How much tuna is too much tuna in regards with the mercury in fish?

Mercury in fish. Some fish, however, contain high amounts of mercury -- enough to damage a fetus or newborn. That is why pregnant and nursing mothers must be very careful about the amounts and types of fish they eat. Young children should also avoid eating fish high in mercury. According to the fda, pregnant women and small children (under 6) should not eat more than 2 servings of fish each week.
Depends on tuna type. Big eye & ahi tuna should be avoided due to high mercury level. Yellow fin & white albacore tuna intake should be limited (no more than 3 – 6 oz servings per month). Skipjack & canned chunk light tuna have a lower amount of mercury (no more than 6 6-oz servings per month).