In the comment section of last week’s post on farmed seafood , readers asked about the safety of regular, everyday seafood that you can find in any supermarket in the country – the popular, easily obtainable species that conventional supermarkets proudly display on ice, in frozen sections, and in cans and packets. Not crayfish, New Zealand green lipped mussels, and boutique tank raised Coho salmon, but tilapia, cod, and crab. They may not be ideal or as sexy as some of the species from last week, but they are common.
So – what’s common? To make this as objective and universal as possible, I’ll examine the ten most common seafoods consumed by Americans. As of 2009, they were , from most eaten to least eaten: shrimp, canned tuna, salmon, pollock, tilapia, catfish, crab, cod, clams, and pangasius. Shrimp I’ll cover in depth next week, catfish and clams were handled last week, and I covered farmed versus wild salmon  a couple years ago, but what about the others? Which are worth eating? Which should be avoided?
Let’s take a look.
The tuna is a big predatory fish, rather high up on the food chain. As such, it tends to accumulate heavy metals present in the food chain, with mercury being the most egregious of the bunch. Mercury in tuna gets a ton of bad press, not because it’s the worst offender – that honor is shared by shark, marlin, king mackerel, and a few other niche fish – but because it’s the second-most consumed fish in the nation, and small children and unborn fetuses are particularly vulnerable to it. You don’t see toddlers clamoring for king mackerel casserole, do you? It’s also affordable, comes in convenient cans, mixes well with mayo , tastes relatively mild (as opposed to canned sardines or mackerel), and is a staple for bodybuilders everywhere. It’s essentially really easy to eat a lot of canned tuna on a regular basis, so the relatively elevated levels of mercury in tuna are problematic.
There are many species of tuna with varying mercury contents. Canned white, or albacore, tuna has more mercury on average than canned light tuna, which is skipjack, tongol, or smaller yellowfin; pregnant women  and small children are advised to eat no more than six ounces of the former or twelve ounces of the latter each week. To be on the safe side, I’d suggest those groups avoid the stuff altogether and maybe eat sardines, mackerel , or wild salmon for the omega-3s  instead. Both canned varieties tend to have less mercury  than tuna steaks or fillets, probably because larger (and thus, more mercury-rich) fish produce better steaks, while smaller fish work better in cans. Other types of fresh or frozen tuna you might run into include ahi, also known as yellowfin (longline caught yellowfin are larger and contain higher levels of mercury, while troll/pole-caught yellowfin are smaller and contain lower levels), and albacore, which is more expensive than ahi and milder.
Bottom line: Tuna is tasty, especially the steaks, and it’s a decent source of omega-3s , but the mercury content can’t be ignored. Avoid if you are pregnant, nursing, or a small child, and don’t make tuna of any kind a daily staple. Look for troll and pole-caught tuna over longline-caught tuna, as the former tend to run smaller and accumulate fewer contaminants than the latter. Also, Atlantic tuna seems to run with higher mercury content  than Pacific tuna, regardless of species, with ahi/yellowfin running lower than albacore.
Regular grocery store salmon is almost always of the farmed Atlantic variety, which happens to be the variety I already lambasted . Avoid it and stick with wild Alaskan salmon, the fisheries of which are extremely well managed and sustainable . There’s also wild Pacific salmon caught off the coasts of California, Washington, and Oregon, which I sometimes get at local farmers’ markets. I still like Alaskan sockeye salmon best, even the frozen stuff, but they’re all worth eating.
Bottom line: Eat wild salmon, which is a great source of protein , omega-3s, and selenium. Avoid farmed salmon (unless it’s that fancy tank-raised Coho salmon I mentioned last week).
