Alosa saposchnikowii, (Grimm, 1887)

Taxonomic description of species

This species features all characteristics typical for predatory shads. Head large, 24.9-29.3% of TL, 27,2% in average. Eye large, its diameter no less than 23% of head length. Pectorals long, 16.2-19.4% of TL, 17.9 % in average. Gill-rakers on first gill arch 27-41, 30 in average. Teeth present. Body deep, "shad-like", compressed laterally, reaching 14-36 cm in length.
Intraspecific forms. Big-eyed shad is a very persistent species, without deviations (no races exist) (Berg, 1915; Navozov-Lavrov, 1947; Svetovidov, 1952).
Related forms:
Clupea maeotica Grimm, 1901: 67, Black and Azov Sea
Caspialosa brauneri - Nikolskii, 1923: 5, Dnestr estuary
Caspialosa brauneri m. elongata - Isachenko, 1925: 28 (Ochakov)
Caspialosa brashnikovi maeotica Svetovidov, 1943:254; Berg, 1948:124
Alosa pontica pontica - Svetovidov, 1973:108
Alosa maeotica - Banarescu, 1964:244; Whitehead, 1985:202; Vasilyeva, 1996:147

Distribution of species within the Caspian Sea

Area of distribution is the whole Caspian; this fish species does not enter the rivers.
Status as per International Red Data Book. N/A
Status as per National Red Data Book. N/A
First record for the Caspian. Clupea saposchnikowii Grimm, 1887: 3-43
Redescription of species: Clupeonella saposhnikowi - Berg, 1913 :15; Caspialosa saposhnikowi - Berg, 1915: 6; Alosa saposhnikowi - Svetovidov, 1952:223

General characteristics of species

Ecologo-taxonomic group. Nekton
Origin. Autochthonous Caspian species
World distribution. Caspian Sea endemic
Habitat. Pelagic zone. From March till September-October, the North Caspian represents a spawning area for big-eyed shad and a feeding area for new generations. During cold winters big-eyed shad keeps in the southern part of the sea at depths 400-600 m. In temperate winters forms aggregations in the Middle Caspian, in areas up to 200-250 m depth.

Apart from water temperature (8-11⁰C), an important requirement for wintering of this species is its dependence on zones of currents, where water aeration is more intensive and food supply is better developed.
Migrations. Spawning migration to the northern part of the sea starts in the second half of March. The main trigger factor is the rise of water temperature up to 5-7⁰C. In autumn, fingerlings migrate southward to the Middle Caspian. The largest part of post-spawners leaves the North Caspian in May-July.

Relation to abiotic environmental factors

Relation to salinity. Brackishwater euryhaline species. Winters in waters with salinity value of 13-14⁰/₀₀. Spawns mainly at shallow areas of the sea where salinity ranges from 0.07 to 11⁰/₀₀ (Pertseva-Ostroumova, 1963), but mostly prefers water within salinity range 4-7.5⁰/₀₀.
Relation to temperature. Eurythermic species adapted to the wide range of habitat temperature: 3-25⁰C
Vertical distribution. Euribathic species. In winter the main part of population keeps in water layers 15-32 m below the surface (Makhmudbekov, Doroshkov, 1941; Lovetskaya, 1940). During cold winters aggregates in waters above 400-600 m depth (Navozov-Lavrov, 1947); in spring and summer - in the upper 10-m layer; in autumn - up to 15 m deep.
Relation to oxygen conditions. Oxyphilic species. In summer, concentration of dissolved oxygen in surface layers of the Caspian Sea is usually close to 100% saturation. Oxygen concentration in the Middle Caspian fluctuates within 7.0-10.6 ml*l^-1.
Relation to fluctuations of the sea level. The rise of the sea level (since 1978) resulted in gradual extension of spawning areas and increased abundance of big-eyed shad (r=0.76). This relation is described by the regression equation:
P=131153+216317 ln (U), where
P- number of underyearlings;
U-sea level.

(Yield expressed in number of specimens per trawling hour)

Feeding

Feeding type. Heterotrophic
Feeding behavior. Preying/ predatory fish species
Food spectrum. Euryphagous fish species, which feeds on fish, higher crustaceans, worms. At early developmental stages big-eyed shad feeds primarily on zooplankton and crustaceans. As growth proceeds, it transits to feeding on underyearlings of other fish species, cannibalism may occur as well.
Food supply. At present, the stocks of small fish consumed by big-eyed shad (common kilka/ sprat, gobies, silverside) are sufficient enough.
Quantitative characteristics of feeding. The daily diet comprises 1.83% of body weight. On average, the population of big-eyed shad annually consumes the quantity of food equal to 600-700% of its weight. Correlation between abundance of big-eyed juveniles(Y) and the yield of common kilka (x) was revealed (r= 0.654): 
Y= - 0.006x³ + 0.0011x² - 0.00474x + 1.3334

