Benthophilus stellatus

Taxonomic description of species

Appearance typical for starry goby. Body covered with small spines and round osseous tubercles. Tubercles spherical, large, with numerous spines on top, arranged in three lines alongside the body. Large (unpaired) frontal and occipital tubercles and two tubercle rows on head. Color: visible dark spots on light gray or sandy background on body and head. Wide skin fold at sides of mouth, conspicuous barbel on chin.
Intraspecific forms: Deepwater populations in the Caspian Sea are separated into specific subspecies, B.stellatus leobergius Iljin, which differs from the basic subspecies with intensive development of spines.
Related forms: 
Benthophilus baeri Kessler, 1877
B. casachicus Rahimov, 1978
B. ctenolepidus Kessler, 1877
B. granulosus Kessler, 1877
B. grimmi Kessler, 1877
B. kessleri Berg, 1927
B. leptocephalus Kessler 1877
B. leptorhynchus Kessler, 1877
B. macrocephalus Pallas, 1787
B. magistri Iljin, 1927
B. mahmudbejovi Rahimov, 1976
B. spinosus Kessler, 1877
B. svetovidovi Pinchuk et Rahimov, 1979

Distribution within the Caspian Sea

Starry goby is not an abundant species but it inhabits a variety of areas within the Caspian; the North Caspian, the western coasts of the Middle and South Caspian, and the south-eastern part of the South Caspian (Ragimov, 1977, 1985; Stepanova, 1987).
Status as per International Red Data Book: N/A
Status as per National Red Data Books: N/A
First record for the Caspian: Benthophilus macrocephalus (Pallas, 1874, cited: K.F.Kessler, 1877.
Redescription of species: Berg, 1933, 1949); Iljin, 1949);. Ragimov, 1969; Vasilieva, 1998..

General characteristics of  species

Ecological-taxonomic group. Starry goby may be referred to both nekton and macrozoobenthos
Origin. Ponto-Caspian zoogeographic group
Distribution. Inhabits the basins of the Black, Azov and Caspian seas. Currently it is found in the reservoirs of the Dnieper, Don and Volga rivers (Gavlena, 1973; Lapitskiy, 1970). Since early 1950-s starry goby has become an abundant species in the Volga River delta.
Habitat. Occurs at different types of sea beds.
Migrations. Does not migrate at long distances. The spawning grounds and feeding areas are in the close vicinity. In winter stays at the depths of 30-50 m, in spring and autumn � in the coastal zones, 3-20 m depth (Ragimov, 1977, 1985; Kazancheev, 1981).

Relation to abiotic environmental factors

Relation to salinity. Marine euryhaline species, which entered fresh water bodies derivatively.
Relation to temperature. Eurythermic species. Prefers warm sea areas with water temperature of 18-26⁰C.
Vertical distribution. Eurybathic species found at depths ranging from 2 to 50-70 m, some specimens were captured at the depths below 100 m (Ragimov, 1977)
Relation to oxygen conditions. Starry goby does not require for high oxygen concentration, like the other inactive bottom fish it prefers bottom areas where concentration of dissolved oxygen is no less than 60% saturation.
Relation to fluctuations of sea level. Rising sea level and increase of the Volga and Ural rivers water discharges resulted in changed hydrochemical conditions. Consequently, desalination of the North Caspian caused reduction of habitat areas and alteration of feeding habits towards prevailing brackishwater and freshwater mollusks and fish (minute species and goby juveniles).

Feeding

Feeding type. Heterotrophic
Feeding behavior. Active seek for food objects
Food spectrum. Euryphagous species, which feeds on mollusks, fish, crustaceans and worms. In the course of growth, feeding on crustaceans becomes less important, the role of mollusks - more significant.
Food supply. Food supply consists mainly of higher crustaceans (77.0%), fish (13.1%), crustaceans - Corophiidae (42.2%) and Gammaridae (23.3%).

