Effects of fishmeal replacement with insect meals (Hermetia illucens and Acheta domesticus) on growth performance, digestibility, digestive enzyme activity, and fatty acid profile of juvenile Totoaba macdonaldi

The search for alternative ingredients to fishmeal is crucial in the feed industry, with insect meals emerging as a promising alternative. This study evaluated the effects of replacing fishmeal with black soldier fly (BSF, Hermetia illucens) and domestic cricket (CKT, Acheta domesticus) meals in juvenile Totoaba macdonaldi diets. Four isonitrogenous (48%) and isolipidic (15%) diets were formulated with 25% or 50% fishmeal replacement (BSF25, BSF50, CKT25, CKT50), plus a control diet without insect meal. A total of 120 totoabas (112 ± 15 g) were randomly distributed into 15 tanks (250 L) in a recirculating system and fed to apparent satiation for 64 days. At the end of the trial, no significant differences were found in final weight, weight gain, or specific growth rate (p > 0.05). However, fish fed CKT25 had a significantly poorer feed conversion ratio and protein efficiency ratio. Apparent digestibility coefficients of dry matter were significantly lower for fish fed the CKT50 (71.7 ± 2.6%) compared to the control (82.4 ± 0.4%). Fish muscle from fish fed the insect meals diets had higher n-6 polyunsaturated fatty acids (n-6 PUFAs), while eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), n-3 PUFAs, and total long-chain PUFA (LC-PUFAs) which remained unaffected by dietary treatment. No significant differences among treatments were observed in digestive enzyme activity. These results suggest that BSF meal can replace up to 50% of fishmeal in totoaba diets without adverse effects on growth, digestibility, or muscle composition, reducing dependence on marine protein sources. However, CKT meals may negatively impact fish performance and digestibility. Further research is needed on specific nutrient digestion, lipid metabolism, and amino acid availability.