Successful conservation and development of the migratory fish population in the RBD Weser requires an overall monitoring of the individual components, such as migration routes and their continuity or spawning and nursery waters and their accessibility. Already by the end of the 1990’s, the existing fish ladders at the 8 large impoundments on Weser between Hameln and Bremen-Hemelingen were systematically investigated. Over the same time period of time, the investigations of the potential spawning areas in the catchment areas of the Upper Weser, Aller, Ochtum, Hache, Wümme and Geeste were performed, and in the next phase also on Werra, Fulda and some further waters in the areas of upper and middle Weser (see also Publications/Series, booklet 15). Following these considerations, a Common Strategy "Migratory fish in the RBD Weser" was developed.

Potential analysis for migratory fish and the activity recommendations derived therefrom allow for the formulation of the ecological requirements regarding the measures for the continuity optimization and development of potentially appropriate spawning and nursery waters, as well as for the prioritization of measure proposals.

Regarding the migration routes of transregional importance Weser, lower Werra and lower Fulda, a temporal and spatial prioritization for the improvement of the ascent and descent of fish was developed in the framework of the implementation strategy for each of the locations, including the estimation of costs. The fish ecological requirements which were agreed on a federal level were thereby considered. Moreover, the locations were assessed individually in regard to their fish ecological importance for the Weser river catchment area. On the basis of these considerations, it was possible to make a selection of measures for fish ascent and descent.

The Common Strategy "Migratory fish in the RBD Weser" represented here is considered to be the recommendation agreed at federal level for the concretization of the transregional activity field "Continuity and migratory fish". It represents thereby a framework for the regional state projects with the aim to improve the continuity.