Friday night is fish night, in our home at least. Recently, I’ve started paying more attention to the type of fish I buy and have learned that bigger isn’t always better. Salmon feels healthy, tuna seems convenient and cod is a classic. However, if you look at the bigger picture – our health, budget and the planet – it becomes clear that smaller fish make for the real “winner winner, fishy dinner”.
Switching from big fish to small fish might not be a glamourous diet trend yet (give it time, perhaps a Kardashian will be the new face of kippers) but it is one of the simplest, most practical ways to eat better while reducing your environmental footprint. Plus, it doesn’t require a total lifestyle overhaul, just a few swaps at the supermarket.
Why eating small fish is better for the planet
Small fish species sit lower on the food chain, which means they require far fewer resources to grow. Unlike large predatory fish like tuna or swordfish, which eat huge quantities of smaller fish throughout their lives, species like sardines and anchovies feed mainly on plankton. That makes them far more energy-efficient and environmentally friendly.
Producing large fish is inherently wasteful because of this food chain dynamic. According to the Food and Agriculture Organization (FAO), it can take up to 10 kilograms of smaller fish to produce just one kilogram of a large predatory fish like tuna. On top of that, small fish grow quickly and reproduce in large numbers, meaning their populations can recover faster from fishing pressure. Larger species take years to mature, making them much more vulnerable to overfishing. When you eat small fish directly, it is more efficient and sustainable.
Why fish is a better protein option overall
Before narrowing in on small fish, it’s worth understanding why fish in general is a good meal choice. Nutritionally, most seafood is hard to beat. It’s rich in high-quality protein, omega-3 fatty acids and essential nutrients like B12 and D vitamins and selenium, while low in calories. The NHS recommends eating at least two portions of fish per week, including one oily fish, to support heart and brain health.
From an environmental perspective, fish also tends to outperform land-based meats. Beef production, for example, generates around 60 kilograms of CO₂ emissions per kilogram of meat, while farmed fish such as salmon typically produces between 5 and 10 kilograms. Smeaky covered this issue in greater detail in our article on different protein types, which ranks them in terms of both diet health and environmental footprint.
On the negative side, issues like overfishing, bycatch (accidentally catching non-target species), habitat damage and pollution from fish farms remain real concerns. The World Wildlife Fund highlights overfishing as one of the biggest threats to ocean ecosystems.
Fish farming versus wild-caught
Fish farming, known as aquaculture, has grown rapidly in recent decades. It can reduce pressure on wild fish populations and for larger fish breeds it is more cost effective than catching them, as they can be harvested in bulk and bred more regularly. But this approach is not perfect. Many systems still rely heavily on feed made from wild-caught fish (so we are catching small wild fish to feed them to large farmed fish that we then eat, rather than eating the wild fish). Poorly managed farms can also quickly cause pollution and disease spread. The FAO has highlighted both the opportunities and environmental challenges of the common aquaculture process. It also outlines how aquaculture systems depend heavily on feed inputs and can contribute to environmental pressures if not managed carefully.
Wild-caught fish can be sustainable, but only if fisheries are well managed. Organisations like the Marine Stewardship Council certify fisheries that meet strict sustainability standards, including not overfishing. I’d suggest checking to see if your favourite brand of seafood appears on its list. When these standards are met, wild catching is considered better for the environment than fish farms, because it generates less land use and pollutants. As it happens, most forms of small fish are wild-caught, because it is more cost effective to do so anyway. The cost of farm infrastructure and feed adds up to more than the small fish are usually sold for, and they breed faster and can be more easily caught in bulk in the wild than larger breeds can. In short, when it comes to small fish, there is less need for farms.
The real answer isn’t simply “wild vs farmed” but about how the fish is sourced and what works for each species. However, across the board, small fish still tend to be the cheapest option and the more environmentally-friendly to produce. That’s another reason they deserve more attention.
Why small fish are better than big fish
If there’s one idea to take away, it’s this: eating lower on the food chain is almost always better for the environment. Large fish are resource-intensive. They consume vast amounts of smaller fish, take years to reach maturity and are often killed before they’ve had a chance to reproduce. This combination makes them highly vulnerable to overfishing. According to NOAA Fisheries research, species that grow slowly and reproduce later are much harder to manage sustainably. Small fish flip the equation. They grow quickly, reproduce in large numbers, require minimal inputs and less farms, and fisheries find it easier to meet sustainability standards. This makes them one of the most efficient sources of animal protein available. Let’s look at three quick examples.
Sardines
Sardines are widely considered one of the most sustainable seafood choices because they are abundant, fast-growing and feed low on the food chain. The Monterey Bay Aquarium’s Seafood Watch programme regularly lists sardines as a “best choice” for sustainability.
Anchovies
I was surprised to learn that a large portion of the world’s anchovy catch is not eaten directly by humans but instead processed into fishmeal to feed larger farmed fish (the fish food discussed above). Research published in Nature says that redirecting these small fish toward direct human consumption could significantly improve global food efficiency and food security.
Mackerel
Mackerel is another strong example. It grows relatively quickly, is rich in nutrients and many fisheries that raise it are considered sustainable. It’s also widely available in UK waters, making it a more local option compared to imported species.
Another often-overlooked factor is transport. The UK imports a large proportion of its seafood from countries like Norway, Iceland and China, where fish is often processed before being shipped back. This global supply chain adds to the carbon footprint, especially when air freight is involved. Small fish can help here too. Species like mackerel and herring are commonly found in UK waters and can be sourced more locally. They are also frequently canned or preserved, which reduces the need for rapid (air-freight) transport and refrigeration. Plus, they tend to be packaged and consumed whole, reducing food waste.
Why small fish are healthier and more affordable
From a health perspective, small fish have a clear edge. They pack the same nutrients we mentioned earlier, just like most larger fish do. However, because they are often eaten whole (including soft bones) they can also provide a significantly greater calcium boost. They also tend to contain far less mercury than large fish. Mercury accumulates in the food chain, meaning predatory fish like tuna and swordfish have much higher levels. The U.S. Food and Drug Administration advises limiting consumption of high-mercury fish while encouraging lower-mercury options like sardines, anchovies and mackerel.
If you’re looking for the healthiest options: sardines, anchovies, mackerel, herring and sprats consistently come out on top. They also take high billing on the British Heart Foundation’s list of oily fish that make excellent choices for maintaining heart health.
Then there’s the cost factor. Small fish are one of the most affordable sources of high-quality protein available. At time of writing, a tin of sardines or mackerel can cost between £0.50 and £3 in London, depending on brand and supermarket chain, while fresh fillets of salmon or tuna are often £7 to £14. For busy people trying to eat well on a budget, that’s a win!
The bottom line
Choosing small fish over big fish is one of those rare decisions that ticks every box. It’s better for your health, better for your wallet and better for the planet. You’re eating lower on the food chain and opting for a fish that is produced more sustainably, reducing your own environmental impact. You’re getting more nutrients with fewer contaminants. Plus, you are often saving money in the process.
Most importantly, it’s an easy change to make. You don’t need to rethink your entire diet. Just start swapping in small fish where you can: try adding sardines to toast, tossing anchovies into pasta (a favourite in our house) or grilling mackerel instead of salmon. Small choices like these add up, and when enough people make them, they can shift demand toward more sustainable, responsible seafood systems.
So next time you’re standing in the supermarket aisle, take a second look at the smaller fish. They might not have prime shelf placement in the shops or a Kardashian on the tin (yet!), but they’re a lot more influential than we think.
