Four Terms You Need to Know When Buying Sustainable Fish

Seafood is a nutritionally dense source of lean animal protein and essential vitamins and minerals. Modern methods of cultivating and harvesting fish can also help us to meet our sustainability goals. Unfortunately, many of the terms used to describe seafood can be misleading. This roundup will examine the four terms you need to know when buying sustainable fish.


"Wild-caught" seafood seems to be self-explanatory. However, the term's full range of implications may not be apparent. When it comes to nutrition, wild-caught fish tend to be leaner, as the fish are more active in their search for food. In addition, their natural diet ensures that they have a slightly higher omega-3 to omega-6 fatty acid ratio, which is optimal for a human diet. Finally, wild-caught fish have higher mineral content, including calcium, iron, and zinc. These fish are generally more nutritionally dense than their farmed counterparts, but there is one caveat: they have higher levels (but still safe!) of heavy metals, including mercury.  

"Wild-caught" is not a synonym for "sustainable." Demand for fish is higher than the natural capacity to replenish the fish population. Moreover, the methods of acquiring wild-caught seafood can emit carbon, pollute the water, and harm non-target species. Therefore, fish caught with fishing poles or trolling mechanisms (longer lines with multiple hooks) are less likely to disturb other species. However, trawling (dragging a submerged net behind a fishing vessel) and fish aggregation devices (FADs) can damage the environment and disturb other species indiscriminately.


Fish farms in the US efficiently produce vast quantities of healthy seafood for human consumption. They typically consist of large pens in oceans, lakes, and rivers. Alternatively, fish can thrive in large holding tanks on land.  

Nutritionally, they are very healthy but have a slightly higher fat-to-protein ratio and lower amounts of omega-3s. They also receive antibiotics, yielding the same concerns as the similar practice among livestock. In addition, they have lower levels of essential minerals; however, they have lower levels of mercury than wild-caught fish.

A well-regulated fish farming industry can be sustainable, but several challenges prevent every facility from meeting its goals. For example, when non-native species escape holding pens, they can threaten the local ecosystem, displacing or harming nearby plants and wildlife. Furthermore, unsanitary water conditions can spread diseases to nearby schools of fish. Fortunately, modern fish farms have access to technology that helps with water filtration and waste disposal.  


"Fresh" fish is a safe source of lean protein for the human diet. However, once it is past its prime, seafood can lead to a host of nasty bacterial infections. Unfortunately, it is not always easy to determine what constitutes "fresh." For example, does it mean "recently caught" or "never frozen"?

The quality of fish is not directly related to its chronological age but to how much its cells have deteriorated. So, in the absence of all other factors, fresh fish is recently caught and provides various health benefits. The protein, omega-3 fats, minerals (calcium, iron, zinc, etc.), and vitamins (A, D, B2, etc.) make fresh fish one of the healthiest animal protein sources.  

Fish dish


On the other hand, fish starts to deteriorate very quickly unless someone preserves it. For sustainability and human health, chemical preservatives are not an option. However, modern freezing techniques maintain all the nutrition of recently caught fish. In addition, properly frozen, stored, and thawed fish is indistinguishable from a recent catch – visually and nutritionally.

The main difficulty with frozen fish is ensuring that it is frozen quickly, stored securely, and defrosted correctly. If not, anaerobic bacteria can thrive in the vacuum-sealed package, or the fish can suffer the same deterioration as a recent catch left out too long.

Fish dish
Key Takeaways
  • Check the Claims – Unfortunately, seafood labeling is inconsistent. However, "frozen fresh" and similar formulations means that the fishermen froze it shortly after they caught it (but not necessarily raw!). On the other hand, "flash frozen" and "quickly frozen" mean they froze the fish immediately to prevent deterioration.
  • Check the Ingredients – If frozen seafood has any additives, particularly any sodium-based chemicals, avoid them. Sodium increases water retention, which drives up the weight of the frozen product but lowers the thawed weight. Of course, you have to pay for the frozen weight.
  • Check Yourself – The best way to defrost your tasty, sustainably-sourced fish is in the fridge. First, remove the fish from its vacuum-sealed plastic, put it on a plate, cover it with plastic wrap, and put it in the fridge overnight.