the fish fillet sitting in your grocery store cooler has been through more than you think.
we've talked a lot about what's in processed food. seed oils, artificial dyes, preservatives with names you can't pronounce. but what about the fish that's supposed to be the "clean" option? the one your doctor recommends, the one people order when they're trying to eat right?
turns out, farmed fish — which makes up over 50% of all fish consumed globally — goes through a series of industrial interventions before it ever reaches your plate. let's walk through what actually happens.
the vaccine
mass vaccination of farmed fish is now standard practice worldwide. companies like PHARMAQ (owned by Zoetis, the largest animal health company in the world) have built machines capable of vaccinating up to 18,000 fish per hour using intraperitoneal injection — meaning a needle goes directly into the fish's abdomen.
the vaccines use oil-based adjuvants to boost immune response. a 2024 study published in the Israeli Journal of Aquaculture found that after vaccination, both european sea bass and barramundi developed granulomas — nodules of encapsulated oil and cellular debris — throughout their abdominal cavities. these lesions persisted through harvest. the study confirmed the granulomas were caused by the vaccine adjuvant, not any infection.
the fish still grew normally. the lesions just stayed there. the researchers noted the nodules "don't tend to dissolve with time."
to be clear: the fillet you eat comes from the muscle, not the abdomen. but the existence of industrial-scale injection programs — and the permanent residue they leave behind — is information most people have never been given.
the feed
what farmed fish eat is its own story.
farmed salmon, trout, and sea bass are fed pellets that typically contain fish meal, fish oil, soy, and a cocktail of additives. one of the most common is ethoxyquin.
ethoxyquin is a synthetic antioxidant used in fish feed to prevent the fats from going rancid. the EU suspended its authorization as a feed additive in 2017, citing insufficient safety data and a finding by the european food safety authority (EFSA) that one of its metabolites may be genotoxic. norway phased it out by 2019. it is still permitted in the united states.
a 2017 analysis by the swiss department for regional affairs found that farmed salmon frequently exceeded set limits for ethoxyquin contamination. the same compound is structurally related to antioxidants used in rubber manufacturing.
on top of ethoxyquin, farmed fish receive antibiotics in their feed to control bacterial infections common in high-density tank conditions — particularly streptococcus. while vaccination has reduced antibiotic use in some regions, it hasn't eliminated it.
the color
wild salmon is pink because of astaxanthin, a carotenoid that comes from the krill and shrimp they eat in the wild. farmed salmon eat pellets. their flesh is naturally gray.
so how do you get a pink fillet? you add astaxanthin to the feed. the synthetic version is made through chemical synthesis. there's even a "salmofan" — a color chart, similar to a paint swatch — that fish farmers use to select the exact shade of pink their salmon will be.
this isn't inherently dangerous, but it's something most people have no idea is happening when they pick up what they think is a natural, clean protein.
then there's carbon monoxide treatment. tuna and other fish are often exposed to carbon monoxide gas, which binds to the myoglobin in the muscle and locks in a bright red color — even as the fish degrades. the FDA permits this practice in the united states if it's disclosed on the label, but enforcement is inconsistent. the practice is banned in the EU, canada, and japan because it masks spoilage that would otherwise be visible.
what this means
none of this means you should never eat fish. wild-caught fish, particularly smaller species lower on the food chain, remain one of the cleaner animal proteins available.
but "farmed fish" is not a neutral label. it encompasses a production system involving mass injection programs, synthetic feed additives with incomplete safety records, synthetic pigments, and color-masking treatments.
the same way tallow exists to help you understand what's actually in your packaged food and restaurant meals, we think you deserve to know what's in your protein, too — not just the macros, but the full picture.
sources:
- Smirnov M, Hershko H, Ron TB. "Fish Welfare – A Case Study: Reviling for the first-time side effects of vaccination in European sea bass and barramundi." Israeli Journal of Aquaculture - Bamidgeh, 2024. doi:10.46989/001c.119024
- PHARMAQ Fishteq vaccination machine specs. pharmaq.com
- Hatchery International. "Advantages of NFT Vaccination Machines." hatcheryinternational.com
- EFSA Panel on Additives. "Safety and efficacy of a feed additive consisting of ethoxyquin." EFSA Journal, 2022. PMC8892239
- Błaszczyk A, Augustyniak A, Skolimowski J. "Ethoxyquin: An Antioxidant Used in Animal Feed." International Journal of Food Science, 2013. PMC4745505
- EFSA. "Ethoxyquin: EFSA safety assessment inconclusive." November 2015. efsa.europa.eu
- FDA. "Selecting and Serving Fresh and Frozen Seafood Safely." March 2024. fda.gov
- Djenane D, et al. "Carbon Monoxide in Meat and Fish Packaging." PMC, 2018. PMC5848116