SEASONAL ABUNDANCE OF FILTH FLIES, LARVAL BIOMASS YIELD, AND THE NUTRITIVE POTENTIAL OF DIPTERAN MAGGOTS AS DIETARY PROTEIN SUPPLEMENTS IN CLARIAS GARIEPINUS FINGERLING PRODUCTION Awe, Omolara. Oluwafunmilola. Department of Biology Adeyemi Federal University of Education, Ondo omolarawe15@gmail.com ABSTRACT The escalating cost of conventional fish meal and its environmental footprint have intensified global interest in alternative protein sources for aquaculture feeds. This study investigated the seasonal abundance and species composition of filth flies (Order: Diptera) across four waste substrates in Ibadan, Nigeria, and evaluated the growth performance of Clarias gariepinus fingerlings fed five isonitrogenous diets incorporating maggots reared on cowdung, brewer's spent grain, and poultry waste. A preliminary survey (September–November) and a wet-season survey (March–April) were conducted at Bodija Abbattoir, Moniya Abbattoir, University Teaching Farm, and Tolafeg Farm. Three fly species were identified: Hermetia illucens (Black Soldier Fly, BSF), Phaenicia sericata (Blowfly), and Musca cuthbertsoni (Housefly). Hermetia illucens predominated during the dry season (September–November) at three sites, while Phaenicia sericata dominated all four sites during the wet season (March–April). Mean larval yields of 2.80 ± 0.22 g and 2.67 ± 0.11 g per 100 g cowdung were recorded at Bodija and Moniya abbattoirs, respectively. Among the five experimental diets fed to 100 six-week-old C. gariepinus fingerlings (20 per tank) over 91 days, Diet 4 (50% maggot from poultry waste substrate + 50% fish meal) produced the highest specific growth rate (SGR = 1.76%/day) and was significantly superior to all other diets (P < 0.05). Diet 1 (100% maggot meal) recorded the lowest overall performance. These findings reinforce the feasibility of insect-based protein integration in sub-Saharan African aquaculture, with strong implications for food security and sustainable feed formulation. Keywords: Hermetia illucens; Clarias gariepinus; filth flies; insect protein; aquaculture feed; maggot meal; Nigeria; sustainable aquaculture