Abstract:

The fishery resource surveys were carried out by Set net in Anqing and Changshu section of the lower reaches of the Changjiang River from March 2003 to March 2010 According to the monitoring result，the dynamic state of fish community was described in this paper，and the variation of fish community structure was analyzed by the multivariate analysis There were 67 species which belong to 50 genera，22 families and 12 orders There were 50 species which belong to 34 genera，11 families and 6 orders in Anqing Section，while 52 species which belong to 44 genera，21 families and 12 orders in Changshu Section The species of Cypriniformes order occupied a dominant position in both Anqing and Changshu section，while the number of diadromous species from Changshu section was 15，which was more than that of Anqing section（ 3 diadromous species）.There were 9 dominant species occurred during seven years in Anqing section The most frequently dominant species were Carassius auratus and Pelteobagrus vachellii，which all occurred 5 times，while Hemiculter leucisculus， Xenocypris davidi and Siniperca chuatsi only occurred 1 time，respectively There were 11 dominant species occurred during seven years in Changshu section，among which Parabramis pekinensis，Hypophthalmichthys molitrix and Carassius auratus occurred every year，Coreius heterodon，Cyprinus carpio and Hemiculter bleekeri only occurred 1 time，respectively The analysis result of cluster analysis and nonmetric multidimensional scaling methods showed that the annual changes of the fish community structure of Changshu section was less than that of Anqing section，and the fish community structure were different in these two sections The similarity percentages analysis verified the conclusion It showed that the average similarity of the fish community composition was 6147% in Anqing section from March 2003 to March 2010，while it was 7336% in Changshu section，and the average dissimilaritiy of the fish community composition was 7684% between Anqing and Changshu section The analysis of similarities result showed that the annual compositions of fish community in Anqing section and Changshu section had highly significant difference The spring fishing moratorium policy have been put in place，and the larger scale of enhancement activities in which the main releasing species were silver carp and bighead carp have been taken continuously Therefore，the dominant position of silver carp and bighead carp from Changshu section increased year by year，but the situation of Anqing section had no change The reasons for this are as follows （1） The release number of silver carp and bighead carp in Anhui section was less than that in Jiangsu section （2） The different organism food level caused the difference of fishery resource density between 2 sections The community structure variance of Anhui and Jiangsu sections belonged to the internal community fluctuation，which had not yet reached the level of succession