Mercury is often a hot media topic, and its connection to seafood can frighten away many consumers. Unfortunately, much of the information shared about mercury when it comes to Australian seafood is at best, inaccurate, and at worst, alarmist.
Today, we're giving you a full rundown on everything you need to know about mercury and seafood, so that you can ensure you're always making the best choices for you and your family.
What is mercury? 
Mercury is a naturally occurring element that is found in air, water, and food. Most people are exposed to mercury via the food they eat.
Mercury has three forms: organic, inorganic, and metallic. The organic form of mercury, particularly a type called methylmercury, is the most dangerous when it comes to consumption.
What is mercury's connection to seafood?
Mercury contained in ocean sediment is transformed into methylmercury by microorganisms. This methylmercury is then absorbed into flesh of fish through their gills as they swim, and through their digestive tracts as they feed.
Mercury levels differ from one type of fish to the next, as a result of their species, size, habitat, diet, and age. Fish that are predatory (i.e. eat other fish) tend to contain higher levels of mercury, as they absorb the mercury within the smaller species they eat through their digestive tract.
Should I be worried about mercury?
Doctors recommend that pregnant women and infants be extra careful about mercury content in their food, but otherwise, mercury is generally not something for the average seafood consumer to be concerned about.
As an average punter, to consume the amount of mercury needed to harm you, you would need to regularly be eating upwards of 3 servings of mercury-susceptible fish every week, or more than 1 serving of high-mercury fish (namely shark and billfish, e.g. Swordfish) per week, which is just not realistic for the vast majority of Aussies.
It's also important to remember that the body can and does get rid of mercury over time. Because of this, you will only exceed safe mercury levels if you eat a lot of high-mercury fish regularly over the course of many months.
Does Sydney Fish Market test for mercury?
Sydney Fish Market regularly tests the fish sold through our auction for high mercury levels, with special attention being paid to the higher risk species like sharks, Orange Roughy, Swordfish, and Barramundi. This is mostly done for research purposes - to track whether the mercury in certain fish species is increasing or decreasing over time - but also provides clear data on the safety of these species.
In 2022, for example, our food safety team tested 11 samples (including Kingfish, Longfin Eel, White-Spotted Guitarfish, Tuna, Tiger and School Prawns, Pipis and Frigate Mackerel) from the auction floor, and all samples came in under .
This means that by purchasing your seafood from Sydney Fish Market, or your own trusted fishmonger, you can feel secure in the knowledge that anything with extraordinarily high mercury levels has not made it to the retail sector.
In conclusion...
While we encourage seafood consumers to make their own choices with regard to their seafood intake (using the information available to them and the advice of their doctors) most people do not have to be concerned about mercury if they are not eating large predatory fish every single week, for months on end. Pregnant women (or those planning pregnancy) can also still enjoy seafood – just make sure you stay within the recommended guidelines.
Essentially, mercury from most fish sold in Australia is not a health risk, when the fish is consumed as part of a normal diet. You can breathe easy!
For more detailed health information about mercury in seafood, click .