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Mercury Levels in Commercial Fish and Shellfish

What is mercury?

Mercury is a heavy metal element that occurs naturally in the environment. Mercury is also created and released into the air through industrial pollution. From the air, mercury can enter the water in streams and oceans and be converted to methylmercury. As fish feed in the contaminated waters, the levels of methylmercury build up in their muscles. As a general rule, the bigger or older the fish, the more mercury will have build up in them. also, certain types of fish seem to accumulate mercury to a greater extent than other types.

Why is mercury a problem?

Methylmercury is the form of mercury that can potentially be harmful to women attemptimg pregnancy, unborn babies and small children. If a person regularly eats types of fish that are high in methylmercury, it can accumulate in their blood over time. Babies and small children are more sensitive to the effects of mercury and are therefore at potentially greater risk. since it takes the body many years to get rid of mercury, women may have high levels even before she attempts pregnancy.

Mercury Levels in Seafood and Fertility

As stated abobe, mercury contamination has been found in many different types of seafood. Most women are now aware of the relationship between eating contaminated seafood while pregnant and the risk of giving birth to babies with birth defects and neurologic impairment. Recent studies have also demonstrated however that mercury consumption may also be related to infertility and miscarriage.

One study found that a group of infertile men and women had higher blood levels of mercury that a similar group of men and women with normal fertility. Men who had an abnormal semen analysis and women with otherwise unexplained infertility also had higher levels. The higher levels corresponded to increased consumption of seafood.

We therefore advise all patients who are attempting to conceive to try to reduce their consumption of mercury contaminated seafood. The table below from the U.S. Department of Health and Human Services lists the levels of mercury found in many different types of seafood. You can use this as a guide but keep in mind that these numbers are subject to change.

What about fish sticks and fast food fish sandwiches?

According to the FDA/ EPA fish sticks and fast food fish sandiches are commonly made from fish that are low in mercury.

Safety tips


  • 1. Do not eat any of the fish that contain high levels of mercury in the list below
  • 2. Eat up to 12 ounces ( 2 average meals) a week of a variety of fish and shellfish that are low in mercury. “ND” means “not detectable”. These fish have no detectable mercury contamination and are the safest. Otherwise, the lower the number in the mercury concentration column, the lower the levels and thus the safer the fish. For example, Tilapia has lower levels than fresh water trout.
  • 3. check local advisories about the safety of fish caught by family and friends in your local lakes, rivers and coastal areas.



FDA Advisory on Mercury in Seafood

Mercury in Fish: FDA Monitoring Program

Table 1. Fish and Shellfish With Highest Levels of Mercury
MACKEREL KING 0.730 N/A N/A 0.230 1.670 213 GULF OF MEXICO REPORT 2000
SHARK 0.988 0.830 0.631 ND 4.540 351 FDA 1990-02
SWORDFISH 0.976 0.860 0.510 ND 3.220 618 FDA 1990-04
TILEFISH (Gulf of Mexico) 1.450 N/A N/A 0.650 3.730 60 NMFS REPORT 1978
Table 2. Fish and Shellfish With Lower Levels of Mercury

