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This study was done in 2008 on agricultural sewage for aquaculture in six stations. Two stations were in AhvazKhorramshahr road near sugar cane plantation sewage in west Karoon, Two stations were in Ahvaz-Abadan road in sugar cane plantation sewage in east Karoon and Azadegan sewage and two stations were in agricultural sewage in the north of Ahvaz. Monthly Samplings of planktons, physical, chemical parameters were taken during Aprile to March 2008. In addition seasonal sampling of benthic fauna and fish were carried out. Heavy metal and toxic samples were done only one time during the study period. Measurement of some parameters such as temperature and pH were done during sampling procedure and other parameters were measured in laboratory based on standard methods. Heavy metal concentrations were measured with polarography and voltammetry techniques and toxic substances were extracted and concentrated to determine the concentration of them in water using GC device. For identifying phytoplanktons, 1 liter water from middle depth was sampled in each station and 4% formalin was added. Zooplankton were sampled monthly using 55µ plankton net. Fish samplings were done using cast net regarding regional condition, and sampling from benthic invertebrate of river were done using Petersen grab with 15.5cm*15.5cm. Results of water quality index (WQI) from Koushk Talaieh (station1), Artificial lake station (station 2) , Farabi(station 3), and Azadegan aquaculture sewage station (station4) showed that water quality is in group four. WQS index was used for Maleh(station 5) and Pumping station ( 6 station) stations due to high levels of salinity. The WQS results showed that water quality of these stations were moderate to low. Heavy metals in water, the ordination is as follows: Ni > Zn > Pb > Cu > Co > Cd > Hg Mercury levels in all cases were less than the standard and all the elements have been somewhat less than chronic toxicity level. The values of all studied metals are lower than the WHO limit. The results indicated that chlorinated pesticides in all samples are at low level and they are at acceptable levels for aquaculture. In this study, 34 genus of phytoplankton from Bacilariophyceae (diatoms), Cyanophyceae, Chlorophyceae and Dinophyceae were present with 11, 8, 14 and one genus respectively and the percentage of frequencies were respectively 37.64, 34.26, 23.24 and 4.87%. In general phytoplanktons of wastewater were in modest condition for using in aquaculture. In this study, about 1,000 samples of zooplankton in 6 stations were identified and counted during the year. The high percentage of zooplankton were belonged to three groups of protozoa (mainly ciliates), Rotifer and copepods were. The Rotifers with more than 90 percent frequency had the maximum prevalence. The dominant rotifer species was Brachionus calciferous. Although in this study the dominant group of zooplanktons was rotifers but the frequency is not high. Therefore we cannot call this circumstance as eutrophic condition, however the growing trend of high food phenomenon has announced. High benthic diversity was observed in Artificial lake wastewater station and Azadegan aquaculture sewage station. The most frequent taxa were in Azadegan aquaculture sewage station during autumn and winter which belonged to resistant Chironemidae larvae. In Koushk Talaieh, Farabi and Maleh stations, Chironemidae was dominanted and in Pumping station Coleoptera was dominant group. Hilsenhoff index showed that most of waste water stations were in poor to very poor condition, indicating that they were heavily contaminated. The data analysis of macrobenthose data in wastewaters based on Satropi and biological value (Z) showed that potential of fish production in Azadegan and artificial lake was high during the year. These two water sources have suitable situation for potential production and biological value, therefore with special plans for culturing low demand fish would be possible. In this study, 7 fish species belongs to 7 genera from 4 families were collected. Freshwater and marine water species was observed in the catch composition. According to the results of the four studied stations, Artificial lake station and Farabi had the highest number of catch which mostly belonged to Acanttopetrus Latus and Liza Abuo. In general, based on biological parameters, such as zooplankton frequency, all stations had similar conditions but in terms of phytoplankton, Azadegan aquaculture sewage station, Pumping stations and Farabi wastewater have better condition for aquaculture. The FBI index showed that the artificial lake station and pumping station are more suitable for aquaculture activity. Low demand fish is recommended for Azadegan aquaculture sewage station. Artificial lake station had lower primary production but it is more suitable for aquaculture because of its lower FBI index value. Most of the fish presence was in the artificial lake station and Farabi wastewater which belonged to two predominant species of Acanttopetrus Latus and Liza Abuo. In general, based on biological and non-biological parameters, artificial lake station in the west Karoon and Azadegan aquaculture sewage station have better water quality than the other stations for aquaculture activities. This requires management action and special schemes. Iranian Fisheries Science Research Institute Published |
