The 0+ fish community structure in a large lowland river: first results of a study from the River Oder
Bischoff, A.; Wolter, C.
The 0+ fish community structure of the River Oder was studied in the Polish German National Park 'Unteres Odertal' near Schwedt (Germany) during the summer of 1997. Fish were sampled in five different types of mesohabitat ('Riprap', 'Connected Backwater', 'Navigable Side-canal', 'Deep Groynefield', 'Meander Inside Groynefield') using Point Abundance Sampling by electrofishing. In each mesohabitat, 50 random point samples were taken during each sampling period. Although a total of 23 species of 0+ fishes and one hybrid were caught during this study, only a few eurytopic species occurred in high abundances. The German stretch of the Polish-German National Park provides a large number of poorly structured mesohabitats and only very few adequate nursery habitats for rheophilic species. Thus the progeny of these species was restricted to structurally more complex groynefield-mesohabitats characterized by sandy substrates and a gentle slope. In order to improve the conditions for the early life stages of fish in the National Park, the re-establishment of a natural flood regime on the German side is highly desirable.