Estimation of natural reproduction efficiency of semi-anadromous and river fish species in inland water bodies of the Republic of Dagestan, Russia

Aim. Estimation of the natural reproduction efficiency and patterns of formation of fish stocks.

Material and Methods. Collection of material was carried out in 2010-2019 in inland water bodies in Dagestan and its shallow Caspian Sea coastal zone. Estimation of the number of juveniles in rivers and canals was carried out using ichthyoplankton cone seines. Fry seines were used to count juveniles of fish in water bodies and in the coastal area. 470 samples of juveniles were collected and 5640 juveniles were analysed. The collection and processing of materials were carried out according to generally accepted methods.

Results. The main environmental factors determining the productivity of fish juveniles in the study area in the long-term have been identified. During the observation period, juvenile fish of 15 species were recorded in spawning grounds of inland water bodies. Roach, bream, carp, crucian carp, rudd and vimba bream dominate. In terms of numbers, roach juveniles predominate: their relative proportion being 31.02% with an increase from 27.1% in 2010 to 35.4% in 2018.The second place was occupied by bream juveniles, whose average relative proportion was 12.1%. The third place was occupied by carp juveniles with an average proportion of 9%. Juvenile zander, catfish, pike and kutum are relatively low in abundance from 2 to 4%. The yield of juvenile fish in 2010-2019 decreased 1.7 times compared to 1990-1995.

Conclusion. It was established that a decrease in the number of juvenile fishes occurs under the influence of unfavorable environmental factors: decrease in sea level; reduction in spawning areas; the shallowing and silting of migration routes due to the lack of a stable water supply. Measures are proposed to improve the living conditions of aquatic biological resources, aimed at increasing the efficiency of their natural reproduction.

1. Chugunov N.L. [Biology of young commercial fish of the Volga-Caspian region]. In: Trudy Astrakhanskoi nauchnoi rybokhozyaistvennoi stantsii [Proceedings of the Astrakhan Scientific Fisheries Station]. Astrakhan, vol. 6, no. 4, pp. 282. (In Russian)

2. Troitskiy S.K. [Materials for assessing the state of reserves of the Azov-don bream]. In: Raboty DonoKubanskoi rybokhozyaistvennoi stantsii [Works of the Dono-Kuban fishing station]. 1935, no. 3, pp. 46-58. (In Russian)

3. Dementieva T.F. Biological cycle of the North Caspian bream. Trudy VNIRO [Trudy VNIRO]. 1952, no. 21, pp. 185-194. (In Russian)

4. Dementieva T.F. Biologicheskoe obosnovanie promyslovykh prognozov [Biological justification of fishing forecasts]. Moscow, Food industry Publ., 1976, 240 p. (In Russian)

5. Dementieva T.F. Methodology for estimating the relative population size, the formation of a commercial herd and the rate of its use by fishing. Trudy VNIRO [Trudy VNIRO]. 1964, no. 50, рp. 7-38. (In Russian)

6. Boyko E.G. Forecasts of the stock and catches of the Azov walleye. Trudy VNIRO [Trudy VNIRO]. 1964, vol. 50, pp. 45-88. (In Russian)

7. Demin D.Z. Nizhne-Terskie ozera i ikh rybokhozyaistvennoe znachenie [lower-Terek lakes and their fisheries value]. Makhachkala, DAI Publ., 1946, 164 p. (In Russian)

8. Demin D.Z. Catadromous fish of the Delta of the Terek River. Voprosy Ikhtiologii [Questions оf Ichthyology]. 1962, vol. 2, no. 1 (22), pp. 90-99. (In Russian)

9. Demin D.Z. Vosproizvodstvo osetrovykh ryb Kaspiya v rekakh Dagestana [Reproduction of sturgeon fish of the Caspian Sea in the rivers of Dagestan]. Moscow, USSR Academy of Sciences Publ., 1963, рp. 34-39. (In Russian)

