The effects of Trout Farms Effluent in Haraz River on population structure of benthic macro invertebrates

Abstract

The goal of this study was the effects comparative of sand and gravel civil works and Trout Farms Effluent in Haraz River on population structure of benthic macro invertebrates. For this purpose selected five stations on Haraz River. Benthic macro invertebrates were investigated for two seasons of summer and fall in 2011, by using a Surber net (30.5×30.5cm, 250μ mesh). About 13329 macro invertebrate specimens at 22 genera, 10 families and 11 orders were collected and dominated with aquatic insect’s larvae. Shannon index, richness, Chironomidae percentage, EPT percentage and EPT /CHIR were significantly difference between the control and stations after fish farms. Indices of EPT richness, EPT percentage and EPT/CHIR (Ephemeroptera + Plecoptera + Trichoptera / Chironomidae) decreased at the immediate vicinity of the fish farms outflows , Shannon index was lower than 1 in all of the stations, On the basis of HFBI index ,we saw three grades of qualities as , good and Possible slight organic pollution in first, second and third station ,relatively poor and Fairly significant organic pollution in fourth section and poor and Significant organic pollution in fifth section ,. The combined results of biotic indices indicated that pollution was higher at the stations at the immediate
vicinity of the fish farms and comparative of sand and gravel civil outflows than the preceding ones, and it shown, the self-purification potential of Haraz River was increased.