The mercury in fish issue might be part of the broader paranoia about meat.

Have you ever noticed how much anti meat (and anti - protein)  propaganda
there is?

l. if you eat  meat raw you're going to die
2. if you eat it too well cooked you'll get cancer
3. if you don't cook ground beef immediately you're going to die
4. if you eat eggs you'll get heart disease
5. if you eat fish you'll get mercury poisoning
6. and on and on

Can you think of some more anti meat myths, these are just a few, the media
is full of them

If they scare you off of meat, you'll eat the (more profitable) grains and
cereals and processed foods

>Back in 1972 the state of New York issued a warning about mercury
>contamination in the food fish caught in Lake Champlain. They (If I remember
>correctly) banned the eating of some species and recommended limitations on
>others. A few years later they rescinded everything. Seems that newer more
>sensitive tests were skewing the data. When they tested dinosaur bones at
>the Museum of Natural History they found high concentrations of mercury.