Abstract:

The Jingjiang section of the Yangtze River, which lies near the estuary with an irregular semidiurnal tide, is the National Aquatic Germplasm Resource Reserve and plays an important role in conserving fishery resources. To clarify the composition and changes in abundance/biomass of fish assemblages of these coastal waters, investigations were carried out along the Jingjiang section of the Yangtze River in the autumns of 2002 to 2011. Results showed that 91 species, belonging to 12 orders and 23 families, were collected from surveys conducted during this period. Fish included 47 species of Cypriniformes, 17 species of Perciformes and 10 species of Siluriformes. Four were migratory species, 13 were estuarine, and 74 were freshwater fish. The average number of different fish species recorded each autumn was 47 (range = 32-61), and mean Jaccard similarity index was 53.72 (range = 38.46-69.09)%. The total number of dominant and common species recorded was 42, with the annual value averaging 19. Dominant and common species were mainly small fish, such as Hemiculter bleekeri, Pseudobrama simony, Pseudobagrus nitidus etc., as well as juveniles of large or medium fish, such as Culter alburnus, Parabramis pekinensis, P. vachellii etc. The mean individual weight (MIW) of the fish assemblage was 6.99 g. The abundance biomass comparison curve indicated that the first dominant species recorded in autumn in all years except 2010 were all very small-sized fish. The most dominant species in 2002-2009 were also of small-size fish, and large-size fish only contributed to the dominant species in 2010 and 2011. Our research also indicated a general increase in abundance or biomass (CPUE_N、CPUE_W), the MIW of the fish assemblage, and the population size of 62% of dominant and common species. This suggested that fishery resources of the waters studied are likely to improve.

Key words: Yangtze River, offshore areas, fish assemblage, temporal pattern, ABC curve