Salmon farming is the practice of raising salmon in controlled environments for food, from egg to harvest. It’s the largest sector of finfish aquaculture and produces the majority of salmon sold in grocery stores and restaurants worldwide. Norway leads global production at roughly 1.5 million tonnes per year, followed by Chile at around 693,000 tonnes. The process typically begins in freshwater hatcheries on land and finishes in floating net pens anchored in coastal waters.
How Farmed Salmon Are Raised
Nearly all commercially farmed salmon are Atlantic salmon. The farming process mimics the natural salmon lifecycle but under controlled conditions. It starts in on-land hatcheries, where eggs are fertilized and incubated in freshwater tanks. After hatching, the juvenile fish (called fry) spend their first months feeding and growing in freshwater. During this stage, they undergo a biological shift called smoltification, which prepares their bodies to survive in saltwater.
Once the young fish are large enough and physiologically ready, they’re transported in aerated water tanks to marine net pens in coastal waters. These are large, open enclosures suspended in the ocean where the salmon continue growing for one to two more years until they reach market size, typically 4 to 5 kilograms. The entire cycle from egg to harvest takes roughly two to three years.
What Farmed Salmon Eat
Salmon are carnivorous fish, and their feed has changed significantly over the past few decades. In the 1980s, fishmeal made up about 70 percent of a farmed salmon’s diet. By 2017, that figure had dropped to around 25 percent. The rest now comes from plant-based ingredients, animal trimmings, added vitamins, minerals, amino acids, and fish oil. This shift was driven partly by sustainability concerns and partly by the rising cost of wild-caught fish used to make fishmeal.
One notable feed additive is astaxanthin, the pigment that gives salmon flesh its characteristic pink-orange color. Wild salmon get astaxanthin naturally by eating shrimp and krill. Farmed salmon receive it through their feed, either synthesized commercially or extracted from microalgae. Beyond color, astaxanthin serves a genuine nutritional purpose: it’s a powerful antioxidant (roughly 100 times more potent than vitamin E) that supports the fish’s immune system, liver function, and reproduction. It also carries over to the fillet, adding antioxidant value for people who eat it.
Feed Efficiency Compared to Other Proteins
One reason salmon farming expanded so rapidly is that salmon convert feed into body mass more efficiently than most land animals. Atlantic salmon have a feed conversion ratio of about 1.1 to 1.2, meaning it takes just over one kilogram of feed to produce one kilogram of fish. For comparison, beef cattle typically require 6 to 8 kilograms of feed per kilogram of weight gained, and pigs need around 3 to 4. This efficiency comes partly from the fact that fish are cold-blooded and don’t burn calories maintaining body temperature, and partly because they’re buoyant in water, so they expend less energy on movement and supporting their own weight.
Nutritional Profile: Farmed vs. Wild
Farmed and wild Atlantic salmon are the same species, and their nutritional profiles are closer than many people assume. A Norwegian study published in the journal Foods found that farmed salmon contains slightly more of the omega-3 fatty acids EPA and DHA than wild salmon: 0.5 grams of EPA per 100-gram serving compared to 0.4 grams in wild fish, and 0.9 grams of DHA compared to 0.8 grams. The higher values in farmed salmon come largely from its greater overall fat content.
Farmed salmon does tend to carry more total fat, including saturated fat, because it lives a less active life and receives a calorie-dense diet. Wild salmon is leaner. Both are considered excellent sources of protein and omega-3s, and both provide the astaxanthin antioxidant, though through different dietary pathways.
Environmental Concerns
Open-net pen farming, the dominant method globally, raises several environmental issues. The pens sit directly in the ocean, which means waste from fish feces and uneaten feed settles on the seafloor beneath them. In areas with poor water circulation, this can deplete oxygen levels and alter the ecosystem on the ocean bottom.
Sea lice are another persistent challenge. These small parasites thrive in the dense populations inside net pens and can spread to wild salmon migrating past farms. Managing sea lice drives significant costs for the industry and has prompted the development of various treatments, from warm-water baths to cleaner fish that eat the parasites off the salmon.
Escapes from net pens also pose a risk. When farmed Atlantic salmon escape into the wild, they can interbreed with wild populations, potentially weakening the genetic fitness of native stocks. They also compete with wild fish for food and habitat.
Land-Based Farming as an Alternative
A growing segment of the industry is moving salmon production entirely onto land using recirculating aquaculture systems, or RAS. These indoor facilities recycle up to 99 percent of their water daily and give operators precise control over temperature, water quality, and biosecurity. Because the fish are fully contained, there’s no risk of escape into wild ecosystems and no direct transmission of parasites to wild fish.
RAS facilities can also be built far from the coast, closer to the markets they serve, which cuts transportation costs and delivers fresher product. The feed conversion ratio in land-based systems averages about 1.125, roughly 11 percent more efficient than traditional sea-pen farming. In Norway, an estimated 70 percent of young salmon destined for sea pens are already raised in freshwater RAS before transfer.
Several large-scale RAS operations are now producing market-size salmon entirely on land. A facility in Denmark produces 4,000 tonnes per year, completing the full cycle in about two years. The Atlantic Sapphire facility in Florida has a planned capacity of 10,000 tonnes annually. Industry estimates suggest a minimum production of 5,000 tonnes per year is needed for a land-based operation to be economically viable, which limits entry to well-capitalized companies. Energy costs remain the biggest hurdle, since these systems require constant pumping, filtration, and temperature control.
Certification and Standards
The Aquaculture Stewardship Council (ASC) runs the most widely recognized certification program for salmon farms. To earn ASC certification, a farm must meet requirements covering biodiversity impact, feed sourcing, pollution control, disease management, and human rights practices. Certified farms are also required to maintain a high level of transparency, regularly monitor key environmental indicators, and make some of that performance data publicly available. Retailers and consumers use the ASC label as a shorthand for farms that meet a baseline of environmental and social responsibility, though certification doesn’t eliminate all concerns associated with open-net farming.