Reply #39: SOME kinds of fish have mercury; others do not.

[alarimer]

The recommendations on limiting fish intake by children and pregnant women refer to top predator species such as king mackerel and shark. Some species of tuna as well. But you are perfectly safe eating things like tilapia or catfish (which are much cheaper anyway).
Mercury is a biologically persistent toxin, meaning it hangs around in the tissues and is not eliminated.

Over time, that toxin accumulated in the tissues but the real problem is with fish at the top of the food chain, which can accumulate high levels of the toxin through bio-magnification. Fish at the top of the food chain eat other fish, each of which may have eaten other fish or organisms containing mercury, so the top predator fish then contains all of the mercury contained in all of the other fish it might have eaten. So you can eat as much fish that feed low on the food chain (like catfish, which are scavengers, or tilapia which primarily are farm-raised and are fed commercial fish feed, which contains little in the way of toxins).

So it is a myth that you must eliminate all fish because of mercury.