Studying the Effects of the Trout Farms Effluents on the Water Quality of the Chafrud and Shafarud Rivers in Guilan Province, Iran, and their Self-Purification Capacity

Although freshwaters especially rivers and streams constitute a small proportion of the whole, earths water, but they have been always important and vital for the human beings. Regarding that aquaculture activities and flowing their effluents into the streams may have some effect and consequences, during a one year period the effects of two 20 ton per year capacity, rain bow trout farm effluents on the receiving streams of Shafarud and Chafrud (western Guilan province, Iran) were studied. 8 and 4 study sites were chosen respectively in Chafrud and Shafarud rivers. Water and Macroinvertebrates were monthly collected and analyzed. Key physicochemical parameters in both river were in their normal ranges and their fluctuated as below: Shafarud: Water T° C:5.4-20.9, mean=13.2 ; DO2 mg/l: 6.3-17.8,mean=11.5 ; BOD5 mg/l: 0- 9.3,mean=1.98 ; total hardness mg/l: 68-165,mean=126 ; NO3 mg/l: 0.151-1.046,mean=0.645 ; NH4 mg/l: 0.197-0.888,mean=0.422 ; PO4 mg/l: 0.025-0.219,mean=0.069 ; pH : 7.32- 8.59,mean=8.07. Chafrud: T° C: 4.2-26, mean=13.6; DO2 mg/l: 7-14,mean=10.9; BOD5 mg/l: 0- 12.4,mean=1.19; total hardness mg/l: 88-266,mean=149; NO3 mg/l: 0.05-1.45,mean=0.714; NH4 mg/l: 0.14-1.19,mean=0.545; PO4 mg/l: 0.01-0.13,mean=0.049; pH: 7.12- 9.94,mean=8.16. Meanwhile 52 and 53 macroinvertebrates taxa were identified in Shafarud and Chafrud respectively, dominated with aquatic insect larvae. No significant differences were detected within physicochemical parameters in both rivers, indicating a high natural purification capacity for them. High diversity and dense population of the most sensitive taxas(EPT : Ephemeroptera+Plecoptera +Trichoptera) along the studied streams proves that there is no meaningful effects on the water quality of the effluent receiving stream .

Iranian Fisheries Science Research Institute

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