Ключевые слова: acipenser, acipenser ruthenus, acipenseridae, acipenseriformes, actinopterygii, animal, animals, aquarium, asia, asian, azov sea, black sea, caspian sea, common rudd, cyprinidae, cypriniformes, danube, endangered, europe, european, fauna, fish, fishes, freshwater, freshwater fish, freshwater fishes, lake, many, many fishes, natural, nature, river, rudd, scardinius, scardinius erythropthalmus, sea, sterlet, sterleth, sterlets, sturgeon, sturgeons, swim, swimming, underwater, volga, water, wild, wild animal, wild life, wildlife, zoo,