Man-made changes to the Danube delta include the improvement of the hydrological infrastructure for navigation and fish production purposes and an elevated nutrient load in the inflowing Danube river water. Records from the commercial fishery over the last 40 years indicate a shift from clear water fish (Tinca tinca, Carassius carassius, and Esox lucius) towards species adapted for turbid water. Since the 1970s the most frequently caught species have been Rutilus rutilus, Scardinius erythrophthalmus and the exotic Carassius auratus gibelio. For this study, the fish community in 13 interconnected lakes was sampled in June from 1996 through 1998 using gill-nets and electrofishing. In total 30 species were caught. The fish dominating catches from the different lakes varied from eurytopic/"grey fish" species to limnophilic/"black fish" species. This range corresponds with differences in lake morphometry, substrate type, hydrological distance from the river and presence of aquatic vegetation. The condition of the lakes ranges from pristine to moderately affected, but taken as a whole, the system has maintained its biological diversity with regard to fish communities in floodplains.
Internat. Rev. Hydrobiol.