The family Thymallidae, commonly known as graylings, consists of freshwater fish primarily found in cold, clear rivers and lakes in the Northern Hemisphere. They are characterized by their elongated bodies, large dorsal fins, and distinctive coloration, which often includes shades of gray, blue, and silver. Graylings are known for their delicate, mild-flavored flesh and are popular among anglers. Graylings are closely related to the family Salmonidae, which includes salmon and trout. They typically inhabit areas with clean, well-oxygenated water and are sensitive to pollution. Their diet mainly consists of insects, making them an important part of the aquatic ecosystem.