Are freshwater fish as healthy to eat as ocean fish? —D.P., by e-mail

That depends. Some freshwater fish, particularly coldwater varieties, can contain about as much healthful omega-3 fish oil as some saltwater fish. But studies have still found worrisome levels of mercury in many freshwater species, including bass, and many lakes and rivers have high concentrations of other toxins, such as dioxins and PCBs, that build up in fish flesh. Your best strategy is to eat a variety of fish, freshwater and saltwater, that are known to have the fewest contaminants. For a list, see our new report on the benefits and risks of eating fish. You can also check local fish advisories on the EPA's web site.