Study of food habits and preference of the Exotic Rainbow trout)Oncorhynchus mykiss (Walbaum, 1792)) in Madarsoo stream, Golestan National Park

Abundance and diet of Oncorhynchus mykiss were examined in Madarsoo River in Golestan National Park. A total of 144 fish specimens investigated (with average Total length of 190mm and Total weight of 80g). Ephemeroptera was the most abundant of collected benthic invertebrates. The Ivelev index showed that Ephemeroptera، Gammaridae and Tricoptera were the most important food items for O. mykiss. Our result has indicated that species is the potential food competitor of fish species، Paracobitis malapterura، Neogobius melanostomus، Neogobius fluviatilis، Albunoides eichwaldii in Golestan National Park stream.