Biomass size distributions as a tool for characterizing lake fish communities

Biomass size distributions (BSDs) can be useful tools to (1) summarize complex information about fish community structure in a condensed graphical form, facilitating the characterization of freshwater fish communities, (2) compare the position of fish communities along environmental gradients and (3) elucidate major trophic interactions in freshwater fish communities. Biomass size distributions are presented by taxonomic and trophic group, for a selection of fish communities from 35 Scandinavian and eight Dutch lakes. They were used for the analysis of taxonomic and trophic shifts in the fish communities along a large environmental gradient, with productivity (expressed as total phosphorus concentration, TP) as its most important component. Regression analysis of fish community variables (such as proportion of cyprinids, or biomass of benthivores) were consistent with the semiquantitative conclusions drawn from BSDs, regarding taxonomic and trophic shifts with changes in TP in both Scandinavian and Dutch lakes, especially an increase in the amount and size of benthivorous fishes with increasing TPlevels. In addition, differences in mortality and growth rates were shown to partly explain differences in BSDs. Biomass size distributions thus provide an integrative tool for qualitative and quantitative comparisons among fish communitie