FAQ
What people ask most about farmed salmon
Short answers taken from the ABC. If you want the detail, each one links to its chapter.
If you came with a specific question, start here. Each answer is the short version. At the end there is a link to the chapter with the full text and sources.
If farmed salmon are treated with antibiotics, are they safe to eat?
Yes. The farmed salmon that reaches the market is safe for human consumption.
As with other animal production for food (chicken, beef or milk), veterinary medicines are strictly regulated. Antibiotics are not used to make fish grow. They are used only to treat bacterial diseases when needed.
When a fish is treated, the rules require a withdrawal period: a mandatory interval between the end of treatment and harvest. During that period the drug is cleared from the fish's body.
In addition, before it is sold, the product must meet the Maximum Residue Limits (MRLs) set by international scientific bodies. If a product does not meet those limits, it cannot be sold or exported.
Chile exports salmon to more than 100 countries, including markets with very strict food safety controls such as the United States, Japan and the European Union. Those authorities run their own independent checks on imported food.
In practice, cases where a salmon product exceeds residue limits are extremely rare, and when it happens the product simply cannot be sold.
What are the main diseases affecting farmed salmon in Chile?
As in any animal production system, salmon can get sick. In Chile, the main health problems in farming are bacterial, parasitic and viral diseases. In the early freshwater stages, fungal infections can also occur.
Today, one of the main health challenges in Chilean salmon farming is SRS, or salmonid rickettsial septicemia, a bacterial disease caused by Piscirickettsia salmonis. Caligidosis is also very important. It is caused by the sea louse (Caligus rogercresseyi), an external parasite that affects the skin and mucus of the fish. Among viral diseases, the best known is infectious salmon anemia (ISA), which remains under permanent health surveillance.
In freshwater, the most important diseases are flavobacteriosis, fungal infections (mycoses) and infectious pancreatic necrosis (IPN), although their importance varies by species. BKD, or bacterial kidney disease, also has to be considered. It is usually associated with that early phase, but it can persist in the fish and show up later, even during grow-out at sea.
These diseases are controlled through a combination of vaccination, health monitoring, coordinated management between farm sites, programs regulated by the authorities and genetic improvement. As a result, many are better controlled today than in earlier decades, although fish health remains one of the industry's major challenges.
Is it true that salmon is a healthy food and a good source of omega-3?
Yes. Salmon is a healthy food and one of the richest natural sources of omega-3, especially EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These nutrients are associated with cardiovascular health benefits and also play important roles in the brain and vision.
One reason salmon stands out is that it provides far more marine omega-3 than most animal proteins common in the diet. A serving of salmon can provide more than one gram of EPA + DHA, while foods such as chicken, beef, pork or eggs usually provide much smaller amounts. Salmon combines high-quality protein with a much higher concentration of marine omega-3.
That is why many dietary guidelines recommend eating oily fish, such as salmon, at least twice a week. Besides omega-3, salmon provides protein of high biological value, vitamin D, vitamin B12, selenium and other essential nutrients.
Do salmon farming companies care about fish welfare?
The welfare of farmed salmon is protected by maintaining good environmental and handling conditions throughout their life cycle. This includes water quality, oxygen levels, temperature, feeding, health status and the number of fish in each farming unit.
When those conditions are not right, fish can become stressed, eat less, get injured or become more vulnerable to disease. That is why farm sites continuously monitor fish behavior, appetite, the condition of skin and gills, and the presence of parasites or disease.
Some moments are especially sensitive, such as treatments, transport and harvest, when handling must be done carefully to reduce stress and avoid unnecessary harm. Fish welfare is a condition for producing healthy fish and running a responsible farm.
How is the condition of the seabed under farm sites assessed?
The condition of the seabed under farm sites is assessed through periodic studies called INFAs (Informaciones Ambientales, a type of environmental report). These assessments check whether the area under the site still has adequate conditions for a new production cycle to begin, that is, for fish to be stocked at the site again.
The studies analyze the sediment and the environment near the seabed, including dissolved oxygen and other physical and chemical indicators. That information determines whether the site is in aerobic or anaerobic condition. An aerobic condition means the seabed still has oxygen and shows no severe signs of disturbance linked to farming. An anaerobic condition means the site has lost those conditions and needs to recover before it can operate again.
If the INFA finds an anaerobic condition, the site cannot stock new fish until a new assessment confirms a return to aerobic condition. The INFA describes the environmental state of the seabed and determines whether the site can start a new production cycle.
What do farmed salmon eat?
