Catfish is a mixed benthic fish, but it doesn't live at the bottom of the polluted ocean as people generally think. In fact, river catfish can only be cultured in places with relatively clean water quality, belonging to the freshwater fish of the Yangtze River. Catfish has a high nutritional value, which is why many people like to buy catfish to eat. Although catfish viscera are often full of toxic wastes and chemical pollutants, catfish can store toxic substances for a long time and accumulate them in its muscles and viscera because of its slow growth.