Abstract: In order to study the effects of n-3 highly unsaturated fatty acids (n-3 HUFA) content in broodstock diets on the reproductive performance and seasonal changes of plasma sex steroids levels,five groups of Plectorhynchus cinctus female broodstocks were respectively fed a natural diet composed of trash fish (D5) and four artificial formulated diets containing 0.16% (D1),1.27% (D2),2.36% (D3) and 3.47% (D4) of n-3 HUFA,during the whole reproductive cycle.Their fecundity,egg and larval quality were evaluated,and the levels of plasma sex steroids were monthly monitored.It was found that the eggs production/kg of female,fertilization rate of eggs,larval survival and length at mouth-opening stage of both D2 and D3 group were equivalent to those of D5 group;however,those of D1 and D4 group were significantly lower than D5 group.Dietary n-3 HUFA content showed no obvious influence on the seasonal change pattern of plasma 17β-estradiol (E2) and testosterone (T).However,the plasma E2 and T levels in gonad developmental and mature seasons of D1 and D4 group were significantly lower than those of D5 group.Dietary n-3 HUFA content also displayed some influence on E2 and T production by in vitro ovarian follicles.Little basic E2 production was observed by ovarian follicles of D4 group.Human chorionic gonadotropin (HCG,100 IU/mL) stimulated E2 and T production by ovarian follicles of D2-D5 group;however,ovarian follicles of D1 group had no response to HCG.The results suggest that the optimum n-3 HUFA requirements in broodstock diet of P.cinctus range between 1.27% and 2.36%,deficient or high dietary n-3 HUFA content may have negative effect on reproductive performance of broodstocks;n-3 HUFA may affect the reproductive performance by influencing the production of sex steroids.