The ecological status of water bodies; achievements... and questions: is the fish population a relevant indicator?

Abstract

Numerous hydrobiologists and limnologists in Europe are mobilised for the application of the European Water Framework Directive (EWFD). It implies the definition of the condition of all aquatic ecosystems (rivers, lakes,~) and the assessment of their quality and functioning. For this purpose methodologies and finalised research works are needed. Interrogations are still remaining about the way to determine the reference condition of an ecosystem and to define the criteria to assess the ecological quality of its various biological components. As an example the case of the fish community illustrates the present knowledge and the questions. About the restoration of the lacustrine ecosystems which is the ultimate objective of the EWFD, positive returns of experience are acquired but methods will have to be transferable to any type of water body at an acceptable socio-economical cost. This latter aspect is by itself a challenge for managers and scientists.