Relative annual diet of big-eyed shad

Food requirements of big-eyed shad

Reproduction

Reproduction type. Sexual
Reproduction areas. Spawning grounds of big-eyed shad are located at shallow areas of the eastern part of the North Caspian (from Zaburunye up to Ural estuarine area, in the regions of Rakusha, Prorva), in the western part - from Suyutkinskaya to Chapurya bars, regions of island Tuleniy, Chistaya bank. The greatest pre-spawning aggregations of big-eyed shad are known (since the Caspian expedition of 1937) to be confined to the eastern part of the sea.

Terms of reproduction. Spawning starts at the end of April and proceeds till the end of May. The peak spawning occurs in the first ten days of May.
Fecundity. The individual fecundity in big-eyed shad females of 19-36 cm TL, aged 2-9 years, is 30,488-318,852 eggs, 176,405 eggs in average. Batch/ intermittent spawning is characteristic of the species. Direct relation between average absolute fecundity (Y) and age of big-eyed shad (x) is expressed distinctly (r2=0.6547):
Y= 36768x - 21900 
Limiting factors. High current velocity, specifically combined with high waves, can cause the damage of eggs and their mortality (Dementieva, 1957).

Life history and development

Life history stages. Brief embryonic period is characteristic of this species. Incubation period lasts up to 156 hours at temperature of 14.80C (Pertseva, 1938). In May, newly-hatched larvae are 3.4-4.5 mm TL. In June, larvae transform into fry at 25-30 mm TL, they attain 72.6 mm TL in August, and by September the fingerlings reach an average of 85-95 mm TL.
Relation to environmental factors. Early life history stages take place at subsurface layer at depths 1-7 m, where the most abrupt fluctuations of water temperature and sea waves are observed. Correlation data analysis showed inverse relation between the number of fingerlings (R, specimens per trawl) and water salinity values (H) for the last years, which is described by regression equation (r= -0.665):
R=22.394 e^-1484H, where
e- the base of natural logarithm
Age of maturity. Maturation in big-eyed shad occurs at the age of 2-5 years. 3-5 year-old fish compose the majority of mature females, 2-3 year-old fish - the majority of mature males.
Thermal conditions of development. Correlation (r=0.79) between water temperature in the North Caspian and abundance of underyearlings is as follows:
Y=0.06e^0.28x, where
Y- yield of big-eyed shad, specimens per trawling hour,
x- water temperature in the North Caspian
The largest number of larvae is recorded in the third 10 days of May at water temperature 19-20⁰C.
Quantitative characteristics of growth. The rate of linear growth during the first year of life is described by Shmalgauzen growth equation (1935):
L=4.52 t ^0.3728, where
L- length of the individual at t age,
t- age, months
The ratio between length (L) and weight (W): W=0.0181 L ^2.7967, persists at juvenile stages. The most rapid linear and weight growth in big-eyed shad is observed at its first month, the length of individuals increases from 3-4 mm (TL of newly-hatched larvae) to 4.52 cm, i.e. almost by a factor of 100. The rate of linear growth gradually decelerates in the following months. The absolute increment for the second month amounts to 1.33 cm, for the third - 0.95 cm, and for the fourth - 0.77cm. Weight growth in juveniles is 2.79-fold more intensive as compared with length growth.
Linear and weight growth in adult fish was calculated upon real data obtained for the long-term period:
L=13.76 t ^0.3639;
W=27,21 t ^1,3095; where
L- length of fish at the age of t,
W- weight at the same age

Growth rate (size and weight) of big-eyed shad in 1998-2000

Structural and functional population characteristics

Sexual structure. Spawning population of big-eyed shad in the North Caspian (estimated from drift net catches) is represented mainly by males, which make up to 90% of the total, except for the Azerbaijani and Dagestan coasts, where sex ratio (estimated from beach seine catches) is close to 1:1.
Age-size structure. 3-6-year-old fish compose the majority of spawning population, i.e., 73.3-93.4 %. A long-term trend to the increase of the average age of fish (from 4.6 to 5.5-year old) is traced. Big-eyed shad is referred to the group of medium-size shads. Fish taken in research catches was 14-36 cm TL, 37.0-650.0 g in weight. Individuals of 21-28 cm TL, 144-265g in weight, represent the main part of the spawning population. Mean TL in females - 25.7 cm, weight - 224.6 g, males are 14-36 cm TL, 37.0-650.0 g in weight. In 2000, the mean TL was 25.7 cm, weight - 265. 9 g, these were above the average long-term values.
Quantitative characteristics. The population number is assessed as 1.1125 billion specimens, the biomass - 33,429 tons.
Population trends. The 30-year ban on fishing at sea and the rise of sea level benefited to the conservation and increase in abundance of marine migratory shads including big-eyed shad.

