Monitoring the Migration of the Danube Shad (Alosa Immaculata) From Km 615 (Gârcov) to Km 863 (Iron Gates Ii) and the Influence of Hydroclimatic Factors

The paper presents the results of research on monitoring the migration of the Danube shad (Alosa immaculata) on the Danube sector between km 615 (Gârcov) and km 863 (Iron Gates II), with an emphasis on the influence of hydroclimatic factors. The Danube shad is an anadromous migratory species of great ecological and economic value that carries out its life cycle between the Black Sea and the river, where it reproduces. Its migration is strongly conditioned by factors such as water temperature, the flow and level of the Danube, turbidity and chemical composition of the water. Physico-chemical and hydrobiological analyses of the water revealed a suitable quality for reproduction. The structure of the phytoplankton and zooplankton indicated a moderate specific diversity, dominated by Bacillariophyta and Rotifera. The study involved experimental fishing and the collection of 208 specimens, analyzed morphologically, biometrically and according to age and sex. The results showed the predominance of 3 and 4 year old specimens, with gonads in stages IV and IV-V, confirming spawning in portions. Prolificity increased with age and gonad stage. The conclusions emphasize the need to correlate environmental regulations with exploitation regulations to ensure sustainable management of shad stocks, in the context of pressures generated by the presence of the Iron Gates dam, overfishing and climate change.