Introduction
The expansion of aquaculture production is driving the development of feed formulation strategies that improve sustainability, increase resilience to fluctuations of raw material prices, and enhance economic efficiency. Fish meal (FM) remains a key ingredient in marine fish diets due to its nutritional value and palatability; however, sustainability targets and formulation economics are encouraging a progressive reduction in FM inclusion. Consequently, cost-saving strategies increasingly focus on reducing FM levels or utilising alternative FM qualities, provided that growth performance and feed efficiency are maintained. Marine peptide concentrates (MPCs), characterised by high digestibility and functional bioactive properties, offer effective support for these approaches by enhancing nutrient utilisation and growth efficiency. This study evaluated the efficacy of a marine peptide concentrate (Pepsea F) as a functional additive in European seabass (Dicentrarchus labrax), assessing its ability to support FM inclusion reduction and FM quality substitution strategies while enhancing biological and economic performance.
Material and Methods
An 11-week feeding trial was conducted using European seabass with an initial mean body weight of 18 g. Fish were reared in a recirculating aquaculture system (RAS) using 150-L tanks stocked with 25 fish per tank under controlled conditions (water temperature 22.7 ± 1.2 °C). Feed was supplied twenty times per day using automatic feeders. Experimental feeds included the marine peptide concentrate, Pepsea F (liquid, 40% crude protein (CP40); Adisseo), at inclusion levels of 0.75%, 1.5% or 2.25% under two cost-reduction strategies: (i) partial replacement of high-quality FM (CP68), reducing inclusion from 20% to 10%, and (ii) substitution of FM quality from CP68 to CP60 at a constant 20% inclusion level. Each treatment was tested in triplicate. All experimental feeds were formulated to be isoproteic, isolipidic and isoenergetic. Growth performance parameters, including feed intake, specific growth rate (SGR), and feed conversion ratio (FCR), were measured. Data were analysed using one-way ANOVA followed by Tukey's post-hoc test (p < 0.05). An economic assessment based on feed cost, feed efficiency, biomass output, and return on investment (ROI) was conducted using Turkish raw material prices as reference (September 2025).
Results
Reduction of FM inclusion from 20% to 10% (CP68) negatively affected SGR and FCR when no functional additive was applied. However, supplementation with Pepsea F significantly restored and improved performance. Inclusion of 1.5% Pepsea F in the 10% FM diet resulted in a numerical 4% increase in feed intake, 5% in SGR and a 4% improvement in FCR compared to the 20% FM control diet, while simultaneously reducing feed formulation cost by 32 €/t. Improved feed efficiency corresponded to approximately 40 kg of feed saved per metric ton of feed, equivalent to 60 €/t in on-farm savings. Combined with feed formulation savings, total economic benefit reached 92 €/t of feed. In addition, increased growth performance resulted in a 5% increase in final biomass, corresponding to an additional 50 kg of fish per metric ton, equivalent to 325 € of extra income (farm-gate price: 6.5 €/kg). This scenario yielded an ROI of the additive of 8.
In the second strategy, replacement of FM quality from CP68 to CP60 negatively impacted growth and feed efficiency. Supplementation with 0.75% Pepsea F not only mitigated these effects but exceeded the performance of the 20% CP68 control diet, numerically improving feed intake by 1%, SGR by 4% and FCR by 2%. Feed reformulation reduced feed cost by 19 €/t, while improved FCR generated an additional 30 €/t in feed savings for producers (49 €/t combined). Biomass gains generated approximately 260 € of additional income per metric ton of fish produced. This scenario resulted in an ROI of 12.
Discussion
The results demonstrate that Pepsea F effectively compensates for both reduced FM inclusion and downgraded FM quality in European seabass feeds, maintaining or improving growth performance and feed efficiency relative to high-FM control diets. The observed improvements in SGR and FCR highlight the functional role of marine peptides beyond their nutritional contribution, linked to enhanced palatability and nutrient utilisation. Importantly, the substantial ROI values obtained across both formulation strategies confirm the economic relevance of Pepsea F inclusion, delivering benefits at both feed mill and farm levels. Overall, these findings support the use of marine peptide concentrates as sustainable, functional tools to optimise seabass feed formulations, reduce dependence on high-quality fish meal, and enhance profitability in marine aquaculture.