Seasonal variation in diet of juvenile Amur sturgeon Acipenser schrenckii in the lower reaches of the Songhua River,Northeast China

We investigated seasonal variation in the diet of hatchery-reared juvenile Amur sturgeon Acipenser schrenckii in the Tongjiang reach of the Songhua River, Northeast China. The results indicated that Amur sturgeon fed mainly on Chironomidae and Ephemeroptera and secondarily on unspecified bony fish, Odonata, and Trichoptera. Diet changed throughout the year, with autumn 2017 and spring 2018 dominated by Ephemeroptera larvae, while summer 2018 prey comprised primarily Chironomidae larvae. Unspecified bony fish were observed at greater frequency in autumn 2017. Amur sturgeon captured in summer contained a greater quantity of Trichoptera larvae compared to those from autumn and spring sampling. Results were consistent with previous reports of Amur sturgeon diet in other areas of its native distribution and suggested that they may be opportunistic feeders throughout the year, although larval Chironomidae and Ephemeroptera appear to be important prey. These results represent the first reported diet composition data for juvenile Amur sturgeon in the lower Songhua River. Results of the study form part of a comprehensive investigation of feeding habits of juvenile Amur sturgeon that provides basic data for study of the biological characteristics of the species.