A biological study was conducted to find out about reproduction and feeding of G. lacustris in Neur Lake from northwest mountains of Iran. Plankton diversity, hydro-chemical factors and substrate characteristic were recorded monthly. Findings showed that reproduction period of this species was short and limited to May and the mean brood size was 10.2 ± 5.3 eggs per female. The hydro-chemical analysis showed the eutrophic characteristic of Neur Lake in which the average of total organic matter was 3.7 ± 3.0 percent. The phyla representative Bacillariophyta, Chlorophyta and Cyanophyta were observed throughout the study and Chlorophyta was the dominant group. Three zooplankton phyla Rotatoria, Ciliophora and Copepoda were abundant respectively. Study on diet using gut content resulted in identification of 15 plankton genera with some resemblance to planktons of the lake.