parameters was done. Important parameters chose for model calibration and then data verified and also the model calibrated. The result of data verification test showed the mean error of oxygen, ammonia, nitrite and nitrate were respectively about 3, 4, 6.3 and 37 percent. Then modeling made according to four different scenarios which defined on the basis of pollutions originated from aquaculture in the bay (scenario 1: aquaculture at the first half year. Scenario 2: aquaculture at the 2nd half year. Scenario 3: aquaculture at the whole of year. Scenario 4: cultivation of bluga for 3 years). Water quality of the bay and also different amount of aquaculture production surveyed during next 29 years under different scenarios of aquacultures. The places under pollution were included the appropriate places for aquacultures in each scenario that was already determined at the bay .Then the reaction of the Gorgan bay was determined under each scenario. The curves of pollution fluctuations were drawn along with amount of cultivation at the each scenario. At last, appropriate amount of cultivation was calculated at each scenario with considering of self-purification of the bay that does not tend to pollution of the bay. On the other hand, the farms arrange, distances between farms and the number of cultivation ponds at the each farm was calculated. Finally, results showed that the aquaculture capacity of the bay is less than 300 tons per year

Ecological study on fisheries important rivers and bays in the south part of the Caspian Sea 2nd phase: Gorgan Bay

In this study ichthyoplankton, phytoplankton, zooplankton, benthic and hydrochemistry parameters were studied. 9 out of 11 sampling stations were in the Gorgan Bay area and 2 of them were in the mouth of the Bay. Ichthyoplankton survey were carried out in 6 stations and the other surveys such as phytoplankton, etc were done in 11 stations in 2009. Gorgan Bay map and position of sampling sites are given at the end of material and methods section. Biomass and frequency of phytoplankton at different stations, months and seasons were calculated that are presented in Tables 1 to 3. Hydro-chemical parameters such as water temperature, air temperature, visibility, DO, BOD5, pH, Alkalinity (bicarbonate, carbonate and total), Hardness (calcium, magnesium), CL,EC, Salinity, N (nitrate, nitrite, NH_3), Phosphate were measured and results are shown Table 11. Biomass (mgr/m^3) and numbers (ind./m^3) of 47 genus of different phylum of phytoplanktons such as Cyanophyta, Chlorophyta, Pyrophyta, Chrysophyta and Euglenaphyta as well as different phylum of zooplanktons consist of Protozoa, Arthropoda, Rotifera and Cyliophora were estimated. Frequency of phytoplanktons (ind/m^3) was 131.2, 1.6, 65.3, 18.9 and 23.8 million respectively. Furthermore, their biomass was 308.4, 1.9, 1358.9, 295.1 and 124.7 mg/m^3, respectively. The maximum and minimum numbers were observed in Leptolingbaya belonged to Cyanophyta and Diatoms of Chrysophyta 84.3 and 0.025 million (ind/ m^3) respectively. The maximum and minimum biomass was observed in Gyrosigma (Chrysophyta) and Tetradron (Chloropyta), 12317.3 and 0.014 mg/m3 respectively. The average biomass of zooplankton was measured 531.74, 30.77, 225.07, and 96.26 mg/m^3 respectively and the total was attained 883.83 mg/m3 Table 5. The maximum and minimum biomass of all zooplanktons was estimated in November and July, 3446.23 and 6 mg/m^3 respectively. Furthermore, the maximum and minimum numbers of zooplanktons were found in September and July which were 48.4 and 0.002 millions respectively and the average number was 8.4 ind/m^3 Table 4. Also numbers and biomass (gr/m^2) of 11 families of benthos which inhabit Gorgan Bay such as Annelida, Mollusca and Arthropoda were investigated in separated stations and distinctive months. The maximum and minimum biomass of benthos was observed in January (42.91 gr/m^2) and March (0.6428 gr/m^2). The biomass was considerable in April, February, August and December (Tables: 4, 5 and 6)