Evaluation on temporal and spatial changes of biological integrity for shallow lakes in the middle reach of the Yangtze River

The purpose of this paper was to introduce the conceptual use of the index of biotic integrity (IBI) to the Chinese ecologists, promoting the IBI system suitable for the Chinese inland waters, with particular emphasis on evaluation of shallow lakes in the middle reach of the Yangtze River. According to the characteristics of fish assemblages in lakes in the reach, we modified the IBI originally developed by Karr. An adaptive IBI was obtained, which included 12 metrics: number of total native fish species, number of species in the family Cyprinidae, number of species in Bagridae catfishes, number of species in the family Cobitidae, percent of crucian carp individuals, number of families in commercial catches, percent of omnivores individuals, percent of insectivores individuals, percent of carnivores individuals, the unit yield of fish, percent of hybrids, and percent of anomalies in the fish assemblages. This IBI was used to assess the ecological integrity of five shallow lakes: Wuhu, Honghu, Baoanhu, Donghu Lakes, and Sanhulianjiang Reservoir. The historical data on fish assemblages obtained from Wuhu Lake were employed as background information to be representative of a natural/undisturbed state of lakes in the reach. Though these data might not be fully reliable as the sampling methods used had not been calibrated and therefore contained some uncertainty, it was believed that data obtained from one lake for extensive time series and data deriving from different lakes for a limited period were sufficient to allow the first attempt to a modified IBI for evaluating on temporal and spatial changes of biological integrity within the research area. Comparing the data from different years in Honghu Lake, the IBI was estimated to be 52, 40, 28, and 26 in 1964, 1981, 1992, and 1998 respectively, showing that in the lake biological integrity decreased gradually in the past 40 years. On the other hand, data comparison of four lakes in early 1990s revealed that the biological integrity was “fair” in Baoanhu Lake and Sanhulianjiang Reservoir, whereas in Honghu and Donghu Lakes the biological integrity represented “poor” and “very poor” conditions, respectively. These results provided a kind of scientific evidence for the state of environmental health in these lakes that could be used in sustainable management. Finally, the applicability of the modified IBI to identify disturbances and the suitability of this method in Chinese inland waters management were discussed. It was expected that such an index may be indicative of the effect of management decisions in terms of sustainability and adaptive resource utilization in China.