Long-term effects of human influence on fish community structure and fisheries in Berlin waters: an urban water system

Commercial catch and fisheries monitoring data were compared with hydrological and water course characteristics conditions to identify the cause of changes in fisheries production in Berlin water courses since the 1950s. The urban parts of Berlin are densely populated, and the waters are under pressure from shipping, hydraulic engineering, pollution and recreation use. Most Berlin waters are polytrophic or hypertrophic, with an annual nutrient input of 595 t of total phosphorous and 8640 t of total nitrogen. A total of 34 fish species were recorded, eight of which were introduced. According to historical records, seven native fish species are extinct or missing. At present, the fish community is dominated by a few eurytopic species, i.e. roach, Rutilus rutilus (L.), common bream, Abramis brama (L.), silver bream, Blicca bjoerkna (L.), and perch, Perca fluviatilis L., which contribute 85% of all individuals caught. Two 'faunal breaks' were identified. The first was the changing of river character from a barbel to bream zone caused by damming and river regulation. This started in the thirteenth century and ended at the beginning of the twentieth century with the extinction of anadromous fishes. The second break was during the 1960s and 1970s, with the eutrophication of Berlin waters and the near total loss of submerged macrophytes. All phytophilic fish species declined greatly and a mass development of eurytopic species started. The catch of pike, Esox lucius L., common carp, Cyprinus carpio L., and tench, Tinca tinca (L.), became negligible, and at present, eel, Anguilla anguilla (L.), and pikeperch, Stizostedion lucioperca (L.), are the main commercial fish species. Concomitantly, the profitability of the fisheries declined and was linked to a decrease in the number of people employed in fisheries by more than 75% compared with 1950.