This is an interesting site. One statement is that selenium, found abundantly in fish; helps draw mercury out of the body. Thus, the benefits of fish (which are significant) far outweigh the hazards.

The site is framed by this quote.

“Eating lots of ocean fish isn’t much of a hazard compared to missing out on the benefits from not eating fish. A slew of scientific reports have shown that eating fish helps protect against cardiovascular disease and enhances brain development before and after birth … Overstating the almost negligible risk of mercury could adversely affect millions of people who face the risk of heart disease.”
— University of Rochester Professor of Environmental Medicine Dr. Thomas Clarkson (1998)

With all of these "food scares," I do wonder what activists think anyone is supposed to eat. I prefer to stick with whole foods, limit my red meat and avoid processed foods and preservatives. When we start adding foods like fish to the no-eat list, it's time to hang up our collective hat.