Rutilus rutilus caspicus (Jakowlew, 1870)

TaxonomyRutilus rutilus caspicus

Phylum: Chordata
Class: Osteichthyes
Order: Cypriniformes Berg, 1940
Family: Cyprinidae Bonaparte, 1832
Genus: Rutilus Rafinesque, 1820
Species: Rutilus rutilus (Linnaeus, 1758)
Synonyms: Leuciscus rutilus var. caspicus Jakowlew, 1870: 103

Common names: Russian: vobla; Kazakh: karakez; Azerbaijani: kulme, bobla; Turkmenian: - kasli akcapagy; Iranian: koolmeh; English: Caspian roach

General view of the organismGeneral view of the organism

Taxonomic description of subspecies

D III 8-10, A III 8-10, more often 10; lateral line scales 40-47, gill-rakers on first gill arch 11-16; vertebrae 39; mouth lower than in other subspecies; pharyngeal teeth on one row (6-5). Eye iris silvery. Fins gray with dark fringe on edges. D originates over V origin.
Intraspecific forms: Kura roach, Rutilus rutilus caspicus natio kurensis Berg; Turkmen roach Rutilus rutilus caspicus natio knipowitschi, Pravdin; Charkhal roach Rutilus rutilus caspicus natio tscharchalensis Berg
Related forms: Rutilus frisii (Nordmann, 1840) – kutumfish

Distribution subspecies within the Caspian SeaDistribution within the Caspian

Forms several separate stocks:

Status as per International Red Data Book: abundant, widely spread species
Status as per National Red Data Books: N/A
First record for the Caspian: Pallas, 1786
Redescription of subspecies:

  1. Pallas, 1831. Cyprinus grislagine (non L.) Pallas, Fauna rosso-asiatica, III: 319;
  2. Eichwald, 1841. Cyprinus grislagine. Fauna caspio-caucasica: 2000;
  3. Jakowlew, 1870. Leuciscus rutilus var. caspicus. Trans. Kazan Soc. Natur.: 103-106;
  4. Sabaneev, 1874. Leuciscus rutilus var. caspicus. Fishes of Russia: 234;
  5. Berg, 1912. Rutilus rutilus caspicus. Fauna of Russia. Fishes, Vol.3, 1:67.

General characteristics of subspecies

Ecologo-taxonomic group. Nekto-benthos
Origin. Freshwater subspecies
Distribution. Caspian Sea endemic
Habitat. Bottom fish, occurs at silt/shell, sand/silt beds and among vegetation.
Migrations. Spawning (in spring), feeding and wintering (in autumn)

Relation to abiotic environmental factors

Relation to salinity. Brackishwater euryhaline species. Numerous occurrence of roach in the North Caspian is restricted to 10-11‰ isohaline, in the southern part of the Caspian - up to 13‰. Most abundant concentrations are aggregations in waters with salinity values 5-9 ‰.
Relation to temperature. Eurythermic subspecies. Found at temperature ranging from 2o to 28-30oC.
Vertical distribution. Typical benthic organism. Occurs above 15 m depth, usually 2-8m.
Relation to oxygen conditions. This subspecies is referred to the group with moderate oxygen requirements. The threshold lethal concentration of dissolved oxygen– 1.0-1.2 ml/l at saturation level 15-18%.
Relation to fluctuations of sea level. Lowering sea level and consequent increase of salinity result in decreased areas/ distribution and species abundance, and vice versa.

Feeding

Feeding type. Heterotrophic, holozoic
Feeding behavior. Feeds on inactive invertebrates, refers to animal-feeders. The main role in preying belongs to tactile and gustatory organs. Oral apparatus of sucking type.
Food spectrum. Euryphagous, benthophagous. Spectrum of food items reflects the composition of benthic animals: brackishwater mollusks, crustaceans, worms, insects, fish, plants and soil were registered.
Diet composition
Food supply. Food supply of adult roach consists mainly of zoobenthic organisms. The most important are: brackishwater mollusks, worms, and crustaceans (Zheltenkova, 1939; Shorygin, 1952; Belova, 1986).

Changes in gross biomass 
of the main food items of roach in the North Caspian (thousand tons)

Period 1935 1950-1955 1956-1962 1970-1977 1990-1995
Biomass of brackishwater mollusks 2285.5 884.0 1268.4 560.1 1470.0

Qualitative characteristics of feeding. The basic food organisms are mollusks of low energy value. E.I. Bokova (1940) assessed food assimilation under experimental conditions: when fed on Dreissena - 28.3%, on Gammaridae – 72.7%. Annual ration is calculated as (weight of fish)*24 when fed on mollusks, (weight of fish)*9 - on crustaceans.

