Summary Thousands of Chinese sturgeon, Acipenser sinensis, have been grown since the 1990s, with some of them being used for close‐cycle captive breeding. However most of the specimens have not yet matured, and there has been no literature on the Chinese sturgeon that matured when spending its entire life cycle in freshwater. We investigated the gonads of cultured Chinese sturgeon at ages ranging between 7 and 11 years when raised from captive broodstocks. Most of the 11 year‐old fish (body weight 45.5–84 kg) were in the gonadal development stage. The maximal oocyte diameter of the females was about 500 μm. In 14 males at age 10–11 years, we found various stages of development but one dead specimen that seemed to have testis in the early stage of maturation, with all types of spermatocytes being present. This specimen was 10 years old (body weight 40.3 kg). According to the results obtained, the Chinese sturgeon cultured in freshwater were not yet fully mature but are assumed to likely reach maturity in the near future.

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Ten females of Kaluga sturgeon (Huso dauricus; 73.8 ± 6.49 kg, total length 204.5 ± 12.8 cm) matured for the first time after a full life-cycle in captivity. Absolute gonad biomass was 8.4 ± 1.3 kg per female and relative fecundity 11.2 ± 1.6%, at maturation stage IV. These fish were induced to spawn by injection of hormone LHRH-A2 at a dosage of 10 lg kg )1 . Male Kaluga was injected one time at 5 lg kg )1 and milt was stripped 16 h after injection of LHRH-A2. Water temperature was about 16 ± 1°C during the induction period. Fertile eggs were obtained 36.8 ± 2.6 h after first injection; they were fertilized by semi-dry method. Fertilization rate was 80.7 ± 3.8%. Fertilized eggs were incubated McDonald jars (hatching rate 85.2 ± 9.8%). There was a strong correlation between body weight (x) and time (y) needed from hormone injection to obtaining fertile oocytes (y = )0.8231x + 98.838 R 2 = 0.8428; P < 0.01). The cultured males ripened as early as at age 5 while females were 8-years old at first maturity.