Yes
The most widely available dietary source of EPA and DHA is cold-water oily fish, such as salmon, herring, mackerel, anchovies, and sardines. Oils from these fish have a profile of around seven times as much omega-3 oils as omega-6 oils. Other oily fish, such as tuna, also contain omega-3 in somewhat lesser amounts.  Both fish oil and flaxseed oil contain omega 3 fatty acids. However, they contain different types of omega 3 fatty acids. And, while all omega 3s are considered healthy, the majority of studies on omega 3s have focused on the kinds in fish oil, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Benefits of Fish Oil in Your Diet-If you are confused about flaxseed oil, omega 3s, or fish oil supplements you are not alone. Both fish oil and flaxseed oil contain omega 3 fatty acids. EPA and DHA are cardio protective – meaning they are good for the heart. A Stacy Wiegman, PharmD, Pharmacy, answered. Fish oil supplements vary in the amount of omega-3 fatty acids they contain. The two omega-3 fatty acids that are thought to offer health benefits and are commonly contained in fish oil supplements are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Some fish oil supplements may have more EPA than DHA, and in others the opposite might be true Not all omega-3s are the same. The three main forms are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). EPA and DHA are considered long-chain forms of omega-3 and are found in fish, fish oil supplements, and algae extract. ALA, the short-chain form, is found in plant sources like walnuts, flax seed, canola and soybean oil, and, to a lesser degree, green leafy vegetables The main essential fatty acids in the human diet are omega-3 and omega-6 fatty acids. Foods that provide omega-3 fatty acids include fish oil and certain plant and nut oils, while omega-6 fatty acids can be found in palm, soybean, rapeseed, and sunflower oils. Omega-9 fatty acids, which are not considered essential, can be found in animal fat and olive oil. There is evidence that recommended amounts of DHA and EPA, taken as fish or fish oil supplements, may lower triglycerides and reduce the risk of heart attack, abnormal heartbeat, and stroke in people who have heart disorders. DHA and EPA may also benefit people who have hardening of the arteries or high blood pressure. Two very important omega-3 fatty acids are eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). They are found in seafood, especially mackerel, salmon, striped bass, rainbow trout, halibut, tuna, and sardines. Supplements of fish oils that contain EPA and DHA are sold over the counter. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are fatty acids that have been shown to help reduce cardiovascular disease, reduce the pain associated with rheumatoid arthritis, as well as showing promise in the treatment of a number of other conditions. Omega-3 fatty acids (omega-3s) are a group of polyunsaturated fatty acids that are important for a number of functions in the body. Some types of omega-3s are found in foods such as fatty fish and shellfish. Another type is found in some vegetable oils. Omega-3s are also available as dietary supplements. 1 Fish liver oils, such as cod liver oil, are not the same as fish oil. 2  Fish liver oils contain vitamins A and D as well as omega-3 fatty acids. 3  Both of these vitamins can be toxic in large doses. 4  The amounts of vitamins in fish liver oil supplements vary from one product to another Overview. Docosahexaenoic acid (DHA) is an omega-3 fatty acid found in cold-water, fatty fish, such as salmon. It is also found in fish oil supplements, along with eicosapentaenoic acid (EPA). Vegetarian sources of DHA come from seaweed. Omega-3 fatty acids are good for your heart, and your body needs DHA for a healthy brain. 
https://en.wikipedia.org/wiki/Fish_oil http://www.drnatura.com/supplements/fish-oil/ https://www.sharecare.com/health/dietary-supplements/amount-fish-oil-supplements-and-omega-3 http://health.usnews.com/health-news/diet-fitness/articles/2009/04/08/fish-oil-supplements-epa-dha-and-ala-does-your-omega-3-source-matter http://www.mayoclinic.org/drugs-supplements/omega-3-fatty-acids-fish-oil-alpha-linolenic-acid/background/hrb-20059372 http://www.raysahelian.com/dha.html https://nccih.nih.gov/health/omega3/introduction.htm http://umm.edu/health/medical/altmed/supplement/docosahexaenoic-acid-dha
does fish oil supplement contain DHA