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"A fine kettle of fish!" - Are today's fish too toxic to eat?

The ideal edible fish has fins and scales and swam free in open, unpolluted waters

Potentially "clean", edible fish have FINS and SCALES

“Whatsoever hath fins and scales in the waters, in the seas,  and in the rivers, them shall ye eat. And all that have NOT fins AND scales in the seas . . . they shall be an abomination unto you.”

– Leviticus 11:9-10

“Once again, the kingdom of heaven is like a net that was let down into the lake and caught all kinds of fish. When it was full, the fishermen pulled it up on the shore. Then they sat down and collected the good fish in baskets, but threw the bad away”.

– Matthew 14:47-48

Biblically "clean", edible Fish:

Dark Blue= Now polluted with high mercury content

Albacore (Crevalle, Horse mackerel)  . Alewives (Branch and river herring) .  Anchovy .  Bass (Fresh Water) . Bass (saltwater) . Black fish . Bluefish . Bowfin . Buffalo . Carp . Characin . Cod . Croaker. Darter . Flounder (Dab, Gray Sole, Yellow Tail) . Gaby .   Grayling . Grouper (Gag) . Haddock .  Halibut . Herring . Jacks (pickerel) . Mackerel . Mackerel (King, Spanish) . Mahi Mahi (Dolphin fish, Dorado) . Minnow . Mooneye . Mullet . Needlefish . Orange Roughy . Perch (Bream) . Pilchard (sardine), Pike (Jack, Northern) . Pollock . Pompano. Red Fish (Red drum) . Salmon (Chinook, Chum, Coho, King, Pink, Red) . Sardines (pilchard) . Shad . Silver sides . Smelt  (Frost fish, Ice fish)  . Snapper . Sole . Sucker (White, Red Striped, Longnose, Northern) . Sunfish . Surf fish . Tarpons . Trout  . Tuna (chunk, skip jack, yellowfin) . Tuna (large, SOLID white albacore) . Weakfish . Whitefish

Also (but not yet checked out for mercury content) Barracuda, blueback (gut herring), black drum, bluebill sunfish, Blue Runner, Bonitos, Butterfish, Chub (Bloate), Longjaw (blackfin), Cobia, Crappie, Frost fish, Grunts, Gulf pike (Robalo, Snook, Sergeant), Hake, Hardhead, Hardtail, Kingcroaker, Kingfish, Lionfish, Marlin, Menhaden, Muskellunge (Jack), Opah, Pangasius,  Pigfish, Porgy (Scup), Redfin (Red Horse Sucker), Red snapper, Redfin, Rockfish, Seabass, Sergeant fish (Gulf Pike), Sheepshead,  Steelhead, Striped Bass, Sunfish, Tuna (bluefin), Walleye, Yellow Perch, Whiting (Silver Hake)

Fish with the LEAST contaminant health hazards include:
•  Farmed rainbow trout
•  Anchovies
•  Sole
•  WILD Pacific salmon (Sockeye, Coho, Chum, Pink, Alaskan) (LEAST contaminated and can be safely consumed fresh, frozen or canned)
•  Wild Atlantic salmon. (currently protected in the U.S. and unavailable)

Also safe are:
•  Cod
•  Mahi mahi
•  Tilapia
•  Canned Light, chunk tuna 
(smaller skipjack or yellowfin tuna,  NOT the solid / chunk white albacore).


Some toxin-absorbing fish are just NOT meant to be eaten

Most biblically “unclean” fish are either bottom-dwellers or predatory scavengers doing an excellent job of absorbing toxins and detoxifying the waters.  

 E.g. swordfish (a predator eating high-mercury content fish ), shark (at the top of the food chain), catfish, and all shellfish.  Shellfish are found in coastal waters, which supply their diet of industrial deposits, sewage, and fish excrement. Shellfish have been directly traced as a cause of gastroenteritis, hepatitis epidemics, and typhoid fever.

