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The sturgeon species inhabiting the Danube River are included in the IUCN Red List and in the Red Book of Bulgaria. The factors responsible for the current status of this fish species are the direct result of human intervention. After more than 10 years of a total ban on sturgeon fishing in Bulgaria, their status as an endangered species is still a fact. The aim of this dissertation is to determine the potential spawning and feeding habitats of sturgeons in the Bulgarian section of the Danube River. Up-to-date information on the status of sturgeon species has been collected. Information was collected on the behaviour of stocked cultured sturgeons, and their growth rate after release into the river. Data are presented regarding length-weight relationships and condition factor for three sturgeon species. The speed of movement of young sturgeons during their migration to the Black Sea was determined. The period during which sturgeons breed in the Bulgarian section of the Lower Danube was established, based on models. The potential spawning habitats of H. huso, A. ruthenus, A. stellatus and A. gueldenstaedtii in the Bulgarian section of the Danube have been determined. The current diet of three sturgeon species was studied. A complete ecological characterization was made of the macrozoobenthos as a food resource. Based on nearly 10 years of research and proposals, a new protected area "Esetrite - Vetren" has been announced with the aim of protecting the habitats of sturgeons.
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