Reproduction

Reproduction type. Sexual
Reproduction areas. Lower reaches of the Caspian rivers (Volga, Ural, Terek, Kura, Atrek, Sefid-Rud). Spawning grounds are mostly represented by flooded meadows; these shallow water bodies are easily warmed up. The best spawning grounds are meadows flooded in early spring (Tanasiychuk, 1951).
Terms of reproduction. Spawning occurs at one stage, in several portions. Reproduces up to 5-6 times during life history. In the North Caspian rivers roach spawns from late April to mid-May (15-30 days). Spawning starts at the temperature 10oC, intense spawning occurs at 13-15oC, maximum at 17-20oC. In the southern rivers (Kura, Atrek, Sefid-Rud) spawning lasts from late March to mid-April at 10-12oC, peak spawning occurs at 14-18oC. Eggs are deposited on vegetation at the depth not exceeding 50 cm.
Fecundity. Mean absolute fecundity of the North Caspian roach (18-20 cm TL) is 35 thousand eggs, it reaches 170 thousand eggs in fish of 30 cm TL.

Absolute fecundity of roach (thousand eggs)

Years Length, cm
14 15 16 17 18 19 20 21 22 23 24 25 26
1975 6.4 13.5 17.8 21.5 23.7 32.7 37.7 46.6 51.0 58.6 63.3 74.1 121.5
1978 13.2 16.7 21.9 27.0 26.7 38.6 42.8 49.7 55.1 69.2 64.9 73.0 110.0
1979 15.3 17.4 25.7 29.1 30.2 37.2 43.5 52.1 57.7 73.4 78.2 81.4 121.2
1986 18.4 23.2 29.7 32.3 33.7 36.3 40.1 53.2 56.1 73.0 74.1 81.0 117.5
1999 - 14.3 15.2 12.7 16.2 16.9 22.8 27.5 30.4 46.2 44.0 56.3 60.2
2000 13.9 15.7 16.6 15.8 19.0 19.2 32.0 41.9 45.1 52.6 58.3 59.0 73.2

Individual absolute fecundity of Azerbaijani and Turkmen roach (12-26 cm TL) - 20-24 thousand eggs in average.
Limiting factors. The main factors limiting reproduction success/yield are: height of river flood in spring, its duration and flow volume. In the Volga river the optimal range of these factors is as follows: flood height – 290-320 cm at Astrakhan depth-gauge, duration – 80-85 days, flow volume in April-June – 120 km3 and more. The optimal river temperature for spawning migration is 6oC, for spawning process – 12-14oC. . The other factors are: wind (surges) and salinity conditions.

Life history and development

Life -history stages.Life-history stages
Development of fertilized eggs at water temperature 16-18oC lasts for 6 days, at 18-20oC – 4 days. Body length of prelarvae at hatching is 4.5-5.5 mm, by the stage of yolk sac absorption (in 4-6 days) it reaches 6-7 mm; two-weeks-old larvae is 10-14 mm TL. At the age of 28-30 days, at 18-20 mm TL, scales appear, larvae transform into fry. By June, fingerlings attain 30 mm TL, and they migrate to the sea. In September-October, average body length of juveniles is 50-55 mm, in the years with favorable flood conditions - 60 mm and more.
Relation to environmental factors. Maximum mortality is recorded at early developmental stages. Only 1% of larvae develop out of the total abundance of produced eggs. The main factors, which increase mortality, are: abrupt fluctuations of water temperature during embryogenesis, unfavorable oxygen conditions, lack of food at larval transition to active/exogenous feeding. Among biotic factors the most significant is predation by fish.
Maturity age. North Caspian roach matures mostly at the age of 3-4 years (Sergeyeva, 1952), Azerbaijani and Turkmen roach – aged 2-3 years (Savenkova, 1989).
Thermal conditions of development. Temperature optimum for embryonic development differs at certain spawning periods: roach of March spawning migration has the highest percentage of eggs survival at 8-12oC, in April – at 13.5-23oC. Maximum total number of prelarvae hatches at 12-20oC, the maximum normally developed prelarvae is confined to the average temperature 16oC at hatching. Thermal optimum for larvae: 16 - 22oC, for fingerlings and juveniles: 18-24oC.
Quantitative characteristics of growth. Caspian roach grows most rapidly during the first 3-4 years of life. At this period the peak of population ichthyomass growth is recorded. From the age of 5-6 years, rate of weight gain slows down. Females grow faster than males. Higher growth rate is characteristic of both Azerbaijani and Turkmen roach, 3- 4-year-old specimens attain mean TL 18.4-20.1 cm and 18.5-20.5 cm, respectively, that is 2 cm larger than the North Caspian roach.

