Evaluation of the Effects of Rrainbow Trout Fish Farms on Quality of Qaleh Roudkhan Forest River in Guilan Province Using Biological Indicators

In recent years, the construction of fish farms along the Qaleh Roudkhan river has increased significantly. The aim of this study was to investigate the effects of effluent from these farms on benthic communities and their population structure in river water. A total of 6 study stations were selected, of which 2 stations are from Fusheh (Shahed) branch and 4 stations are from Qaleh Roudkhan branch. Among the stations, Station 2 of Qaleh Roudkhan is located at the exit of the effluent of the fish farm. The results of analysis of variance using SPSS for all biological indicators indicate that there is a significant difference between the stations. Also, according to Duncan's test at 5% level in Shannon-Wiener index between stations 1 and 2 of Fosheh and stations 1 and 2 of Qaleh Roudkhan, in Margalf index between stations 1 and 2 of Qaleh Roudkhan with other stations, in Simpson dominance index between all stations except station 1 Fusheh and 4 Qaleh Roudkhan, in Helsinghof and EPT index between all stations and in BMWP / ASPT index between 2 Qaleh Roudkhan stations and other stations, there are significant differences. Based on the results, the fish pond workshop has caused changes in the groups of benthic invertebrates during the study period, which indicates a sharp decline in water quality at the effluent outlet.