Rutilus frisii, (Nordmann, 1840)

Taxonomic description of subspecies

Body depth moderate, less than head length or equal. Scales in lateral line 53-62, usually 55-58. D III 9; A III 10. Mouth subterminal. Pharyngeal teeth 6-5. Posterior part of swim bladder elongated.
Intraspecific forms. Kutum has ecological forms, which differ with morphological (specifically, plastic) features (Kuliev, 1997). 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).
Related forms. R. frisii frisii (Nordmann, 1840) � �vyrezub�, Black Sea subspecies, inhabits the Black and Azov Sea basins. Kutum is distinguished by certain body proportions, size of the scales (larger), and the number of fins rays (Abdurakhmanov, 1962).

Distribution of subspecies within the Caspian Sea

Kutum is distributed from the mouth of the Volga River up to the Astrabadskiy bay. Main aggregations are confined to the south-western part of the sea adjacent to the Enzeliyskiy and Kyzylagachskiy bays. At the eastern coast occurs at the Atrek estuarine areas and in the Iranian waters.
Status as per International Red Data Book: N/A.
Status as per National Red Data Book: N/A.
First record for the Caspian Sea: Pallas, 1811
Redescription of subspecies: see synonyms.

General characteristics of subspecies

Ecologico-taxonomic group. Nekton. Anadromous fish
Origin. Ponto-Caspian
World distribution. Caspian Sea endemic
Habitat. Feeds in the coastal areas at shell/ sand bottom. Spends the most of its life in the sea and only spawns in the rivers.
Migrations. The spawning run takes place at water temperature 6-22⁰C. Kutum enters the rivers of Iran from December till April, the Kumbashinka River - from mid-February till late April, the Volga and Ural Rivers - in March-April. The peak of the run is observed in late March � early April. Post-spawners migrate downstream to the sea. Fry migrate in July-August and move away from the coast to the deep-water area, later grown fish approach the coasts.

Relation to abiotic environmental factors

Relation to salinity. Brackishwater euryhaline subspecies. For the most of its life inhabits the sea at salinity up to 13 ⁰/₀₀. Spawns in fresh water.
Vertical distribution. Inhabits coastal waters usually at the depth ranging from 20 to 30 m.
Relation to oxygen conditions. Oxyphilic subspecies. Occurs in well-aerated water with high oxygen concentration.
Relation to fluctuations of the sea level: N/A

Feeding

Feeding type. Heterotrophic
Feeding behavior. N/A
Food spectrum. Benthophagous fish. The main food items are mollusks, shrimps, amphipods and crabs. Larvae and fry feed on rotifers, minute forms of cladocerans, diatom algae, and larvae of Copepods.
Food supply. Unlimited
Quantitative characteristics of feeding. N/A

Reproduction

Reproduction type. Sexual
Reproduction areas. In the Middle Caspian enters for spawning the Divichinskiy firth and the Samur fish-rearing farm; in the Sulak River migrates 100 km upward where reproduces at gravel bottom. The main spawning ground in the south-western part of the sea is the overflow channel of Malyi Kyzylagachskiy bay. The Kumbashinka River has currently lost its importance as a spawning area. The main spawning grounds in the Iranian waters are located in the Sefid-Rud River.
Terms of reproduction. The spawning run starts in February at water temperature ranging from 6.0 to 7.2 ⁰C. The mass migration is recorded in March at water temperature 12.3-13.8⁰C. Duration of spawning run - 55-70 days - depends on hydro-meteorological conditions. Spawning initiates at water temperature 9-12⁰C.
Fecundity. The absolute fecundity (dependent of the fish size) ranges from 27 thousand to 280 thousand eggs, 109.6 thousand eggs in average (Adburakhmanov, 1962).
Limiting factors

• Availability of the spawning grounds;
• Sufficient water exchange/ flow in the areas of egg deposition;
• Availability of clarified water.

Life history and development

Life history stages. Based on certain morphological and physiological features, 6 stages are described for larval development, fingerling period is divided into 2 stages.
Relation to environmental factors. N/A
Age of maturity. Maturation comes at the age of 4 years; single specimens (predominantly males) mature in the third year. Fish aged 5-6 years compose the basis of the spawning stock.
Thermal conditions of development. Incubation of the eggs lasts for 11-15 days at temperature 8-11⁰C; hatching occurs on the 7-8th day at temperature 15-17⁰C; duration of embryogenesis reduces to three days at temperature 23.0-24.8⁰C.
Quantitative characteristics of growth. At hatching, larvae have an average of 8.6 mm TL, by 36 days after hatching - 19-33 mm. Body length of juveniles by the end of the first year averages 6.8 cm, weight � 5.4 g; in the third year - 32-40 cm and 600-700 g, respectively.