Interspecific relations

Big-eyed shad feeds on kilka, which also serves as the feeding item for the other fish species: predatory shads (black-backed shad, dolginka shad, Agrakhana shad), stellate sturgeon, and zander (Shorygin, 1939; Ostroumova, 1947).

Ratio of feeding similarity between some species within genus Alosa
(Ostroumov, 1974)

Importance of species to bioresources production of the Caspian Sea

Economic significance of species. Big-eyed shad has excellent edibility characteristics; its fat content is 5.7-6.7%.
Commercial characteristics of species, catches. Currently no fishing
Fishing gears and fishing zones. Fishing in the Caspian Sea is carried out with stationary nets and beach seines. Stationary nets are used in shallow areas, drift nets - in deep-water areas of the open sea.

Impact of fisheries on the population status

None
Impact of the Anthropogenic Factors. Considerable pollution of the North Caspian will sacrifice spawning areas for big-eyed shad as well as for the other marine shads, and kilka (their main food item). Oxygen deficiency will increase in bottom layers of the North Caspian and along the western coast of the Middle Caspian. This factor is probable to play an important role in altering migration patterns/ routes for big-eyed shad.
Conservation measures. None

References

Andrianova, S.B. 1995. Big-eyed shad (Alosa saposhnikovi Gr.) as a possible species object of shad fishing in the Northern Caspian . In: Caspian Sea - the present and the future. The abstracts of the International Conference .(Astrakhan, November 16-17, 1995). 148 p.
Berg, L.S. 1915. The preliminary report on shads sampled in the Caspian Sea. The 1913 Caspian expedition. In: Materials for learning Russian fishery. Vol.4, 6:3-8.
Grimm, O.A. 1887. Astrakhan shad. S.-Petersburg. Pp.3-43.
Dementieva, T.F. 1975. The methods and results of investigations in the causes of fluctuations in Azov anchovy abundance .J. Voprosy ekologii (Problems of ecology) Vol.1. (Materials of the 3rd Ecol.Conference). 243 p.
Kazancheev, E.N. 1969. The ecological characteristics of the Caspian fish of the family Clupeidae and the state of their stocks. Author's abstract of the Doctor of Biological Sciences. Kazan .65 p.
Kyong, U.H. 1972. Biological characteristics of the big-eyed shad Alosa sopochnikowi Gr. In the Northern caspian and the state of its stock. Author' Abstract. Moscow. 25 p.
Lovetskaya, A.A. 1940. The materials on the biology and fishing of big-eyed shad (Alosa saposhnikovi Gr. ) in the Middle and Southern Caspian. News of the Azerbaijan Research Fishery Station. Issue 5 : 29-50.
Makhmutbekov, A.A. and P.K. Doroshkov, 1941. Shads of the Middle and Southern Caspian. News of the Azerbaijani Fisheries research Station. Baku. 22 p. 
Navozov-Lavrov, N.P. 1947. The biology and fishing of big-eyed shad (Caspialosa saposhnikovi Gr.). VNIRO Reports. No.10:11-15. 
Ostroumova, A.A. 1947. Feeding of Dolginka shad (Caspialosa brashnikovi Br.) and big-eyed shad (Caspialosa saposhnikovi) in the Norhtern Caspian. Proceedings of the Volga-Caspian Research Fisheries Station. Vol.9, 1: 82-94.
Pertseva, T.A. 1938. Anew method for establishing new spawning grounds of Caspian shads. J. Fisheries, 7: 28-32.
Pertseva, T.A. 1940 The spawning of Caspian shads in the Northern Caspian according to the distribution of their eggs and larvae. VNIRO Proceedings. Vol.14:109-148.
Pertseva-Ostroumova, T.A. 1963. Spawning areas and conditions for the shads of the genus Alosa in the Northern Caspian in 1934-1937. Proceedings of Institute of Oceanography. Vol.62 : 28-48.
Svetovidov, A.N. 1952. Herrings Clupeidae. Series "The USSR Fauna" Vol.II, 1 USSR AS Press. Moscow-Leningrad. Pp.223.
Shorygin, A.A. 1952. Feeding and feeding relations of fish in the Caspian Sea. Pishchepromizdat. Moscow. Pp.48-49.
Shmalgauzen, I.I. 1935. Growth and total body size in view of their biological importance. Growth of animals. Moscow. Pp.8-61.

Compiled by:

S.B. Andrianova, CaspNIRKH, Astrakhan, Russia