Aquaculture, the farming of aquatic organisms, has become a primary source of seafood globally, supplying over half of the world’s fish. The manufactured diet provided to these farmed fish, often termed aquafeed, is arguably the single most influential factor in modern aquaculture production. Aquafeed is a nutritionally complete pellet designed to meet the specific biological needs of the farmed species at various stages of their life. Formulating this feed represents the largest operating expense for fish farmers, which drives continuous innovation to find the most cost-effective and biologically optimal ingredients available.
Core Components of Modern Aquaculture Feed
Marine-Derived Ingredients
The historical foundation of aquafeed was fishmeal and fish oil (FMFO), derived from small, wild-caught forage fish like anchovies and sardines. Fishmeal is a highly digestible protein source providing a nearly perfect balance of amino acids. Fish oil is rich in essential long-chain Omega-3 fatty acids. These ingredients were initially indispensable for carnivorous species like salmon and trout, which naturally consume other fish high in these nutrients.
The industry has significantly reduced its reliance on FMFO due to concerns over wild fish stock stability and the high, fluctuating cost of these ingredients. However, they remain necessary at certain inclusion levels for some species. The unique fatty acids in fish oil are not synthesized by the fish itself but are concentrated from their marine diet, making them important to the nutritional quality of the final product consumed by humans.
Plant-Based Ingredients
The shift away from marine resources led to the widespread adoption of terrestrial plant-based ingredients as primary protein and energy sources. Soybean meal is the most commonly used plant protein, valued for its high protein content, widespread availability, and cost-effectiveness. Other ingredients include concentrates from corn and wheat, which serve as sources of energy and carbohydrates.
Plant proteins lack the complete amino acid profile that fish require compared to fishmeal. Formulators must supplement these plant-heavy diets with specific synthetic amino acids, such as lysine and methionine, to ensure the fish receives all essential nutrients. Wheat products also function as binders to create the stable, water-resistant pellet structure required for efficient feeding.
Specialized Diets and Species-Specific Needs
A single, universal “fish feed” does not exist, as nutritional requirements vary based on the species being farmed. The primary distinction in feed formulation is made between carnivorous, omnivorous, and herbivorous species. Carnivorous fish, such as Atlantic salmon and marine finfish, require diets high in protein and fat, traditionally needing higher levels of marine ingredients to match their natural diet.
In contrast, herbivorous species like grass carp and omnivorous fish such as tilapia and catfish have a greater physiological tolerance for plant-based proteins. Their digestive systems are better adapted to efficiently utilize nutrients from ingredients like soybean meal and corn. Feed for omnivorous fish can therefore be formulated with significantly lower, or even negligible, amounts of marine products compared to feed for carnivorous species.
Beyond the species, the fish’s life stage dictates significant changes in its diet formulation. Newly hatched fry require a highly concentrated, energy-dense feed with easily digestible proteins to support rapid early development. As the fish enters the grow-out phase, the focus shifts to maximizing feed efficiency and growth, involving adjustments to protein-to-energy ratios. Broodstock, the mature fish kept for reproduction, receive specialized feeds fortified with vitamins and lipids to enhance egg quality and reproductive success.
Emerging Novel Ingredients for Sustainability
The drive for sustainability and cost reduction has spurred substantial investment in developing novel ingredients to replace traditional feed sources. Insect protein, particularly from black soldier fly larvae (BSFL), has emerged as a promising alternative protein source. These insects can be grown on agricultural byproducts and waste streams, offering a protein source that is highly digestible for many fish species.
Algae and microbes are increasingly cultivated as a reliable, land-independent source of the long-chain Omega-3 fatty acids EPA and DHA. By using microalgae, feed producers can directly provide these essential fatty acids, reducing the need for fish oil derived from wild-caught fish. Single-cell proteins (SCPs), derived from yeast or bacteria, offer a high-quality, high-volume protein option. SCP production is consistent and not subject to the volatility of agricultural harvests.
The industry is also embracing circularity by utilizing processing waste and byproducts from other food sectors. This includes processed animal proteins from poultry or rendered products, as well as trimmings and offcuts from fish processing, which are diverted into aquafeed production. This approach maximizes the use of existing resources and minimizes the environmental footprint.
Feed Additives and Regulatory Oversight
A small but important fraction of aquafeed is composed of functional feed additives, included for specific purposes beyond bulk nutrition. Pigments, such as the carotenoid astaxanthin, are added to the feed for salmon and trout to achieve the characteristic pink or red color. Since farmed fish do not consume the small crustaceans that provide this pigment in the wild, it must be supplemented.
Other non-nutritive additions include specialized premixes of vitamins and minerals, which ensure the fish’s complete micronutrient requirements are met. Additives like probiotics and prebiotics are incorporated to promote a healthy gut microbiome, which enhances nutrient absorption and supports the fish’s immune system, helping to prevent disease. Technological additives, such as organic acids and preservatives, are also used to inhibit microbial growth and extend the shelf life of the feed pellets.
The manufacture and composition of aquafeed are subject to stringent regulatory oversight by governmental bodies, such as the Food and Drug Administration in the US and the European Commission in the EU. These regulations ensure that all ingredients and additives are safe for the fish, the environment, and the consumer. The approval process requires extensive evaluation to confirm effectiveness and prevent unauthorized substances from entering the food supply chain.