Broken-line regression analysis on WGR, whole-body Cu concentration, hepatic Cu–Zn SOD activity and serum ceruloplasmin activity indicated that the minimum Cu level in semi-purified diet for 12–70 g Russian sturgeon was 7–8mgkg−1. What we want to remind is that the supplemented Cu content should be adjusted according to the source of Cu, type of feed ingredients and the size of fish.