Taxonomic description of species
Body length 7.5 � 14. 5 cm, 9.0 cm in average. Body low, elongate, and terete. Greatest body depth 16-19.2 %, average 17.8 % of TL. Head short and low, 20.4 � 23.1 cm, in average 21.4 % of TL. Head depth 12 �14.4%, in average 13.4 % of TL. Eye
diameter 21.6 � 27.3%, in average 24.9 % of head length. Pectorals short, 13.2 � 16.2%, in average 14.9% of TL. Gill rakers 56 � 67, in average 61.3. Vertebrae 44 � 47, in average 46.1. Color: back and top of head dark violet.
Weight ranges from 3.0 to 15.0 g, in average 6.0 g.
Intraspecific forms. A great number of panmyctic biological groups exists in the Caspian Sea, which enables spawning ten months a year. The species has euryhaline and freshwater forms.
Related forms. The species is related to tropical fish, which originate from the common parental form together with the other clupeids (genus
Alosa). The most related species are:
Clupeonella cultriventris caspia (Nordmann, 1840); Clupeonella grimmi Kessler, 1877.
Distribution of species within the Caspian Sea
Distributed in the open areas of the Middle and South Caspian and in the deepwater part (depths below 20 m) of the North Caspian.
Status as per International Red Data Book: N/A
Status as per National Red Data Books: N/A
First record for the Caspian Sea: N.A.Borodin, data of the First �clupeid� expedition to the Caspian, 1904
Redescription of species. Berg, 1923; Svetovidov, 1952
General characteristics of species
Ecologo-taxonomic group. Nekton
Origin. Autochthonous Caspian species
World distribution. Caspian Sea endemic
Biotope. Pelagic zone.
Migration. Feeding, wintering, spawning
Wintering migration to the South Caspian is caused by the drop of water temperature in the Middle Caspian. For the major part of life cycle undertakes feeding migrations in the streams of the Caspian circular
current following zooplankton aggregations. Spawning migrations last from May till December, fish migrate to the areas in the Middle and South Caspian with water temperatures
17-200C.
Relation to abiotic environmental factors
Relation to salinity. Brackishwater stenohaline species. Tolerates salinity fluctuations within the range 8 -14
0/00, the main part of the population is restricted to the waters at salinity range 10 -120/00.
Relation to temperature. Stenothermic thermophilic species. Found at surface water temperatures between 4.6 � 28.00C. The main part of the population occurs at water temperature above 8.00C.
Vertical distribution. Distributed in the areas with the depths of more than 15-20 m.
Vertical migrations are related to the season and time of the day. In winter the fish keeps at the depths 50-75 m, in spring ascends to the surface and aggregates at the depths
10-20 m. In summer and autumn, descends to the less heated water layers (depths 20-40 m and 40-60 m, respectively). Makes seasonal and daily vertical migrations down to 100 m deep. Daily migrations are connected with the movements of food zooplankton.
Relation to oxygen conditions. Oxyphilic species. Occurs in well-aerated water, frequently over-saturated.
Relation to fluctuations of the sea level. The greatest abundance of the species was recorded during the period of minimum sea level, 1960-1980. The stocks decreased over the last decades of the sea level
rise.
Feeding
Feeding type. Heterotrophic
Feeding behavior. Active preying and selected capture of food items.
Food spectrum. Euryphagous. The main food items are Copepods, which contribute up to 90-97% of the diet in different years, out of them the share of
Eurytemora amounts to 70% in average.
Food supply. The food supply averages more than 50% of the total zooplankton biomass in the pelagic zone of the sea. Over the recent years the proportion of food zooplankton tends to decrease. In 2000-2001, the abundance of Copepods decreased by a factor of 50, their biomass - by a factor of 10.
Quantitative characteristics of feeding. Circadian feeding pattern is characteristic of the species. The annual ration is calculated as (fish weight)*7.
Reproduction
Reproduction type. Sexual, annual cycle of gonad development and spawning of single type
Reproduction areas. Spawning occurs throughout the Middle and South Caspian. The main spawning area is the eastern part of the South Caspian where more than 42% of the population reproduces. The western part of the South Caspian (24%), the south-eastern part of the Middle Caspian (16%), and the north-western part of the Middle Caspian (10%) are less important. About 8% of the spawning population reproduces in the south-eastern and south-eastern parts of the Middle Caspian.
Terms of reproduction. Spawning occurs from May till December. About 20% of the spawning population reproduces in the interval May - September. The main part of the population (80%) spawns from October till December. The peak spawning (70%) is recorded in October - November.
Fecundity. The individual fecundity ranges from 9.8 to 6.1 thousand eggs, average - 38.4 thousand.
