| Freshwater mussels is one of very important aquatic organisms in freshwater ecosystems. With slow motion, living area relatively fixed, weak tolerance to environmental change, freshwater mussels that one of the freshwater taxonomic groups is the most vulnerable to the threat. Ganjiang River, the largest river in Jiangxi Province, is rich of freshwater mollusks. Freshwater mussels of Nanchang section of the lower reaches of Ganjiang river were surveyed in November 2011 to February 2011 and October 2012. Species composition, distribution, biomass and its adaptation to hydrological characteristics were analyzed in the study area, meanwhile the resource protection measures and countermeasures were proposed, and it provided a scientific basis for the protection of freshwater mussels. The main results are as follows:1. A total of 29 species belonging to 11 genera of freshwater mussels were found in Nanchang section of the lower reaches of Ganjiang River. The dominant species in the zone were Unio douglasiae, Acuticosta chinensis and Acuticosta ovata. Relative abundance of three unionids was 35.13%、14.65% and 10.76%. The biomass and density of freshwater mussels in the 8 sections were 44.90±3.43g/m2 and 4.65±0.43 ind/m2.2. Shannon-Wiener diversity index, Pielou uniformity index and Margalef richness index were used to analyze the diversity of freshwater mussel community. The data show that species biodiversity of sections Ⅳ (Nanchang bridge), Ⅶ (Champagne Square) and Ⅷ (Shengmi Bridge) were higher than these of section Ⅰ (the bayi Bridge); Ecological dominance index showed that this of section Ⅰ (the bayi Bridge) was higher, these indicated that number of species in the community of section Ⅰ (the bayi Bridge) was small and uneven distribution, dominated by the dominant populations.3. Founa similarity analysis showed that 8 sections can be divided into 3 categories. Section Ⅱ (Xinlong building), Ⅴ (Ganjiang park), Ⅶ (Champagne Square) were a group. The sediment was mainly sandy and the species composition is very relatively similar; Section I (Bayi Bridge) and Section Ⅷ (Shengmi Bridge) formed a group, they were drought in winter and had a fast-flowing water in the summer. Sediment was more complexed, most samples were empty shells in the quantitative collection; The section III (Qiushui Square), IV (Nanchang bridge), VI (Music Square) were a group, the water was gentle and slow, and the Sediment was mainly muddy.4. Population structures of 21 species mussels were analyzed.6 species were consided as growth form,12 species as stable population and 3 species as involution form, meanwhile,2 species were considered as rare, and no alive individual of Lepidodesma languilati and Solenaia carinata were found.5. The impact of environmental factors on species number and standing crop of mussels were analyzed. The results showed that water depth<2.0 m, the species number of mussels, biomass and density were higher; when water depth> 6.0 m, these values were smaller. The number of mussel species, biomass and density in silt sediment habitate were more than in hard mud. The number of mussel species, biomass and density in the habitate with flow rate of 0-0.3 m/s were higher than that of 0.4-0.7m /s. The number of mussel species, biomass and density when Transparency< 50 cm especially in the 65-80cm were higher than transparency> 80cm. These results meant when the depth of water is less than 2m, water flow in the range of 0 to 0.3 for m/s, transparency between 65cm to 80cm and silt sediment water, this may be freshwater mussel’s ideal habitat. |
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