Age-related mean length (L,cm) and weight (P, g) of roach in the Volga river delta

Years Age, years
3 4 5 6 7 T
L P L P L P L P L P L P
1996 15.7 80.0 18.5 133.7 19.4 164.3 22.4 236.2 25.2 344.9 21.4 215.0
1997 16.3 80.5 18.0 122.9 19.5 160.1 21.6 210.2 24.1 297.3 20.9 197.3
1998 16.7 105.6 18.8 129.3 19.7 161.1 22.0 224.5 24.5 306.5 20.4 183.8
1999 16.0 80.0 17.7 116.1 19.2 144.9 22.3 191.5 23.7 245.9 19.8 158.2
2000 16.1 90.7 18.1 123.1 20.0 162.6 21.6 199.5 23.5 253.8 19.5 154.1

Growth is isometric, described by equation W = glb, where coefficient b is close to 3. Growth parameters for von Bertalanffy equation were calculated upon long-term data: 
L = 32.6 cm, K = 0.147, to = -1.76, where
L - mean hypothetical maximum length,
k - growth retardation coefficient
to - age correspondent to TL=0

Structural and functional population characteristics

Sexual structure. Up to mid-1960-s sex ratio calculated from seine catches was close to 1:1. At present, due to selective fishing regime both in the Volga delta and in Ural, catches consist mostly of females (more than 90%).

Characteristics of roach spawning population in the Ural river

Years Length,
cm
Weight,
kg
Females,
%
Fecundity
*103
Mean age,
years
Catches,
tons*103
1995 23.2 0.28 89 - - 0.78
1996 23.3 0.26 92 - - 1.96
1997 23.4 0.25 85 48.5 4.7 1.65
1998 26.5 0.39 85 89.6 6.4 0.89
1999 24.9 0.27 85 62.3 4.3 1.7
Similar trend is observed in commercial catches of Azerbaijani (61-65% females) and Turkmen roach (57-98%).
Age-size structure. Maximum life duration of the North Caspian roach does not exceed 10-11 years, attained size - 32-35 cm TL and weight - 800 g. Smaller sizes are recorded in commercial catches: from 15-16 to 27-28 cm. The major part of spawning population is represented by 3- 6-year-old fish, 16-22 cm TL.

Age composition of roach in the Volga river delta, %
Years Age, years Mean T Mean TL Mean Wt
3 4 5 6 7 8 9
1977-1980 21.7 49.3 24.3 3.2 0.6 0.2 - 4.1 19.8 171.1
46.9 37.7 8.6 0.8 0.1 - - 3.4 17.7 101.1
1995 0.3 12.6 26.7 45.8 12.8 1.3 0.5 5.6 21.2 211.4
1996 2.6 21.9 30.2 34.5 9.5 1.1 0.2 5.3 21.4 218.0
1997 0.1 7.7 37.8 47.2 5.3 1.4 0.5 5.6 20.9 197.3
1998 2.3 25.6 33.2 31.2 6.6 0.8 0.3 5.2 21.4 183.8
1999 0.4 18.8 55.3 23.3 1.8 0.2 0.2 5.1 19.8 158.2
0.6 22.9 48.3 25.2 2.2 0.7 0.1 5.0 19.4 149.1
2000 4.7 31.2 32.5 27.7 3.5 0.1 0.1 5.0 19.8 154.1
.7 45.9 35.4 12.7 1.1 0.1 - 4.6 19.2 151.3

Quantitative characteristics. Based on trawl surveys data (1954-2000), abundance and biomass of the North Caspian roach were calculated. During these years, two periods of high abundance and biomass (2+ - 8+ years) were recorded: 1954-1960 (171.4 thousand tons) and 1991-1995 (208.6 thousand tons), and two periods of low abundance and biomass: 1976-1978 (43.6 thousand tons) and 1998-1999 (about 60 thousand tons) (Chernyavsky, Malinovskaya, 2000).
Population trends. Since 1999-2000, North Caspian population tends to increase  in abundance due to introduction into fisheries high-yield generations of 1997-1998. Increased water discharges in the Volga river were recorded during these years.

Interspecific relations

Food competitor to the other benthic-feeding fish, primarily, to bream. Roach (juvenile, in particular) is a food item for predatory species – sturgeons (beluga) and the Caspian seal.

