Composition of fish communities in German lakes as related to lake morphology, trophic state, shore structure and human-use intensity

1. Previous comparative analyses of fish communities in European lakes have mainly focused on the response of community composition to eutrophication. In addition, frequently only one or two lake habitats have been sampled. 2. Here, we present fish community data from 67 lakes in north-east Germany. Fish abundance was estimated in littoral, benthic and pelagic habitats from which a composite parameter indicating lake-wide relative species abundances was derived. This parameter was used in group comparisons and non-metric ordination procedures to explore, among 40 lake habitat descriptors sampled, those most important in structuring community composition. 3. Fish community composition was mainly determined by maximum and mean depth, chlorophyll a content and lake volume. The impact of anthropogenic alterations of shore structure and human-use intensity of lakes were of minor importance. The dominant fish species were vendace Coregonus albula, perch Perca fluviatilis, smelt Osmerus eperlanus and several cyprinids (roach Rutilus rutilus, bream Abramis brama, white bream Abramis bjoerkna and bleak Alburnus alburnus). 4. A response of relative species abundance to lake productivity could be demonstrated for small perch, ruffe and bream. However, when the relationship between lake morphology and productivity was controlled for, differences in species abundances were not longer attributable to differences in productivity, but to maximum lake depth. 5. This suggests that there are two distinct fish community types in Germany, namely the cold-water community with vendace and perch inhabiting deeper lakes, and the warm-water cyprinid community inhabiting more shallow lakes. The previously established conceptual model of a community succession from salmonids through perch to cyprinids with increasing eutrophication is hence not continous, but includes a switch between two lake and fish community types.