Evaluating the Effect of the Hydrotechnical Works from the Danube’s Caleia Branch on the Spawning Migration of Sturgeons

Abstract

Over the years, to maintain navigation along the Danube, the implementation of a series of hydrotechnical works was imposed in order to ensure the continuity of economic activities. Between 2011 and 2014, one such project was built in the vicinity of the county of Braila, on a secondary branch of the Danube - The Caleia branch. The main goal was to redistribute water discharge from the secondary channel to the main branch by construction of a bottom sill. The bottom sill and subsequent discharge redistribution led to hydrodynamic alterations caused by increased water current velocities. These modifications of the hydrodynamic regime may affect the migration of anadromous sturgeon species that swim from the Black Sea to spawn upstream, therefore making the monitoring of the impact paramount. Considering the fact that the anadromous migrating species are internationally protected species, by a series of agreements and conventions, and that the stocks of the species are still in decline, a complex monitoring program was implemented in the affected area. This study presents important information regarding the site utilization during spawning migration and an evaluation of the behavior of sturgeons tagged with ultrasonic transmitters that migrated upstream over the bottom sill. During the monitoring period, the studies show that five sturgeons passed the bottom sill during their upstream migration, swimming against maximum water current velocities of 2.5 m/s.

Morphological changes analysis using 3D bathymetric surveys in Chilia Branch - Bystroe Channel bifurcation area

“…The National Institute for Research and Development in Environmental Protection Bucharest (INCDPM) carried out studies since 2013 [8] [9] [10] regarding monitoring the quality of the physical and biological components for the Danube Delta considering the transboundary impact of the Bystroe Channel project.…”

Captive growth analysis of Siberian sturgeon juveniles (Acipenser baerii J. F. Brandt, 1869) fed on a commercial fodder and its importance to a sustainable development of the aquaculture sector

“…Considerable efforts have been made to improve the farming conditions of the species to counter the over-exploitation of natural populations [2], and subsequently standardize the growing conditions. While, at least for Romania and the EU zone, sturgeon research in the wild developed at a fast pace, addressing various problematics, from age determination [3,4], telemetry [5][6][7][8], selection of reproduction habitats [9], body mass mathematical modeling [10] and migration [5,6,[11][12][13][14][15], in what concerns captive growth and breeding of the endangered sturgeon species, the scientific interest was significantly lower. 1216 (2023) 012021 IOP Publishing doi:10.1088/1755-1315/1216/1/012021 2 Environmental temperature and oxygen saturation are known to affect sturgeon development and physiology even at the larval state [16] as temperatures above 22 °C induce in A. baerii an increase in cortisol levels as a result of a probably higher metabolic rate.…”