Share this on Facebook
download .zip with all pictures
Yes, actually! The concentration of mercury in the water is at safe concentrations for drinking and other uses.
The fish become toxic because they live *in* the water. Also, the fish we catch are generally pretty high up on the food chain — they have to eat a lot of smaller fish or other organisms to survive.
Each of these preyed-upon organisms accumulate small amounts of mercury by virtue of living in the water or by consuming food that has taken up mercury.
Hopefully you can see that if a large fish eats a lot of these smaller fish, then the large fish ends up inheriting the sum of the mercury from all the small fish eaten. This process is called [biomagnification](http://en.wikipedia.org/wiki/Bioamplification).