SPATIAL-TEMPORAL DISTRIBUTION CHARACTERISTICS OF FISH RESOURCES IN ERHAI LAKE BASED ON HYDROACOUSTICS AND CATCH SURVEY METHODS

Erhai Lake, the second largest plateau freshwater lake in Yunnan Province, is known for its unique fish resources. In order to understand the temporal and spatial dynamics of fish resources, this study evaluated the community structure and spatial-temporal distribution of fish in Erhai Lake by using hydroacoustics and catch survey methods from 2022 to 2023. Additionally, the relationship anmong fish community structure, fish distribution characteristics, and environmental factors was analyzed. A total of 22 fish species were identified in the fishery survey, belonging to 17 genera, 8 families, and 4 orders, with Rhinogobius giurinus being the dominant species. The hydroacoustic survey results showed that the TS value of fish mainly ranged from –70 to –58 dB (total length 1.2—5.0 cm) in four seasons, accounting for 88.40%, 83.03%, 84.53%, and 82.92% in summer, autumn, winter, and spring, respectively. The average target intensity of fish in summer, autumn, winter, and spring were –59.08±0.08 dB, –54.99±0.15 dB, –55.90±0.16 dB, and –58.07±0.18 dB, respectively. Fish densities were as follows: 23851.61±889.30 ind./ha in summer, 14185.69±1106.54 ind./ha in autumn, 2423.19±179.54 ind./ha in winter, and 3382.16±440.71 ind./ha in spring. Spatially, fish in summer and spring were primarily concentrated in the northern region. Vertically, a higher proportion of fish were found in the 2.5—6.5 m water layer during summer, autumn, and spring, accounting for 32.99%, 30.65%, and 62.78%, respectively, whereas in winter, 34.05% of the fish were found in the 14.5—18.5 m water layer. significant vertical migration was observed in winter and spring. Redundancy analysis (RDA) showed that water temperature (WT), ammonia nitrogen (NH₃-N), transparency (SD), and high salinity index (COD_Mn) significantly affected the distribution of small fish in Erhai Lake. This study demonstrates the feasibility of combining acoustic surveys with catch surveys to investigate the spatial and temporal distribution of fish resources. The results provide a scientific basis for the protection and restoration of fish resources in Erhai Lake.