A typology for fish-based assessment of the ecological status of lowland lakes with description of the reference fish communities

We compared the potential of different lake typologies to discriminate fish communities in least disturbed sites. The typologies tested were based on morphometric and geographical descriptors. The best discrimination was achieved by distinguishing three lake types according to depth and mixes regime: polymictic lakes, stratified lakes with less than 30 m of maximum depth and deep, stratified lakes with maximum depths above 30 m. We conclude that the proposed typology is appropriate for a system to assess the ecological status of German lakes with the fish fauna according to the Water Framework Directive and might well be transferable to other European assessment systems. The fish communities in all lake types were similar and dominated by few fish species. Perch and roach were the most abundant ones, followed by ruffe, bream, rudd and pike. The fish communities in least disturbed sites might be used as reference conditions in future fish-based assessment systems.