In the 1990s, the divide between wild and farmed fish felt moral as much as culinary. Farmed salmon became shorthand for industrial excess—crowded pens, antibiotics, polluted bays, and the irony of feeding wild fish to captive ones. Wild fish, meanwhile, carried an aura of purity, even as global stocks were thinning under overfishing.

Over time, that simple story has shifted. Aquaculture expanded and, in many regions, improved: antibiotics declined, feeds became more efficient, and certification schemes promised accountability. At the same time, wild fisheries revealed their own vulnerabilities—bycatch, habitat destruction, and fragile management regimes.

Today, the question is less about which fish feels virtuous and more about which system can endure in a changing climate—and which has the lesser carbon footprint. The answer is not as straightforward as you might wish. It depends not just on the species, but where, when, and how it was caught. And new advances continue to change the math as well.

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Wild Fish Math

1.  Follow the Fuel. A whopping 60-90% of fishing’s carbon emissions come from just one source: boat fuel, typically some form of gasoline, diesel, natural gas, or other petrochemicals. This means that a huge part of any seafood’s carbon footprint comes down to how far boats have to go—and how much fuel they have to burn—to reach their catch. Case in point, many crustaceans like lobster and crab can be especially carbon intensive, since fishers have to chug their boat from distant crab pot to distant crab pot (rather than, say, capturing a whole school of sardines at once). Greener fuels and getting boats on battery power is something the industry is working on (including this demonstration project for electric lobster boats), but it’s been slow-going.

2.  Beware of Averages. The number crunching gurus Hannah Richie and Max Roser over at Our World in Data have made an excellent chart comparing the carbon footprint of wild vs farmed fish. It packs a lot of information, but if there’s one take-home message, it is beware of the averages. Take salmon, for example. The carbon footprint of wild-caught salmon can be lower than either its farmed counterpart or even chicken, but that huge bar represents a wide range of actual carbon costs. Farmed, meanwhile, has a much narrower range. Richie and Roser’s conclusion: while wild could be better, picking farmed may actually be a safer bet for low-carbon protein.

Source: Our World in Data

3. Tuna Salad Surprise. In 2025, scientists from Johns Hopkins did a huge analysis of the environmental impacts of different kinds of seafood. One option that might be better than you’d guess: canned tuna. But not necessarily because it’s tuna, but because it’s canned. About 25% of the seafood harvest (farmed or wild) is lost to food waste. Food waste can generate emissions on its own, by releasing methane as it rots—but waste also drives up the cost-per-pound of the stuff we do eat. If you let half a fish go bad, you don’t get half your money back; you just made the bit you did eat twice as expensive. Same with the carbon “spent” while fishing. But shelf-stable options, like canned tuna, can last for years and years. In fact, Johns Hopkins found that a kilo of canned seafood only released a bit over 5 kilos of carbon dioxide on average, compared to roughly 15 for fresh or frozen options.

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Farmed Fish Math

1.  Follow the Feed. If boat fuel is the biggest carbon cost for wild-caught fish, fish feed is the one for farms. A 2023 study found that feed accounted for more than 55% of farmed salmon’s emissions. This is partly due to the fact that farmed fish are fed other fish, including wild-caught ones—which means we then have to add the carbon cost of those fish into the equation. Salmon are particularly voracious pescivores, needing to eat about two pounds of other fish for each pound they put on. That said, other farmed fish, such as tilapia, carp, or catfishes, need almost no other fish in their feed nowadays. And scientists continue to explore ways to make less-carbon-intense feed out of other ingredients, including soybeans or even methane from industrial waste.

2.  Negative Numbers. Farmed oysters have a rare distinction among all seafood: their carbon footprint can actually be negative. A 2025 study out of Ireland found that one ton of oysters, which use carbon to build their shells, took in the equivalent of about 275 kilograms more carbon dioxide than the humans spent raising and harvesting them. After adding in the carbon cost of processing them, the overall carbon cost in that study did peek into the positives again, but just barely.

3. The Electricity Variable. Fish farms built in coastal areas can take advantage of natural currents to keep new water flowing in for their fish, but not every fish farm is built on the coast. Farms built more in-land need to pump their water instead. And that takes electricity. A 2025 study in Europe found that for the same species, land-based farms can use more than ten times the electricity of a coastal one, driving up the carbon cost. That said, where power’s coming from matters—solar panels positioned above the ponds or experimental wave-energy converter? Or a giant coal-burning plant?

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What to Keep An Eye On

1.  Declining Wild Fish Stocks. NOAA suggested that thanks to climate change, some species of wild salmon may essentially disappear and areas around the tropics may see overall catches decline by up to 40% by 2050. Meanwhile, new deregulations may defang the government’s ability to protect existing stocks. If fishing boats have to travel further and further, burning more fuel to catch fewer and fewer fish, the carbon math will change again.

2.  Two-for-One Solutions. In 2025, a research model predicted that sprinkling iron ore around fish farms could bind-up pollution from the farms, resulting in both healthier fish and carbon capture. If it  can work in real world farms at scale, it is precisely the kind of carbon math the industry needs.

3. Chickens. Comparing fish to other fish is informative. But you might also want to key an eye on how seafood compares to the carbon footprint of other animal protein. The Our World in Data chart above uses chickens as a baseline, for example, which not only have a carbon footprint similar to (and in some cases lower than) many types of seafood but some of the same challenges. Eating low-carbon isn’t as simple as land vs. sea.

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