Biblically “Unclean” fish / SHELLFISH / SOFT BODY, include:

Abalone, Bullhead, Catfish, Clam, Crab, Crayfish, Eel, Jellyfish, Krill, Lobster, Marlin, Moonfish, Mussel, Octopus, Oyster,  Paddlefish, Scallop, Sculpin, Shark, Shrimp, Skate, Squid, Stickleback, Sturgeon (caviar), Swai (catfish family), Swordfish, Tilefish, All Shellfish, Whale U

Health effects linked to exposure to contaminates in fish

MercuryDetrimental effects on the central nervous system, such as:
• impairment of vision
•  Motor in-coordination
•  Loss of feeling
•  Seizures, very severe neurological impairment, and death -at high doses
•  Impair development in fetuses and infants.
PCBs• Reproductive and developmental effects in humans and animals
•  Lower IQ, hyperactivity, shortened attention span, and delayed acquisition of reading skills with exposure before birth
Dioxins• Reproductive and developmental effects
•  Altered immune function
•  Disruption of the endocrine system.
Toxaphene and dieldrinExposure can damage the nervous system

Farm-raised fish tend to contain more pollutants

“Big fish in a small pond” – Farmed fish are kept in pens (either open or contained) bred and raised for human food (a process called aquaculture).  Crowded conditions spread diseases requiring farmed fish to be treated with antibiotics. Rarely found on juvenile fish in the wild, sea lice are increasingly seen in fish in net pens.  50% of the world’s salmon is farmed, and this percentage is growing rapidly.

Fish pens
Aqua culture off Vestmanna on Streymoy, Faroe Islands by Erik Christensen, Porken Licensed CC BY-SA 3.0

Saltwater pens are close to shore where there is more industrial waste in the water

ALL trout in main U.S. markets are farm-raised (mainly from Idaho and N. Carolina) in fresh water troughs.   Lake trout are dealing with industrial run-off.

Pollutants in the fish we eat

We should make wise choices

We can take into account the relative contamination level of different fish.   Even some biblically “clean” fish have higher contaminants than others, for example:

USDA data (~2002) shows that:

PCB levels of wild trout are on par with farm-raised trout (11ng/g)

PCB levels of farm-raised trout are ~50% less than farm-raised salmon

Farm-raised trout have low methylmercury levels.


Consuming contaminated seafood is the single leading source of mercury exposure for people.   Mercury levels in shallow waters have tripled since preindustrial times

The “Big Fish” (ALL large predators) contain high mercury levels –  Including:  King mackerel,  Marlin (imported), Tilefish (high: 1.45 ppm mercury), Shark,  Swordfish (high: 0.98 ppm mercury),  Orange roughy, Tuna (large, e.g. Albacore, Bluefin, Bigeye).  The U.S. FDA and EPA advises pregnant women, nursing mothers and small children not to eat any of these.  Mercury doesn’t easily leave the body once absorbed, so the amount of mercury builds up in species as they go higher up the food chain.

Contaminants depend on where fish is caught

The 10 most contaminated tuna were found in the NE Pacific Ocean, the Gulf of Mexico, and the NE Atlantic Ocean.  The 10 least contaminated fish, taken from the NW and SW Pacific Ocean, the South China Sea, and the Indian Ocean had pollutant levels lower by a factor of about 10.   9 of the 10 fish from the NE Atlantic and 5 of the 8 fish from the Gulf of Mexico would trigger health advisories for those eating even less than the two 3.5 oz. servings of cooked fish / week recommended by the American Heart Association (AHA)   NNicklisch et al, 2017

All 50 U.S. states have a fish consumption advisory.  E.g. Florida lists fish contamination concerns by county and specific water body (lake, river or coastal water).  

Mercury (Hg) and Pcbs in some common fish
Ocean Perch0 MahiMahi.15Low
Whiting0 Perch (freshwater).14 
WILD Pacific Salmon (incl. canned)<.05~5-10Skate.14 
Tilapia (Nile Perch).01 Carp.14High
FARMED salmon (incl. canned).01~27Monkfish.18 
Sardines.02 Spanishmackerel (S. Atlantic).18 
FARMED Lake / Rainbow Trout.02~11Snapper.19 
WILD Rainbow Trout.03~ 9Buffalo fish.19 
Haddock, Hake.03LowSablefish22 
Anchovies.04 Weakfish (Sea Trout).25 
Herring.04 Halibut.26 
Croaker (Atlantic).05 Saltwater Bass.27High
N. Atlantic Mackerel.05 White croaker (Pacific).29 
Mullet.05 Bluefish.31High
Plaice, sole, flounder.05LowTuna (Canned, solid/chunk white Albacore).35 
Pollock.06 Tuna (Fresh/Frozen).38 
Whitefish.07 Spanish mackerel-Gulf of Mexico.45 
Butterfish  Orange Roughy.54 
Cod.10LowKing Mackerel (Gulf of Mexico).73H
Chunk light tuna (skipjack).12Low   

Where do these pollutants come from?

