L. Forró szerk.: Miscellanea Zoologica Hungarica 10. 1995 (Budapest, 1995)

Kappus, B., Jansen, W. , Fok, P.; Rahmann, H.: Threatened lamprey (Lampetra planeri) populations of the Danube Basin within Baden-Württemberg, Germany

Table 3. Ranking (according to number of occurrences) of hazards endangering brook lamprey populations within the upper Danube Basin of Baden-Württemberg Rank Hazard n % 1 Migration barriers 32 80,0 2 Armoring of river banks with stone blocks 22 55,0 3 Input of organic nutrients 17 42,5 4 Channelization 12 30,0 5 Diverted river section with minimal flow regulation 10 25.0 6 Sediment removal 7 17,5 7 Toxic spill 4 10,0 8 Stocking 4 10,0 Others 8 20,0 j continuum, is the construction of in-stream rainwater retention ponds. The Danube headwaters are particularly affected, with several of these types of impoundments located on the rivers Kirnach, Linach and Brändbach. River maintenance River bank reconstruction and "stabilization", which affect approximately 2/3 of all rivers within the "Alb" region and 1/3 of the Danube headwaters, threaten 55% of all lamprey Fig. 2. Gauging station at the Breg River, an example of an impassable migration barrier