Observations on gonadal development of 7–11 year old Chinese sturgeon Acipenser sinensis cultured in freshwater

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.