When the KDHE refers to serving size, it means the weight of skinless fish fillets before cooking. These are the appropriate sizes depending on the person’s age. Adults and children age 13 and older = 8 ounces Children age 6 to 12 = 4 ounces Children younger than 6 = 2 ounces Mercury advisory The KDHE and the KDWP say that all fish contain some amount of mercury. Therefore, anyone who routinely eats fish or serves fish to children should carefully consider the types and amounts they eat, including store-bought fish.