Association of algae diversity and Hyriopsis schlegelii growth in mixed fish-mussel aquaculture

From January to December 2019, the algae in three fish and mussel mixed culture ponds in Hyriopsis schlegelii culture base in Nancheng County, Jiangxi Province were tracked and investigated, and the changes of water quality and mussel growth were analyzed. The identification results of algae and phytoplankton showed that a total of 8 phyla and 276 species of algae and phytoplankton were detected, of which Chlorophyta was the dominant phytoplankton. Diversity analysis showed that the species diversity and richness were higher in summer and autumn, and decreased in spring and winter, and there was little difference in the whole year. Correlation analysis showed that the water quality factors that had great influence on algae and phytoplankton were ammonia nitrogen, dissolved oxygen, temperature and so on. Hyriopsis schlegelii is an important freshwater pearl mussel in China, it feeds on algae and phytoplankton, so its growth rate is related to algae and phytoplankton. The mussel growth calculation results showed that H. schlegelii grows faster in spring and summer and slower in winter, which is in line with the seasonal variation law of algae and phytoplankton. According to the results of stepwise regression analysis of water quality and mussel weight gain, the most relevant factors of mussel weight gain were consistent with the dominant species at the same time. Some algae species, including Synedra, Chlorella and Nitzschia, are good bait for H. schlegelii.