You can't tell if a fish has mercury just by looking at it; you need to check advisories for locally caught fish or know which species are high in mercury (like shark, swordfish, marlin, orange roughy) and limit those, especially if pregnant, nursing, or feeding young children, as high levels cause neurological issues like tremors or memory loss over time, with doctors using blood/urine tests for exposure confirmation.
Mercury is detected by the cold vapour atomic absorption spectrometry technique using an automatic mercury analyzer developed at the National Institute for Minamata Disease (NIMD).
If you choose to eat more than 2-3 serves of fish per week it is important to eat a variety of fish, and avoid those that could have elevated mercury levels, such as Shark (Flake) or Billfish (Swordfish, Marlin).
Fish that contain high levels of mercury include shark, ray, swordfish, barramundi, gemfish, orange roughy, ling and southern bluefin tuna.
Removing mercury from the water can be achieved using four processes: Coagulation/Filtration, Granular Activated Carbon, Lime Softening, and Reverse Osmosis. Coagulation/filtration is a common treatment which uses AlSO4 that reacts with the mercury to form a solid which can precipitate out of the water.
The unhealthiest fish to eat are typically large, predatory species high in mercury like shark, swordfish, king mackerel, and imported tilefish, plus bluefin tuna, which are dangerous for brain/nerve health, especially for pregnant women and children; also, farmed salmon and some imported tilapia/catfish raise concerns for contaminants and antibiotics, while orange roughy and Atlantic cod are often cited for high mercury and overfishing/sustainability issues.
Choices to Avoid.
These fish have the highest levels of mercury. Avoid eating tilefish from the Gulf of Mexico, swordfish, and shark. Also avoid king mackerel, bigeye tuna, orange roughy, and marlin.
Choose fish and shellfish that are lower in mercury such as salmon, trout, tilapia, cod, sole, sardines, shrimp, oysters, and other shellfish. For the most health benefits, choose fatty fish such as salmon, trout, herring, chub mackerel, and sardines. o These fish have healthy omega-3 fatty acids.
The Dietary Guidelines for Americans states that to consume those higher amounts, children should only be fed fish from the “Best Choices” list that are even lower in mercury – these fish are anchovies, Atlantic mackerel, catfish, clams, crab, crawfish, flounder, haddock, mullet, oysters, plaice, pollock, salmon, ...
Trimming skin and fat and cooking method do not reduce mercury exposure. The only way to reduce mercury exposure is to reduce consumption of contaminated fish. Thus, the DSHS recommends eating smaller, younger fish that have had less time to accumulate mercury in their tissues.
The healthiest fish in Australia are oily fish rich in omega-3s and low in mercury, like salmon, sardines, mackerel, herring, and canned salmon/sardines, alongside white fish such as barramundi, snapper, and flathead, which offer protein and nutrients; prioritize grilling, baking, or steaming for healthy preparation.
Wild-caught and farm-raised Barramundi contain different mercury levels due to their very different diets. Mercury is primarily a concern in large predatory fish that consume other fish, so large wild-caught barramundi have a higher risk of containing mercury than our farmed barramundi.
Stonefish stings in Australia
The stonefish is the most venomous known fish in the world and stings can cause death if not treated.
Symptoms of organic mercury poisoning from long-term exposure include:
Other mercury removal options include home remedies such as eating a nutrient- and vitamin-rich diet, increasing fibre intake, and drinking more water to flush out mercury from the body.
For most people, the risk from mercury by eating fish and shellfish is not a health concern. Yet some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child's developing nervous system.
Avoid Chilean sea bass, bluefin tuna,orange roughy, imported sturgeon caviar, and imported shrimp wheneverpossible. Just because it's on the menu at a famous chef's restaurantdoes not mean it's okay to eat.
Here are the top 7 best types of sustainable fish to eat for your health.
These non-game fish are the ugly, sucker-mouthed, snaggle-toothed, mottled menagerie of undesirables which includes suckers, gar, bowfin, snakehead, carp, buffalo, freshwater drum, and many others.
Levels of contamination
The danger level from consuming fish depends on species and size. Size is the best predictor of increased levels of accumulated mercury. Sharks, such as the mako shark, have very high levels of mercury.
It is safe for everyone (including pregnant women) to consume canned tuna as part of their fish intake. Canned tuna generally has lower levels of mercury than tuna fillets because smaller tuna species are used and the tuna are generally younger when caught.
Low estimates of mercury concentrations in shrimp (0.012 ppm, wet weight [ww]; Smith & Guentzel, 2010) may suggest that shrimp should be consumed more often than other, higher trophic marine species.
The mercury removal efficiency depends on the cysteine concentration and its ratio to fish muscle. Using 1.2 wt% cysteine enables a reduction of mercury in canned Albacore tuna by 25–35%, depending on the fish product type and the exposure time of up to 2 weeks.
Fish are largely linked to mercury poisoning because of the water they live in. All seafood contains small amounts of mercury, but large fish tend to have higher levels of mercury because of their consumption of smaller fish that carry it as well.
Everyone should try to eat 2-3 servings of fish per week. People who are nursing, pregnant or planning to be pregnant, and young children, should not eat fish from the “Choices to Avoid” list. These fish are high in mercury, which can be harmful to a developing nervous system.