Sabzkooh in Ardal and Gandoman region in Charmahal province with annual production of 1300 metric tons of rainbow trout, is one of the most important rivers in the province. The effects of fish farms effluent on the river water quality and the possibilities to develop or limit the existing ones were studied. Flora and fauna of the river including Phyto and zooplankton, macroinvertebrates and fishes were sampled and studied. Moreover some key physico-chemical water quality parameters, concentrations of stable pollutants (heavy metals: Zn, Cu, Fe, Pb, Cd and agricultural poisons (herbicides or pesticides: DDT, Lindane, Alderine and indosulfate) and Coliform contamination were also measured. All phytoplankton genus were of tow taxa, Cianophyta and Chrysophyta and zooplankton fauna belonged to Rotatoria, Protozoa and meroplanktonic chirinomids and nematodes. Four fish species from 3 families were identified of which rainbow trout had the highest relative frequency (94.6%).All the measured heavy metals including Zn, Cu, Fe, Pb, Cd and the agricultural poisons concentrations such as DDT, Lindane, Alderine and indosulfate were lower than the hazardous level suggested for the surface waters. According to the benthic macroinvertebrates populations study, stations at downstream (no. 6 and 7) which received the Chartakhteh and Rudarud farms effluent had least EPT richness and the hilsenhof family level biotic index at this locations was greater than 5.25, classifying them as having organic pollution. Even though measured key physico-chemical parameters such as nutrients (N and P compounds and BOD5) in the receiving stations and effluent water never exceed the maximum permitted range but in downstream stations these factors were very close to the range. One way analyze of variance (P 95%) for TN, TP, No_2, NH_4, BOD_5, pH, PO_4 and Ec revealed no significant differences between stations before and just after receiving the effluents, however these parameters in the effluents themselves significantly differ from upstream stations 1,2 and 3 proving relatively lower organic pollution and the potential for constructing new farms or expanding the existed ones in upstream region from Chartagh to Dehnoo. At downstream from Dehnoo to Rudarud and lower parts, dense trout farm effluents in addition with point and non point pollution (municipal, agricultural and other coming run off from the catchments area) had remarkable effects on the river water quality and as a result no farm construction or expansion is recommended. To avoid or reduce the existing farms effects on the river system there should be certainly some remediation actions carried out. Constructing sedimentation ponds before releasing the effluents, obeying the rule of water extracting, preventing fish escape, increasing feeding efficiency and controlling the lateral inlets from catchments area which are potentially pollutant, should be considered to improve the situation and prevent further environmental problems caused by fish farms effluent in these area.
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