Aquaculture, or fish farming, is a major global source of seafood, supplying over half of the fish consumed worldwide. The careful selection and formulation of feed is central to this industry, directly influencing the growth rate, health, and nutritional profile of the farmed fish. A modern aquaculture diet is a highly engineered product designed to deliver precise energy and nutrient requirements for a specific species at a particular stage of development. This specialized feed is a significant factor in the overall cost of production and determines the environmental footprint of the farming operation.
The Standard Aquaculture Diet
The food provided to most farmed fish is manufactured into dry, energy-dense pellets using a process called extrusion, similar to how dry pet food or breakfast cereal is made. This process ensures the pellets float or sink slowly, allowing the fish to consume them efficiently before they dissolve, which minimizes waste in the water. The formulation is a carefully balanced blend of ingredients intended to create a complete diet, containing all necessary proteins, lipids, carbohydrates, vitamins, and minerals.
A typical modern feed pellet draws protein from plant sources such as soy meal, corn gluten, and wheat, which serve as the primary building blocks for muscle tissue. Energy is supplied through a combination of fats (lipids) and starches (carbohydrates), with oils providing a concentrated source of energy that fish metabolize efficiently. The final composition is adjusted based on the species’ specific nutritional requirements, ensuring the correct balance of amino acids for optimal growth.
The Role of Fishmeal and Fish Oil
Historically, the highest quality protein and lipid sources in aquaculture diets were derived from marine ingredients: fishmeal (FM) and fish oil (FO). Fishmeal is a fine powder made from cooking, pressing, and drying small, bony forage fish, though a growing amount now comes from fish processing trimmings. Fishmeal provides a highly digestible protein source with an ideal balance of amino acids required for fish growth.
Fish oil is particularly valued for its concentration of long-chain Omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which fish cannot synthesize in sufficient quantities themselves. These fatty acids are transferred directly to the farmed fish, contributing to the final product’s nutritional benefits. While these marine components were once a large percentage of many fish diets, the industry has significantly reduced their inclusion to alleviate pressure on wild forage fish stocks.
Feeding Different Fish Species
Diets for farmed fish are tailored to the natural feeding habits, or trophic level, of each species. Carnivorous species, such as Atlantic salmon, trout, and marine finfish like sea bass, naturally consume other fish in the wild and therefore require a diet high in protein and fat, historically relying heavily on fishmeal and fish oil. These species may require a diet containing 40 to 50 percent crude protein to support their growth.
In contrast, omnivorous species like tilapia, catfish, and carp have a more flexible diet and thrive on feeds containing a larger proportion of plant-based ingredients. These fish generally require a lower protein percentage, often ranging from 25 to 35 percent, and can effectively utilize proteins and oils from sources like soybeans and grains. The ability of these species to flourish on diets with minimal marine ingredients makes them a more environmentally efficient option in terms of feed resource use.
Sustainable Feed Innovation
The aquaculture industry is actively investing in new technologies to replace traditional ingredients, particularly fishmeal and fish oil, to improve sustainability and secure future feed supply. One major area of innovation is the use of novel protein sources that do not rely on agricultural land or wild-caught fish. These include insect meals, such as black soldier fly larvae, which can be grown on organic by-products and offer a high-quality protein and fat profile.
Another advancing alternative is single-cell protein, which refers to microbial biomass like bacteria, yeast, and microalgae grown in controlled fermentation systems. These cultivated microorganisms can provide a high concentration of protein and a favorable amino acid composition suitable for fish diets.
Furthermore, microalgae are being commercially cultivated specifically to produce oils rich in EPA and DHA, serving as a direct, land-based source of the Omega-3 fatty acids that traditionally came exclusively from fish oil.