Feeding habits of starry goby in the North Caspian (August, 1974)
(T.G. Stepanova, authentic data)

In the southern part of the Middle Caspian starry goby feeds exclusively on mollusks (97.3%), mainly on Cardium, Mytilaster, Abra and Adacna.
Quantitative characteristics of feeding. In August, 1974, index of stomach fullness in starry goby was sufficiently high, 107.5 ^o/_ooo.

Reproduction

Reproduction type. Sexual
Reproduction areas. Spawns both in fresh and salt water (Kazanova, 1951) at different depths. In the North and Middle Caspian spawning occurs in shallow water (1.5-10 m), in the South Caspian � at the depth of 30-35 m (Ragimov, 1985). In the Volga delta females lay eggs in running water on different substrates: dead shells of mollusks, wood, iron and other objects (Koblitskaya, 1981).
Terms of reproduction. Spawning is prolonged, in the North Caspian it lasts from late April to September, in the Middle and South Caspian - from March-April to October-December (Ragimov, 1985). In the Volga delta the species spawns from the second half of April until July (Koblitskaya, 1981).
Fecundity. Fecundity is assessed as moderate, dependent of female size. Minimum absolute fecundity (470 eggs) was recorded in the female of 4.7 cm TL, 2.8 g weight; maximum (3098 eggs) - for the female of 7.5 cm TL, 13.4 g weight.
Limiting factors. Male protects the nest where the eggs were deposited. Without protection, eggs are eaten completely by crustaceans in 2-3 hours. The main reason for eggs mortality is oxygen deficit in bottom layer, pollution of coastal zones/ spawning grounds with oil products, and tidal processes (significant bottom areas are drained).

Life history and development

Life history stages. First larvae appear in May, in 15-20 days after spawning. At hatching, the body length is 4.5-5.0 mm, larva has developed rays in all fins, organs of vision, digestion, and respiration, while the yolk sac is rather big. Larvae inhabit bottom water layers. At TL 5.5-6.5 mm the yolk sac is absorbed and fry transit to external/ active feeding.
In the North Caspian juveniles reach 23-30 mm TL, 0.34-4.0 g weight, in early August (Ragimov, 1985).
Relation to environmental factors. N/A
Age of maturity. Matures at the first year of life. In the North Caspian maturation starts in September-October, by mid-November the large males attain maturity stage III-IV, females - stage II-III (Ragimov, 1985).
Thermal conditions of development. Embryonic development of gobies of genus Benthophilus occurs at water temperature 18-25^oC (Vasnetsov, 1953; Kryzhanovskiy et al., 1953).
Quantitative characteristics of growth. In the North Caspian juveniles reach 23-35 mm TL and of 0.34-4.0 g weight in early August (Ragimov, 1985). By September, juveniles of starry goby reach 28-35 mm (Koblitskaya, 1981).

Structural and functional population characteristics

Sexual structure. Females prevail in number over the males. In the North Caspian, in 1974, the number of captured females was more by a factor of 1.8 (Stepanova, 1987).
Age-size structure. In the North Caspian average weight of starry goby comprises 1.47 g, size varies from 20 to 60 mm, the average value � 36.6 mm. Average weight of females is 1.31 g, males � 1.82 g.
Quantitative characteristics. In 1974, starry goby contributed to 1.7% of total abundance of 5 goby species in the North Caspian. Absolute abundance of starry goby was estimated to be 39.08 million individuals, stocks � 5.7 tons (Stepanova, 1987).
Population trends. Decrease in abundance and stocks was recorded of late years in the North Caspian.

Interspecific relations

Starry goby competes with the other benthos-feeding fish, e.g., roach and bream. Nevertheless, the rate of competition is insignificant: 39.5 and 39%, respectively (Shorygin, 1952). Food item for predatory fish and seal.

Importance of species to bioresources production of the Caspian Sea

Economic significance of species. None.
Commercial characteristics of species, catches. No fishing.
Fishing gears and fishing zones. None.

