i'd want to see results from independent testers before believing govt. scientists.
Consumer reports has been reporting on mercury and other toxin levels in fish for many years. They have had articles comparing various types of fish (freshwater, ocean, etc), species within each type, as well as discussion comparing and contrasting what you get with farm grown vs. wild fish.
In a nutshell, all types of fish that you can buy in a supermarket are "safe", as long as you don't eat too much. They have recommendations for the number of servings of each type per week, for various types of people. For example, children and pregnant women can eat 2-3 servings of tuna per week, but only one serving of albacore, due to different concentrations of mercury and other toxins.
The caveat to this of course is that some locations really do have nasty fish due to sewage runoff. For example, fish in several areas downstream of large populations will test positive for a hideous coctail of prescription medication because people flush unused drugs down the toilet so they end up in the water and concentrate in fish. For that matter, you can probably avoid ever going to the doc just by eating fish in those areas because they have medically significant amounts of certain drugs (seems like anti-depressants and painkillers get flushed a lot) if you eat a lot of those fish.
