Which fish have the most mercury?
It depends on the species. A 2025 analysis tracking mercury in fish over a decade found large predatory fish like tuna and swordfish carry the most.
Why some fish have more mercury
Mercury gets into waterways from industrial pollution. Small fish absorb it, and bigger fish eat the small ones. The higher up the food chain, the more mercury builds up. That's why large predatory fish carry the highest levels.
What the research says
A 2025 analysis in Environ Res tracked mercury levels in fish across species from 2011 to 2021. Tuna, swordfish, and shark consistently had the highest mercury levels. Some species showed declining trends over the decade, while others stayed the same or even increased.
Smaller fish like salmon, sardines, and anchovies had much lower mercury. The gap between high-mercury and low-mercury fish was large and consistent across the full decade of data.
What you can do
Stick to low-mercury fish: salmon, sardines, anchovies, herring, and trout. Limit tuna to once or twice a week, especially for kids and pregnant women. Avoid swordfish, shark, tilefish, and king mackerel. Check local advisories if you eat locally caught fish.
The research at a glance
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