U.S. Soybean Export Council-backed study finds soy protein concentrate can fully replace fish meal in sea bass diets

TÜRKİYE – A collaborative aquaculture feeding trial conducted by Aquaspin Ltd., Çukurova University, and feed manufacturer Özpekler Yem has found that soy protein concentrate derived from U.S. soybeans can fully replace fish meal in European sea bass diets without negatively affecting fish growth, feed conversion, or survival rates.

The study, supported by the U.S. Soybean Export Council (USSEC), evaluated the use of soy protein concentrate (SPC) in diets for European sea bass (Dicentrarchus labrax), one of the Mediterranean region’s most valuable farmed marine fish species.

Researchers tested five commercial-style diets in which SPC replaced fish meal at levels ranging from 0% to 100% during an eight-week feeding trial conducted in a fully automated marine recirculating aquaculture system (RAS) in Türkiye.

According to the findings, fish performance remained statistically comparable across all treatments despite the gradual removal of fish meal from the formulations.

Final body weight ranged from 114.5 g to 120.2 g per fish, while feed conversion ratios remained between 1.06 and 1.14. 

Survival rates ranged from 98.9% to 100%, with researchers also reporting no significant differences in daily feed intake, indicating strong palatability of the soy-based diets.

The study concluded that U.S. SPC could replace up to 100% of fish meal in European sea bass diets without compromising weight gain, feed efficiency, or fish health.

Aquafeed sector seeks alternatives to fish meal

The findings come as aquafeed manufacturers globally continue to search for scalable and cost-effective alternatives to fishmeal amid tightening marine resource supplies and increasingly volatile prices.

Fish meal has traditionally served as the primary protein source in diets for carnivorous fish species such as sea bass, salmon, and sea bream because of its high digestibility and amino acid profile. 

However, rising sustainability concerns and fluctuating supply linked to wild fish catches have accelerated interest in plant-based proteins.

The pressure is particularly significant in the Mediterranean, Middle East, and North Africa regions, where marine aquaculture production continues to expand rapidly.

According to the Food and Agriculture Organization, global aquaculture production has surpassed 130 million metric tons in recent years, supplying more than half of the seafood consumed worldwide.

European sea bass remains one of the region’s most commercially important species, especially in Türkiye, Egypt, Greece, and other Mediterranean markets.

Türkiye alone has become one of Europe’s leading sea bass producers, supported by strong export demand and expanding investments in marine farming.

Additional insights for RAS production systems

Beyond growth performance, the trial also evaluated faecal characteristics and particle-size distribution, factors that are increasingly important in intensive RAS production systems, where water quality and solids removal efficiency directly affect operational performance.

Researchers found that moderate SPC inclusion levels of 25%-50% produced the most stable faecal aggregates, thereby supporting efficient solids capture in recirculating systems.

At higher inclusion levels of 75% to 100%, faecal particles shifted toward smaller intermediate fractions. 

The study suggested that formulation adjustments such as extrusion optimisation, ingredient blending, or the use of functional binders could further improve performance at maximum inclusion rates.

The findings are expected to strengthen the case for wider adoption of U.S. soy protein concentrate in marine aquafeed formulations for European sea bass, as well as other high-value carnivorous fish species farmed across the Mediterranean, Middle East, Africa, and global aquaculture markets.

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