Taxonomic description of subspecies
Body elongate, fusiform, covered with large cycloid scales, belly rounded. Mouth terminal, with fine teeth. Eye large, eye diameter up to 1/3 of head length. No scales on top of head. Color: silvery lateral band along sides. No lateral line. Pectorals set high. Dorsals 2. Second dorsal originates behind vertical of vent. Transverse rows of
scales 44-52. Vertebrae 45-48. D VII-IX, I 10-13; AI 13-15. Gill rakers 22-26.
Intraspecific forms: none
Related forms: subspecies A. boyeri pontica (Eichwald, 1838) occurs in the Black, Azov and Aral seas. Two species,
A. hepsetus L. and A. bonapartei Blgr. were reported for the Black sea (Nikolskiy, 1950).
Distribution of subspecies within the Caspian Sea
Distributed within the entire Caspian Sea, as well as estuaries of the Volga, Ural, Kura, Atrek, Sefid-Rud
Status as per International Red Data Book: N/A
Status as per National Red Data Books: N/A
First record for the Caspian: Eichwald, Bull. Soc. Natur. Moscou, 1838.Vol. 11,1:125-147
Redescription of species: Atherina pontica var. caspia Kessler, 1874;
Atherina pontica caspia Berg, 1916; Atherina mochon pontica natio caspia
Berg, 1933
General characteristics of subspecies
Ecologo-taxonomic group. Marine pelagic fish
Origin. Mediterranean
Distribution. Caspian Sea endemic
Habitat. Pelagic zone.
The subspecies is distributed throughout the Caspian, occurs in the wide range of salinities including sea zones with high salinity (e.g., Kaydak bay, salinity � 60�) and mouths of the rivers (Volga, Ural, Kura, minor rivers in Lenkoran valley). In spring and summer occurs mainly at the coastal zones. Spawning takes place in shallow waters among vegetation.
Migrations. Enters the North Caspian abundantly in April-May and stays there until October-November; wintering takes place outside the North Caspian. Migrations are studied insufficiently.
Relation to abiotic environmental factors
Relation to salinity. Eurythermic species. Inhabits the waters with salinity range 0 - 60 �, mostly 3 - 12 �. Spawns at salinity values up to 42�.
Relation to temperature. Eurythermic species. Inhabits the waters of wide temperature range, from
6oC to 25oC.
Vertical distribution. Eurybathic species. Occurs in the surface layer 0-50 m depth throughout the Caspian. In summer it is found mainly in the coastal area above 25-30
m depth, may be found near the coastal line at the depth of several cm.
Relation to oxygen conditions. Oxyphilic species. In summer, oxygen saturation of the surface layers in the Caspian Sea reaches 100%.
Relation to fluctuations of the sea level. Fluctuations of the sea level lead to destruction of coastal zone habitats and degraded spawning conditions.
Feeding
Feeding type. Heterotrophic
Feeding behavior. N/A
Food spectrum. The food contains plankton (larvae of mollusks and Ostracoda), nectobenthic crustaceans
(Mysids, Gammarids), benthic organisms (Oligochaeta, Nereis), and fish larvae.
Food supply. At present, the food supply (basic food items) for silverside is unlimited.
Quantitative characteristics of feeding. Throughout a year, rations vary from 0.051 to 0.506 feeding units per day. Food consumption rate corresponds to 4.3-20.2% in fingerlings, 4.09-12.5% for one-year old fish, 3.9-9.8 - two-year old, 3.9-8.4% - three-year old
(referred to fish weight). Rate of food assimilation decreases from 18-44% (fingerlings) to 3-6% (four-year old fish) (Klovach, 1980).
Reproduction
Reproduction type. Sexual
Reproduction areas. Reproduces in the coastal areas of the Middle and South Caspian. Spawning areas were noted in the south-western part of the North Caspian at Kulaly island and Kaydak bay.
Terms of reproduction. Batch spawning.
Spawning starts in spring at water temperature 10-12oC and continues throughout the summer.
Fecundity. Varies from 360 to 5500 eggs in females of 4 - 12 cm TL.
Limiting factors. Availability of habitats favorable for spawning and releasing
eggs
Life history and development
Life history stages. Eggs are benthic, 1.2-1.7 mm in diameter, thick membrane is supported with sticky threads, which
enable
attaching to underwater plants. The length of newly hatched larvae is 5-5.5 mm. Larvae are confined to the surface layers of water salinity up to 45 �.
Relation to environmental factors. N/A
Age of maturity. Matures at the age of 1 year, mainly at 2-3 years, upon
attaining 4.5-9.6 cm TL.
Thermal conditions of development. Develops at the temperature of 12-24oC.
Quantitative characteristics of growth. N/A
Structural and functional population characteristics
Sexual structure. In the North Caspian the males/ females ratio is close to 1:1; males, somehow, prevail (up to 56%).
Age- size structure. In spring and summer, the population in the North Caspian is represented by one-year-old (21%), two-year-old (29%), three-year-old (37%), four-year-old (12%), and five-year-old (1%) specimens. The mean population age is 3.8 years, TL - 9-13 cm.
Quantitative characteristics. Population biomass was estimated by Z.A. Yusufova
(1968) as 500-600 thousand tons. According to the other estimations biomass comprises 100-180 tons (Klovach, 1980).
Population trends. N/A
Interspecific relations
Food competitor to sprats and shads. Food item in diets of predatory fish species and the Caspian seal.
Importance of species to bioresources production of the Caspian Sea
Economic significance of species. Silverside is an abundant fish species but of little economic value. It is caught
as by-catch to kilka seine fishing. No special fishing is conducted. Used for fish flour production.
Impact of fisheries on the population status. None
Human impact/Threats. N/A
Conservation measures. None
References
Abdurakhmanov, Yu.A. 1962. Azerbaijan freshwater fish, AzSSR AS Press pp. 324-327
Berg, L.S. 1949. Fish of the freshwater bodies of the USSR and adjacent states. Part 3 USSR AS Press. Moscow-Leningrad pp. 1001-1004.
Klovach, P.V. 1980. Energy metabolism and food requirements of sand smelt (Atherina mochon pontica Eichwald) in the Azov and Caspian Seas. Author's Abstract of Candidate Dissertation, Moscow. 23 p.
Yusufova, Z.A. 1968. Sand smelt feeding in the Caspian Sea. In: Fish and invertebrate acclimatization in the USSR water bodies. pp. 82-86.
Compiled by:
Z.M.Kuliev, AzerNIRKh, Baku, Azerbaijan
T.S. Zarbalieva,
AzerNIRKh, Baku, Azerbaijan