Importance of subspecies to bioresources production of the Caspian Sea

Economic significance of subspecies. Valuable fisheries item of significant social demand. Mainly used as salted and dried product.
Commercial characteristics of subspecies, catches. Historic review of the Caspian fisheries reveals considerable fluctuations of catches, mainly related to fluctuations of abundance. Maximum catches in the North Caspian were recorded in early 1930-s (exceeding 200.0 thousand tons) (Tanasiychuk, 1951). Minimal catch in the North Caspian, 3.0 thousand tons, was recorded in 1981. In 1990-1993, mean annual catch in the North Caspian comprised appr. 20.0 thousand tons. In Azerbaijan, in the 20th century, the catches varied from 6.2 (1911) to 0.1 (1995) thousand tons. In Turkmenistan roach fisheries was highly significant in 1930-s, annual catches composed 7.5 thousand tons in average; in mid-1970-s – 0.64 thousand tons. Later the catches declined to 0.1-0.2 thousand tons.
Fishing gears and fishing zones. Roach is harvested in the river deltas - Volga, Ural, rivers of Kalmykia and Dagestan, mainly, with beach seines. In the Volga delta the chief fishing area is Glavnyi bank. In Azerbaijan roach is harvested mostly in spring, in Kyzylagach bay area and coastal area of Sara peninsula and adjacent areas. Fishing is carried out in spring at the mouth river areas of Kura (with stationary nets) and Atrek (beach seines).

Impact of fisheries on the population status

Currently, commercial stock removal of the North Caspian roach does not exceed 20%, 4-5-year-old fish are underused in harvests. Exploitation rate of Azerbaijani and Turkmen roach stocks is higher that that of the North Caspian (about 40%).
Human impact/Threats. Water toxicity at the Volga flooded meadows is the direct cause of mortality at early life history stages as this fish easily accumulates heavy metals in its body.

Concentrations of heavy metals in different organs and tissues of Ural roach,
mg/kg dry weight (Ergaliev, 1990).

Metal Muscles Liver Gills Digestive tract Gonads
Lead 3.9 3.2 6.98 3.9 3.2
Cadmium 0.23 0.5 0.4 0.72 0.74
Zinc 24.2 74.8 84.8 72.3 77.01

Conservation Measures. Stock reproduction of the North Caspian roach is determined by spring flood conditionsin the Volga and Ural rivers (duration, flow volume and flood level at the spawning grounds) as well as feeding conditions in the North Caspian (areas of desalinated/ freshened zones, food supply, etc.). Hence, the main fisheries requirement for aquatic balance is convergence of existent flood hydrograph with natural Volga flow regime. Regulation of Kura and Atrek river flows combined with intensive fishing activities impacted negatively the reproduction of southern stocks. Measures needed for conservation of these populations are: reclamate floodlands in Atrek area, increase water discharges in Kura river, and decrease fisheries load.

References

Belova, L.N. 1986. Long-term feeding dynamics of roach Rutilus rutilus caspicus. J. Voprosy Ikhtiologii (Problems of Ichthyology). Vol. 26, 2: 253-258.
Berg, L.S. 1949. Fish of freshwater bodies of the USSR and adjacent states. Part 2 p.925
Bokova, E.N. 1940. Consumption and assimilation of food by roach. VNIRO Proceedings. Vol. 11, pp. 5-25.
Chernyavsky, V.I. and L.V. Malinovskaya, 2000 .Food supply and potential productivity of the Northern Caspian roach. In: Biodiversity of aquatic ecosystems of south-east of the European part of Russia. Part 2, pp. 244-257.
Ergaliev, T.Zh. 1990. Content of heavy metals in the ecosystem of the low Ural and basic commercial fish species
Reshetnikov, Yu. S. 1998. Annotated catalogue of Cyclostomata and fish of Russian continental waters. Nauka Press. 218 p.
Sergeeva, A.I. 1952. Rate of maturation. Proceedings of VNORO Caspian Basin Branch. Vol. 12, pp. 89-97.
Savenkova, T.P. 1989. Turkmen roach. In: Caspian Sea. Ichthyofauna and commercial resources. Nauka Press. Moscow pp. 137-139.
Shorygin, A.A. 1952. Feeding and nutritional relations of fish. Pishchepromizdat. Moscow. 267 p.
Tanasiichuk, N.P. 1951. Commercial fish species of the Volga-Caspian. Pishchepromizdat. Moscow. 88 p.
Zheltenkova, M.V. 1939. Roach (Rutilus rutilus caspicus) feeding in the northern part of the Caspian Sea. VNIRO Proceedings. Vol. 10, pp. 129-177. 
Zhukinsky, V.N. 1986. Effect of abiotic factors on the diversity and viability of fish in early ontogenesis. Agropromizdat. Moscow. 243 p.

Compiled by:

V.I.Chernyavsky, (CaspNIRKh, Astrakhan, Russia)
Z.M.Kuliev,
(AzerNIRKh, Baku, Azerbaijan)
I.M.Aminova,
KazNIIRKh Atyrau branch, Kazakhstan)
L.N.Belova,
(CaspNIRKh, Astrakhan, Russia.