HYDROACOUSTIC ASSESSMENT OF SPATIO-TEMPORAL DISTRIBUTION AND ABUNDANCE OF FISH RESOURCES IN THE XIANGXI RIVER

In order to better understand the spatial-temporal distribution and the biomass of fish in the Xiangxi River, we applied hydroacoustic analysis with Simrad EY60 split-beam echo sounder and investigated the fish grounds in the Xiangxi River in May and November of 2013. We found 41 fish species in the survey, and the dominant species included Pseudobrama simoni, Hemiculter bleekeri, Hemiculter leucisculus, Squalidus argentatus, and Saurogobio dabryi. The fish density was higher in spring than autume, with the typical values of 53.4 ind./1000 m3 in May and 15.4 ind./1000 m3 in November. The spatial distribution of fish in the Xiangxi River showed an uneven pattern. Horizontally the fish density decreased from the Gaolan River to the estuary of the Xiangxi River. Vertically the fish abundance followed the order: the surface layer the middle layer the bottom layer, and the distribution was the same in both spring and autumn. Here we suggested two biomanipulation methods to improve the water quality in the Xiangxi River: (1) to suppress the small fishes by increasing the population of piscivorous fishes, (2) to suppress the phytoplankton by raising planktivorous silver carp and bighead carp.