Industrial agriculture produces a toxic runoff into our rivers and streams, and then on into the oceans.  Industrial processes release chemicals into the air, which also end up in our waters. There are legitimate concerns over the level of contaminants in our fish supply, including:

 PCBs (polychlorinated biphenyls).   Industrial lubricants banned by U.S. in ’70s, still used overseas

Pesticides /Insecticides.   E.g. toxaphene , dieldrin (banned in ’80s in U.S.);

Dioxins (industrial byproducts);

Mercury (in its most toxic, water-soluble form: methylmercury) and other heavy metals (e.g. cadmium, lead).

Generally, the larger the fish, those that have lived longest, and those at the top of the food chain have absorbed the most contaminants (this would include albacore tuna, mackerel, pike and bass).

Where is the contaminant mercury coming from?

~40% is from natural sources.   E.g. the earth’s crust, volcanoes

~26% from coal-fired utilities.   40 tons mercury/year in the U.S.

~34% from other polluting sources.  E.g. after coal-burning plants, the top source of mercury pollution in the environment is the manufacture of shampoo and other detergents.

Weighing the risk of eating possibly contaminated fish against its potential benefits

Eating fish is healthier than not eating fish at all

Unfortunately, most fish available in the U.S. market are either farmed (including most restaurant fish), or locally caught, either of which almost certainly contain some health-risking contaminants. 

The National Heart, Lung and Blood Institute sponsored a thorough clinical review of the evidence, published in JAMA, October 2006, and concluded that:

“The benefits of modest fish consumption (2- 3 servings per week) greatly outweigh the risks”, and that the benefits are greater for oily fish. Also, “Avoidance of modest fish consumption due to confusion regarding risks and benefits could result in thousands of excess CHD deaths annually, and suboptimal neurodevelopment in children.”

The researchers focused on cardiovascular health in adults and brain development in infants, finding that eating fish reduces coronary death by 36% and total mortality by 17%. They also found no definite evidence that LOW- level mercury exposure from seafood consumption had harmful effects on health in adults, although they did find that mercury from eating some fish may lessen the cardiovascular benefit. Their findings agreed with the recommendations of the EPA and FDA that women of childbearing age, nursing mothers and young children should eat 2 servings per week, but exclude the “Big Fish” (ALL large predators containing high mercury levels), which include:  King mackerel, tilefish,  shark, swordfish, Tuna (large, albacore).

Co- author of the JAMA published review, Eric Rimm, Associate Professor of Epidemiology and Nutrition at the Harvard School of Public Health, emphasized:

“The health benefits of the protein and omega- 3 fatty acids found in wild salmon, or farmed salmon from Canada or Chile, where the US gets most of its salmon, will almost definitely outweigh the risks for American adults, where the leading cause of death is from cardiovascular diseases.”

To put contaminant levels in perspective, we need to consider that fish account for only 9% of contaminants in the U.S. food supply.   90% of US contaminants come from meat, vegetables and dairy.

For example, even though a serving of farmed salmon contains many more PCBs than a serving of other foods, the more meaningful PCB level comparison should be made with the typical amounts of each food we eat each year, for example, we eat far more beef than salmon.

More information on mercury and PCBs


Mercury levels vary greatly in different fish. See chart above.

Mercury is found predominantly in the body of the fish, not so much in its liver oil.   Since mercury is water soluble. The U.S. government cautions pregnant women and small children against eating certain fish likely to have high mercury content. The chart above provides a guideline by giving average mercury content in only the “bible-clean”fish, taken from FDA surveys 1990-2003. Studies show that selenium, also found in fish, has a protective effect against methylmercury (MeHg) toxicity.


PCBs come from what the fish eats.  Primarily from fishmeal (ground up smaller fish) when farm-raised.

PCBs primarily accumulate in fat.   Locally caught fatty fish tend to have the highest evels of these neurotoxins. With emission bans, PCB levels have declined ~90%, but they still persist in the environment.

PCBs Standards for “Bought vs. Caught” in U.S.

•  Caught.    The strict EPA health-based standard for pcbs in recreationally caught fish, allows for no more than a 1 in 100,000 risk for cancer, but was designed to protect native Indian populations (surveys found that Oregon tribes consume upwards of 12oz. fish per person per day!).

•  Bought.   Commercially sold salmon must comply with the 1984 FDA PCB standard, which allows 500 times more PCBs than the EPA standard. FDA tolerances have not, however, been updated for findings of more recent studies on PCB cognitive impairment.