First Insights into the Migration Route and Spatial Distribution of the Endangered Chinese Sturgeon (Acipenser sinensis) in the Yangtze River Estuary

Chinese sturgeon (Acipenser sinensis) is an endangered species, and the Yangtze River Estuary is an important migration channel for this species. With the scale of Chinese sturgeon restocking along the Yangtze River gradually increasing, an increasing number of artificially bred Chinese sturgeon will come to the estuary. It is urgent to make the first insights about the distribution characteristics and migration strategy of the endangered Chinese sturgeon in the Yangtze River Estuary available. So, to balance the need for information about this endangered species and its conservation, a total of 14 Chinese sturgeons were released in the waters near Chongming Island on 9 April 2021 and 20 October 2022, and 50% of them have been successfully recovered. The data demonstrated that Chinese sturgeon had a good migration ability in the Yangtze River Estuary and its adjacent waters. One sturgeon returned to the freshwater area of the estuary after spending approximately 46 days in the sea at a maximum depth of 54.5 m, and two sturgeons returned to the Yangtze River mainstream within 3.5 days after release. We propose that the Northern Channel of the estuary may be the main passway for Chinese sturgeon to undertake the river-sea migration. The bycatch data of Chinese sturgeon showed that this species may prefer the southern area of the estuary. We hypothesize that the food resources and salinity regime are the main factors that promote Chinese sturgeon to enter the shoals around the coast of Chongming Island. The ocean currents, river runoff, salinity, and food resource may affect the distribution of Chinese sturgeon along the Chinese coast. Future work on the conservation of Chinese sturgeon should focus on the marine life history and continuously enrich the research data to improve conservation strategies.