Auswirkungen des Wasserkraftausbaues auf die Fischfauna der steirischen Mur | The effects of hydro-electric development on the fish fauna of the River Mur in Styria, Austria
2011
There are at present 29 power stations on the River Mur in Styria. The impounded sections account for 26 % of the river and 11 % is diverted (with flow left in the river bed). A satisfactory hydro-morphological condition is still found in about 25 % of the river course. Major free-flowing sections have survived between the boundary with the province of Salzburg and the confluence of the Mur with the River Mürz near the town of Bruck. The population of Danube salmon in the Mur is still capable of independent reproduction and is accorded a high protection priority at an international level. But having now declined to an adult population of 1,500, the Danube salmon in the Mur has dropped below the critical limit of minimum population sizes deemed capable of survival in the long term. Partial populations of more than 100 adults are found only in major free-flowing sections, mainly upstream of the town of Leoben above Bruck. Disappearance of the Danube salmon in a section qualified as having a good status in terms of the FIA system of analysis would degrade this section to moderate quality. Impounded river sections are generally severely deficient in species diversity and fish ecological quality (Fish Ecology Class 4 to 5). The good to very good status is found in 89 % of the natural free-flowing sections, while only 77 % of the residual-flow sections have a good status. As the percentage of impounded and residual-flow sections increases, the fish ecological quality declines.
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