The simple answer is absolutely. Mercury occurs naturally in the environment, can be released into the air through industrial pollution and accumulates in streams and oceans where it is turned into methylmercury. Fish absorb the methylmercury as they feed in these waters, it accumulates, and then we consume it when we eat the fish. Nearly all fish and shellfish contain levels of methylmercury. Fish that are more likely to have higher levels of mercury are the larger, longer living or predatory species.
There are numerous nutritional benefits from regularly eating fish, but given the ongoing and unresolved concerns regarding mercury exposure, it is recommended that people should limit their consumption of some types of fish to 1 – 2 portions per fortnight (150 g or 75 g for children under 6) and no other fish that fortnight. High methylmercury containing fish include: billfish (swordfish/broadbill and marlin), shark/flake, orange roughy (sea perch) and catfish (bassa). Other important species to limit include barramundi, gemfish, ling, bluefin tuna, other types of tuna – including canned white chunk or albacore, halibut, mahi mahi, pike, ray, seabass, tilefish, walleye & white croaker. Freshwater fish in geothermal lakes and rivers in New Zealand may also accumulate higher levels of mercury.
The canned tuna debate is tricky. It is believed that smaller and younger species of tuna are used for canned varieties. Remember that most canned tuna in Australia is from Thai waters whose Mercury control standards differ from our Australian guidelines. As such, limit consumption and replace with tinned salmon, sardines and mackerel.
Well what do I eat then? Blue mackerel, herring, John Dory, ocean trout, salmon, sardines, silver trevally, silver warehou, anchovy, blue eyed cod, bream, flathead, garfish, mullet, snapper, whiting and many others are your safest choices. Speak to your local fishmonger for more ideas!