Answer to Question 1
Salmon and other fatty fish are excellent sources of -3 fatty acids, and their concentrations do not depend on whether they were caught in the wild or raised commercially.
Answer to Question 2
As with all foods, including reasonable amounts of either butter or margarine in your diet does not pose a problem. However, because we now know that trans fatty acids may be a bigger risk factor for heart disease than saturated fatty acids, choosing butter over margarine may be the wiser choice.