Costco’s farm-raised Atlantic salmon is safe to eat. Its contaminant levels fall well below regulatory safety limits, and the retailer has taken concrete steps over the past decade to clean up its supply chain. That said, there are a few nuances worth understanding about farmed salmon in general, from antibiotics to how often you should eat it.
Contaminant Levels Are Low
The two contaminants people worry most about in fish are mercury and PCBs (industrial pollutants that persist in the environment). Farmed Atlantic salmon is one of the lowest-mercury fish you can buy. Fresh and frozen salmon averages just 0.022 parts per million of mercury, according to FDA testing. The FDA’s safety threshold is 1.0 ppm, meaning salmon comes in at roughly 45 times below that limit.
A large Norwegian study measuring farmed, escaped, and wild Atlantic salmon found that farmed fish actually had lower mercury and PCB levels than wild salmon. Farmed salmon averaged about 0.018 ppm mercury compared to 0.056 ppm in wild fish, both far below the EU maximum of 0.5 ppm. PCB levels in farmed salmon were also lower, at about 0.003 ppm versus 0.005 ppm in wild salmon. Every sample in the study came in well under regulatory safety limits.
Dioxins and dioxin-like compounds are a separate category of concern. These are present in farmed salmon at very low levels, but they do accumulate in the body over time, which matters for how often you eat it (more on that below).
Costco Shifted Away From Heavy Antibiotic Use
Antibiotics in farmed salmon became a major issue in the mid-2010s, and Costco responded by restructuring its supply chain. Chile’s salmon industry was using enormous quantities of antibiotics: roughly 1.2 million pounds to produce 895,000 tons of fish in 2014, with usage jumping 25 percent from the prior year. Norway, by contrast, produced 1.3 million tons of salmon using just 972 kilograms of antibiotics in 2013. That’s a staggering difference.
Costco announced plans to source 60 percent of its salmon from Norway, cutting Chilean salmon by 40 percent. Much of Costco’s farmed salmon now carries Aquaculture Stewardship Council (ASC) certification, which prohibits the preventive use of antibiotics. Under ASC standards, medicines can only be administered after a veterinarian has diagnosed a specific disease, and farms must maintain a formal fish health management plan with strict biosecurity protocols.
What ASC Certification Actually Requires
The ASC label on Costco’s salmon packaging isn’t just marketing. Certified farms must keep sea lice (a common parasite) at low levels, monitor water quality at regular intervals for oxygen and phosphorus, minimize copper release from net pens, and track their feed ingredients back to responsibly managed sources. Wild fish used in feed must be traceable to sustainable fisheries, and soy ingredients face similar requirements.
Farms must also maintain high fish survival rates and publicly disclose any lethal incidents involving wildlife, such as seals or birds killed by farm infrastructure. None of this makes farmed salmon a perfect product, but it does set a floor for responsible production that uncertified farms don’t have to meet.
The Pink Color Comes From an Antioxidant
Wild salmon get their pink-to-red color from eating krill, algae, and small crustaceans that contain a pigment called astaxanthin. Farmed salmon eat pelletized feed, so astaxanthin is added to their diet to produce the same color. This sometimes alarms people, but astaxanthin is a naturally occurring antioxidant, not an artificial dye. The version added to feed is either synthesized to be chemically identical to the natural form or extracted directly from microalgae. It provides the same antioxidant benefits either way.
One Recall in Recent Years
In October 2024, Kirkland Signature smoked salmon was recalled after lab testing confirmed Listeria contamination. The recall was limited: 111 cases of a single lot distributed to Costco stores in Florida over a four-day window. No illnesses were reported. This was a smoked salmon product made by a third-party processor, not an issue with the raw farmed fish itself. Listeria recalls happen across the food industry and don’t indicate a systemic problem with Costco’s salmon supply.
How Often You Can Safely Eat It
This is where the picture gets more complicated. The EPA and FDA recommend two to three servings of fish per week for general health, and salmon is on their “best choices” list. Omega-3 fatty acids in salmon provide well-documented cardiovascular and cognitive benefits.
However, a risk analysis published in Environmental Health Perspectives found that dioxin-like compounds in farmed Atlantic salmon warrant some moderation. To stay within the lower end of the World Health Organization’s tolerable daily intake, the researchers recommended limiting most farmed salmon to fewer than 10 meals per month. For farmed salmon specifically from northern European sources like Norway and Scotland, the suggested limit was more conservative, generally fewer than four meals per month. Wild Pacific salmon had the most favorable profile, safe at four or more meals per week.
These recommendations reflect a precautionary approach. The contaminant levels in farmed salmon have declined since this research was conducted, as feed formulations have shifted to include more plant-based ingredients and less fish oil. Still, if you eat salmon several times a week, mixing in wild-caught varieties is a reasonable strategy. For most people eating farmed salmon once or twice a week, the health benefits of the omega-3s comfortably outweigh the trace contaminant exposure.
Special Considerations for Women and Children
Dioxin-like compounds have exceptionally long half-lives in the body, meaning they accumulate over years and decades. This is most relevant for girls, young women, and anyone who may become pregnant, because these compounds can affect fetal development. For this group, staying toward the lower end of consumption frequency for farmed salmon, and choosing wild Pacific salmon when possible, offers an extra margin of safety. Children benefit significantly from the omega-3s in fish, so the goal is moderation rather than avoidance.