Aquaculture has emerged as a vital contributor to global food security, with species such as seabass (Dicentrarchus labrax) and seabream (Sparus aurata) occupying a central role in European and Mediterranean production systems. However, the sustainability of this sector is increasingly challenged by the environmental and economic costs associated with aquafeeds. Feed production represents the largest contributor to both environmental impact and operational expenditure in aquaculture, making innovation in feed formulation essential for the long-term viability of the industry.
The Limitations of Conventional Fishmeal-Based Diets
Traditional aquafeeds for carnivorous fish rely heavily on fishmeal and fish oil derived from wild fisheries. These ingredients provide high-quality protein, essential fatty acids and excellent digestibility, making them ideal for supporting growth and health. Nevertheless, their use raises significant sustainability concerns. The extraction of wild fish for feed contributes to overfishing, ecosystem disruption and biodiversity loss, while also competing with human food resources. Furthermore, the volatility in supply and pricing of fishmeal has prompted the industry to seek more stable and sustainable alternatives.
As aquaculture production continues to expand, reducing dependence on marine-derived ingredients has become a priority. This has driven the development of innovative feed formulations incorporating alternative protein sources.
Blended Low-Fishmeal Diets: A Practical Solution
One of the most effective approaches to reducing fishmeal reliance is the development of blended diets, which combine multiple alternative ingredients to achieve a balanced nutritional profile. A notable example involves replacing approximately 50 percent of fishmeal with a mixture of fermented soybean meal, pea protein, yeast, krill meal and squid meal. In this formulation, fishmeal inclusion was reduced from around 51 to 25 percent, while maintaining overall dietary balance.
Importantly, this innovative diet did not negatively affect growth performance or survival in gilthead seabream. Physiological indicators, including blood parameters, remained stable and immune-related markers suggested enhanced innate defence capacity. Behavioural observations revealed only minor differences, such as slight variations in swimming activity, which were not indicative of reduced welfare. Overall, these findings demonstrate that substantial reductions in fishmeal are achievable without compromising fish health or performance.
Plant-Based and Fermented Ingredients
Plant-derived proteins are among the most widely explored alternatives to fishmeal. Ingredients such as soybean meal, pea protein and wheat gluten are attractive due to their availability and cost-effectiveness. However, their use is often limited by anti-nutritional factors that can impair nutrient absorption and affect fish health.
To address these challenges, processing techniques such as fermentation have been introduced. Fermented soybean meal, for example, exhibits improved digestibility and reduced levels of anti-nutritional compounds, making it more suitable for inclusion in carnivorous fish diets. When carefully formulated, plant-based diets can support satisfactory growth and physiological stability, although balancing essential amino acids remains a critical consideration.
Insect-Based Diets and Novel Protein Sources
Insect meals have gained significant attention as a sustainable alternative to conventional protein sources. Species such as the black soldier fly (Hermetia illucens) and the mealworm (Tenebrio molitor) are particularly promising due to their ability to convert organic waste into high-quality protein efficiently. These systems require substantially less land and water than traditional livestock production, contributing to reduced environmental impact.
From a nutritional perspective, insect meals provide a favourable composition of proteins and lipids, making them suitable for aquafeeds. Their inclusion has been associated with comparable growth performance in several fish species, although further research is needed to optimise inclusion levels and assess long-term effects.
Animal By-Products and Circular Economy Approaches
Another important category of alternative ingredients is animal by-products, particularly poultry by-product meal (PBM). Derived from parts of poultry not used for human consumption, PBM offers a protein profile similar to fishmeal and represents an efficient use of existing resources. Its incorporation into aquafeeds aligns with circular economy principles by reducing waste and adding value to by-products.
Studies have shown that diets incorporating PBM can maintain growth performance while lowering environmental impact compared to traditional fishmeal-based feeds. However, ensuring consistent quality and nutritional balance remains essential for its successful application.
Functional Ingredients from Aquaculture Side Streams
Innovation in aquafeeds is not limited to replacing fishmeal but also extends to the valorisation of aquaculture by-products. Processing residues such as heads, bones, and viscera can be converted into protein hydrolysates through enzymatic hydrolysis. These hydrolysates are rich in bioactive peptides and exhibit high digestibility.
Research indicates that such ingredients possess functional properties, including antioxidant activity and potential health benefits, which may enhance fish performance and resilience. This approach contributes to improved resource efficiency and supports the development of circular production systems within aquaculture.
Environmental Assessment and Sustainability Benefits
The environmental performance of innovative aquafeeds is commonly evaluated using Life Cycle Assessment (LCA). This methodology considers the entire production chain, from raw material sourcing to feed manufacturing. Studies have demonstrated that replacing fishmeal with alternative ingredients such as insect meal or poultry by-products can significantly reduce greenhouse gas emissions, in some cases by up to 60 percent.
Nevertheless, the sustainability of these diets depends not only on ingredient selection but also on production processes, energy use, and supply chain logistics. Optimising these factors is crucial to maximising environmental benefits.
Balancing Sustainability with Fish Welfare
A central challenge in feed innovation is ensuring that sustainability gains do not come at the expense of fish welfare. Diets must support not only growth but also immune function, physiological stability, and natural behaviour. This is particularly important in organic aquaculture systems, where the use of antibiotics is restricted.
Evidence from recent studies indicates that well-formulated alternative diets can meet these requirements. Blended diets, in particular, offer a practical solution by combining complementary ingredients to achieve nutritional adequacy while reducing environmental impact. Advances in monitoring technologies, including behavioural tracking and physiological sensors, are further enhancing our understanding of how diet influences fish welfare.
Future Perspectives
Despite significant progress, challenges remain in the widespread adoption of innovative aquafeeds. Regulatory constraints, variability in ingredient supply, and economic considerations all influence their feasibility. Additionally, consumer perceptions of novel feed ingredients may affect market acceptance.
Future research should focus on refining feed formulations, improving processing technologies, and integrating circular economy principles into aquaculture systems. Continued use of tools such as LCA will be essential in guiding sustainable decision-making.
Conclusion
Innovation in seabass and seabream diets is driving the transition towards more sustainable aquaculture systems. The development of specific feed strategies—including blended low-fishmeal diets, plant-based formulations, insect meals, animal by-products, and protein hydrolysates—demonstrates that environmental impact can be reduced without compromising fish health or performance. By combining technological innovation with responsible resource management, aquaculture can move towards a more resilient and sustainable future.
