MIGRATION OF LARVAE AND YOUNG BLACKBACK SHADS IN NON-REGULATED PART OF THE river VOLGA (IN 2016-2017)

The paper explores the influence of hydrological regime in non-regulated part of the Volga River on the sloping migration of blackback shads larvae in different water years (2016-2017). The authors make the regression model in order to determine the effect of water discharge in non-regulated part of the Volga River on the concentration of blackback shads larvae during the migration period. The relation between water discharge amount and larval concentration in the years is calculated and approximated by means of the power equation with the determination coefficient. The model, built on the data of 2016, has a determination coefficient R2=0.87, which indicates the high quality of the regression model and the data used in its making. The model of 2017 with the determination coefficient R2=0.14 is a regression model of low quality and shows the discrepancy of the data used. The authors show changes in the daily and seasonal dynamics of the larval slope . In 2017, the authors observed less young fish in June. The number of young fish was 30.5 % of the total population, which is 2 times lower than that in 2016. The authors observed breaches in daily dynamics. In previous years, the part of larvae in the daytime was lower than in the night. This change is caused by peculiarities of hydrological regime in the Volga river during the migration of larvae, high flow rates and amount of water in 2017. The paper shows age groups of larvae which participate in the slope migration. Prolarvae prevailed in the slope in the research period in 2017. The number of prolarvae was 60 %, their part was 1.5 times higher than in 2016. The article estimates the conditions and efficiency of natural reproduction, the influence of changes in water discharges on the main indicators of blackback shads slope intensity.

blackback shads, downstream migration, concentration, fall dynamics, daily dynamics, hydrological regime, larvae, spillover, the Volga

1. Vodovskaja V. V. Jekologicheskie aspekty biologii prohodnoj sel’di Kaspija., (Ecological aspects of the biology of the Caspian herring), KaspNIRH Astrahan», 2001, 74 p.

2. Vojnova T. V. Rybnoe hozjajstvo, 2013, No. 3, pp 25–29. (In Russ.)

3. Pjatikopova O. V., Fomin S. S. Vosproizvodstvo estestvennyh populjacij cennyh vidov ryb (Reproduction of natural populations of valuable fish species), Proceeding of the International Scientific Conference), 16–18 aprel», Sankt-Petersburg, 2013 g., 2013. pp. 324–326. (In Russ.)

4. O. V. Pjatikopova, N. I. Chavychalova, S. A. Vlasenko, S. S. Fomin, Bassejn Volgi v ХХI veke: struktura i funkcionirovanie jekosistem vodohranilishh (The Volga Basin in the 21st Century: Structure and Functioning of Reservoir Ecosystems): Proceeding of the All-Russian Conference, oktjabr» 22–25, Jaroslavskaja oblast», 2012 g.,. 2012, pp. 231–233. (In Russ.)

5. Pjatikopova O. V. Vojnova T. V., Raspopov V. M. Rybnoe hozjajstvo, 2014, No. 2, pp. 56–61. (In Russ.)

6. Pavlov D. S. Biologicheskie osnovy upravlenija povedeniem ryb v potoke vody (Biological principles of controlling the behavior of fish in the flow of water). Moskva: Nauka, 1979, 319 p.

7. Instrukcii po sboru i pervichnoj obrabotke materialov vodnyh bioresursov Kaspijskogo bassejna i sredy ih obitanija (Instructions on collecting and primary processing of materials of aquatic bioresources of the Caspian basin and their habitat), Astrahan», 2011, pp. 26–38, 83–87.

8. Koblickaja A. F. Opredelitel» molodi presnovodnyh ryb (Determinant of juvenile freshwater fish) Moscow: Nauka, 1981, 208 р.

9. Somova S. G. Materialy po biologii sel’dej Severnogo Kaspija (Materialy po biologii sel’dej Severnogo Kaspija) trudy VNIRO., No. 14, 1940, pp. 149–209.

10. Fomichev O. A., Taradina D. G. Sovremennoe sostojanie i puti sovershenstvovanija nauchnyh issledovanij v Kaspijskom bassejne (Current state and ways to improve scientific research in the Caspian basin) Proceeding of the Conference maj 16–18, Astrahan», 2006 g., 2006, pp. 233– 236. (In Russ.)