Impact of Stocking Density on Growth, Feeding Behavior, and Flesh Quality of Largemouth Bass (Micropterus salmoides) in Coupled Aquaponic Systems

Stocking density is a key driver of performance in aquaponics, affecting both fish welfare and crop yield. This study evaluated the impact of three initial stocking densities (3.1, 4.1, and 6.2 kg/m3) on survival, growth, feeding behavior, carcass and filet quality of largemouth bass (Micropterus salmoides), as well as on the yield of lettuce (Lactuca sativa), sweet basil (Ocimum basilicum), and Swiss chard (Beta vulgaris var. cicla) cultivated in vertical coupled aquaponic units. A total of 184 fish (109 ± 28 g) were reared for 176 days in nine independent recirculating systems. Fish reared at the lowest density achieved the highest final live weight and specific growth rate, with a better feed conversion ratio, whereas performance declined at higher densities despite similar survival rates. Feeding behavior was generally consistent across groups, although feed intake rate was reduced at the highest density. Carcass and filet quality traits were unaffected by stocking density. Vegetable yield was enhanced by higher fish biomass, with significant increases in lettuce production and a positive trend for basil. These findings indicate that intermediate stocking densities may represent the most sustainable compromise, ensuring fish welfare and acceptable growth while supporting efficient plant production in largemouth bass–based aquaponics.