What is the downside of farmed salmon?

December 25, 2025 •

3 min read

Over 70% of the world's salmon now comes from farms, yet many consumers are unaware of the significant downside of farmed salmon that affects both environmental health and human nutrition.

Quick Summary

This article investigates the critical environmental issues and potential health concerns associated with farmed salmon, comparing it to its wild counterpart and exploring the consequences of intensive aquaculture.

Key Points

Environmental Damage: Open-net salmon farms release concentrated waste, including feces and uneaten feed, leading to water pollution and oxygen-depleted 'dead zones' that harm marine ecosystems.
Disease and Parasite Spread: The high density of farmed salmon promotes the spread of diseases and parasites, like sea lice, which can then infect vulnerable wild salmon populations.
Contaminants in Feed: Farmed salmon have been shown to contain higher levels of industrial contaminants, such as PCBs and dioxins, which can accumulate in the fish's fatty tissues from their diet.
Less Favorable Nutritional Profile: Compared to wild salmon, farmed varieties have a higher overall fat content and a less optimal ratio of healthy omega-3 to inflammatory omega-6 fatty acids.
Impact on Wild Fish: Escapee farmed salmon threaten wild populations by competing for resources and potentially interbreeding, which can compromise the genetic integrity of wild stocks.
Increased Antibiotic Use: Crowded farm conditions necessitate the use of antibiotics to control disease, contributing to the broader public health issue of antibiotic resistance.

The Environmental Impact of Intensive Salmon Farming

Open-net pen systems commonly used in salmon farming pose significant environmental challenges as they exchange water with the surrounding ocean.

Waste and Water Pollution

Farms produce substantial waste, including feces and uneaten food, rich in nutrients like nitrogen and phosphorus. This waste settles on the seafloor, potentially leading to eutrophication, harmful algal blooms, and depleted oxygen levels that create 'dead zones' and threaten marine life.

Disease and Parasite Transfer

High fish densities in pens facilitate the rapid spread of diseases and parasites, which can then transfer to wild fish populations. Sea lice, for instance, can reach epidemic levels on farms and harm wild juvenile salmon. Treating outbreaks with pesticides and antibiotics introduces more chemicals into the environment.

Escapees and Genetic Threat

Farm-raised salmon escapes are frequent, releasing non-native species that compete with wild fish for resources. Interbreeding between farmed and wild salmon can weaken the genetic diversity and resilience of wild stocks.

Potential Health Concerns from Farmed Salmon

Farmed salmon's environment and diet can influence its nutritional value and present potential health considerations.

Higher Levels of Contaminants

Historically, farmed salmon contained higher levels of contaminants like PCBs and dioxins linked to feed ingredients. While improved practices have reduced these, some concerns about toxin exposure remain.

Increased Saturated Fat and Omega Imbalance

Farmed salmon typically has more fat, including omega-3s, but also a higher ratio of omega-6 to omega-3 fatty acids due to plant-based feed. An imbalanced ratio can contribute to inflammation.

Antibiotic Use and Resistance

Antibiotics are used to manage diseases in crowded farm conditions. This practice raises concerns about the development and spread of antibiotic-resistant bacteria.

Comparison: Wild vs. Farmed Salmon


Feature	Wild Salmon	Farmed Salmon
Environment	Free-ranging, oceans and rivers.	Confined open-net pens or tanks.
Diet	Natural diet of smaller fish and crustaceans.	Processed, high-fat pellets, some plant-based.
Nutritional Fat	Lower in fat, high omega-3 content.	Higher in total fat, may have less optimal omega-3 to omega-6 ratio.
Contaminants	Typically lower levels of pollutants.	Potential for higher levels of PCBs and dioxins.
Coloration	Naturally vibrant pink/red from diet.	Naturally paler; fed astaxanthin pigment to achieve color.
Environmental Impact	Minimal if responsibly managed.	Waste pollution, disease transfer, escapes, feed source issues.
Animal Welfare	Natural migratory behaviors.	Confinement can cause stress and disease.
Cost & Availability	More expensive, seasonal.	More affordable, available year-round.

Conclusion: Navigating Your Salmon Choices

The downsides of farmed salmon include environmental damage and potential health and nutritional differences. While aquaculture is improving, open-net pens still pose risks. Informed consumers can look for certifications like ASC or BAP, or choose wild-caught salmon when possible. Weighing cost and availability against environmental and health factors is key. More information on responsible choices is available from Seafood Watch.

What you can do to make informed choices

Look for certifications: Seek certifications from organizations like ASC or BAP for farmed salmon.
Understand your source: Check labels for farmed versus wild-caught and ask retailers for information.
Balance your intake: Include a variety of fish and protein sources in your diet.
Prioritize sustainable options: Choose sustainably sourced wild-caught salmon when feasible.
Cook intelligently: Trim fat, skin, and the belly flap to potentially reduce contaminant exposure.

Frequently Asked Questions

Yes, farmed salmon is generally considered safe to eat, with contaminant levels typically regulated by government food safety standards. However, some studies have found higher levels of certain pollutants in farmed fish compared to wild salmon.

Wild salmon get their distinct pinkish-red color from a natural diet rich in astaxanthin, a carotenoid found in krill and shrimp. Farmed salmon have a naturally gray flesh and are fed synthetic astaxanthin to achieve the desired color for marketability.

Farmed salmon can negatively affect wild populations through several mechanisms, including the transfer of diseases and parasites from densely packed pens, competition from escaped farmed fish, and potential genetic interference from interbreeding.

Farmed salmon is higher in total fat and calories, and while rich in omega-3s, its diet can result in a less favorable omega-3 to omega-6 ratio compared to leaner, wild salmon. Wild salmon often has more minerals due to its natural diet.

The sustainability of salmon farming is highly debated. While it reduces pressure on wild fish stocks, common open-net pen practices can cause significant environmental harm through pollution, parasite transfer, and fish escapes. Some modern practices and certifications aim to mitigate these impacts.

Farmed salmon typically has a milder, fattier taste and a softer texture due to its high-fat diet and sedentary lifestyle. Wild salmon, which swims long distances, is leaner with a firmer texture and a more complex, robust flavor.

Antibiotics are used in salmon farms to prevent and treat diseases that flourish in the crowded, high-density conditions of the pens. The practice raises concerns about antibiotic resistance both in the environment and in humans.

The choice depends on your priorities. For lower cost and year-year-round availability, farmed salmon is a choice. For a more natural flavor, better omega-3 ratio, and lower contaminant levels, wild-caught is preferable, though more expensive. Prioritizing certified, sustainably-sourced options is a good practice.