High mortality during the early developmental stages of the large yellow croaker (Larimichthys crocea) poses a significant challenge to aquaculture. To assess the effects of low-concentration hydrogen peroxide exposure on larval and juvenile survival and growth, 13-day-old fry were exposed to six nominal concentrations of hydrogen peroxide (0.0, 0.5, 1.0, 2.5, 5.0, and 10.0 μL/L) for 50 days under controlled hatchery conditions, with daily monitoring of seawater quality parameters. Results indicated no significant differences in growth performance or survival between the 0.5 μL/L treatment and the control group. In contrast, juveniles exposed to 1.0, 2.5, and 5.0 μL/L hydrogen peroxide exhibited significantly higher survival rates than the control. Although the survival rate of juveniles in the 10.0 μL/L group was significantly elevated compared to the control group, all measured growth indices—including average body length, body weight, specific growth rate (SGR), and weight gain rate (WGR)—were significantly suppressed. Regarding water quality, ammonia nitrogen concentrations were significantly reduced during the first 7 days in the 5.0 and 10.0 μL/L groups, while nitrite concentrations remained significantly lower from day 13 onward compared to the control. Throughout the experiment, culturable Vibrio counts in hatchery tank water exhibited pronounced temporal fluctuations, with no consistent suppression trend attributable to hydrogen peroxide exposure. Collectively, these findings suggest that hydrogen peroxide at concentrations of 1.0–5.0 μL/L enhances juvenile survival without compromising growth performance.