Tilapia is fast-becoming a consumer favorite, for a few reasons. It’s cheap to raise. It isn’t carnivorous, meaning farmers can use corn and soy pellets without springing for comparatively pricey fishmeal. The fish’s vegetarianism also endears tilapia to those who worry about the state of wild fish stocks (a concern that, though I also share it, must be meted out against concerns about corn  and soy subsidies). Parents and schools love it because it’s bland enough to feed to picky kids with dysfunctional industrial taste buds (just add ketchup). Plus, it’s technically fish and therefore “healthy,” meaning heart disease patients and hospitals can satisfy the AHA’s recommendations that folks eat at least two servings of fish a week by eating a few inexpensive, inoffensive tilapia fillets.
Don’t tell them that they aren’t getting much omega-3 out of it, though. According to the USDA nutrient database, tilapia contains very few omega-3 fatty acids at just 200 milligrams per 100 gram serving. In fact, that same 100 gram portion contains very few fatty acids in general – 800 mg saturated fat, 700 mg monounsaturated fat, and 200 mg omega-6 polyunsaturated fat. According to a recent study , however, tilapia has far more omega-6  than the database would suggest, with most of it coming as arachidonic acid  (which admittedly isn’t as problematic as excessive dietary linoleic acid). Overall, it’s a lean fish, akin to chicken breast. I find it pretty inoffensive if uninteresting. It’s low in contaminants , inexpensive, and melds into any dish without asserting itself. Good as a cheap source of protein, but not as a source of unique marine nutrition.
Tilapia comes frozen, whole, live, or in fresh fillets. Most frozen tilapia comes from China or Taiwan, while fresh comes either from US or South/Central American farms. Live tilapia are US farmed, and pretty rare (go to Asian supermarkets for these). Asian tilapia is inexpensive, but the Monterey Bay Seafood Watch  recommends against eating it very often due to poor farming conditions. Stick to US farmed tilapia if possible. South/Central American also gets good marks. Tilapia farming is fairly intensive, and caged tilapia raised in freshwater ponds can pollute surrounding waters , but standards seem to be changing for the better .
Bottom line: American and S/C. American tilapia is a safe source of protein, but it’s not a good source of omega-3s. If environmental impact matters, buy American. Avoid Asian imports (at least until the aforementioned farming standards are adopted worldwide).
Who doesn’t enjoy crab? Some might balk at the prospect of dismantling an exoskeleton for a modicum of interior meat, but it’s difficult to deny that the meat itself tastes great. But is regular, everyday grocery store crab safe to eat, let alone healthy? Yes. Dungeness, Alaskan king, snow, kona (also known as spanner or frog crab), and stone crab are all excellent choices. All are wild-caught – as a commenter pointed out last week, there are no commercial farmed crabs – and all are low in contaminants. They’re even harvesting crabs from the Thames  in London and finding that they’re relatively low in toxins and metals.
Crab meat is lean, except when dipped in clarified butter, and it’s a good source of selenium, B-vitamins, and zinc. The shell isn’t edible, but it does make a fine stock, so be sure to save your shells.
The crab’s main internal organ, the hepatopancreas, is a delicacy also known as “crab mustard” or “crab butter.” It’s tasty, smooth, and high in fat, but it’s also where industrial contaminants tend to accumulate. In fact, one study (PDF ) of blue crabs caught in the Newark Bay region of New Jersey found that the hepatopancreases contained astronomical levels of dioxins – over ten times as much as the muscle meat, enough that, in the authors’ opinion, regular consumption would drastically increase cancer incidence. This is an extreme example, not indicative of most crabs  sold for food. Newark Bay blue crabs aren’t available in stores near you (or anywhere; they’re actually banned), and as a whole, blue crabs are relatively free of contaminants. Just be aware that the potential exists for toxin accumulation, especially in the hepatopancreas. I know you guys love slurping up the weird bits of the animals you eat, and the hepatopancreas is undoubtedly chock full of fat and micronutrients, so check your sources before guzzling crustacean digestive glands and viscera. If the waters are clean, you’re in the clear.
Bottom line: Go for it. Grocery store crabs are wild-caught, low in contaminants, and perfectly good to eat.