The ratio gonad weight/ total fish weight increases during the first years of life history (5.59-8.21%), reaches maximum on the third �fourth year (8.65-8.66%), and decreases by the end (7.83-7.01%). Similar trend has dynamics of individual absolute fecundity.
Limiting factors. Early stages of development take place in the near-surface biotope of the pelagic zone, where high density of food organisms is recorded. At the same time, this stratum is subject to fluctuations of such environmental factors as water temperature and waves. A close correlation between storm conditions and the number of survived embryos is observed; it could be described by the regression equation:
Y=1378.19-0.0057X2; (r=0.58)
Impact of the water temperature on the embryos abundance is described by the following equation:
Y=-2372.7 + 329.12X - 8.22X2 ; (r=0.86)
This, probably, explains the reverse correlation between the yield of juveniles and water temperatures during autumn period (r=0.71). Water cooling in autumn promotes migration of anchovy sprat to warm areas of the Middle and South Caspian and speeds up approach of mature spawners to the spawning areas. Early intensive spawning influences favorably on the recruitment abundance, as in this case embryos and larvae develop at the temperature
17-200C, which ensures higher survival.
Life history and development
Life history stages. The species is characterized by the short embryonic period (twenty four hours) and long larval period (6 - 7 months). In April- May, scales are developed at TL 3.7 �3.9 cm, and young fish transfer into the fry stage.
Relation to environmental factors. Embryonic development is considered to be the critical period in the early ontogenesis. Mortality during embryonic period (twenty-four hours) constitutes 72.3%, during the period of yolk/ internal feeding - 28.8 %, at the period of mixed feeding � 12.0%. Temperature range providing for the best survival of embryos and larvae is restricted to
17-20oC. Larvae start feeding on the third day after hatching at the latest. Food deprivation under trial conditions lead to depression of larval development on the 4-th day, starvation occurs the 5-6-th day after hatching. No correlation was revealed between biomass of food zooplankton in summer and yield characteristics of juveniles
(r=0.28), which may be accounted, on the one hand, by seasonal fluctuations of food biomass (inadequate data), and on the other hand, by the predominance of abiotic factors over the biotic.
Age of maturity. Upon classification developed by Monastyrskiy (1949) and Dryagin (1953), the population of anchovy sprat may be divided into three categories, �juveniles, �recruitment�, and �remainder/ rest�. In the first year, juvenile fish averages 81%, recruitment - 19%. The portion of maturing virgin females amounts to 5%, males - 14%. At the age of two years, recruitment comprises about 81%, the rest - 19%. At the age of three years, there is no recruitment and all specimens, who take part in the spawning, are the �remainder�.
Thermal conditions of development. Spawning occurs from May till December at temperature ranging from
150C to 250C, in the areas of mass spawning � 20.00C; in November �
17.90C; in December �16.20C. The optimum conditions for embryos� survival generally coincide with the period of mass autumn spawning (October-November).
Quantitative characteristics of growth. The annual increment of the linear growth makes up 8-10 mm during the first three years of
life; the maximum is observed in the first year (10 mm); it decreases (6-7 mm) at the age of 4-5 years old, and reaches minimum in the 6-th year (3 mm). The weight growth is
also rapid during the first three years (1.6-2.1g). The maximum annual weight increment is observed in the third year (2.1g). The weight growth is lower (1.8-1.5 g) at the age of 4-5 years old, its minimum is recorded in the 6-th year (0.8 g).
Structural and functional populations characteristics
Sexual structure. The total long-term ratio of females and males in the population is invariant, close to 1:1, with slight predominance of males in spring (50.3%), and of females in autumn (53.3%). Certain differences are observed within the age groups. Predominance of females (by a factor of 1.2) is recorded at the age of 6 years, later their number increase appr. 3-fold compared with that of the males.
Age-size structure. The population of anchovy sprat consists of eight age groups. The most abundant (91.2% in average) are age groups 0+,
1+, 2+, 3+. Proportion of fish aged 4+ and 5+ years corresponds to 8.5%, aged 6+, 7+ years � 0.3%. Annual mean population age ranges within 1.7 - 2.5 years old, averaging 2.1 years. The maximum age of anchovy sprat sampled from electrofishing catches was defined as
7+ years (Prikhodko, 1963), size 7.0 � 14.5 cm. The average TL varies in different years from 7.1 to 9.7 cm. Over the past 15 years the length of anchovy sprat averaged 8.8 cm, average weight � 5.8 g.
Quantitative characteristics. The abundance of anchovy sprat population in 2000 amounted to 293 billion specimens, biomass - 825 thousand tons. The main part of the stock (60 -70% of total abundance) was distributed in the Middle Caspian
(with regard to the season).
