7 Things Everyone Should Know About Farmed Fish

If you eat seafood, unless you catch it yourself or ask the right questions, odds are that it comes from a fish farm. Farmed fish now accounts for half the fish eaten in the U.S and is seen as a way to meet the world’s growing demand. But is fish farming really the silver bullet to solve the Earth’s food needs? Can marine farms reliably satisfy the seafood cravings of three billion people around the globe?

Here’s a look at aquaculture and its long-term effects on fish, people, and other animals. While some fish farms can follow sustainable practices, that's not always the case. And with this industry regularly touted as a paragon of food production, whether you eat seafood or not, you should know these seven key concerns about farmed fish.

Here’s a frustrating paradox for those who eat fish for their health: the nutritional benefits of fish can be lower, depending on the fishs’ diet. Take omega-3 fatty acids, for example. Wild fish get their omega-3’s from marine lipids (or fats). Farmed fish, however, are often fed corn, soy, or other vegetable oils that contain little to no omega-3’s.

When fish consume this type of feed, they can accumulate higher levels of saturated fats and have a higher omega-6 to omega-3 ratio, which isn’t as desirable as the reverse. 

While some farmed fish can live on diets of corn or soy, others need to eat fish–and lots of it. Tuna and salmon, for example, need to eat up to five pounds of fish for each pound of body weight. The result is that prey (fish like anchovies and herring) are being fished to the brink of extinction to feed the world’s fish farms.

“We have caught all the big fish and now we are going after their food,” says the non-profit Oceana, which blames aquaculture and commercial fishing's voracious hunger for declines of whales, dolphins, seals, sea lions, tuna, bass, salmon, albatross, penguins, and other species.

Contrary to the wishful thinking of many a catch-and-release angler, the latest research shows that fish can experience pain and stress1. Farmed fish are subject to the routine stresses2 of hyper-confinement throughout their lives or through exhausting harvesting methods. The recognition that fish do experience stress and pain has called for improved welfare practices of farmed fish. 

Conventionally farmed fish are often packed in their net or pen as tightly as coins in a purse. These unnatural conditions give rise to diseases and parasites, which often migrate off the farm and infect wild fish populations. On Canada’s Pacific coast, for example, sea lice infestations are responsible for mass kill-offs of young salmon, increasing their likelihood of dying from sea lice by 73%.

But the damage doesn’t end there, because eagles, bears, orcas, and other predators depend on salmon for their existence. Drops in wild salmon numbers cause these species to decline as well.

Antibiotics and chemicals may be used on fish farms to control the spread of disease and parasites.This can damage local ecosystems in ways we’re just beginning to understand. One study found that a drug used to combat sea lice kills a variety of non-target marine invertebrates, travels up to half a mile, and persists in the water for hours.

In the North Atlantic region alone, up to two million runaway salmon escape into the wild each year. The result is that at least 20% of supposedly wild salmon caught in the North Atlantic are of farmed origin (although, this is old data published in 1999). Escaped fish breed with wild fish and compromise the gene pool, harming the wild population. Embryonic hybrid salmon, for example, are far less viable than their wild counterparts. 

This counterintuitive economic theory says that as production methods grow more efficient, demand for resources actually increases–rather than decreasing, as you might expect. Accordingly, as aquaculture makes fish production increasingly efficient, and fish become more widely available and less expensive, demand may increase across the board.

According to this theory then, fish farms would actually drive more fishing, which can hurt wild populations. The net result: Fish farming might crank up the pressure on already-depleted populations of wild fish around the world.

The sustainability of fish farms emerges as a fishy story. With higher incidence of disease, chemical use waste, and pressure on wild species, fish farms remain a contested subject. While these examples of fish farming harms presented are backed by evidence, they are not true for every fish farm. In fact, some farmed fish are even more sustainable and healthful compared to their wild counterparts.

If you want guidance on selecting a sustainable fish to eat, check out these resources from Seafood Watch (a program from the Monterey Bay Aquarium) and the Environmental Defense Fund. 

The bottom line? Here’s one solution to the farmed fish dilemma: Shop for sustainable seafood, wild or farmed.