The majority of migratory fishes in the river basin district of Weser spawn in the fresh water of streams and rivers. An intact river bed, diverse water structures and various current conditions represent important prerequisites for a successful development of fishes and lampreys.

Beginning with the historical and actual dissemination of the above mentioned species, the identification of spawning and nursery waters of potential transregional significance was made. The reference fish fauna was considered thereby, as well as species-specific requirements and important characteristics of water and water structures, local continuity and material pressures. Spawning and nursery waters represent a significant factor necessary for successful repopulation of migratory fish, completing the efforts for the continuity restoration in the context of the Common strategy for continuity of Weser.

The potentially appropriate waters identified mostly feature good status regarding the water structure and water quality. In order to preserve and develop such status also in the future, there are certain special requirements to be considered. For this purpose recommendations are acquired and agreed on the level of the federated states, in order to provide instructions about ecological development and water renaturation to competent authorities and interested persons concerned with the subject.