If you're female, too much tuna fish can have a negative effect on fertility.
Fresh water fish, is very good for you. Many markets that sell fresh fish have package information about where it comes from. (lake fish and fish off clean coastal waters, is less dangerous to eat than SOME ocean fish)
The best fish comes from less industrialized areas, though there is no guaruntee if it is your only source of protien. There are many types of vegetarian fish that are made completely out of soy and taste exactly like fish that would reduce over-exposure to mercury for those who like to eat it every day.
Hope this helps.
Best regards,
YP