Structural and functional population characteristics

Sex ratio. N/A
Age-size structure. The age of kutum from the catches data is estimated to be 3-8 years old; the majority is represented by fish aged 4-5 years.

In the previous years, the majority was composed by the specimens aged 5-6 years, and even 7 years old (Derzhavin, 1961). Body length of fish harvested in Kyzylagchskii bay ranges within 34-55 cm (base stock - 35-50 cm), weight � 658-2.920 g. Single specimens reach the length of 67 cm and the weight of 3.9 kg.
Quantitative characteristics. N/A
Population trends. As compared with 1950-s, considerable decline of the catches occurred due to substantial reduction of the spawning areas.

Interspecific relations

Currently, kutum is not a competitor for feeding to the other fish species due to the sharp decline of its stocks.

Importance of subspecies to bioresources production of the Caspian Sea

Economic significance of subspecies. A valuable commercial fish for Azerbaijan and Iran.
Kutum (fresh, smoked and salted fish) is of great demand in regard to its high taste quality and cuisine customs of the local residents, consumed all the year round.
Commercial characteristics of subspecies, catches. The average annual catches of kutum in Azerbaijan amounted to 2.5 thousand tons in 1931-1935 and reached 1.9- 5.0 thousand tons in harvests along the southern coast of the Caspian including the I.R. Iran. The catches of kutum in the Caspian Sea peaked 7.0 thousand tons in 1939. The present catches in Azerbaijan decreased to 55.9 tons in 1985, to 3.8 tons in 1993. The harvest in the waters of Dagestan is insignificant, 0.2 thousand tons were caught in 1968. 90% of all kutum is now harvested illegally.
Fishing gears and fishing zones. In the waters of Azerbaijan and Dagestan fishing is carried out with fixed/ stationary nets and drags/ sweep nets in spring during the spawning run; in Iran � with fixed nets in the sea coastal areas.

Impact of fisheries on the population status

The stocks are depleted heavily due to the insufficient number of spawners accessed to the spawning grounds since 1960, and heavy load of fishing, which is carried out along the spawning routes.
Human impact/ Threats

• High rate of illegal fishing;
• Unsustainable fisheries management;
• Reduction of spawning areas as a result of economic activities.

Conservation measures. At present, artificial propagation should become the chief way for the maintenance and increase of kutum abundance. Experimental studies in this field were initiated in 1924 at the Kumbashinka River and the Samur fish-rearing farm, later they were replicated at a larger scale (in 1950-s). In 1980, a special facility for propagation of kutum (with annual capacity of 50 million specimens) was installed. However, the scale of artificial propagation in Dagestan and Azerbaijan considerably decreased, which became the cause of sharp decline of catches. In order to enhance the efficiency of natural reproduction of kutum in the rivers of Azerbaijan and Dagestan, melioration of spawning grounds and upgrading the scale of artificial propagation is necessary to be implemented. About 140 million specimens of kutum fingerlings (1-2 g weight) are released into the sea annually from two Iranian hatcheries; this resulted in noticeable increase of catches of I.R. Iran in recent years.

References

Abdurakhmanov, Yu.A. 1962. Fish of freshwater bodies of Azerbaijan. Azerbaijan SSR AS. Pp.89-96.
Bagirova, Sh. M. 1967. Stages of development of the Black Sea roach in the Ust-Kura fish breeding farm. Biological productive capacity of the Kura-Caspian fishing district. Baku. Pp. 226-236
Derzhavin, A.E. 1951. Essays of the history of the Caspian Sea and freshwater bodies of Azerbaijan . Animal kingdom of Azerbaijan pp.34-83.
Kuliev, Z.M. 1997. Carps and perches of the Southern and Middle Caspian (structure of the population, ecology, distribution and measures for population restocking). Author' Abstract of the Dissertation for the Doctor's Degree. Baku. Pp. 14-15.
Rezavi, S. et al. 1997 . Breeding and rearing of the Black Sea roach in the Islamic Republic of Iran . The 1st Congress of Ichthyologists of Russia. Book of Abstracts. VNIRO Press. Moscow. P. 452.
Tamarin, A.E. and Z.M. Kuliev, 1989. Black Sea roach. In : Caspian Sea: Ichthyofauna and commercial stocks. Nauka Press. Moscow. Pp.144-145.

Compiled by:

Kuliev Z.M., AzerNIRKh, Baku, Azerbaijan