SAMPLESSOURCE OF DATAMEANMEDIANSTDEVMINMAXANCHOVIES0.043N/AN/AND0.34040NMFS REPORT 1978BUTTERFISH0.058N/AN/AND0.36089NMFS REPORT 1978CATFISH0.049ND0.084ND0.31423FDA 1990-04CLAM *NDNDNDNDND6FDA 1990-02COD0.0950.0870.080ND0.42039FDA 1990-04CRAB 10.0600.0300.112ND0.61063FDA 1990-04CRAWFISH0.0330.0350.012ND0.05144FDA 2002-04CROAKER ATLANTIC (Atlantic)0.0720.0730.0360.0130.14835FDA 1990-03FLATFISH 2*0.0450.0350.049ND0.18023FDA 1990-04HADDOCK (Atlantic)0.0310.0410.021ND0.0414FDA 1990-02HAKE0.014ND0.021ND0.0489FDA 1990-02HERRING0.044N/AN/AND0.13538NMFS REPORT 1978JACKSMELT0.1080.0600.1150.0400.50016FDA 1990-02LOBSTER (Spiny)0.090.14‡ND0.279FDA SURVEY 1990-02MACKEREL ATLANTIC (N.Atlantic)0.050N/AN/A0.0200.16080NMFS REPORT 1978MACKEREL CHUB (Pacific)0.088N/AN/A0.0300.19030NMFS REPORT 1978MULLET0.046N/AN/AND0.130191NMFS REPORT 1978OYSTER0.013ND0.042ND0.25038FDA 1990-04PERCH OCEAN *NDNDNDND0.0306FDA 1990-02POLLOCK0.041ND0.106ND0.78062FDA 1990-04SALMON (CANNED) *NDNDNDNDND23FDA 1990-02SALMON (FRESH/FROZEN) *0.014ND0.041ND0.19034FDA 1990-02SARDINE0.0160.0130.0070.0040.03529FDA 2002-04SCALLOP0.050N/AN/AND0.22066NMFS REPORT 1978SHAD AMERICAN0.065N/AN/AND0.22059NMFS REPORT 1978SHRIMP *NDNDNDND0.05024FDA 1990-02SQUID0.070N/AN/AND0.400200NMFS REPORT 1978TILAPIA *0.010ND0.023ND0.0709FDA 1990-02TROUT (FRESHWATER)0.0720.0250.143ND0.67834FDA 2002-04TUNA (CANNED, LIGHT)0.1180.0750.119ND0.852347FDA 2002-04WHITEFISH0.0690.0540.067ND0.31028FDA 2002-04WHITINGNDND‡NDND2FDA SURVEY 1990-02

Table 3. Mercury Levels of Other Fish and Shellfish

SAMPLESSOURCE OF DATAMEANMEDIANSTDEVMINMAXBASS (SALTWATER, BLACK, STRIPED)30.2190.1300.227ND0.96047FDA 1990-04BASS CHILEAN0.3860.3030.3640.0852.18040FDA 1990-04BLUEFISH0.3370.3030.1270.1390.63452FDA 2002-04BUFFALOFISH0.190.14‡0.050.434FDA SURVEY 1990-02CARP0.140.14‡0.010.272FDA SURVEY 1990-02CROAKER WHITE (Pacific)0.2870.2800.0690.1800.41015FDA 1990-03GROUPER (ALL SPECIES)0.4650.4100.2930.0531.20543FDA 2002-04HALIBUT0.2520.2000.233ND1.52046FDA 1990-04LOBSTER (NORTHERN/AMERICAN)0.310N/AN/A0.0501.31088NMFS REPORT 1978LOBSTER (Species Unknown)0.1690.1820.089ND0.30916FDA 1991-2004MACKEREL SPANISH (Gulf of Mexico)0.454N/AN/A0.0701.56066NMFS REPORT 1978MACKEREL SPANISH (S. Atlantic)0.182N/AN/A0.0500.73043NMFS REPORT 1978MARLIN *0.4850.3900.2370.1000.92016FDA 1990-02MONKFISH0.180N/AN/A0.0201.02081NMFS REPORT 1978ORANGE ROUGHY0.5540.5630.1480.2960.85549FDA 1990-04PERCH (Freshwater)0.140.15‡ND0.315FDA SURVEY 1990-02SABLEFISH0.220N/AN/AND0.700102NMFS REPORT 1978SCORPIONFISH0.286N/AN/A0.0201.34578NMFS REPORT 1978SHEEPSHEAD0.128N/AN/A0.0200.62559NMFS REPORT 1978SKATE0.137N/AN/A0.0400.36056NMFS REPORT 1978SNAPPER0.1890.1140.274ND1.36643FDA 2002-04TILEFISH (Atlantic)0.1440.0990.1220.0420.53332FDA 2002-04TUNA (CANNED, ALBACORE)0.3530.3390.126ND0.853399FDA 2002-04TUNA(FRESH/FROZEN, ALL)0.3830.3220.269ND1.300228FDA 2002-04TUNA (FRESH/FROZEN, ALBACORE)0.3570.3550.152ND0.82026FDA 2002-04TUNA (FRESH/FROZEN, BIGEYE)0.6390.5600.1840.4101.04013FDA 2002-04TUNA (FRESH/FROZEN, SKIPJACK)0.205N/A0.0780.2050.2602FDA 1993TUNA (FRESH/FROZEN, YELLOWFIN)0.3250.2700.220ND1.07987FDA 2002-04TUNA (FRESH/FROZEN, Species Unknown)0.4140.3390.316ND1.300100FDA 1991-2004WEAKFISH (SEA TROUT)0.2560.1680.226ND0.74439FDA 2002-04