The survey of distribution and species diversity of fish in the Haraz River

This research was carried out in two seasons of summer and autumn in 2014. Fish sampling was done using a 2.3kW electrofishing in 7 stations. The purpose of this study was to investigate the effects of sand and gravel harvesting on abundance and variation of Shannon Wiener Index of Haraz River community. The results showed that the species diversity increased from the upstream (0.55) to the downstream (2.83) of the river and there was a significant difference in Shannon wiener index at different stations (p<0.05). The results of the survey on fish populations in the Haraz river showed that rainbow trout (Onchorhyncus mykiss) had the predominant fish population in the upstream of the river, in which could be a food competitor for the indigenous species of brown trout (Salmo fario) which led to a decrease in the populations of brown trout and its absence in catch and sampling was in the main stream of the river. Also, the catches from the cyprinidae were of a lower variety and density than the past, so that no specimens were collected from the species of fish Barbus spp. groups, and other species such as Squalius cephalus, Capoeta capoeta, Alburnoides eichwaldii, and brown trout (S. fario) has a very low abundance, which could be due to fish aquaculture, the increased activity of the sand and gravel extraction, the lack of attention to the installation of filtration apparatus for rocks washing, increasing the water turbidity and its effect on the eggs and larvae of fish.