The target intakes for omega-3 fatty acids (including DHA+ EPA) as for other nutrients are typically done on a per daily basis. However, this does not require that such targets be maintained each and every day but are provided as average daily intakes over time intervals of weeks or longer such that missing such nutrient intakes on a sporadic basis does no pose a problem in general. For target intakes (daily) of DHA/EPA (combined), such can be consumed from fish sources, supplementation, or functional foods containing DHA/EPA. The main goal is to meet the targeted intakes of omega-3 fatty acids via the aforementioned 3 sources (alone or in combination). A 4 oz (100 g) serving of salmon would provide approximately 1200 mg of DHA/EPA (combined) which is the equivalent omega-3 content as found in approximately 3 servings (2 g each) of the fish oil supplement based on the information which you have provided in the supplement that you are using. One serving of salmon (as mentioned) on a given day would provide the approximate equivalent of DHA/EPA (combined) via supplementation over a three day period if you were supplementing at the level of 450 mg of DHA/EPA (combined) per day as indicated.