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What’s in the Fish You Eat? What About Local Fish?

July 01, 2020

Fish is a nutritional Hall of Fame protein loaded with heart-healthy omega-3 fatty acids, vitamins D and B2, calcium, phosphorous and minerals. Eating low-fat fish at least twice a week, says the American Heart Association, can lower your blood pressure and your risk of a heart attack of stroke.

Unless, of course, the fish you buy is also loaded with PCBs that cause liver damage, dioxins linked to cancer or possible radioactive contaminants. Arsenic, cadmium, chromium and lead are other possible contaminants buried in fish flesh. But mercury, which can cause neurological disease, is perhaps the most notorious and a prime reason fish lovers have become so selective.

A safe amount of mercury, according to the U.S. Environmental Protection Agency, is no more than 0.1 micrograms a day for each kilogram of body weight. For the average adult woman — 170.5 pounds, according to the Centers for Disease Control and Prevention, or about 4 pounds heavier than a 1960s-era male — that’s 7.73 micrograms a day. For the average adult male (197.8 pounds), it’s 8.97 micrograms a day.

A 4-ounce can of albacore tuna contains 40 micrograms of mercury. (A 4-ounce can of light tuna, with only 13 micrograms of mercury, still exceeds the daily recommendation.)

What Happens When You Eat Seafood Containing Mercury?

If you eat fish that contains mercury, your body will absorb the mercury. Eventually, your body expels  it in urine, feces and breast milk. But mercury, at high levels, can be harmful.

What’s In Your Fish?

First Number (good):  milligrams of omega-3 fatty acids (Eicosapentaenoic Acid, or EPA, and Docosahexaenoic, or DHA) per 4 ounces of cooked fish.
Second number (bad): micrograms of mercury per 4 ounces of cooked fish.

  • Salmon (Atlantic, Chinook, Coho): 1,200-2,400/2
  • Salmon (Pink & Sockeye): 700- 900/2
  • Anchovies, Herring, and Shad: 2,300-2,400/5-10
  • Mackerel: Atlantic & Pacific (not King): 1,350-2,100/8-13
  • Tuna: Bluefin & Albacore: 1,700/54-58
  • Tuna (Skipjack & Yellowfin): 150-350/31-49
  • Tuna (White Albacore, canned): 1,000/40
  • Sardines (Atlantic & Pacific): 1,100-1,600/2
  • Oysters (Pacific): 1,550/2
  • Trout (Freshwater): 1,000-1,100/11
  • Mussels (Blue): 900/NA*
  • Squid: 750/11
  • Pollock (Atlantic & Walleye): 600/6
  • Marlin: 250-1030**/69
  • Crab (Blue, King, Snow, Queen, & Dungeness) 200-550/9
  • Flounder, Plaice & Sole (Flatfish): 350/7
  • Clams: 200-300/ less than 1
  • Tuna (Light canned): 150-300/13
  • Catfish: 100-250/7
  • Cod (Atlantic & Pacific): 200/14
  • Scallops (Bay & Sea): 200/8
  • Haddock & Hake: 200/2-5
  • Lobster (American): 200/47
  • Crayfish: 200/5
  • Tilapia: 150/ 2
  • Shrimp: 100/ less than 1
  • Orange Roughy: 42/80

Varieties That Should Not be Consumed by Women Who Are Pregnant or Breastfeeding or by Young Children:

  • Shark: 1,250/151
  • Tilefish (Gulf of Mexico): 1,000/219
  • Swordfish: 1,000/147
  • Mackerel (King): 450/110

*Not available. It is likely to be comparable to the levels in oysters and clams.

**250 is the value for blue marlin and 1030 is the value for striped marlin.

The Fish List

Here’s a list of fish, rated best to must-avoid, by the Environmental Protection Agency and Food and Drug Administration:


Eat two or three servings a week (one serving is 4 ounces).

  • Anchovy Atlantic croaker, Atlantic mackerel.
  • Black sea bass, Butterfish.
  • Catfish, Clam, Cod, Crab, Crawfish.
  • Flounder.
  • Haddock, Hake, Herring.
  • Lobster (American and spiny).
  • Mullet.
  • Oyster.
  • Pacific chub mackerel, Perch (freshwater and ocean), Pickerel, Plaice, Pollock.
  • Salmon, Sardine, Scallop, Shad, Shrimp, Skate, Smelt, Sole, Squid.
  • Whitefish, Whiting.


Eat one serving (4 ounces) a week.

  • Bluefish
  • Buffalofish
  • Carp
  • Chilean sea bass.
  • Sheepshead
  • Grouper
  • Halibut
  • Mahi mahi
  • Monkfish
  • Rockfish
  • Sablefish
  • Snapper
  • Spanish mackerel
  • Striped bass (ocean)
  • Tilefish (Atlantic Ocean)
  • Tuna: albacore/white tuna, canned and fresh/frozen; Tuna, yellowfin
  • Weakfish/seatrout
  • White croaker/ Pacific croaker


These have the highest mercury levels and should not be eaten.

  • King mackerel
  • Marlin
  • Orange roughy
  • Shark
  • Swordfish
  • Tilefish (Gulf of Mexico)
  •  Tuna, bigeye


Wild Caught or Farmed-Raised?

Not all wild-caught fish is better for your health than farmed fish, but salmon highlights some extreme differences. Tons of antibiotics used to fight infection and disease in high-density salmon farms cause both environmental and health issues.

A 198-gram, half fillet of wild salmon has 131 fewer calories (281 vs. 412), less than half the fat (13 grams vs. 27 grams) and less than a third of the saturated fat (1.9 grams vs. 6 grams). Farmed salmon has slightly more omega-3 fatty acids and more than five times the amount of omega-6 fatty acids (1,944 milligrams vs. 341 milligrams), which area also good for the heart.

Wild-caught salmon has fewer persistent organic pollutants, or POPs, but both wild and farmed salmon eaten in large quantities contain risky amounts of cancer-causing chemicals and contaminants. When eaten in moderation, however, wild-caught salmon is considered safer.

Country of Origin

Whether wild-caught or farmed, it’s usually better to keep it local — as in the United States — for lower toxicity and greater sustainability. Avoid antibiotics by buying fish from Norway and Iceland. Avoid fish countries with less-restrictive seafood regulations, such as China, Thailand, Indonesia and Vietnam.

Local Fish

When catching fish in our lakes, rivers and Long Island Sound, pay attention to state advisories. The state Department of Public Health says most freshwater fish in Connecticut contain enough mercury or PCBs to recommend limiting consumption.

High-risk groups — pregnant woman, a woman planning pregnancy within a year, a nursing mother or a child under 6 — should eat these fish no more than once a month. Low-risk groups are advised to include locally caught fish in no more than one meal per week.

Fish caught in the Housatonic River, part of the Quinnipiac River, some lakes and species from Long Island Sound contain higher levels of contaminants. In the Housatonic, above Lake Lillinonah, the state recommends you do not eat trout, catfish, eels, carp and Northern Pike because of PCBs. Catfish from the Connecticut River, though can be eaten once a week by both risk groups.

Striped bass and bluefish over 25 inches long from Long Island Sound should be limited to one meal per month by those in the low-risk group and avoided by the high-risk group. Smaller bluefish, 13 to 25 inches, are OK once a month for both risk groups.

Trout from Connecticut’s rivers are an exception because they have minimal contamination and are restocked regularly.

Don’t blame the fish. Our waterways still contain mercury and polychlorinated biphenyls (PCBs), dumped directly into the water for decades by factories and other businesses.

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