A multi-level concept for fish-based, river-type-specific assessment of ecological integrity

We propose a multi-level concept for fish-based assessment (MuLFA) of the e cological integrity of running waters. This concept is designed for large-s cale monitoring programmes such as required for the proposed Water Framewor k Directive of the EU. Out of five different biological organisation levels (fauna, community, guild, population and individual), we propose seven cri teria: River-type-specific species, species with self-sustaining population s, fish region, number of guilds, guild composition, population size and po pulation age structure. The principle of the MuLFA is based on assessing th e deviation from undisturbed reference conditions. Reference conditions hav e to be compiled for every distinct river type using historical fish and ab iotic data, present river-type-specific reference sites and reference model s. The final assessment procedure is done by comparing the assessment reach with the reference conditions using a 5-tiered normative scheme and assign ing that reach to the level of highest coincidence. The benefit of the MuLF A is its potential for consistent sensitivity to low- and high-dose human a lterations, and due to its general character, its adaptability to all river types.