Lateral migration of fish between China’s second largest freshwater lake (Dongting Lake) and the mainstem of the Yangtze River

Abstract

Lateral migration of fish between Dongting Lake and the mainstem of Yangtze River was investigated at the channel connecting these two systems to identify its regular pattern and possible affecting factors. During the sampling period, a total of 55 fish species were recorded, with the lake-river migratory fish species dominating abundance all the time. Hierarchical clustering analysis found four temporal fish assemblages: Feb–Mar, Apr–Jun, Jul–Sep and Oct–Jan, which was consistent with the rising and falling of water temperature and water level. The “Movement index” was used to measure the direction of fish migration, which was found closely associated with variations of water temperature, water level and flow discharge. Particularly, when water temperature and water level rose from March to July, fish migration showed the tendency of entering the lake; when they receded from August to February of the next year, fish migration showed the opposite tendency. Based on our results, we concluded that maintaining the river-lake connection is essential for the river-lake migratory fishes and the natural flow regime was the key driver in this floodplain ecosystem.