Biomass size distributions as a tool for characterizing lake fish communities J. J. DE L EEUW *‡†, L. A. J. N AGELKERKE *‡, W. L. T. VAN D ENSEN *, K. H OLMGREN §, P. A. J ANSEN { AND J. V IJVERBERG ‡ *Wageningen University, Department of Animal Sciences, Fish Culture and Fisheries Group, P. O. Box 338, 6700 AH Wageningen, The Netherlands, ‡Netherlands Institute of Ecological Research, Centre for Limnology, Rijksstraatweg 6, 3631 AC Nieuwersluis, The Netherlands, §Institute of Freshwater Research, National Board of Fisheries, 7893 Drottningholm, Sweden and {Norwegian University of Science and Technology, Department of Zoology, 7034 Trondheim, Norway (Received 4 January 2003, Accepted 10 September 2003) Biomass size distributions (BSDs) can be useful tools to (1) summarize complex information about fish community structure in a condensed graphical form, facilitating the characteriza- tion 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 semi- quantitative 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 TP-levels. In addition, differences in mortality and growth rates were shown to partly explain differences in BSDs. Biomass size distribu- tions thus provide an integrative tool for qualitative and quantitative comparisons among fish communities. # 2003 The Fisheries Society of the British Isles Key words: European lakes; fish community; productivity; size distribution. INTRODUCTION Analysis of fish community structure is widely considered as an integrative indicator of the ecological status of water bodies since Karr (1981) launched his index of biotic integrity. Aspects of the fish community that contribute to community structure are species composition, species abundance, size (or age) †Author to whom correspondence should be addressed at present address: Netherlands Institute for Fisheries Research, P. O. Box 68, 1970 AB IJmuiden, The Netherlands. Tel.: þ31 255 564 646; fax: þ31 255 564 644; email: joep.deleeuw@wur.nl Journal of Fish Biology (2003) 63, 1454–1475 doi:10.1046/j.1095-8649.2003.00258.x, available online at http://www.blackwell-synergy.com 1454 # 2003 The Fisheries Society of the British Isles