People who have been diagnosed with coronary heart disease should eat about 1 gram of fish omega-3s per day, preferably from fatty fish. While fish contain varying levels of omega-3s, that might work out to around 3 ounces of salmon or tuna, or 6 ounces of pollock, flounder, or sole, according to the AHA web site.
Young children, along with women who are pregnant, planning to become pregnant, or nursing, should avoid fish with higher levels of mercury, like shark, swordfish according to the FDA. Everyone else can eat up to 7 ounces of high-mercury fish per week.