Assessment of Different Fish Feeds on the Growth of Rabbitfish (Siganus sutor; Achille Valenciennes, 1835) at Kijiweni, Kwale County

Fish feed is one of the biggest challenges in aquaculture. It accounts for up to 80% of production costs and limits the profitability and sustainability of small-scale mariculture in Kenya (Munguti et, al., 2021). This study assessed different dietary treatments on the growth performance of Siganus sutor cultured in floating cages within an Integrated Multi-Trophic Aquaculture (IMTA) system at Kijiweni, Kwale County, Kenya. The experiment compared three feeding regimes: formulated feed, raw seaweed (Eucheuma denticulatum), and a mixed diet combining both feed types over a period of 6–8 weeks. Growth performance was assessed using mean total length, weight gain, survival rate, and length–weight relationships, alongside monitoring of key water quality parameters. Results showed that all treatments supported growth; however, fish fed on the mixed diet exhibited superior performance, recording the highest mean length (13.3 ± 0.2 cm) and weight gain (30.3 ± 1.3 g). Fish fed on raw seaweed demonstrated moderate but consistent growth, while those fed solely on formulated feed showed the lowest growth performance. Length–weight analysis revealed a weak relationship under formulated feed (R² = 0.0007), a moderate relationship under mixed diet (R² = 0.2929), and the strongest relationship under raw seaweed (R² = 0.5025), indicating differences in feeding efficiency and growth consistency across treatments. Water quality parameters remained within optimal ranges, suggesting that environmental conditions did not limit growth. From this study, a mixed diet of formulated feed and seaweed enhances growth and sustainability in cage-cultured rabbitfish.