Impact of fisheries on the population status

None.
Human impact/ Treats. Starry goby is particularly sensitive to pollution accumulated in bottom sediments, for two reasons - as a benthic species, the first; and as no long-distance migrations undertaken, the second. No specific studies of pollution impacts on starry goby were carried out. Hystopathological changes in kidneys, liver and other internal organs, associated with general pollution of the Caspian sea, were recorded.
Conservation measures. Measures needed for species conservation imply decrease of general pollution of the Caspian sea with oil products, heavy metals, chlororganic and other high-molecular weight compounds.

References

Berg, L.S. 1933. Fishes of freshwater bodies of the USSR and adjacent states. Part II. USSR AS Press. Moscow-Leningrad pp. 347-899.
Berg, L.S. 1949 b. Fishes of freshwater bodies of the USSR and adjacent states. Part III. USSR AS Press. Moscow-Leningrad pp. 930-1382.
Eichwald, E. 1831. Ecologia Zoologia specialis III, p. 76.
Gavlena, F.K. 1973. Starry goby Benthophilus stellatus (Sauvage) in the Kuibyshev water reservoir. J. Voprosy Ikhtiologii (Problems of Ichthyology). Vol. 13, 1 (78): 174-175.
Ilyin, B.S. 1949. Gobiidae. In: Atlas of Commercial fish of the USSR. Pishchepromizdat. Moscow pp. 642-644.
Kazanova, I.M. 1951. Goby juveniles (Gobiidae) of the northern part of the Caspian sea. VNIRO Proceedings. Vol. 18, pp. 66-98.
Kazancheev, E.N. 1981. Fish of the Caspian Sea, Moscow. 166 p.
Koblitskaya, A.F. 1981. Key of freshwater fish juveniles. Light and Food Industry, 208 p.
Kryzhanovsky S.G., N.N. Disler and E.N. Smirnova. 1953. Ecological-morphological patterns of Percoidei fish development. Proceedings of the USSR AS Institute of Animal Morphology. 10:. 3-138.
Lapitsky, N.I. 1970. Directed formation of ichthyofauna and management of fish population abundance in Tsimlyansk water reservoir. Proceedings of the Volgograd Research Institute of Lake and River Fisheries. Vol. 4. 278 p.
Nordmann, A. 1840. Observation sur la faune pontigue. Voyage dans la Russe mtridionale et la Grimee�, execute en 1837 par A. de Demidoff. V.III, Paris, 756 p.
Ragimov, D.B. 1969. Some morphological characteristics of Caspian and starry gobies. In: Programme and proceedings of the scientific conference of biology faculty graduates dedicated to the 50th anniversary of Azer. State Univer. ASU Press. Baku. pp. 76-77.
Ragimov, D.B. 1977. On the distribution and abundance of starry goby Benthophilus and small gobies at the eastern coast of the Middle and Southern Caspian (second message), Azer. SSR AS. No 4 pp. 87-92.
Ragimov, D.B. 1985. Data on reproduction of some Caspian species of gobies of the genus Benthophilus Eichwald (Gobiidae). J. Voprosy Ikhthyologii (Problems of Ichthyology). Vol. 25, 2: 242-247.
Sauvage H.E. Notices ichthyologgiques, Rev. Zool. 1874, vol. 22, pp. 332-340. 
Stepanova, T.G. 1987. Gobies Benthophilus of the Northern Caspian. In: Complex and sustainable use of aquatic and biological resources of the Azov and Caspian Sea basins, Rostov-on-Don. pp. 83-85.
Shorygin, A.A. 1952. Nutrition and food interrelations of the Caspian Sea fish. Pishchepromizdat. pp. 268.
Vasilieva, E.D. 1998. The family Gobiidae. In: Annotated catalogue of Cyclostomata and fish of Russian continental waters. Nauka. Moscow pp.125-145.
Vasnetzov, V.V. 1953. Stages of bony fish development. In: Assays on general problems of ichthyology. USSR AS Press. 18 p.

Compiled by:

Ragimov D.B., Institute of Zoology Azerbaijan AS, Baku, Azerbaijan
Stepanova T.G., CaspNIRKh, Astrakhan, Russia
Mitrofanov I.V., Institute of Zoology Kazakhstan AS, Almaty, Kazakhstan