Farm-raised salmon eat compressed pellets made from a mix of fishmeal, fish oil, and plant-based proteins. The recipe has changed dramatically over the past few decades. In the 1980s, salmon feed was about 70% fishmeal. By 2017, that figure had dropped to roughly 25%, with plant ingredients filling the gap.
Fishmeal and Fish Oil
Salmon are carnivores in the wild, eating smaller fish, krill, and shrimp. Traditional farm feed mimicked this by using 30 to 50% fishmeal and fish oil. Fishmeal is made by grinding and drying small forage fish like anchovies, sardines, and herring. Fish oil is pressed from the same species and provides omega-3 fatty acids that salmon need for healthy growth and that consumers value nutritionally.
The industry has steadily reduced its reliance on these marine ingredients, partly because of cost and partly because harvesting massive quantities of wild forage fish raises environmental concerns. Fishmeal and fish oil haven’t disappeared from the pellet, but they now share space with a growing list of terrestrial alternatives.
Plant Proteins in Modern Feed
Soy protein concentrate is one of the most common fishmeal replacements. It can supply up to 50% of the total protein in diets for younger salmon, and for larger fish, it can replace fishmeal entirely as a protein source. Other plant proteins used in feed include pea protein, corn gluten, and wheat gluten. Canola (rapeseed) meal also appears in many commercial formulas.
These substitutions aren’t perfect. Soy-heavy diets can leave salmon short on certain amino acids. Methionine, an essential building block for protein, typically needs to be added as a supplement. Taurine, another amino acid found naturally in fish-based diets, has also been identified as a beneficial addition when plant proteins dominate. Studies on Atlantic salmon found that diets with 20% soy protein produced growth comparable to pure fishmeal diets, but bumping soy to 40% of total protein led to significantly slower growth.
Fats and Omega-3s
Fish oil was historically the main fat source in salmon feed, providing the EPA and DHA omega-3 fatty acids that make salmon nutritionally valuable to humans. As fish oil has been partially replaced with plant oils like canola and soybean oil, the omega-3 content of farmed salmon has declined. Farmed Atlantic salmon contains roughly 1.2 grams of EPA plus DHA per 100 grams of flesh, which is lower than some wild species but still a significant dietary source.
The tradeoff is straightforward: less fish oil in the feed means less omega-3 in the fillet. This is one reason some producers are turning to algae-derived oils as a replacement. Algae are the original source of omega-3s in the marine food chain (small fish eat algae, bigger fish eat those small fish), so harvesting the fatty acids directly from fermented algae cells can restore omega-3 levels without requiring more wild-caught fish.
Astaxanthin for Color
Wild salmon get their pink-to-red flesh color from eating krill and shrimp, which are rich in a pigment called astaxanthin. Salmon cannot produce this pigment on their own. Without it in their diet, farmed salmon flesh would be gray. To replicate the natural color, producers add astaxanthin to the feed pellets at concentrations of 20 to 100 milligrams per kilogram of feed, administered throughout most of the growing period.
Wild salmon can accumulate up to 35 milligrams of astaxanthin per kilogram of muscle. Farmed salmon fed the standard range of 20 to 100 mg/kg of feed over about two weeks reach 3 to 8 mg/kg in their flesh. Higher feed concentrations produce higher muscle levels, but with diminishing returns. Most commercial astaxanthin is synthetic, though some producers use natural sources derived from yeast or microalgae, often marketing it as a premium feature.
How Feed Changes as Salmon Grow
Salmon don’t eat the same pellet their entire lives. Feed is adjusted in both size and composition as the fish grow from tiny fry to market-weight adults. Young salmon (2 to 70 grams) receive small, protein-dense pellets containing around 49% protein and 11 to 15% fat. These fish may be fed 7 to 14 times per day depending on whether feeding is done by hand or by automatic dispenser.
As salmon mature and move into sea pens, pellet size increases and the fat content rises significantly, sometimes reaching 30% or more. Adult salmon need more energy-dense feed to support rapid growth in cold ocean water. Feeding frequency drops as well. At water temperatures below 10°C or above 20°C, fish eat less actively and may only receive one to three meals per day.
Medications and Regulatory Oversight
Salmon feed can sometimes contain approved medications, typically antibiotics or antiparasitic treatments mixed into the pellets. In the United States, only drugs specifically approved by the FDA may be given to farmed fish. Strict withdrawal periods are enforced before harvest, meaning enough time must pass after medication for drug residues to clear the fish’s system. If a seafood product tests positive for unapproved drug residues, or for approved drugs above established tolerance levels, the FDA can take regulatory action against the producer.
The list of approved drugs for aquaculture is relatively short compared to land-based livestock. Norwegian and Scottish producers, who raise the majority of Atlantic salmon globally, operate under similarly strict European regulations on permitted feed additives and veterinary medicines.
Emerging Alternatives to Fishmeal
The salmon feed industry is actively testing ingredients that could further reduce dependence on both fishmeal and conventional crops. Black soldier fly larvae are one of the most promising options. The insects are high in protein, can be raised on food waste, and have a small environmental footprint. Single-celled organisms like yeast, bacteria, and mold are also being developed as protein sources through fermentation.
Some of these alternatives have already moved beyond the lab. Researchers in Hawaii successfully raised a marine fish species on a completely fish-free diet, using algae-based oil in place of fish oil. While fully fish-free diets aren’t yet standard for commercial salmon farming, they demonstrate where the industry is heading. The core challenge remains balancing cost, nutritional quality for the fish, and the omega-3 content that consumers expect in the final product.