Abstract: Lactobacilli bacteria are gram positive without spore, catalase-negative and filamentous bacteria that mainly ferment different carbohydrates into lactate and acetate. During this research about 50 perch (Perca fluviatilis) hunted from Aras Dam, Iran, randomly. The samples were transported to the Microbiology Laboratory of Veterinary Medicine, Faculty of Tabriz under sterile conditions and in the vicinity of ice and after dissection according to sterile method 1 g of stool was sampled from the anterior part of intestine and cultured in MRS agar plates. After phonotypical and biochemical identity of bacteria, for distinction of lactobacillus species molecular characterization, 16S rDNA gene was amplified and PCR products were sequenced. Results of sequencing about 3 isolated bacteria indicated that this species has been Lactobacillus fermentum and the founding’s corresponding to produce results from biochemical tests and determine cutting pattern for this species.