The Kutum (Rutilus frisii kutum, family Cyprinidae) also known as “Caspian White Fish”, or “Caspian Roach”, is a medium sized fresh water and brackish water fish native to the Caspian Sea. It is a subspecies of the Black Sea Roach Rutilus frisii frisii. It is typically a medium sized fish, reaching 17.72-21.65 in (45-55 cm) in length, rarely 27.56 in (70 cm), and weighing up to 8.82 lb (4.00 kg), rarely 11.02 lb (5.00 kg). It used to be very common and was harvested commercially. The population seems to have collapsed due to over exploitation and pollution. Its flesh and roe is enjoyed as food, and highly prized in Gilan and Mazandaran provinces in Iran.
The main food items the Kutum consumes are mollusks, shrimps, amphipods and crabs. Larvae and fry feed on rotifers, minute forms of cladocerans, diatom algae, and larvae of Copepods.
Three populations (one autumn and two spring populations) were found in the rivers of Iran (Rezavi, 1997); a riverine/freshwater form exists in the South Caspian (Derzhavin, 1934).
Kutum is endemic to the Caspian Sea. It is distributed from the mouth of the Volga River up to the Miankaleh peninsula. Main aggregations are confined to the south-western part of the sea adjacent to the Anzali and Qizilchay bays. At the eastern coast, it occurs at the Atrak estuarine areas and in the Iranian waters.
The Kutum lives in small schools in deep water, but spawns in shallow water in the tributaries in April-May. The eggs are laid among weeds or over gravel, and hatch in about 10 days. It becomes sexually mature in 3-5 years. Resilience of this species is low. Minimum population doubling time is 4.5 – 14 years.