FEEDING STRATEGY

Optimal feeding strategy identified for European sea bass in brackish RAS

Lubinas juveniles bajo el agua

Researchers from the American University in Cairo, Egypt, have pinpointed an optimal feeding regime for European sea bass (Dicentrarchus labrax) reared in brackish water recirculating aquaculture systems (RAS), offering producers a practical route to improve performance while reducing costs.

Over a 16-week trial, the team tested two dietary protein levels (42% and 44%) and three feeding frequencies (once, twice, or three times a day) with juvenile fish reared at 7 parts per thousand (ppt) salinity. The results were conclusive: feeding a 42% protein diet twice daily to satiation delivered the best growth rates, feed conversion, survival, and economic returns.

Brackish RAS are gaining traction in aquaculture for both practical and environmental reasons. They allow marine and euryhaline species, such as sea bass, to be farmed inland or in areas where seawater supply is limited or inconsistent. On-site salinity control ensures stable growing conditions, helps reduce biofouling and the risk of certain pathogens, and minimises environmental impact by cutting high-salinity effluent discharge.

Operationally, brackish RAS offer flexibility: farmers can adjust salinity to match a species’ optimal growth range or to acclimate fish before transfer to seawater. This capability also opens opportunities for production in estuarine and non-coastal regions, extending market reach.

Feed typically represents the largest operational cost in commercial aquaculture. This study confirms that more frequent feeding or higher protein content does not necessarily improve performance. Instead, brackish RAS operators can achieve stronger growth, better fish health, and greater feed efficiency by providing a 42% protein diet twice daily—supporting both profitability and sustainability.

By adopting this strategy, producers can reduce waste, improve biosecurity, and consistently deliver high-quality fish to market, reinforcing the role of controlled-environment systems in the future of sustainable aquaculture.