The effect of salmonidae farms on the changes of the macrobenthos society of the Haraz River from Gazanak to Niyak region (Mazandaran Province of Iran)

Rivers are the most important sources of drinking water supply as well as agricultural activities. Among the rivers of Iran, the Haraz River, with a length of about 180 km in Mazandaran province, is one of the most important and most popular among them, which is one of the common activities in those cold-water fish farms. These farms, through the discharge of their effluent, may lead to environmental pollution and threaten the continuation of aquatic life in the river. Therefore, the purpose of this project was to study large communities of macrobenthic inoculants to evaluate the impact of contaminants on the biological conditions of this ecosystem in the months of October, November, December and in two Niyak areas (including 3 stations N1, N2, and N3 ) And Gazanak (including 3 stations G1, G2, and G3). The frequency of benthos samples from Baetide sp. (40.31%), Caenidae sp. (17.37%), Plecoptera sp. (9.04%), Hydropcyche sp. (16.03%), Chironomidae (13.80%) and Tubifex (3.45%) were counted. In order to investigate the relationships between quantitative traits, the Pearson correlation coefficient, the analysis was performed using SAS software version 4.9, and mean comparison using Duncan's multiple range test. The error level for all attributes was considered 0.05. The results show an increase in the relative pollution of station 1 (Niyak) towards station 6 (Gazanak), which can be said at station G2, the highest percentage of pollution and the lowest rate of pollution at station N1. Based on the Pearson correlation coefficient, Benthos of the Chironomidae and Tubifex family which indicate water pollution, according to the measurements of all water qualitative factors such as BOD, COD, DO, EC, Temp, pH, nitrate, phosphate, carbonate, ammonium, TDS, and chlorine in the research records, with all the factors except to DO, the direct relationship and other benthoses that are usually indicators of freshwater, are related to all factors, except DO. Therefore, based on all the results, the pollution of the Haraz river in the studied area does not have environmental concerns about contamination.