Dietary fish & seafood: Which are/are not healthful – and why

Salmon for sale

By Catherine Haug, January 8, 2017 (Photo right, from Wikimedia Commons)

Growing up here in the Flathead, I loved fish – hook to table – from the very beginning. Back then we had landlocked salmon and lots of native cutthroat trout in Flathead Lake, not to mention the huge salmon run up the Swan River every fall. Other than lutefisk, I’d not had much exposure to ocean fish (other than canned tuna). That changed when I went moved to the west coast for college and my career.

Things have changed since my 1950s childhood. Many wild fisheries are now endangered, or gone (like Atlantic salmon). Science has found dangerously high levels of toxic methyl-mercury in the larger game fish. Fish from fish farms are nutritionally deprived and may carry disease. What’s a fish lover to do?

Read on for discussion on which fish are more healthful than others. See also my 2014 posting: Sustainable Seafood in Summertime.

Good Fish

First and foremost, wild-caught fish are generally more healthful and nutritious than farmed. At the top of this list are wild-caught Alaskan  and sockeye salmon. They have low risk of mercury and other toxic contamination, and are among the highest in healthful omega-3 fats. (1)

Second, choose species that are at the bottom of the food chain – the smaller the species, the better. In addition to salmon, this includes: sardines, anchovies, mackerel and herring. If you buy these canned, your best choice will be those from Spain; and choose those packed in water rather than olive oil (because there’s a lot of fraud in the olive oil industry; see my post Adulterated or Fake Olive Oil for more) (1).

Sustainable and healthful recommendations

If you want sustainable AND healthful,  the Center for Food Safety provides the following five tips (5), which are the basis of their seafood recommendations:

  1. Choose local seafood if possible, and always choose domestic over imported;
  2. Choose wild;
  3. If it’s farmed, choose seafood that is from the U.S., especially in low- or no- output, recirculating systems; however, if you want to avoid antibiotics and/or PCBs in your fish, avoid farmed fish.
  4. Favor fish caught by hook and line, handline, troll (not to be confused with “trawl” fishing, which can be very destructive), jig or speargun;
  5. Avoid fish that are high in mercury, PCBs or farmed fish that are given antibiotics (6). See also What is the Problem with Mercury, below.

Fish/seafood to avoid

An emerging problem with fish and seafood is ‘food fraud’ which involves chopping up lesser quality fish so that it resembles other species.

However, the biggest problem with fish/seafood is mercury contamination; the following have some of the highest levels of contamination. Avoid these altogether if you are pregnant of planning a pregnancy; otherwise, keep to a minimum (1a, b,c):

  • Sea species:
    • Canned tuna
    • mackerel, swordfish
    • grouper
    • marlin
    • orange roughy
    • Oysters (Gulf of Mexico)
    • snapper
    • halibut
    • shark
    • swordfish
  • Freshwater: 
    • walleye
    • northern pike
    • largemouth bass

Two excellent sources/guides regarding mercury in fish:

  • “Mercury and Fish: The Facts.”  from Mercury Policy Project (2a), and their helpful printable pdf guide (2b) They have a helpful guide you can print out for reference.
  • Investigate West’s 2015 article includes a guide for how many meals per week you can safely eat based on any given seafood’s contamination level. (3a) It includes an image you can cut out that provides recommended seafood meals per week of various species. That image is also included below (right click on the image to save it as a file on your desktop; or print out the image saved as a pdf file – see reference 3b, below)

Seafood Meals per Week Guide

What is the problem with mercury?

It is the most toxic element; in elemental form or as methyl mercury, it does extensive damage to nerve and brain tissue. In addition to fish and seafood, a significant source of mercury contamination is ‘silver’ fillings in your teeth (mercury-amalgam fillings) (1c), and in some vaccines where it is added as an adjuvant (4).

The most common form of mercury present in fish and seafood is methyl mercury:

Mercury is released from the smokestacks of coal-fired power plants, cement kilns and certain types of mining activities. Once in the air, the toxic mercury rains down into bodies of water. From there it is converted by bacteria into a particularly dangerous form called methylmercury, where it finds its way into fish, accumulating especially in fish that are higher up the food chain. (1b)

Fish like tuna, sea bass, marlin and halibut show some of the worst contamination, but dozens of species and thousands of water bodies have been seriously polluted. (1c)


Mercury exposure is especially dangerous for pregnant women and small children, whose brains are still developing. If infants or fetuses are exposed to mercury, it can cause (1b):

  • Mental retardation
  • Cerebral palsy
  • Deafness
  • Blindness

In adults, mercury exposure can cause:

  • Fertility problems
  • Memory and vision loss
  • Trouble with blood pressure regulation
  • Extreme fatigue
  • Neuro-muscular dysfunction

Other contaminants in fish:

  • polychlorinated biphenyls (PCBs)
  • dioxins, especially in farmed fish
  • disease, especially in farmed fish


  1. Mercola articles: (1a); (1b) (1c)
  2. Mercury Policy Project: (a) Mercury and Fish: The Facts, and (b) Guide to mercury levels in different varieties of fish and shellfish (PDF)
  3. Investigate West, March 10, 2015: (3a) Balancing Risks and Rewards of a Seafood Diet , (3b) Mealsperweek-fish-seafood
  4. Wikipedia on ‘adjuvant’:
  5. Center for Food Safety, Best Sustainable Summer Seafood (
  6. Food and Water Watch  (


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