Growth and Physiological Responses of Siberian Sturgeon (Acipenser baerii) to Partial Fishmeal Replacement by Mealworm and Silkworm Pupae, Individually and in Combination.

This study investigated how partially replacing fishmeal (FM) with silkworm pupae (SWPs) (Bombyx mori) and yellow mealworm (MW) larvae (Tenebrio molitor) affects the growth, health, and metabolism of Siberian sturgeon (Acipenser baeri). Four experimental diets were tested: a control with 60% FM and no insect meal, 45% FM with 15% MW, 45% FM with 15% SWPs, and a combined diet containing 45% FM plus both insect proteins: 7.5% MW, as well as 7.5% SWPs (SMW). Fish were reared under controlled conditions, including water temperature 18 ± 1°C, dissolved oxygen 8.5-9.3 mg L-1, pH 7.6, and a fixed feeding regime. Sturgeon fed MW and SMW diets showed significantly improved growth, higher final weight, better specific growth rate (SGR), and more efficient protein utilization, along with a lower feed conversion ratio (FCR) compared to the control. Sturgeon fed MW and SMW diets showed significantly improved growth, higher final weight, better SGR, and more efficient protein utilization, along with a lower FCR compared to the control. Digestive enzyme activities (amylase [AMS], protease, lipase [LP]) and key serum metabolites-including protein, albumin, cholesterol, triglycerides, and glucose-were elevated in insect-fed groups. Immune and antioxidant defenses, such as lysozyme, immunoglobulin M (IgM), glutathione peroxidase (GPX), and superoxide dismutase (SOD), were enhanced, particularly in the SMW and MW treatments, while oxidative stress markers (malondialdehyde [MDA]) were favorably modulated. Gene expression analysis revealed upregulation of growth-related (growth hormone [GH], IGF1), protein metabolism (target of rapamycin [TOR]), lipid metabolism (Apolipoprotein [ApoE]), and immune genes (interleukin-1 [IL-1]), with the strongest response in the combined SMW diet. Overall, partially replacing FM with insect meals, especially the MW and SWP combination, effectively supports growth, metabolism, immune function, and antioxidant capacity in Siberian sturgeon. These findings highlight the promise of insect-based proteins as a sustainable and effective alternative in Siberian sturgeon aquaculture.