European Otter (Lutra lutra), is an aquatic and semi-aquatic animal from the carnivores and sub-family from Lutrinae of the Mustelidea family that lives alongside rivers and wetlands. Lutra lutra is an indicator species, and its loss somehow threatens human life, because one species is the head of the food chain and its loss is a sign of environmental degradation of other species. It has good distribution in Iran and the world, including Eurasia and North Africa. Lutra lutra has appearance characteristics such as a large body, cylindrical shape, a wide snout with long and thick mustaches, small ears and eyes, the tail is long and tubular, which at the base becomes wide and thick, the hands and feet are short and there is a curtain among the fingers, the hair is soft and dense, brown to brownish, under the chin and white throat. In recent years, widespread deaths have occurred in several aquatic mammal populations, which has reduced the population of Lutra lutra compared to the past. Due to various reasons such as loss of prey, indiscriminate hunting, contamination caused by agricultural pesticides, especially chlorine toxins, industrial pollution, and floods, its population is rapidly declining and has been totally destroyed in some areas.