CHARACTERIZATION OF THE TYPICAL FISH COMMUNITY OF INLAND WATERWAYS OFTHE NORTH-EASTERN LOWLANDS IN GERMANY

A representative number of 11 inland waterways of the north-eastern lo wlands in Germany was surveyed between 1992 and 1994 using different f ishing methods. Data were pooled for sites and waterways. From the 234 sites investigated, a total of 53432 fish were collected and 29 speci es recorded. The typical fish assemblage of the waterways was subdivid ed into three defined classes according to presence and relative abund ance of species: reference, accompanying and minor species. The fish f auna was characterized by the dominance of roach (Rutilus rutilus) and perch (Perca fluviatilis). Both fish species showed a mean abundance of 70.61% (SD = 10.91%), whereas more than half of the species recorde d had a relative abundance < 1%. Two trends could be identified in the fish assemblage owing to human influences: an increase in the dominan ce of roach and perch and a decrease in species number. In particular, intolerant fish with a preference for sand or gravel substrata and cu rrent diversity have become rare and endangered. The typical fish asse mblage of waterways in the lowlands differed from that in the uplands with respect to the higher abundance of rheophilic lithophils in the u plands. (C) 1997 by John Wiley & Sons, Ltd.