10. Saidov Yu.S. [State of commercial fish stocks of the Dagestan ASSR and ways of their rational use]. In: Vnutrikhozyaistvennoe osvoenie vnutrennikh vodoemov SSSR [On-farm development of internal reservoirs of the USSR]. Makhachkala, 1963, рp. 27-31. (In Russian)

11. Saidov Yu.S. Promyslovye ryby Dagestana, ikh zapasy i promysel [Commercial fish of Dagestan, their stocks and fishing]. Materialy III Dagestanskoi nauchnotekhnicheskoi konferentsii po okhrane prirody, Makhachkala, 1974 [Materials of the III Dagestan scientific and technical conference on nature protection, Makhachkala, 1974]. Makhachkala, 1974, рp. 38-60. (In Russian)

12. Amirkhanov M.N. Reproduction of sturgeon in the Agrakhan Bay. Trudy TsNIORKh [Trudy TSNIORKH]. 1970, no. 2, pp. 164-166. (In Russian)

13. Magomedov G.M. Promyslovye ryby Dagestana, na zapasy i promysel [Commercial fish of Dagestan, on stocks and fishing]. Makhachkala, Dagestan book Publ., 1981, 233 p. (In Russian)

14. Abdusamadov A.S., Karpyuk M.I., Abdurakhmanov G.M. Sovremennoe sostoyanie i ekologo ekonomicheskie perspektivy razvitiya rybnogo khozyaistva v zapadnom kaspiiskom regione Rossii [Current state and ecological and economic prospects of fisheries development in the Western Caspian region of Russia]. Moscow, Nauka Publ., 2004, 497 p. (In Russian)

15. Koblitskaya A. F. Izuchenie nerestilishch presnovodnykh ryb (metodicheskoe posobie) [Study of freshwater fish spawning grounds (methodological guide)]. Astrakhan, 1963, 64 p. (In Russian)

16. Koblitskaya A.F. Izuchenie neresta presnovodnykh ryb [Study of freshwater fish spawning]. Moscow, Food industry Publ., 1966, 109 p. (In Russian)

17. Koblitskaya A.F. Opredelitel' molodi ryb del'ty Volgi [Determinant of juvenile fish of the Volga Delta]. Moscow, Nauka Publ., 1966, 166 p. (In Russian)

18. Koblitskaya A. F. Opredelitel' molodi ryb del'ty Volgi [Determinant of juvenile fish of the Volga Delta]. Moscow, Nauka Publ., 1981, рp. 178-188. (In Russian)

19. Pravdin I.F. Rukovodstvo po izucheniyu ryb (preimushchestvenno presnovodnykh) [Guide to the study of fish (mainly freshwater)]. Moscow, 1966, 78 p. (In Russian)

20. Khoroshko P.P., Vlasenko A.D. Migration pattern of early aged young Sevryuga in the Volga river. Trudy TsNIORKh [Trudy TSNIORKH]. 1972, vol. 4, рp. 52-58. (In Russian)

21. Monastyrsky G.N. Roach Reserves of the Northern Caspian Sea and methods of their assessment. Trudy VNIRO [Trudy VNIRO]. 1940, vol. 11, pp. 115-170. (In Russian)

22. Abdusamadov A.S., Mirzoev M.Z. Analiz sostoyaniya rybnogo khozyaistva Agrakhanskogo zaliva i perspektivy ego vozrozhdeniya [Analysis of the state of fisheries in the Agrakhan Bay and prospects for its revival]. Mezhdunarodnaya konferentsiya «Rybokhozyaistvennaya nauka na Kaspii: zadachi i perspektivy», Astrakhan', 2003 [International conference "Fisheries science in the Caspian sea: challenges and prospects", Astrakhan, 2003]. Astrakhan, 2003, рp. 15-19. (In Russian)

23. Barkhalov R.M., Mirzoev M.Z., Kuniev K.M. Ryby gosudarstvennogo prirodnogo zapovednika «Dagestanskii» [Fish of the state nature reserve "Dagestan"]. Makhachkala, Alef Publ., 2012, 232 p. (In Russian)