No, DHA can also come from other sources such as seeds, eggs and some plants, but in much weaker concentrations than in fish. Also in non-fish forms, it’s generally produced by an inefficient conversion process from another omega-3 fatty acid called alpha-linolenic acid (ALA). As an example flaxseed oil (FLO) comes from the flax plant and contains both omega-3 and omega-6 fatty acids. FLO contains the plant-derived omega-3 fatty acid alpha-linolenic acid (ALA), which can be converted to EPA & DHA but very inefficiently (8-20% of ALA to EPA; .5-9% to DHA); therefore, it is not considered a good source of the two potentially beneficial compounds. If you are looking for the specific benefits, such as maintaining heart, brain, hearing and vision health, associated with omega-3s, look for fish oil capsules containing ~600mgs of omega -3s made up of 360mgs EPA & 240mgs DHA. Take 1 capsule daily if not consuming 2-4 svgs/wk of fatty fish, unless a qualified physician advises more for a specific condition.