Today farmed salmon eat mainly extruded feed: small dry pellets that contain the nutrients the fish needs to grow.
Although salmon is a carnivorous species, its diet today depends much less on fishmeal and fish oil than it did decades ago. Feeds now combine a larger share of plant-based ingredients (soy, wheat and vegetable oils) with a smaller share of marine ingredients, plus vitamins, minerals and other nutritional additives.
This shift came from decades of research in aquaculture nutrition. The goal has been to maintain the fish's growth, health and production efficiency while reducing reliance on resources from fisheries.
Salmon is still one of the most efficient animals for producing protein. Its feed conversion ratio is usually close to 1.2: it needs just over 1 kg of feed to gain 1 kg of weight. That is a low figure compared with other commonly eaten animal proteins.
What are El Niño and La Niña, and how can they affect salmon farming?
El Niño and La Niña are phases of a natural climate phenomenon called ENSO (El Niño-Southern Oscillation), which occurs in the equatorial Pacific Ocean and can change sea temperature, rainfall, winds and marine productivity in different regions of the world.
El Niño is an unusual warming of surface waters in the central and eastern Pacific: the area stretching from the middle of the Pacific Ocean toward the coasts of South America. La Niña is the opposite phase, linked to the cooling of those waters.
In Chilean salmon farming, these phenomena can influence the environmental conditions where fish are farmed. El Niño can raise risks linked to higher water temperature, lower oxygen availability, changes in the water column and harmful algal blooms. A landmark case was the 2015-2016 El Niño event, known as the “Godzilla El Niño” for its intensity. During the southern summer of 2016, this event, together with other regional climate factors, contributed to a massive bloom of Pseudochattonella cf. verruculosa in Chilean Patagonia, which killed about 12% of Chile's salmon production.
La Niña is usually associated with colder waters and, in some areas, higher marine productivity. That does not automatically make it a favorable condition. Its effects depend on how they combine with local temperature, rainfall, winds, salinity, oxygen, the presence of microalgae and the health status of the fish.
El Niño and La Niña are relevant climate signals, not direct predictions of what will happen at each farm site. The best response is to strengthen environmental monitoring, early warning systems and preventive management plans.
What is melanosis?
Melanosis is the appearance of dark spots in salmon muscle, mainly in Atlantic salmon (Salmo salar), the most farmed species in Chile and Norway. These spots are also known as “black spots” or focal melanized changes.
In recent years it has become a significant problem for the industry, because it affects the appearance of the fillet and can lower its commercial value. Chile has no official, public, industry-wide figure, but various technical and industry reports indicate that in Atlantic salmon it may affect around 15-20% of fillets, with some recent estimates putting it as high as about 22%.
It is not considered a food safety problem for people. It is a product quality problem: affected areas may have to be trimmed, or the fillet may be downgraded.
The spot is caused by a buildup of dark pigments, mainly melanin, associated with persistent inflammation and cell damage in the fish's muscle. Melanin is a natural pigment involved in defense and repair responses. When it is deposited in muscle, it can create these dark areas visible in the fillet.
Its causes are not fully understood. The evidence points to a multifactorial phenomenon, associated with chronic inflammation, immune response, vaccination, infections, muscle damage, stress, nutrition, genetics and farming conditions. It cannot be attributed to a single cause.
Prevention aims to reduce the factors that promote inflammation or tissue damage: improving the fish's overall health, avoiding rough handling, optimizing vaccination, controlling disease, reducing stress and ensuring well-formulated diets with adequate levels of antioxidants and essential fatty acids.
Why are lights used in salmon farming?
Salmon farms use lights to manage the photoperiod, that is, the number of hours of light and darkness the fish perceive. For salmon, light works as an environmental signal that tells them whether they are in a season of long days, such as spring and summer, or short days, such as fall and winter.
This signal is picked up mainly by the eyes and by the pineal gland, a structure involved in producing melatonin. Melatonin is a hormone that rises in darkness and helps set the fish's biological clock. When long days or continuous light are applied, the nighttime melatonin signal drops, which makes it possible to influence processes such as smoltification, growth and sexual maturation.
In freshwater, lights are used to schedule or bring forward smoltification, the process through which salmon prepare physiologically to move from freshwater to the sea. At sea, they are used mainly to delay sexual maturation and support growth, since early maturation can affect fillet quality and commercial value.
Many lights used at farm sites look green or blue-green at night. That is deliberate: salmon perceive those wavelengths efficiently, and they help reduce the nighttime melatonin signal. Lights are also used with broodstock to manage maturation and spawning periods, which allows more planned production of eggs and juvenile fish.