Interactive effects of dietary fishmeal level and feeding frequency on growth performance, nutrient utilization, and waste outputs in juvenile largemouth bass (Micropterus salmoides)

Optimizing feeding strategies that balance growth performance with environmental sustainability is critical for intensive aquaculture. This study evaluated the interactive effects of dietary fishmeal and feeding frequency on the growth performance; body composition; balance of nitrogen, carbon, and phosphorus; and waste output in largemouth bass Micropterus salmoides . A 2 × 3 experimental design was used, with two fishmeal levels, 350 g kg −1 (high fishmeal, HFM) and 210 g kg −1 (low fishmeal, LFM), at three feeding frequencies—once a day (F1), twice a day (F2), and three times a day (F3)—forming six treatments: HFMF1, HFMF2, HFMF3, LFMF1, LFMF2, and LFMF3. The experiment lasted for 5 weeks due to typhoon. Growth performance improved significantly with increasing feeding frequency across both diets, with fish fed three times daily displaying the highest weight gain. The LFM diets resulted in moderately lower growth; however, increasing the feeding frequency compensated for much of this reduction. The retention efficiencies for nitrogen (N), phosphorus (P), and carbon (C) declined at the highest feeding frequency, indicating a reduced metabolic efficiency. Waste output modeling showed that higher feeding frequencies increased both solid and dissolved nutrient losses, with LFM diets producing proportionally more dissolved nutrient waste relative to HFM diets. Although three meals per day maximized growth, it also intensified the nutrient discharge per unit of production. Feeding twice daily provided a balanced strategy, achieving high growth performance while limiting nutrient waste. The findings demonstrate that 350 g kg −1 fishmeal combined with two meals per day provides high growth performance, efficient nutrient utilization, and lower environmental waste load. Moreover, increasing the feeding frequency can mitigate reduced fishmeal inclusion, but at the cost of higher waste outputs. The study stresses the importance of the integration of feeding frequency with diet formulation to improve nutrient utilization and sustainability in largemouth bass aquaculture.