Abstract
Background:
Aquaculture is a cornerstone in global food security, offering an essential source of protein and nutrition to an ever-growing human population. Fishmeal is a high protein feed ingredient typically made out of wild fish, which increases the depletion of wild fish. Insects such as black soldier fly (Hermetia illucens) and mealworm (Tenebrio molitor) larvae meal are promising alternative protein sources for aquafeeds. However, their effects on Labeo rohita remained underexplored.

Aim:
The present research evaluated the impact of substituting fishmeal with black soldier fly (BSF) and mealworm (MW) larvae meal on nutrient digestibility, body and mineral composition of Labeo rohita fingerlings.

Methods:
A 60 day feeding trial was conducted using varying levels (0%, 25%, 50%, 75%, and 100%) of BSF and MW diets replacing fishmeal. Growth performance was assessed through weight gain, feed conversion ratio (FCR), and specific growth rate (SGR). Digestibility trials measured apparent digestibility coefficients (ADCs) for protein, lipid, and gross energy. Proximate and mineral compositions of fish were also analyzed. Data were subjected to one-way ANOVA and Tukey’s test at P < 0.05.

Results:
The 75% BSF and 50% MW diets showed the best growth performance, with significant improvements in WG, FCR, and SGR. Protein digestibility improved significantly, rising from 49.22% (control) to 75.15% in the BSF 75% group, and from 50.91% (control) to 75.33% in the MW 50% group. BSF inclusion reduced body fat while increasing protein and ash content, whereas MW showed variable effects on lipid content. Both insect meals enhanced mineral retention, particularly calcium, sodium, phosphorus, and magnesium, with peak values observed in the BSF 75% and MW 50% diets.

Conclusion:
Replacing fishmeal with BSF and MW larvae meals improves growth, nutrient digestibility, and mineral composition of Labeo rohita fingerlings. BSF at 75% and MW at 50% inclusion levels yielded the best results. Insect meals are therefore viable, sustainable alternatives to fishmeal in aquafeeds, though careful attention to inclusion levels and chitin content is required to optimize benefits.

Key words: Aqua-feed; Aquaculture; Fishmeal; Insect protein; Sustainability.