Cod, Pollock, and Haddock
Purists may disown me, but I’m grouping cod, pollock, and haddock together because they are extremely similar to the lay fish-eater: lean, white, firm, wild-caught fish that people confuse. Cod, pollock, and haddock are even leaner than tilapia and almost as mild, with firm flesh. They’re also wild caught as a rule, which makes for a very clean and contaminant-free fish. I’ve noticed that it’s getting more and more expensive, probably due to lowered worldwide fish stocks. Multiple seafood advisory groups have actually listed  cod as endangered and a “poor choice” for regular eating, but not because it’s dangerous or unhealthy.
These fish are perfectly healthy, but they’re also fairly devoid of impressive nutrition, except for decent amounts of selenium and B-vitamins. Like tilapia, consider them sources of lean protein. If environmental concerns speak to you, go easy on it or stick to “bottom longline, jig, or trap” caught Pacific cod, as the Monterey Bay Seafood Watch recommends . You won’t be missing anything vital. All haddock seems acceptable, but Icelandic pollock trapped using Danish seines or trawls is apparently unsustainable.
If you can find them, canned cod livers are delicious, an excellent source (PDF ) of vitamin A, vitamin D, and omega-3 fats, and far more interesting than regular cod fillets. Just be sure to buy livers canned in their own cod liver oil.
Bottom line: Healthy and low in contaminants, but sustainability may be an issue. Stick to Pacific cod, specifically bottom longline, jig, or trap caught Pacific cod, to minimize impact on wild fish stocks. Avoid Icelandic pollock caught using Danish seines  or trawls. All haddock is good to go. None are strong sources of omega-3s.
Pangasius, which sells for cut-rate prices and hails from Vietnam, is an intensively farmed river catfish. Retailers often call it basa, or simply “catfish.” It runs lean and mild, contains very few omega-3s, absorbs all flavors, and works well as a canvas for batter and dipping sauce, making pangasius another one of those “fish for people who hate fish.” Whether it’s unsafe or not depends on who you ask – and it’s difficult to figure out who’s telling the truth. Domestic catfish farmers will say imported basa is raised in filthy Mekong river waters and pumped full of cheap feed and antibiotics, and that it isn’t even a true catfish; they also put out a television ad  saying as much. The other side says the opposite . For what it’s worth, the Seafood Watch approves  (though it prefers American catfish).
Bottom line: Pangasius is another bland, boring fish that may or may not be raised in horrid, unhealthy, polluted conditions. It’s probably safe, but is cheap protein worth the trouble? It might be.
- Let your nose be the guide when shopping for fresh (or previously frozen, which often masquerades as “fresh fish”) fish at the supermarket. Don’t be shy; position your snout inches from the product and breathe deeply. You’ll know it when it’s bad, because the smell of bad fish is unmistakably and unavoidably putrid. Saltwater fish and shellfish may smell faintly of the sea, which is okay, but freshwater fish should be close to odorless.
- Visit dedicated fish markets for fresh fish. There, the turnover rate is high and fish is usually fresh and of high quality. At most grocery stores, fish languishes on ice and doesn’t sell as quickly. Hardier meats like beef, pork, or whole chickens can handle a few days without the quality changing, but seafood quality goes downhill fast. If you have an Asian supermarket nearby, they’re also a good source of fresh seafood, since they serve a customer base that eats far more seafood than most Americans.
- If you’re going to buy the “local catch of the day,” check the local fish consumption advisories for heavy metals and other contaminants using this tool .
- Ask the fishmonger how the seafood was raised or, if wild, where it was caught and what method was used to catch it. Be wary of imported seafood from Asia.
I know I’ve missed a few examples of store-bought seafood in my attempt to be as universal as possible. Heck, I’ll probably hear it from non-US readers who feel left out, but I can take it. Lay it on me. Let me know what local offering I’ve missed (remember, I’ll bee covering shrimp next week) and I’ll try to get to them. Thanks for reading!