Consumers are up in arms over plans by the U.S. Food & Drug Administration to approve the first genetically engineered fish—dubbed “frankenfish.” But what many consumers may not realize is that much of the non-GMO fish, especially farmed fish, in today’s supermarkets is equally detrimental to human health. It’s also harmful to the environment and economically unsustainable.

That’s not to say that all wild-caught fish is safe or sustainable. Nearly a third of the world's fisheries are currently in collapse, "unable to regenerate their populations fast enough to keep pace with the rate at which they are being caught or killed, according to an interview, conducted by the Rodale Institute, with actor Ted Danson, author of . To help consumers navigate the waters of wild-caught fish, the Rodale Institute recommends consumers follow the Monterey Bay Aquarium’s “Seafood Watch” guide (also available as a downloadable smartphone app).

But GMO salmon, if approved, will be a farmed fish—and consumers should be aware that farmed fish in general should be avoided, even though there are some distinctions within the farmed fish market.

Fish farming isn’t new.

Fish farming, in the form of cages, nets, and enclosures submerged in marine or fresh water, dates as far back as ancient China. Today, an increased demand for the lean proteins and Omega-3 fatty acids contained in fish has helped make “aquaculture” the most rapidly growing animal industry. Just last year, farmed fish made up more than half of all global fish consumption, and even surpassed beef production. The number of wild-caught fish, meanwhile, has plateaued in recent years—in many cases due to over-fishing.

Proponents of aquaculture cite its high efficiency of protein production, reduced burdens on overfished natural stocks, and economic and environmental sustainability.

But the practice of fish farming isn’t quite as cut-and-dried as its proponents would have you believe. Here are some important facts to consider before purchasing farmed fish.

Farmed fish are stressed fish.

Contrary to popular wisdom, goldfish are unhappy in bowls. They just need more space to grow and flourish. The same is true of fish raised for human consumption. Unfortunately, farms that use the cage system tend to maintain fish in very high densities. The result is a stressed fish that is more susceptible to injury and disease.

To curb sickness and prevent the whole stock from becoming infected, farmed fish may be fed antibiotics and chemicals that remain in their systems until they make it to our tables. While the U.S. regulates certain antibiotics and pesticides, many common chemicals are not controlled. Imported fish, in particular, are suspect: the U.S. inspects just 2 percent of all imported seafood for drug residues.

Farmed fish are escape artists.

No matter how secure its enclosures, any large farming facility is bound to have escapees. While the fish may count themselves lucky, their escape is not so lucky for local ecosystems. Escaped fish, often larger than their wild counterparts, can out-compete local stocks for food and resources. If they breed with wild species, genetic differences in the farmed fish may lead to less fit offspring, thus further diminishing the wild stock. Worse yet, sick escaped fish can infect wild populations: A 2008 study showed that even low levels of sea lice in farmed fish cause reductions in local wild fish populations.

It’s a fish-eat-fish world.

While some farmed fish are satisfied with leafy greens, popular species like salmon and tuna are carnivorous, meaning that they are fed fish products derived from small species like anchovies or herring. Anywhere from two to five pounds of wild-caught fish may be required to produce a single pound of farm-raised fish. These numbers, of course, significantly challenge the sustainability claim of many fish farming advocates.

Even in the case where fish are fed soy or other animal products, there is no way for consumers to know what is in the farmed fish they are buying. Must a customer who has pledged to eat GMO-free abstain from all farmed fish, on the off chance it has been raised on GMO soy meal?

Fish make waste.

In addition to any antibiotics, pesticides or food remnants that are leaked from farmed fish enclosures, fishes’ natural waste products in concentrated amounts can negatively impact local ecosystems. Studies show that carbon, nitrogen and phosphate levels are all elevated within marine farming regions, and become accumulated in the ocean sediment. This nutrient-rich waste may lead to algal growth and water de-oxygenation sufficient to deplete local sea life in the immediate vicinity, further negating the sustainability myth.

Fish farms compete with local fishermen.

As the aquaculture industry grows, farmed fish become both cheaper and more prevalent. Naturally, the cheapest fish comes from the regions subject to fewer regulations—one of the reasons local farm-raised fish is perhaps a lesser evil than imported stocks. For the fishermen who normally catch these species, however, all fish farms are competition.

The fact that fish farms employ local workers is not necessarily a benefit, as much of this growth occurs outside the U.S. About 62 percent of all farmed fish, for example, come from China. Furthermore, the majority of fish farms are managed by large companies with a vested interest in keeping production costs low.

Individual fishermen, in contrast, have little say in the living conditions of their hauls. When you buy wild-caught fish, chances are you know where it comes from and you are contributing to your local economy.

Not all fish farms are created equal.

From Canadian salmon farms to Chinese carp farms, there is as much diversity to be found in the type of farm as the species of fish it produces. Fish farming is a business like any other, and it is up to individual producers to regulate their own operations. For example, the primary factor in the healthful fatty acid content of farmed fish is their diet. This is also a factor directly controlled by individual farmers.

Small local farms may raise fewer, and exclusively native fish, thus have a smaller impact on nearby ecosystems. They may also have a system for recycling certain waste products. Plants or shellfish that help filter nutrients are increasingly prevalent.

But ultimately wild fish provide a healthful meal with a lot fewer questions.

Additional seafood resources

For region-specific healthy seafood:
http://www.seafoodwatch.org/cr/cr_seafoodwatch/download.aspx

For wild-caught sustainability listings:
http://blueocean.org/seafoods/

Hannah Bewsey is a researcher/writer for the Organic Consumers Association.