Population trends. Over the last two decades, the population abundance fluctuated from 129 to 293 billion specimens, 191 bn in average, annual recruitment - from 48 to 150 bn, the total annual decrease (due to commercial harvest and natural losses) - from 59 to 126 bn. For the past 20 years, these numbers were similar and amounted to 77 bn specimens that enabled stability of population abundance. Decline of abundance was recorded in 1988 -1991 when recruitment rate was below the total annual decrease; enhancement was recorded since 1998 when generations of moderate and high abundance entered the population.
Interspecific relations
The anchovy sprat is a competitor to the other sprats/ kilkas and plankton-feeding shads, specifically to the Caspian shad and partly to the Volga shad, as one of the main consumers of the Caspian plankton. At the same time anchovy sprat is the main food item for predators (shads, zander, salmon, inconnu, beluga, and Russian sturgeon) as well as for the Caspian seal. The annual predation on anchovy sprat was assessed as 280 thousand tons (Prikhodko, 1975).
Importance of species to bioresources production of the Caspian Sea
Economic significance of species. The anchovy sprat is the main item of commercial fishing in the Caspian Sea harvested by all the littoral states. The species contributes to about 70% of total catches at the Caspian fisheries basin.
Commercial characteristics of species, catches. Over the past three decades, the annual catch ranged from 150 to 377 thousand tons, averaging 225 thousand tons. The average daily catches per one medium-tonnage vessel varied monthly from 11 to 22 tons, the mean annual daily catch - 17 tons; for the long-term period this index did not change more than 19%. Recently, the catches tend to decline due to drastic reduction of the stock, in 1999 �150 thousand tons, in 2000 - 120 thousand tons, in 2001 - 50 thousand tons.
Fishing gears and fishing zones. Harvesting practice/ electrofishing is conducted mainly in the South Caspian at the depths 50-120 m with fishpumps RB-200 mounted on the medium tonnage vessels (of six types). The south-western part of the South Caspian is the most significant and sustainable fishing area providing for the average 48% of the total catch. The south-eastern area of the South Caspian (22%) is the next important. In the north-eastern part of the Southern Caspian fishing is conducted only in autumn (18%); appr. 12% of catches come from the Middle Caspian areas.
Impact of fisheries on the population status
Up to the present, fishing is carried out throughout the whole year disregarding the species biology. By-catch of juveniles at the fishing areas of the South Caspian (Livanov Bank, island Ogurchinskiy, Ulskiy Bank, Gryaznyi Vulkan Bank), where spawning and early development occur in spring and summer, incurs damage to the stocks.
Human impact/threats. Anthropogenic factors impact greatly the stock dynamics. At present, concentration of oil hydrocarbons in the sea water exceeds 19-fold fisheries requirements for maximum allowable concentration (MAC); in some areas it goes to the extreme, e.g., 81 MAC at the �Neftyanye Kamni� area. Increased concentrations of oil, multiring aromatic hydrocarbons, volatile phenols and heavy metals are traced in the surface waters of the Middle and South Caspian. Contamination of the Caspian Sea may attribute to the chronic toxicosis. In the year of 2000, an outburst of
Mnemiopsis abundance, a severe competitor to plankton-feeding fish, primarily, anchovy sprat, was recorded in the Caspian.
Conservation measures:
- Diminish fisheries pressure, develop selective fishing technology for both big-eyed and anchovy sprats;
- Develop fishing areas in the Middle Caspian and deep-water zones to provide for the uniform exploitation of kilka stocks;
- Impose a ban at the eastern part of the South Caspian in terms of 01 April � 15 September, as a restricted area for all fishing vessels;
- Introduce restrictions in regard to the type of fishing vessels used at certain areas;
- Take measures to reduce level of pollution from industrial and oil extraction wastes to the Middle and South Caspian;
- Undertake measures to control development of Mnemiopsis.
References
Borodin, N.A. 1906.A new species of the Caspian shad. Bulletin of Fish Industry. 4: 197-203
Dryagin, P.A. 1953. On the age structure of fish population .Zoological J. Vol. XXXII, 1: 88-93. USSR AS Press.
Monastyrsky, G.N. 1949. On the types of fish spawning population .Zoological J. Vol.28, 6: 535-542
Prikhodko, B.I. 1963. On the seasonal changes in Caspian kilka behavior in the zone of the electric light. VNIRO Proceedings. Vol. 17:58-64
Prikhodko, B.I. 1975. Caspian kilka and its abundance. VNIRO Proceedings. Vol. 108: 144-153
Urbakh, V.Yu. 1963. Mathematical statistics for biologists and medical men. USSR AS Press. Moscow p.322
Compiled by:
Yu.A Paritsky, CaspNIRKh, Astrakhan, Russia