The use of historical data to characterize fish-faunistic reference conditions for large lowland rivers in northern Germany.
Wolter, Christian; Bischoff, Antje; Wysujack, Klaus
This study aims to implement a method for characterizing historical fish species composition. Historical data on fish communities and human alterations of rivers have been extracted from a broad range of historical sources as well as archaeological studies. Two large lowland river systems in Germany, Elbe and Oder, serve as an example to summarize and evaluate available historical information, to characterize historical changes of fish communities, and to derive semi-quantitative fish-faunistic references. It is recommended to date the historical baseline for fish-faunistic references back to the year 1850, before the large river regulations of the 19th century had a negative effect on fish, and before numerous neozoans spread out. The reference fish communities exemplified for the bream region of the rivers Elbe and Oder comprise 42 fish species, each with a rough but calibrated description of relative species abundance integrating 300 years of fish records. According to our fishfaunistic reference, slow-flowing metapotamal river stretches are characterized by a) about 36-37 % of rheophilic fish, b) about 10-12 % of lithophilic and 9-10 % psammophilic spawners, c) a high species diversity (H' = 2.90-2.93), and d) a relatively even dominance structure. A consistent methodological approach to develop fish-faunistic references for various river types is a prerequisite for fish-based assessment of ecological integrity of river systems and, thus, for the implementation of the new EU Water Framework Directive (WFD) (2000/60/EG).