I can’t count how many times I’ve heard both of these phrases:
“I only eat wild fish, because farmed fish is unsustainable.”
“I only eat farmed fish, because wild fisheries are overfished.”
Both of these statements have some scientific basis, but they are vastly oversimplifying the issue. There are good reasons to eat wild fish, but there are excellent examples of farmed fish as well.
Here are a couple questions you can ask to help make decisions about whether you should go with farmed or wild fish for a given species. Be aware that there are going to be exceptions, but these are some decent rules of thumb:
Is the fish carnivorous?
Generally better to go wild. Carnivorous fish farms tend to use high levels of fish meal and fish oil as feed. For example, if it takes two pounds of fish meal to get one pound of salable fish from the farm, we are dealing with a 50% net decrease in protein through the feed process. This directs our demand to a higher level on the food chain and is not a sustainable way to raise our food.
Is it a filter feeder?
Go for farmed product. Farmed mussels and oysters are often raised in suspension systems where they are harvested without any impact to the seabed. Additionally, their presence actually helps to filter the water around the farm.
Is it a freshwater fish?
Farmed is usually the way to go here. Freshwater farms are often contained tank or pond systems (like trout, freshwater prawns, or striped bass) that tend to have low impact levels on the surrounding environment.
As I said, there are numerous exceptions to the above suggestions, but they can help to create a rough gauge of the seafood landscape. For more in-depth information on particular fish, visit the page specific to the fish in question.