中文摘要：

2003—2004年对天鹅洲和老江河两个长江故道的调查表明，该类水体的底栖动物在类群组成上与阻隔湖泊类似，以螺类和水生昆虫为主，但是有较多的流水性和冷水性种类．纵向比较表明两个故道底栖动物生物量比20世纪90年代下降了48.3％-78．6％，软体动物尤为突出．底栖动物资源衰退的原因主要有两个，一是过度渔业，二是江湖阻隔．与长江流域其他类型水体的比较表明在中等程度水文连通的水体中底栖动物种类最多，软体动物尤其是双壳类的现存量明显较高．为发挥长江故道群对泛滥平原生物多样性维持的重要作用，文末提出了关于合理放养和季节性通江的管理建议．

英文摘要：

Ecological surveys in Tian-e-zhou Oxbow and Laojianghe Oxbow along the middle reaches of Yangtze River were carried out during April 2003 to February 2004 Results indicated that macrozoobenthos communities of oxbows were similar to those of river-isolated lakes in the composition of standing crops, dominated by gastropods and aquatic insects, but were richer in potamophilus and psychrophilic species. Compared with the data of 1990＇s, biomass of macrozoobenthos decreased by 48.3%-78.6%, mainly due to the decline of mollusks. The resource deterioration was mainly ascribed to overfishing and river-lake disconnection. Comparison with other types of Yangtze waters indicated that the floodplain waterbodies with an intermediate level of hydrological connectivity have the highest species biodiversities of macrozoobenthos, and have abundant mollusks, especially bivalves. To restore the important function of the oxbows in maintaining biodiversity of the Yangtze floodplain, it is suggested to stock animals rationally and to reconnect with the Yangtze River as frequently as possible.