(Mis)labeled fish

Humans eat only a few species of livestock, but eat hundreds of different kinds of fish. How do consumers know that the species they are eating is actually what is listed on the menu or on the packaging? After all, many different species of fish look the same on the inside. In this post, we talk about why seafood is mislabeled and what the implications are for consumers and sustainability, while also discussing traceability and ecolabels as solutions.

Why are fish mislabeled?

Fish are unique among animal proteins in that they are wild animals, not domesticated. Domestic livestock around the world are typically all the same species. There is one species of cow, one species of chicken, and one species of pig that are eaten everywhere. However, within each species there are different breeds, similar to how German shepherds and Chihuahuas are the same species but different breeds. Most people have no idea what breed of meat they are eating unless it is specifically marketed, like Kobe beef or Kurobuta pig.

Wild fish are harvested, not bred, so distinct species are the norm; there are over 30,000 different fish species. And unlike domesticated animals, slight differences in appearance are speciated. For example, can you tell the difference between these two species?

Or these two?

Fish can be even more difficult to tell apart, especially on land, or after they have been processed into filets. There are several different species in the genus Gadus that all taste nearly identical and perform the same in the kitchen. Furthermore, the Gadidae family has several other fish that all look and taste the same. You may know these fish as “cod,” even though only the Gadus genus are considered true cod.

Once a member of the Gadidae family is caught, it is processed into the seafood product it will become, be it fish sticks or filets. After processing, it is practically impossible to tell the difference in species. Though there are some regulations in place for keeping track of species through the supply chain, it is easy to make mistakes when common names like “cod” do not match the scientific name. Mistranslations across import/export countries can also lead to mislabeling.

With so many species of “cod” that taste and look the same, mislabeling them is understandable and often an accident. This kind of mislabeling is not bad for people’s health as the nutritional profiles of very similar fish are…very similar. Though uncommon, if a fish has a drastically different nutritional profile than its label would indicate, some people, particularly women, could be at risk as mercury in fish can cause birth defects. Pregnant women are advised to avoid certain species of high-mercury fish during pregnancy. If a high-mercury fish was passed off as a low-mercury fish, a mother and unborn child could be at risk. Here is a handy chart.

True Seafood Fraud

Though most mislabeling is probably accidental, there are sinister reasons to mislabel fish. Catching protected species and disguising them as another species is illegal; however, there is some nuance to the conservation implications. Fishing boats purposefully targeting protected species happens, but often those fish are targeted for being exactly what they are (e.g. totoaba); mislabeling them as something different would decrease their value. Disguising illegal fish as legal is more common when fishing boats accidently pull up fish they are not supposed to. Sometimes there is a protected bluefin tuna in a net targeting yellowfin tuna. If authorities find the bluefin, the fishing boat could be in trouble so the boat has two options: throw the dead fish overboard or process it with the yellowfin. Though illegal, the sustainable answer is to mislabel the fish as yellowfin so it is not wasted.

More commonly, passing off cheaper, easier to obtain fish as expensive, in-demand fish is truly seafood fraud. This can happen at any point in the supply chain, but is most common in restaurants, as most everyday restaurant patrons do not have the expertise to tell that their Pacific snapper is actually just rockfish. Deceiving consumers is morally dubious, but has little bearing on sustainability. A recent paper found that, generally, mislabeled fish have a slightly better conservation status than the fish they are passed off as, though not in every case.

Traceability & Ecolabels

Aside from consumers being cheated out of ‘expensive’ fish, the group of people most impacted by mislabeled fish are women. Fish are a great source of nutrition (especially protein) that all women can benefit from, but those that are pregnant or trying to have children need to monitor the kinds of fish they eat due to mercury concentrations in fish. A mislabeled fish could unexpectedly raise mercury levels in the body and create problems for an unborn baby.

Traceability through the supply chain, or tracking where a piece of seafood is caught, processed, and sold is one of the best ways to ensure the species on the label is correct. Many environmental NGOs have ramped up traceability efforts to the point where knowing where a meal was caught has become a marketing technique.


Traceability also helps with sustainability as many packaging labels or restaurants can show what country a piece of seafood is from, and, though it is not a perfect indicator of sustainability, this figure from Melnychuk et al. 2016 is a good guideline for sustainability.


Ecolabels take sustainability and traceability to the next level. The idea behind an ecolabel is that a third-party examines a particular fishery deeming it sustainable (or not). If certified as sustainable, the fishing companies can label their catch as such and charge a bit more. In exchange, consumers get peace of mind that they are purchasing sustainable fish.

Chances are you’ve seen this label on seafood sold at your local grocery store.

The Marine Stewardship Council (MSC above) is the world’s most prominent ecolabel, but many others exist. It is important to note that fishing companies still have to follow the rules and regulations set in place by a governing body, which should ideally be sustainable practices. We get into fishery management in another section. Ecolabeling should work to supplement good fishery management.

However, ecolabeling can be controversial. Each ecolabel has its own set of scientific guidelines to determine a “sustainable” certification. These guidelines are not policed by any governing body, so some certifications have been contentious. Further, ecolabeling is expensive. Getting a certification can cost upwards of $250,000 for a fishing company. This hurts small and independent fishing companies who fish sustainably but can’t afford to pay for certification and add the value to their products that large companies can. MSC has started a scholarship program to alleviate some of the equity imbalance, but more is needed.

Seafood buying guides are also a fine way to purchase sustainable fish with peace of mind. NOAA’s Fishwatch and Monterey Bay Aquarium’s Seafood Watch programs are easy ways to look up a fish and see if it is sustainable or not. Seafood Watch even has an app you can download to your smartphone for easy shopping at the store or restaurant. Like ecolabels, these buying guides have their own standards for what is “sustainable” so listing decisions can vary. Additionally, evaluating fisheries takes a lot of time and money, so databases are incomplete and not every fish or seafood product is listed in the buying guide. In many cases, using the country of origin is a fine way to determine sustainability.

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This post is part of Sustainable Seafood 101

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