Evaluating Spirulina (Arthrospira sp.) as a sustainable fishmeal alternative in African Catfish larviculture: Effects on performance and survival across altitudes

High feed costs and the increasing scarcity of fishmeal continue to constrain sustainable aquaculture production, particularly during the sensitive larval stages. This study evaluated the potential of Spirulina (Arthrospira sp.) as an alternative protein source in starter diets for African catfish (Clarias gariepinus) larvae, with emphasis on growth performance, feed utilization and survival. Spirulina was incorporated into isonitrogenous (40% crude protein) starter diets to replace fishmeal at 0, 25, 50, 75, and 100% inclusion levels. Feeding trials were conducted at two sites representing low (Sangoro) and high (Kegati) altitudes. Catfish larvae with an initial mean weight of 0.0071±0.00006 g were stocked in 15 aquaria tanks, fed four times daily ad libitum and growth monitored biweekly. At Sangoro, fish fed diets with 50% and 75% Spirulina inclusion had the most efficient feed conversion ratios (2.05–2.08) and significantly (p<0.05) higher weight gain and specific growth rate, while maintaining consistent survival across treatments (20–24%). In contrast, growth performance at Kegati was markedly lower, with weight gain ranging from 0.020 to 0.071 g and a low survival ranging from 1–10%. Although the highest weight gain, specific growth rate (7.99%), and lowest feed conversion ratio (0.71) were observed at 100% Spirulina inclusion, these values were strongly influenced by severe cannibalism and selective survival among a small number of individuals. Overall, larvae reared at the low-altitude site exhibited significantly superior growth and survival compared with those reared at the high-altitude site. Present results suggest that moderate to high Spirulina inclusion (50–75%) enhances growth performance and nutrient utilization both in low and high altitude African catfish larviculture.