Description: In the tidal Elbe River between Hamburg and the estuary an assessment of fish stocks and fish diseases had been carried out in 1981-1986. Despite the decline of local fisheries, the river today still carries a rich fish fauna. Smelt and shad together contribute to 70 % of the fish biomass of anchor net catches. The remaining fishery today is sustained by eel catches. In the early 1980s, 70 % of the yearly income was from the sale of consumable eel, another 20 % from stock eel. Marketing of Elbe eel for human consumption, however, is forbidden due to high levels of toxicants in the fish. A rough comparison with anchor net catches from the end of the last century does not indicate serious changes in the frequency of the dominating fish species, except for a significant decrease in ruffe and a significant increase in pikeperch. The reduced fishing mortality today is partly compensated by power plants, which together with the cooling water take considerable amounts of fish out of the river. Recent surveys revealed a !arge variety of disease types and highly pathogenic parasites, some of which occur at very high prevalences. An ecological evaluation of this finding at present is not possible due to lacking data from other streams. High disease prevalences and low nutritional condition of flounder in the central estuary are attributed to naturally fluctuating salinities, which prevent the establishment of larger zoobenthos communities which could serve as fish food. The most serious problem for fish is seen in oxygen depletion which is observed regularly every year. However, the majority of fish emigrates from the Iow oxygen zone into shallow side arms and tributary rivers or assembles downstream in front of the low oxygen zone. Efficient rehabilitation measures are seen in a reduction of discharge of fertilizing substances into the river and in a re-opening or new construction of larger side arms.