Current status of feeding stocks of the kaluga sturgeon Huso dauricus Georgi, 1775, and Amur sturgeon Acipenser schrenckii Brandt, 1889, in Russian waters

Abstract

Summary Biological parameters of the kaluga Huso dauricus and Amur Acipenser schrenckii sturgeons have been analyzed in their foraging areas in Russian waters. Results show that both species are now sufficiently abundant only in catches from the lower Amur River, its mouth, and the Amur Estuary. The largest Amur sturgeon individuals occur in the estuary, while the largest kaluga sturgeon reside in the estuary as well as in the Sea of Okhotsk. Catches made in the river consist mainly of juvenile fish. The average body sizes of kaluga and Amur sturgeons in catches from the lower Amur River and the Amur Estuary have decreased significantly compared to records from 1929 to 1930. Between 2006 and 2011, the proportions of mature kaluga and Amur sturgeons in the river catches averaged 2.9 and 5.1%, respectively, and at its mouth and in the estuary by 42.6 and 32.8%, respectively. Abundance of kaluga sturgeon (age >1 year) in the lower Amur and the estuary in 2011 reached 345 000 individuals at a biomass of 7110 tonnes (t). Abundance of Amur sturgeon (age >1 year) in the same area and time reached 289 000 individuals at a biomass of 1946 t. The main stocks of the respective species (324 300 individuals or 94% in Kaluga, 263 570 individuals or 91.2% in Amur sturgeon) are concentrated in the Amur Estuary. To restore their populations in the Amur, a ban on all types of commercial fishing at the spawning grounds and juvenile foraging grounds should be implemented. It is also necessary to increase the number of hatchery-reared juveniles and allow them to grow to a greater body size before release into the Amur.