| Summary: | Comparison of the results of later investigations of the Danube in the part flowing through in the Iron Gate (Đerdap) National Park with those of research conducted earlier (20 to 40 years ago) shows that changes have occurred in regard to the presence and especially the abundance of certain hydrobionts on this sector of the river, a finding that applies to all groups examined. The paper discusses the potential and results of conservation measures realized through both legal regulations and medium-term plans for the advancement of fishing in this region. In addition to in situ study during the period from 1999 to 2003, a large number of species (especially of macroinvertebrates and fish) were also investigated under artificial conditions (in the Kragujevac Aquarium) in order to gain a better understanding of their ecological characteristics, especially their sensitivity to various environmental stress factors. The presented results indicate that weight of specimens and success of culturing under ex situ conditions are correlated with their sensitivity under natural conditions.
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