Evaluation of distribution pattern of Macrobenthos in the Gamasyab and Biston's river in Kermanshah province

The present research attempts to examine the quality of Gamasiab River and one of its main branches Bistoon ponds and also the impacts of such branch on the main river (Gamasiab) by using Hilsenhoff and Simpson index indices. The present study was conducted in a period of one year since 2014-2015 in 12 time periods in three stations. Benthic invertebrates were collected using Surber quantitative sampler, then fixed (Formalin %4) in laboratory and separated in laboratory using separation loop, and they were identified at the family level. In addition, while conducting sampling over benthic invertebrates variables at each station were measured as well. The greatest Simpson's Diversity Index was observed in the second station. Overall, 11 families of benthic invertebrates (totally, 5492), were identified in Gamasiab and Bistoon, which the highest the highest rate of density was related to Diptera present in all seasons at each three stations. Other orders (Gastropoda, Ephemeroptera, Amphipoda), were most frequencies in River. In this research 7 order (Diptera, Ephemeroptera,Trichoptera, Coleoptera, Pulmonata, Amphipoda, Clitellata) and 11 Famylies (Chironomida, Simuliidae, Tipulidae, Baetidae, Heptageniidae, Hydroptilidae, Elmidae, Planorbidae, Physidae, Gammaridae, Lumbricidae) were identified in Gamasiab and Bistoon Rivers.